# Early Mustangs-performance/experience?



## IdahoRenegade (Dec 9, 2017)

The success of the 2-stage/2 speed Merlin equipped P-51Bs and later models is well documented and justifiably famous. I'm fairly familiar with it's combat success from December '43 on, as are most casual aviation enthusiasts. I believe most know the plane was developed as a result of a British purchase order. This order was somewhat out of desperation, with the British being desperate for more fighters, most any fighters, with the original contact with NAA being a request to build P-40s-in spite of its limited performance. NAA engineers offered to develop what became the P-51 instead and the results are history.

While I'm pretty familiar with the results of the Merlin Mustangs, what I haven't found is a great deal of discussion of the early, Allison equipped British birds (MK-1s?) equipped with single stage superchargers. Does anyone have any sources discussing the use/performance of this plane by the British and how it fared against the opposition, as well as how it compared to its British contemporaries? What theaters did it operate in? I understood (anecdotally anyway) that it performed well at lower altitudes compared to the Spit in terms of speed, being significantly faster at the same power level due to the low drag airframe (true or am I mistaken?). I also believe that even in the early variations with no rear fuselage tank that it had a considerable range advantage over the Spit due to it's lower drag airframe. Did it also carry significantly more fuel even in this variation, and was it used to a significant extent over occupied Europe?

Similar questions concerning the US utilized P-51A model. Where was it utilized and how did it well did it succeed at it's missions. I know virtually nothing about the A-36 dive bomber version. "Version" perhaps not being accurate-was this basically a '51 with dive flaps or were the changes more extensive? How did it perform in that roll? It seems like a plane with a single liquid cooled engine would be pretty susceptible to loss in that role, given the susceptibility of the cooling system to damage. Was the A-36 produced due to it's performance, or more as a way to keep the NAA production line in operation?

Finally-the story of the Mustang being re-engined at Rolls with the Merlin is well known-but I know nothing of the details. Any information on the backstory? Who's idea was it, when did it happen, reviews of the test flights? Other than the prototypes retrofitted at Rolls, were any production Mustangs built for the British before the US P-51B model went into production?

Sorry about all the basic questions. Compared to the vast amount of knowledge so many here have, I'm just a rookie. Thanks.

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## Greyman (Dec 9, 2017)

Interesting US report on British Mustang I use over at wwiiaircraftperformance E-GEH-16


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## tomo pauk (Dec 9, 2017)

Bill (drgondog) will cover the origins of the idea to install Merlin on Mustang. There was also a short-lived proposal to re-engine the Mustang with 1-stage 2-speed Merlin, but it was skipped.
USAF used P-51A in CBI (China, Burma, India) thatre, and in the MTO. IIRC RAF also got a handful of those.
A-36 was an useful dive bomber, the losses were nothing extravagant. It was also used as escort fighter in the MTO, to escort medium bombers. It have had dive brakes installed, flaps were not changed for that version. Production of the A-36 was a way to keep the NAA production line open. Susceptibility of liquid cooling to enemy fire is over-exgagerated IMO.
British operated the Mustang I/Ia exclusively in the ETO*. Range was excellent, but Spitfire was also able to carry a drop tank that gave SPitfire a comparable rage, or better range if the 170 gal tank was used. Tests of the Allison-engined Mustangs: link.
The Mustang I was well liked by the RAF and operated as long as 1944, though it's main use was of recon.

*ETO, not MTO here

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## drgondog (Dec 9, 2017)

Don't have much time today:

Early Merlin - NAA Kindleberger had a knock down fight with Allison beginning in early December 1941, went as far as getting Mossie engine mount drawings, engine specs from Packard for Merlin 28 (1650-1) and preliminary estimates to convert from Schmued. The meeting occurred in January 1942 with two GM Board members including Breech and Allison CEO. Ronnie Harker, Test pilot for RR, made recommendation to install new Merlin 61 in Mustang I on May 1, 1942. Hives, Managing Director of RR/Hucknall approved on May 4, and set up meetings with Ministry and RAF Air Staff - project go-ahead on 5/19/142 with Mustang I AG518 allocated to project.

Thanks to active interest by Maj Tommy Hitchcock, who was extremely well connected to not only Ambassador Winant but also Roosevelt, His constant prodding enabled NAA to invest preliminary cycles to look further into converting to both the Merlin XX (16501-) and Merlin 61 (1650-3 with longer dimension because of supercharger) in June 1942. Despite foot dragging by AAF Mat'l Command (Echols and others) contract NA-101 dated 7-25-1942 was executed for two prototype Mustang/Merlin (as yet not determined which one) as XP-78. It allocated two P-51-1 to the project.

David Burch's Rolls Royce and The Mustang is THE book for the narrative from RR point of view.

The RAF loved the Mustang I, and IA for its range and speed and overall maneuverability - They used it quite effectively as Armed Recon and intruder into Germany, shooting up rail and barge traffic as well as airfields.

The biggest issue with the Mustang I as far as AAF concerned is that it a.) wasn't requested by Material Cmd, b.) It was a drain on Allison's capacity to produce engines, and c.) the political intrigue was almost Not overcome. Echols was a friend of Arnold and did have a degree of influence, but at the end of the day, the Arnold/Fairchild connection, after the A-36 proposal and contract was let, was STILL required to keep Echols from not proceeding with the follow on P-51A contract immediately after A-36 run completed/

The period April, 1942 through May, 1943 was characterized by Echols trying to keep the P-51 bottled up, which did not help him later career wise when the reports of the Mustang X, then Xp-51B, then P-51B-1 emerged from other sources than Material Command - particularly as the Eglin Field tests emerged.

IMO the P-51B could not possibly have been operational in ETO before they actually began Dec 1, 1943 - simply because the ability of Packard to take the RR Merlin 61 and tool for it, produce a couple in October, lose two to engine failures and actually delay the first flight of the Xp-51B by six weeks - pointed to the real critical path. Packard simply couldn't get functional engines in the hands of NAA until late June/early July, 1943.

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## pbehn (Dec 9, 2017)

As far as I know the RAF were interested in putting a Merlin in the Mustang as soon as they test flew it, some may have been interested as soon as they found out its internal fuel load. 

The first air victory and loss of Mustangs was in the Dieppe raid, a mustang pilot downed a FW190 who had just downed his wingman. The victory was by American Holis Hills flying with RCAF 414 Sqrn while the "loss" flt Clarke was picked up and survived ditching being picked up by a landing craft.

Some useful info here.
P-51 Mustang - History, Pictures, and Specs


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## davebender (Dec 9, 2017)

ability of Packard to take the RR Merlin 61 and tool for it
Lancaster bomber was competing for those engines.
When did British made Lancaster bombers start using Packard made Merlin engines?


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## tomo pauk (Dec 9, 2017)

drgondog said:


> Don't have much time today:
> 
> Early Merlin - NAA Kindleberger had a knock down fight with Allison beginning in early December 1941, went as far as getting Mossie engine mount drawings, engine specs from Packard for Merlin 28 (1650-1) and preliminary estimates to convert from Schmued. The meeting occurred in January 1942 with two GM Board members including Breech and Allison CEO.
> ...



Talk about missed oportunity - the Mustang with V-1650-1. Ready to hit Luftwaffe in 1943 above Germany proper.



davebender said:


> ability of Packard to take the RR Merlin 61 and tool for it
> Lancaster bomber was competing for those engines.
> When did British made Lancaster bombers start using Packard made Merlin engines?



Lancester never used Merlin 61, the two-stage supercharged Merlin. Only Merlin 20s (1-stage), those were in good supply from early 1941 on, plus Packard started producing them from late 1941 on.

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## wuzak (Dec 9, 2017)

davebender said:


> ability of Packard to take the RR Merlin 61 and tool for it
> Lancaster bomber was competing for those engines.
> When did British made Lancaster bombers start using Packard made Merlin engines?



Since the original contract specified 2/3 (6000/9000 IIRC) of Packard production was to go to the British, I imagine Lancasters received the V-1650-1/Merlin 28 as soon as the factory started making them. Similarly for the Mosquito and Canadian Hurricanes.

The issue for the P-51B was the change at Packard to also build the V-1650-3/Merlin 61/63. It was the production of the -3 which was problematic for the Mustang program.

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## wuzak (Dec 9, 2017)

tomo pauk said:


> Lancester never used Merlin 61, the two-stage supercharged Merlin. Only Merlin 20s (1-stage), those were in good supply from early 1941 on, plus Packard started producing them from late 1941 on.



Not in quantity, anyway. 

The Mk VI had later versions of the 61.

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## MIflyer (Dec 9, 2017)

There's an Osprey book "Allison Engined P-51 Mustang" that covers the airplane pretty well. I also read in a book about Canadian airmen, "All The Fine Young Eagles" that while it was ostensibly a "army cooperation aircraft" the RAF used the Mustang Mk 1 as a long range intruder, even popping in at Luftwaffe basic training airfields to give the students a rude shock. Even though the Mk1 was not equipped to carry drop tanks, it still had a 1000 mile range with a full internal fuel load.

There was an issue of Air Enthusiast that covered the Allison Mustangs' service pretty well. Last known kill by an RAF Mk1 was on 1 Jan 1945, when one shot down a Ju88 that was one of the navigational aircraft used for Operation Bodenplate 

The book "Straight Down" covers the A-36A quite well. The RAF wanted to use the Mustang Mk1 in the Med for low altitude recon but had none available. They did borrow one or two A-36A's from the USAAF to use for that role and found out that for long range low altitude missions the Spitfires they tired to provide as escorts could not hack it. The Apaches could throttle back and cruise along so much faster and longer than the Spitfires that escort was impossible. The book "Those Were the Days" was written by an A-36A pilot and is one of the few to cover personal experiences of those pilots. And it turns out that some P-51-1's, the USAAF version of the Mustang Mk 1A, with four 20MM cannon were used by the A-36A units as well. 

A friend of mine who was in the CBI said that they found that while the P-47 could carry much larger bombloads, the P-51A's were better at carrying bombs out of short jungle strips. The P-51A's were also found to be better than the RAF fighters at CAS in Burma because they were still equipped with HF radios that could talk to the ground troops and thus get some FAC help. The RAF fighters had switched over to VHF, could not talk to the ground troops and asserted that, "We don't need to talk to the troops because we thoroughly brief our pilots on the targets they are to attack." Of course, everyone eventually figured out that "Target is 200 yards west of the red smoke" was a much better way to do things.

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## Shortround6 (Dec 9, 2017)

According to "AHT" the British were using 5 squadrons of Allison powered Mustangs at the time of D-day and were still using 2 squadrons of them at VE day. Which is certainly not too shabby considering the last Allison powered Mustang left the factory in May of 1943 . The last 310 Allison Mustangs are P-51As and the British got 50 (?) and called them Mustang IIs. These were "pay back" for the 57 P-51s (with 20mm cannon) the Americans had held back from the lend-lease contract for the Mustang-IA. 

They were probably running into a spare parts problem keeping them in service at that point. They had gotten 93 of the Mustang IA (P-51) with four 20mm cannon. 
21 British squadrons operated Mustang Is at the peak of use, but the last Mustang I left the production line in July of 1942.


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## MIflyer (Dec 10, 2017)

By the way, the roll rate of the early Mustangs was not that great and the Farnborough people worked to develop better ailerons for the later airplanes. They did come up with a aileron design that improved the roll, and Capt Eric Brown said it was better in that regard than the new ones North American used on the Merlin engined models. I don't know if the P-51A got the new ailerons or if they were retrofitted to earlier models the way the new metal ailerons were on the Spitfires; I would guess not.

So the Allison engined models were much lighter than the Merlin models, among other things the Allison engine was 400 lb lighter than the Merlin 61. But the Merlin engined models had a better roll rate.

Oh, and the Allison engined models did not have a cockpit floor; the seat was simply bolted to the wing. The Merlin engined models had a plywood cockpit floor.

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## drgondog (Dec 10, 2017)

I'm still trying to find the production break between the old/original aileron and the sealed aileron, that for sure was installed in B-1 and all succeeding Mustangs. Chilton tested both A-36 and P-51A for Roll rate so it is entirely possible that both received the improved aileron.

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## davebender (Dec 10, 2017)

Lancester never used Merlin 61
Perhaps not that exact model but they were competing for Packard made Merlin engines along with the P-51, some makes of the P-40 etc.


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## tomo pauk (Dec 10, 2017)

davebender said:


> Lancester never used Merlin 61
> Perhaps not that exact model but they were competing for Packard made Merlin engines along with the P-51, some makes of the P-40 etc.



Hopefully this will not be turned into an anti-Lancaster tirade 
The P-40 with Packard Merlin V-1650-1 was barely passable fighter in 1942 (imagine a slower Spitfire V that also climbs slower, has better range and rolls better), and by 1943 it was a waste of crucial engines. On the other hand, Lancaster was prossecuting a crucial bomb war that was far costlier for Germany to pay for defences, damage and lost work hours than it was for the UK to wage that war. There was no competition for engines between Lanc and P-51 - Packard was producing plenty of both -1 engines from Spring of 1942, let alone in 1943 when they also started manufacturing the production of 2-stage supercharged -3 and, swithching to -7 engines in 1944.

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## MIflyer (Dec 10, 2017)

Yes, a point I have made elsewhere and been criticized for it. The V-1650-1 started production at the same time the Mustang Mk1 started production. If those engines had gone into Mustangs rather than P-40's you would have had a far more useful airplane. The P-51A as delivered had basically the same top speed as a Spitfire Mk IX at 20,000 ft. With an engine that enabled two critical altitudes, one at 15,000 and one at 20,000 ft, it would have run away from a Spitfire Mk IX and had an improved climb rate as well.

No, it would not have been nearly as good as a P-51B. But it would have been better than just about anything else around at the time.

Now, there was no earthly reason that Allison could not have built a two speed supercharger to bolt onto the V-1710 crankcase. Unlike the Merlin the V-1710 came in three main pieces, the gearcase, crankcase, and rear accessory section with supercharger. Building another version of the accessory section would have not affected the rest of the production. They probably could have even gotten another company to build the new accessory case and supercharger; it would have been simple. 

Imagine getting Continental or GM or someone to build the new two speed V-1710 accessory section and telling Fisher to stop fooling around with that ridiculous XP-75 and start building Mustangs. Mustangs over Berlin in March of 1943 rather than 1944. And the two speed supercharger could have gone into the P-40 and P-39 as well.


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## tomo pauk (Dec 10, 2017)

MIflyer said:


> Yes, a point I have made elsewhere and been criticized for it. The V-1650-1 started production at the same time the Mustang Mk1 started production. If those engines had gone into Mustangs rather than P-40's you would have had a far more useful airplane. The P-51A as delivered had basically the same top speed as a Spitfire Mk IX at 20,000 ft. With an engine that enabled two critical altitudes, one at 15,000 and one at 20,000 ft, it would have run away from a Spitfire Mk IX and had an improved climb rate as well.



To be fair to the Spitfire IX, the engines in service in 1943 made it go more than 400 mph at 25000 ft and above, the P-51A can't compete. Especially once the wing racks are accounted for, cost was 12 mph on the P-51A/B/C (improved racks came with P-51D, cost was 4 mph). Spitfire's sigle drop tank facility was barely noticeable speed-wise. Rate of speed was firmly Spitfire's territory, P-51A is even less able to compete here.
More about critical altitudes in a second.



> No, it would not have been nearly as good as a P-51B. But it would have been better than just about anything else around at the time.



The main benefit with going with Merlin early on is that there is a very useful long range fighter, without vices, in mass production, before 1943. Use it in 1943 as escort fighter in the ETO and LW can be hit hard above Germany proper.



> Now, there was no earthly reason that Allison could not have built a two speed supercharger to bolt onto the V-1710 crankcase. Unlike the Merlin the V-1710 came in three main pieces, the gearcase, crankcase, and rear accessory section with supercharger. Building another version of the accessory section would have not affected the rest of the production. They probably could have even gotten another company to build the new accessory case and supercharger; it would have been simple.
> 
> Imagine getting Continental or GM or someone to build the new two speed V-1710 accessory section and telling Fisher to stop fooling around with that ridiculous XP-75 and start building Mustangs. Mustangs over Berlin in March of 1943 rather than 1944. And the two speed supercharger could have gone into the P-40 and P-39 as well.



Having a gearbox with more SC speeds can't help the V-1710, at least not in the vein that it can improve much the altirude power. The impeller was too small - 9.5 in, vs. 10.25 in on most of the Merlin 1-stage engines, V-1650-1 and Merlin included. The V-1710 with 'faster' geared impeller was still lacking 3000-3500 ft worth of rated (or critical) altitude vs. V-1650-1 or the Merlin 45 that was an 1-speed supercharged engine. Or some 12% lack in power above 15000 ft.
Without going to a 2-stage supercharger, the V-1710 will never hope to match what 2-stage Merlin was offering.

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## Shortround6 (Dec 10, 2017)

davebender said:


> Lancester never used Merlin 61
> Perhaps not that exact model but they were competing for Packard made Merlin engines along with the P-51, some makes of the P-40 etc.


You had 3 basic types of Merlins.
1, single speed-single stage. Never made by Packard. 
2. two speed-single stage, Made by Packard as shown in the chart posted by Tomo. In ten versions although some were NOT massed produced. 
3. Two speed-two stage, also made by Packard as shown in the chart posted by Tomo. 

Now please note that the _initial _contract for Packard Built Merlins was for 9,000 two speed single engines and at a max delivery rate of 800 engines a month. The US was to get 3000 engines and the British 6000 engines. Please note that the initial contract was completed some time in March of 1943. 
Obviously a number of contracts were placed to cover the additional 17,759 singe stage engines and the over 20,000 two stage engines (chart above only goes to Dec 1944, not the entire war) 

There seem to have been a grand total of *NINE* Lancasters using two stage engines ( Merlin 85/87s), any other "Lancasters" using two stage Merlins got different wings and were called Lincolns. 

Also note that it took until the summer of 1942 for NA to complete the first 620 Mustang Is which, I believe, the British had paid for cash, and had purchased the Alison engines for (also cash?) so trying to swap engines around gets somewhat difficult. 

Curtiss was turning out over 300 P-40s a month for most of 1942, NA would not exceed 150 fighters per month until Dec of 1943. For most of 1942 they didn't go over 90 fighters a month. Without some _SERIOUS _revamping of production facilities, engine allocations, and hundreds of subcontractor contracts you are simply not going to get large numbers of single stage Merlins all that early. Please consider that the XP-40F first flew on June 30th 1941 but it took until Jan 3rd 1942 for the first production example to leave the factory The last of 1561 P-40Fs leaves the factory in Jan of 1943, Curtiss built over 5000 Allison powered P-40s in the same time period. 

I would note that the Curtiss factory was only about 215-220 miles from Packard if you cut through Canada ( Lake Erie is in the way) but it is just under 2000 air miles from Packard to NA in Los Angles. The engines have to go by train, not air, though. Forget cross country truck in 1941

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## wuzak (Dec 10, 2017)

tomo pauk said:


> Having a gearbox with more SC speeds can't help the V-1710, at least not in the vein that it can improve much the altirude power. The impeller was too small - 9.5 in, vs. 10.25 in on most of the Merlin 1-stage engines, V-1650-1 and Merlin included. The V-1710 with 'faster' geared impeller was still lacking 3000-3500 ft worth of rated (or critical) altitude vs. V-1650-1 or the Merlin 45 that was an 1-speed supercharged engine. Or some 12% lack in power above 15000 ft.



Without changing the supercharger, a second speed would add power at lower altitudes and not increase the critical altitude.

Though, for the V-1710 it could have allowed the 9.6:1 gears for HI gear and 8.8 (?) for LO gear, so as gaining some altitude performance without losing low altitude performance.

Apparently there was a 2 speed V-1710 prototype model at some stage, but it did not make it into production.

Regarding supercharger impeller sizes, the V-3420 used a single 10" impeller. Which would seem to be way undersized.

For comparison, the Vulture (2600ci) had a 12" impeller, the Griffon (2240ci) had ~13" impeller.

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## Shortround6 (Dec 10, 2017)

wuzak said:


> Without changing the supercharger, a second speed would add power at lower altitudes and not increase the critical altitude.
> 
> Though, for the V-1710 it could have allowed the 9.6:1 gears for HI gear and 8.8 (?) for LO gear, so as gaining some altitude performance without losing low altitude performance.


Or the Allison could have used 7:48 gears or lower for low and kept the 9.6 gear for high,not enough change between 8.8 and 9.6 to be worthwhile.


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## tomo pauk (Dec 11, 2017)

wuzak said:


> Apparently there was a 2 speed V-1710 prototype model at some stage, but it did not make it into production.



All two-speed V-1710s (a handfu of examples produced, plus projects) were outfitted with bigger S/C, typically 10.25 in diameter of impeller. Gear ratios were of 6.44:1 and 8.80:1 on the F series (just 1 produced); 7.48:1 (plus 7.76:1) and 9.60:1 on the G series, obviously for 1st and 2nd gear respectively. The G3R (V-1710-131) seem to be only of the G series produced as such, 8 pcs.
The V-1710s with bigger impeller were making around 100 HP more power at 15000 ft than the best in-service 1-stage versions with 9.50 in impeller.



Shortround6 said:


> Or the Allison could have used 7:48 gears or lower for low and kept the 9.6 gear for high,not enough change between 8.8 and 9.6 to be worthwhile.



Choosing the 7:48 gear ratio allows for greater take off power on same or a bit lower boost, eg. 1450 HP for on 50.5 in Hg (possible for the low-alt V-1710, eg. as on the A-36), vs. 1325 HP HP at 51in (engine on P-40K).

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## drgondog (Dec 11, 2017)

MIflyer said:


> Yes, a point I have made elsewhere and been criticized for it. The V-1650-1 started production at the same time the Mustang Mk1 started production. If those engines had gone into Mustangs rather than P-40's you would have had a far more useful airplane. The P-51A as delivered had basically the same top speed as a Spitfire Mk IX at 20,000 ft. With an engine that enabled two critical altitudes, one at 15,000 and one at 20,000 ft, it would have run away from a Spitfire Mk IX and had an improved climb rate as well.
> 
> No, it would not have been nearly as good as a P-51B. But it would have been better than just about anything else around at the time.
> 
> ...



As much as I would like to agree the scenario - Rolls Royce was far ahead of Allison in both reliable production and change management communications with RAF as well as development of their integral two stage superchargers. NAA tried to bolt from GM owned Allison in early 1942 because Allison was killing them with unannounced changes affecting engine mounts, etc. The Packard 1650-1 was available but there were barriers (AAF-MC/Echols/Kelsey/Timberlake, etc) that wanted nothing to do with NAA Mustang and probably would have cited the 'critical requirement' for the P-40F.

In addition, the AAF was pushing P-63 in same timeframe as the Mustang X/XP-51B development started which would have been more fodder to reject the new Allison inclusion into the Mustang (thank God). The new Allison configuration was never reputed to be fully reliable in concept with the P-63 and certainly not with XP-51J and P-82.

The first serious test of the 'new Allison V-1710-119 didn't occur until XP-51J in April, 1945. It never worked to Specs for NAA and they turned it over to Allison. AFAIK, it never worked properly. Nor was the configuration of the -93, or -117 in the P-63 fully reliable.

Additionally, the engine was longer with the 'two piece engine/supercharger combo' which would have


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## tomo pauk (Dec 11, 2017)

drgondog said:


> In addition, the AAF was pushing P-63 in same timeframe as the Mustang X/XP-51B development started which would have been more fodder to reject the new Allison inclusion into the Mustang (thank God). The new Allison configuration was never reputed to be fully reliable in concept with the P-63 and certainly not with XP-51J and P-82.
> 
> The first serious test of the 'new Allison V-1710-119 didn't occur until XP-51J in April, 1945. It never worked to Specs for NAA and they turned it over to Allison. AFAIK, it never worked properly. Nor was the configuration of the -93, or -117 in the P-63 fully reliable.



Bill - do you have some definitive data about (un)reliability of V-1710s installed on P-63?


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## bobbysocks (Dec 11, 2017)

there is a website for an A-36 outfit online. I don't have the time right now to look for it but there were personal accounts from the pilots. it was well used in Italy. from what I remember with the dive brakes they could fly it at an extremely steep dive giving it pretty good accuracy.

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## bobbysocks (Dec 11, 2017)

found it....the 86th Fighter Bomb group

86th Fighter-Bomber Group

and the 27th bombardment...or fighter group.


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## drgondog (Dec 11, 2017)

tomo pauk said:


> Bill - do you have some definitive data about (un)reliability of V-1710s installed on P-63?


Tomo - strictly anecdotal by way of test flights where the testing authority cited issues at 61" and Water Injection. Ditto NAA pilot reports including Chilton who flew all of our mainstream fighters plus P-63 plus 109G and FW 190A-5 in December 1943 at Eglin.


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## wuzak (Dec 11, 2017)

MIflyer said:


> Imagine getting Continental or GM or someone to build the new two speed V-1710 accessory section and telling Fisher to stop fooling around with that ridiculous XP-75 and start building Mustangs.



Perhaps would have been better for Fisher to not start messing with the XP-75 and instead continue with developing the V-3420 installation for the XB-39. The XB-39 may have been able to fly a year, or more, earlier than it did historically (December 1944).

That probably would have been a far more valuable contribution to the war effort than the XP-75 was.


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## tomo pauk (Dec 11, 2017)

drgondog said:


> Tomo - strictly anecdotal by way of test flights where the testing authority cited issues at 61" and Water Injection. Ditto NAA pilot reports including Chilton who flew all of our mainstream fighters plus P-63 plus 109G and FW 190A-5 in December 1943 at Eglin.



Thank you. Can the test report be found on-line? 
Looking at the test of the XP-40Q (2-stage V-1710) there were no major reliability ssues reported, even thogh the engine went to 3200 rpm and 75 in Hg.


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## pbehn (Dec 11, 2017)

There was another thread discussing getting the RR engine Mustang into service earlier and as far as I could see any improvement would only be a matter of weeks. To have Mustangs with Rolls Royce engines in service in strength in England at the start of 1943 needs an Anglo American agreement to provide a long range escort fighter before anyone thought it was needed or possible and also before the fuels, superchargers and possibly even NACA aerofoils were known.


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## tomo pauk (Dec 11, 2017)

Superchager (on the complete Merln 20) was there in 1940, fuel was good in 1940, getteing better in 1941, 1942 saw standardization at 100/130 PN, NACA airfoils were around for half a decade, XP-51 was flying in 1940, Mustang I was produced from late 1941 in token numbers, and in 1942 in good numbers.
Need for escort of own bombers stemmed back from ww1, re-appeared in Spanish Civil War, bacame obvoius during the BoB. Drop tank was no novelty before 1940.

It just took people to connect the dots. Even installing Merlin 45s on RAF's Mustang Is and drop tank facility would've worked wonders.


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## pbehn (Dec 11, 2017)

tomo pauk said:


> Superchager (on the complete Merln 20) was there in 1940, fuel was good in 1940, getteing better in 1941, 1942 saw standardization at 100/130 PN, NACA airfoils were around for half a decade, XP-51 was flying in 1940, Mustang I was produced from late 1941 in token numbers, and in 1942 in good numbers.
> Need for escort of own bombers stemmed back from ww1, re-appeared in Spanish Civil War, bacame obvoius during the BoB. Drop tank was no novelty before 1940.
> 
> It just took people to connect the dots. Even installing Merlin 45s on RAF's Mustang Is and drop tank facility would've worked wonders.




Very little points towards a plane capable of flying to Berlin and back escorting bombers at 25,000 ft until shortly (in design and production terms) before it did. In my opinion it needs the USA to declare war at least one and possibly two years before it actually did, For example when was the first NACA new aerofoil developed when was this new profile wing flown, when was it realised what this did or could mean?


Installing Merlin 45s and drop tanks on a Mustang is a great idea if you have enough Merlin 45s and also at the time the Mustang 1 was ordered the UK was much more concerned with staving off invasion not escorting bombers.

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## Shortround6 (Dec 11, 2017)

Production timeline for Mustang Is.

May 29th 1940, British order 320 Mustangs.
July/Aug 1940, Packard gets contract for Merlins. 
Sept 9th, 1940, prototype is rolled out-minus engine.
Sept 1940 British order 300 additional Mustangs.
Oct 26th 1940 NA-73X makes first flight.
May 1941 XP-51 makes first flight
July 1941 British order 150 Mustang IAs 
Aug 1941........2 Accepted 
Sept 1941.......6 Accepted 4 Packard Merlins delivered 
Oct 1941.........25 " 5 Packard Merlins delivered 
Nov 1941........37 " 10 Packard Merlins delivered 
Dec 1941........68 " 26 Packard Merlins delivered 
Jan 1942........84 "Packard builds over 100 Merlins. 
Feb 1942........84 "
March 42........52 "
April 1942.......86 " contract is signed for 500 A-36s.
May 1942.......84 " British Mustangs make first fighter raid into France 
June 1942......84 "
July 1942.......76 ", production changes to Mustang IA, 1200 P-51As ordered,
Aug 1942.......24 "
Sept 1942......60 "production changes to the A-36. 

Now just how much delay can you put into the Mustang program by playing around with the engines?

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## wuzak (Dec 11, 2017)

Shortround6 said:


> Production timeline for Mustang Is.
> 
> May 29th 1940, British order 320 Mustangs.
> July/Aug 1940, Packard gets contract for Merlins.
> ...



I wonder how many Merlins could the British have spared for the start of the Mustang program.

I am sure they could have delivered a single Merlin XX variant to NAA to install on the prototype, but not enough to ramp up production of the Mustang before Packard production was up to speed.


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## tomo pauk (Dec 12, 2017)

pbehn said:


> Very little points towards a plane capable of flying to Berlin and back escorting bombers at 25,000 ft until shortly (in design and production terms) before it did. In my opinion it needs the USA to declare war at least one and possibly two years before it actually did, For example when was the first NACA new aerofoil developed when was this new profile wing flown, when was it realised what this did or could mean?
> 
> Installing Merlin 45s and drop tanks on a Mustang is a great idea if you have enough Merlin 45s and also at the time the Mustang 1 was ordered the UK was much more concerned with staving off invasion not escorting bombers.



I'm not trying to sell a 'Berlin and back' escort fighter as a reasult of the changes to Mustang in 1941/42 (use in 1943). There is plenty of factories in Ruhr that need bombing, and LW can't just retreat further back in Germany, thus achieving good chance of delivering series of good blows to the LW, while lowering the losses to the B-17s.
P-51 was in production by 1941, it already featured a laminar-flow wing and other improvements that enabled it to go fast and far. What the program lacked was USAAF support and embracing the need for fighter escort much earlier than historically.

By 1941, let alone 1942 the invasion was out of the question, Merlin 45 was in mass production, by late 1942 it was in use in ETO, MTO, Soviet union, Australia. USAF used it. 



Shortround6 said:


> Production timeline for Mustang Is.
> 
> May 29th 1940, British order 320 Mustangs.
> July/Aug 1940, Packard gets contract for Merlins.
> ...



No delay.
As with XP-40F ( where Curtiss got the engine from the British), the British ship one Merlin 28 engine to the NAA, that has a prototype flying with that engine by late 1941. The A-36 is never produced, instead the NAA gets the contract for Packard Merlin-engined P-51 in April 1942. The resulting fighter enters production by Autumn of 1942.


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## drgondog (Dec 12, 2017)

Tomo - two points. First, the Allison issues in 1943 for two stage/two speed designs in P-39 show up in the MP vs altitude which reduce SL power to 1050 HP at altitudes ranging from 15,000 upwards. Spitfireperformance has several test reports where MP could not be achieved beyond 59.5 ".

Second - all the speculation about Merlin Mustang requires General Echols to be replaced by a pro NAA advocate with the ear of Arnold, and intervention at GM to kill the backlog of Allisons from a sister company to NAA in favor of a competitor, and the BPC stating specifically that the engine be converted from V-1710 to Merlin 1650-1 ASAP and releasing Packard from their committed RAF/AAF delivery numbers. Had the Brits been able to strike a deal for co-manufacturing in 1940 as part of the agreement, they would have worked earlier with NAA than the actual May 1942 Rolls Royce project. That said, the RAF was never focused on long range/high altitude daylight escort so the urgency to focus on Merlin 61 may or may not have transpired as first priority. 

In short - an amazing amount of prescient ability of the key players - and a complimentary displacement of profit motive by GM Board to pivot on the NA-73 into a NA-83+ (NA 83 already in preliminary spec process following first flight tests and review by AAF/NAA in mid-1941 before the NA-91)

It also required that Eaker and Spaatz suspend belief that a S/E fighter could never be developed to escort B-17s to Target... had either spoken up forcefully with Arnold, based on a 'vision', the acceptance by Material Command could have been forced by assigning a high level NAA Project Manager in 1941.

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## tomo pauk (Dec 12, 2017)

drgondog said:


> Tomo - two points. First, the Allison issues in 1943 for two stage/two speed designs in P-39 show up in the MP vs altitude which reduce SL power to 1050 HP at altitudes ranging from 15,000 upwards. Spitfireperformance has several test reports where MP could not be achieved beyond 59.5 ".



You have scratching my head by now, Bill, I'll admit that.
There was no V-1710 with 2-stage supercharger that also used 2-speed drive, apart from perhaps one prototype. That is in 1942, not in 1943. The 2-stage superchargers always used variable-speed drive for the 1st stage, and 1-speed drive for the 2nd stage.
Then - there was no P-39 with 2-stage engine in production, only the much modified XP-39E got a 2-stage supercharged engine. I've yet to read a test report on the XP-39E. A single-stage supercharged V-1710 from Autumn of 1942 was capable to deliver 1050 HP at 15000 ft.
The boost of 59-60-60.5 in Hg was achieved in war emergency mode without water injection ('dry'; link). Boost of 75in Hg was obtained via usage of water injection kit, as in this case: link to the Wright Field test.
Please note the engine power of 1100 HP at 22000 ft, with next to no ram effect. Lagging significantly after 2-stage Merlin, but much better than Merlin 28, let alone the best 1-stage V-1710.



> Second
> <snip>



Thank you.
I keep talking to the people that non-appearance of early Merlin Mustang was more a thing of politics, bickering and perhaps feuds than it was due to shortcomings of a particular piece of kit


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## Shortround6 (Dec 12, 2017)

Another thing with "early" changes is "who was promising what when"?

Allison had promised 9.60 supercharger gear *when* for example. They built around 50 engine with them (25 for P-49s and 25 for P-40s) but the supercharger drive gears failed and the engines had to be re-worked with 8.80 gears. It took almost another year for 9.60 gears to show up in service.
I am sure Allison had _promised _the 9.60 gears months before they built those 50 engines. 
We *KNOW* when certain engines and airframes showed up and we KNOW in what quantities. What the people in charge *knew *or *guessed *6 months to year before it actually happened is something else. 

What the British _wanted_ in the spring of 1940 vs what they wanted in the fall of 1940 may have changed only a little bit. What they wanted in the spring of 1941 may have changed a bit more and what was wanted in the fall of 1941 may be somewhat different than what was wanted 18 months earlier. However allocations of machine tools and raw materials have been made months before the production starts and trying to shift things around gets difficult. 

Not trying to cover up for Allison and GM but Allison had 530 employees in 1938, 786 in 1939, 4303 in 1940, 9,673 in 1941, 14,323 in 1942, and 23.019 in 1943. These are at years end. They also do not count the employees at the GM Cadillac plant that were making crankshafts and connecting rods or the thousands of subcontractors supplying many small parts. It is little wonder that there were shortages of engines at certain times. 
Jerking around production plans can result in lost time, lost material and late/reduced deliveries of what you do get. 

How much was political I have no idea, but GM was paid 12.30 *billion *dollars for war material in WW II. 1.04 Billion was for Allison. 1.35 Billion was for licence built P & W engines. and 1.35 billion was for marine diesels.2.09 billion was for military trucks.
I am sure GM didn't like the idea of Rolls Royce engines being used in American aircraft but GM had quite enough on their plate (complete aircraft, parts propellers, tanks/armoured cars, ammunition, etc) that I doubt that the lobbying of congressmen or service officers went very far. or maybe it did?


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## MIflyer (Dec 12, 2017)

Well, I think the main "what If" airplane for the V-3420 application was the Douglas XB-42. It offered a level of performance unequaled until jet bombers came along. I'll be posting some XB-42 design info later this week.

Most dual engines were failures. The RR Vulture did make a great contribution by accident when its supercharger was used as the 1st stage of the RR Merlin 60 series. The V-3420 seems to have done quite well in all its applications, but with possible exception of the XB-42 the designs themselves were either bad ideas or not really needed.

The two stage supercharged Merlin was more or less stumbled onto by mistake. By 1942 every knew that you needed much bigger engines than 1649 cu in and that was where the focus was. The Merlin was clearly too small; in fact it was the smallest displacement front line engine of the war. Even the A6M3 had 1700 cu in. The too slow F4F and P-36 had 1830 cu in. Even the in-line engined French fighters of 1940 had over 1800 cu in. Taking the first stage off the Vulture and adding it to the Merlin was just to make it a back up to the turbocharged radial to be used on the high altitude Wellington. The truly brilliant part was Sir Hooker's liquid cooled aftercooler. Only after they built that back up engine to support what turned out to be a bad idea did they realize they had produced a war-winner.


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## tomo pauk (Dec 12, 2017)

MIflyer said:


> ...
> The two stage supercharged Merlin was more or less stumbled onto by mistake. By 1942 every knew that you needed much bigger engines than 1649 cu in and that was where the focus was. The Merlin was clearly too small; in fact it was the smallest displacement front line engine of the war. Even the A6M3 had 1700 cu in. The too slow F4F and P-36 had 1830 cu in. Even the in-line engined French fighters of 1940 had over 1800 cu in. Taking the first stage off the Vulture and adding it to the Merlin was just to make it a back up to the turbocharged radial to be used on the high altitude Wellington. The truly brilliant part was Sir Hooker's liquid cooled aftercooler. Only after they built that back up engine to support what turned out to be a bad idea did they realize they had produced a war-winner.



Let's give Sir Stanley (and Lord Ernest, of course) some due credit. They knew that low compression ratio, big/elaborate supercharges and strong engines are the way to go.
The 2-stage supercharging was known already in early 1930s to bring advantage at high altitudes. The 2-stage system desingned by Hooker's team was compact item (as it is possible for a big S/C system), attached on a compact engine and worked probably better than anyone was hoping for. Merlin was perhaps a small-ish engine, but it was not a light one, and it turned enough of extra RPM over radials of the time to negate much of their displacemnt advantage. There was plenty of inherent strenth (not found in HS 12Y, for example), especially once chages in the block were introduced.
Too slow F4F was with too big a wing, fat fuselage and radial engine - everything needed to go slower than fighters with smaller wing, slender fuselage and V12 engine.


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## Shortround6 (Dec 12, 2017)

MIflyer said:


> The two stage supercharged Merlin was more or less stumbled onto by mistake. By 1942 every knew that you needed much bigger engines than 1649 cu in and that was where the focus was. The Merlin was clearly too small; in fact it was the smallest displacement front line engine of the war. Even the A6M3 had 1700 cu in. The too slow F4F and P-36 had 1830 cu in. Even the in-line engined French fighters of 1940 had over 1800 cu in. Taking the first stage off the Vulture and adding it to the Merlin was just to make it a back up to the turbocharged radial to be used on the high altitude Wellington. The truly brilliant part was Sir Hooker's liquid cooled aftercooler. Only after they built that back up engine to support what turned out to be a bad idea did they realize they had produced a war-winner.



You really need to use displacement X RPM to _begin_ to compare the engines. The R-1830 turning 10% fewer rpm which rather offsets it 10.9% larger displacement. Throw in the fact/s that 
1. liquid cooled engines are easier to cool (higher compression or boost).
2. Liquid cooled engines built enbloc are stronger than radials. 

In the case of the Merlin they already knew the engine could survive rather high power outputs from the work/testing done for the Speed Spitfire project back in 1938. It was just a question of getting enough air into the engine (bigger supercharger) and having fuel that would work at that level of boost instead of a special racing brew. 

In the case of the French the HIspano V-12 actually had 2197 cu in (33% bigger than the Merlin) but ran at 20% slower (in most service versions) and because it was over 200lbs lighter than the Merlin it could not operate at the BMEP levels the Merlin could.


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## wuzak (Dec 12, 2017)

MIflyer said:


> Well, I think the main "what If" airplane for the V-3420 application was the Douglas XB-42. It offered a level of performance unequaled until jet bombers came along. I'll be posting some XB-42 design info later this week.



The XB-42 used 2 V-1710s mounted on either side of the fuselage, not a single V-3420.




MIflyer said:


> Most dual engines were failures. The RR Vulture did make a great contribution by accident when its supercharger was used as the 1st stage of the RR Merlin 60 series. The V-3420 seems to have done quite well in all its applications, but with possible exception of the XB-42 the designs themselves were either bad ideas or not really needed.
> 
> The two stage supercharged Merlin was more or less stumbled onto by mistake.



The Vulture's supercharger impeller may have been used in tests for the 2 stage supercharger, but the Merlin 60 did not use it.

And it was no accident that Rolls-Royce were experimenting with 2 stage engines. It was a plan to create a high altitude engine for a high altitude bomber.




MIflyer said:


> By 1942 every knew that you needed much bigger engines than 1649 cu in and that was where the focus was. The Merlin was clearly too small; in fact it was the smallest displacement front line engine of the war. Even the A6M3 had 1700 cu in. The too slow F4F and P-36 had 1830 cu in. Even the in-line engined French fighters of 1940 had over 1800 cu in. Taking the first stage off the Vulture and adding it to the Merlin was just to make it a back up to the turbocharged radial to be used on the high altitude Wellington. The truly brilliant part was Sir Hooker's liquid cooled aftercooler. Only after they built that back up engine to support what turned out to be a bad idea did they realize they had produced a war-winner.



Since 1929 and the Schneider Trophy 'R' engine, Rolls-Royce knew the answer was rpm and boost. Rolls-Royce used that formula more than any other manufacturer of the war.


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## MIflyer (Dec 12, 2017)

They used two V-1710's but fed them into a V-3420 gearbox. A V-3420 could have been used.

Yes, as I mentioned they were developing a high altitude version of the Wellington and wanted a back-up to the radial with turbo, American style, which was the preferred option. They were not trying to super-supercharge a Merlin to make a better fighter engine. They built the modified Wellington and it went into service to a very limited degree, but, like the Ju-88R that inspired it, was pretty much a waste of time. The future focus was on larger engines, Naiper Sabre and Griffon and so forth.

The first stage of the Merlin supercharger was based on the Vulture, according to the man who designed it. Of course Packard redesigned it.


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## wuzak (Dec 12, 2017)

MIflyer said:


> They used two V-1710's but fed them into a V-3420 gearbox. A V-3420 could have been used.



Maybe, maybe not.

The engines were located quite a way forward and on either side of the fuselage. Shafts from the engines were angled to the gearbox at the rear.

So any engine equipped with a drive shaft could have driven them.

I doubt a production version would have adopted the V-3420, as the twin V-1710s were a more developed package.




MIflyer said:


> Yes, as I mentioned they were developing a high altitude version of the Wellington and wanted a back-up to the radial with turbo, American style, which was the preferred option. They were not trying to super-supercharge a Merlin to make a better fighter engine.



It was Hives who suggested that the two stage engine be used in the Spitfire. So, no, it wasn't originally intended for fighters, but was quickly adopted for the role.




MIflyer said:


> The first stage of the Merlin supercharger was based on the Vulture, according to the man who designed it. Of course Packard redesigned it.



I would have to read his book again, but I believe the original test rig used the Vulture supercharger impeller.

The Merlin 61 used a 11.5" first stage impeller, the Vulture had a 12" impeller.

In any case, Rolls-Royce were working on the Griffon, which had a ~13" impeller. That could have been adapted to the role as well, but only for testing.

The majority of the 2 stage Merlins had a 12" first stage impeller. The RM.17SM had a 12.7" first stage and a larger second stage (10.7"?) compared to the normal (10.1"?).

Packard did not redesign the supercharger - they used a different drive system, an epicyclic gearbox which, IIRC, was engineered by Wright.

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## IdahoRenegade (Dec 13, 2017)

wuzak said:


> Without changing the supercharger, a second speed would add power at lower altitudes and not increase the critical altitude.
> 
> Though, for the V-1710 it could have allowed the 9.6:1 gears for HI gear and 8.8 (?) for LO gear, so as gaining some altitude performance without losing low altitude performance.
> 
> ...



Was there a particular reason a larger impeller and housing was never incorporated on the Allison? Given that the SC was a separate assembly bolted on the rear of block (correct?) it seems like it wouldn't have been that difficult to cut in. OTOH, funds and engineering resources were in short supply from Allison with their current production, which I guess explains so little effort to develop a 2 stage/2 speed SC. 

BTW, thanks to all that took the time to reply to the thread. Very interesting and informative, still going through the links. In awe of the amount of knowledge here.


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## wuzak (Dec 13, 2017)

IdahoRenegade said:


> Was there a particular reason a larger impeller and housing was never incorporated on the Allison? Given that the SC was a separate assembly bolted on the rear of block (correct?) it seems like it wouldn't have been that difficult to cut in. OTOH, funds and engineering resources were in short supply from Allison with their current production, which I guess explains so little effort to develop a 2 stage/2 speed SC.
> 
> BTW, thanks to all that took the time to reply to the thread. Very interesting and informative, still going through the links. In awe of the amount of knowledge here.



Money, perhaps. Or time.

Or they were still wedded to the idea of the turbo, as the supercharger did not need to do as much.

Tomo mentioned some experimental V-1710s that had larger impellers, and the 2 stage engines had a larger 1st stage/auxiliary supercharger impeller (12 1/8"), but used the standard 9.5" main supercharger impeller. This was because the V-1710 2nd stage was set up to mimic a turbo (ie variable speed), as much as possible.

Most single stage Merlins had 10.25" impellers (vs 9.5" for the V-1710), while most 2 stage engines had 12.0"/10.1"

The RM.17SM had 12.7"/10.7" impellers.

The single stage Griffons, at least the early ones, had superchargers of 9.75" or 10.1" diameter, while the 2 stage ones had 13.4" and 11.3".

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## tomo pauk (Dec 13, 2017)

IdahoRenegade said:


> Was there a particular reason a larger impeller and housing was never incorporated on the Allison? Given that the SC was a separate assembly bolted on the rear of block (correct?) it seems like it wouldn't have been that difficult to cut in. OTOH, funds and engineering resources were in short supply from Allison with their current production, which I guess explains so little effort to develop a 2 stage/2 speed SC.



Combination of lack of time (V-1710 was already lagging back vs. for example DB 601, let alone Merlin), small design team at Allison, dilution of effort towards several sub-versions of the engine (turbo/non-turbo, external + internal spur reduction gear, pusher + tractor engine, with or without extension shaft, plus flirting with X24 and W24 spin-offs), along with USAAC favorizing (= money) hi-per engines that they showed through the throat of Continental and Lycoming - all of this meant that the V-1710 got a better engine-driven S/C too late.
Focus towards turboing every military engine by USAAC/AAF was also a factor for over-looking 2-stage supecharging by the AAC/AAF, while USN materialy supported the work at P&W (possibly at Wright, too) with 2-stage S/C. Thus there was a 2-stage R-1830 in series production by mid-1941, and 2-stage R-2800 by winter of 1941/42.

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## drgondog (Dec 13, 2017)

Tomo - brain fart on P-39. I meant P-63 as that is what we were talking about. The P-39 was not long enough to stuff the various Allison's designed for two speed/stage supercharged engines.


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## Shortround6 (Dec 13, 2017)

tomo pauk said:


> Combination of lack of time (V-1710 was already lagging back vs. for example DB 601, let alone Merlin), small design team at Allison, dilution of effort towards several sub-versions of the engine (turbo/non-turbo, external + internal spur reduction gear, pusher + tractor engine, with or without extension shaft, plus flirting with X24 and W24 spin-offs), along with USAAC favorizing (= money)* hi-per engines that they showed through the throat of Continental and Lycoming* - all of this meant that the V-1710 got a better engine-driven S/C too late.
> Focus towards turboing every military engine by USAAC/AAF was also a factor for over-looking 2-stage supecharging by the AAC/AAF, while USN materialy supported the work at P&W (possibly at Wright, too) with 2-stage S/C. Thus there was a 2-stage R-1830 in series production by mid-1941, and 2-stage R-2800 by winter of 1941/42.



A very good post except for the bolded part. The early development of the Continental was a strange combination of design by Army but manufacture and test by Continental, with the Army paying for development and testing in very small stages, lots of single cylinder and two cylinder test rigs. Continental put either none of their own money (or very little) into the project. The Lycoming project either started later or crept along at very slow speed (a few test cylinders?) until a few Continental engineers, fed up with slow pace of development at Continental left and joined Lycoming. Lycoming did put about 1/2 a million dollars of their own money into the project with the Army coming up with another 1/2 million (but not all at once). 

If the Continental and Lycoming projects were run like the Allison projects ( I have no information one way or the other) then the Army was continually late in payment for work done, which would make any company hesitant to expend too much time/effort in advance of payment. Army owed Allison around 900,000 dollars at some point in 1939 and Allison had to "forgive" the Army debt (agree to not get paid) in return for permission to sell engines to the French and British. Hardly a situation in which a small company (or even large ones) would spend large amounts of money on experimental projects.

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## Peter Gunn (Dec 13, 2017)

IdahoRenegade said:


> *SNIP*
> 
> BTW, thanks to all that took the time to reply to the thread. Very interesting and informative, still going through the links. *In awe of the amount of knowledge here*.



I'll second that with enthusiasm. Not much these gents don't know on the subject.

Also, this is the type of thread that warms the cockles of my heart, Mustangs and 1710 Allison's? Sign me up.

More to the point, is seems to me that if the 1710 had a 2 speed 2 stage supercharger, it would have fit in the original frame of the Mustang yes? And if so I'll assume that the snazzy little "smiling" intake under the prop would be still on top of the cowl ala P-51A. If so that'd be a small cosmetic price to pay I'll admit, but my other question, wasn't the Allison a couple hundred pounds lighter then the Merlin and had fewer moving parts? Or is my memory failing.

Also fuel consumption, which is more efficient? Just curious that if the V-1710 could deliver Merlin like performance using the two stage/two speed supercharger (or close to it), would it have had better fuel economy?

I realize there are a lot of "ifs" in that, but I always thought the V-1710 got short changed for many of the reasons SR6, Tomo et al have provided.

Thanks.

PS By the way *Idaho*, I give you Bacon for starting this thread.


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## IdahoRenegade (Dec 13, 2017)

Peter Gunn said:


> I'll second that with enthusiasm. Not much these gents don't know on the subject.
> 
> Also, this is the type of thread that warms the cockles of my heart, Mustangs and 1710 Allison's? Sign me up.
> 
> ...



From what others have posted here, the core Allison engine (block, heads, crank, etc) as opposed to "powerplant" with SCs, intercoolers, etc, was in some ways superior to the Merlin. (OK, maybe not superior but better in some areas). Significantly fewer parts, and much longer life between major rebuilds. I believe it also proved stronger in post-war racing applications, able to tolerate more boost. I believe others have posted that Allison con-rods were modified to use in Merlins in racing trim. Could be wrong-will be interesting to hear from the pros.

Bacon good!


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## tomo pauk (Dec 13, 2017)

Peter Gunn said:


> ...
> More to the point, is seems to me that if the 1710 had a 2 speed 2 stage supercharger, it would have fit in the original frame of the Mustang yes? And if so I'll assume that the snazzy little "smiling" intake under the prop would be still on top of the cowl ala P-51A. If so that'd be a small cosmetic price to pay I'll admit, but my other question, wasn't the Allison a couple hundred pounds lighter then the Merlin and had fewer moving parts? Or is my memory failing.



People at NAA managed to shove in the 2-stage supercharged V-1710 under the hood of the XP-51J, plus under the hood of the P-82. The XP-51J was to feature intercooler, unlike other 2-stage V-1710s.
Please note that 2-stage S/Ced V-1710s didn't use 2-speed drive. Instead they used variable speed drive for 1st stage (like the well known DB engines used for their S/C), while the 2nd stage was always driven via just one set of gears, ie. 1-speed drive.
2-stage V-1710 was almost as heavy as the 2-stage Merlin, ~1650 lbs dry (plus another 100 lbs if they were to feature intercooler) vs. 1690 lbs for eg. Packard Merlin V-1650-3 (that was intercooled as-is); those V-1710s were longer by ~15 in. Extra length can be seen when the XP-40Q is compared with usual P-40s.
1-stage 1-speed S/Ced Merlin and V-1710 were within a few lbs, with Merlin making better power earlier; the 2-speed Merlins were a bit heavier (it was worth it).
Number of moving parts was probably in the ballaprk, though it is claimed the V-1710 have had less different parts.



> Also fuel consumption, which is more efficient? Just curious that if the V-1710 could deliver Merlin like performance using the two stage/two speed supercharger (or close to it), would it have had better fuel economy?



Fuel consumption was also in the ballpark, though the V-1710 was able to better handle low rpm foer 'extra-low' power and better consumption. That setting worked well when there was no danger that some Axis aircraft might jump up around.
The best potential for favorable consumption was with turbo V-1710, however that choice was not always applicable in realities of ww2.

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## tomo pauk (Dec 13, 2017)

IdahoRenegade said:


> From what others have posted here, the core Allison engine (block, heads, crank, etc) as opposed to "powerplant" with SCs, intercoolers, etc, was in some ways superior to the Merlin. (OK, maybe not superior but better in some areas). Significantly fewer parts, and much longer life between major rebuilds. I believe it also proved stronger in post-war racing applications, able to tolerate more boost. Could be wrong-will be interesting to hear from the pros.



Until the pros chime in.
Merlin was designed with one of lowest compression ratios of the era (carry-over from days of RR Kestrel, if not earlier) - 6:1, vs. for example V-1710 6.65:1. For a supercharged engine: lower CR = engine is supposed to withstand bigger boost; more boost = more power. In reality it was so - Merlin was using more boost and made more power on same fuel and supercharger size. Especially with changes in construction of the engine block. 
Time between overhauls was indeed ~50% longer for the V-1710.


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## pbehn (Dec 13, 2017)

IdahoRenegade said:


> From what others have posted here, the core Allison engine (block, heads, crank, etc) as opposed to "powerplant" with SCs, intercoolers, etc, was in some ways superior to the Merlin. (OK, maybe not superior but better in some areas). Significantly fewer parts, and much longer life between major rebuilds. I believe it also proved stronger in post-war racing applications, able to tolerate more boost. I believe others have posted that Allison con-rods were modified to use in Merlins in racing trim. Could be wrong-will be interesting to hear from the pros.
> 
> Bacon good!


Much of the construction of the Merlin v the Allison was to do with production engineering. The Merlin should have been a side note in history used only on the Spitfire Hurricane Defiant and Battle, which were to be replaced by the Typhoon/Tornado. This would probably have been just a few thousand units over many years. To produce more, much more quickly and with enough investment you can have bigger castings but they need more dedicated machine tools jigs etc.

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## wuzak (Dec 13, 2017)

pbehn said:


> Much of the construction of the Merlin v the Allison was to do with production engineering. The Merlin should have been a side note in history used only on the Spitfire Hurricane Defiant and Battle, which were to be replaced by the Typhoon/Tornado. This would probably have been just a few thousand units over many years. To produce more, much more quickly and with enough investment you can have bigger castings but they need more dedicated machine tools jigs etc.



Don't forget the Lancaster and Mosquito.

The reality is that the Merlin was in demand for a number of aircraft and, had the Spitfire been superseded by the Typhoon, there would have been other uses.

And without the Merlin, the P-51B, D, etc would not have been possible and the USAAF would not have had a performance benchmark for the V-1710, which may have improved less rapidly than historically.

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## tomo pauk (Dec 13, 2017)

Merlin also powered the 1st Halifaxes, and it turned the Whitley into an useful bomber. Plus, Tornado/Typhoon was ill suited to replace the Battle, that was a long range bomber, nor they could do any of night fighting well. Merlin-powered Fulmar was no great performer, but it got it's job done.
With Merlin, Rolly Royce hit the sweet spot - neither to small/light, nor too big/heavy, with a capable supercharger that got substantially better several times as development progressed, with improvement in power (partialy due to it's internal stregth, partialy due to fuel, plus improvements and refinements), not too thirsty. Basically, what 40mm Bofors was to light AAA, Merlin was to the aircraft engines, with a catch that aircraft engines were far more important in the big picture of ww2 than any kind of light AAA.

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## pbehn (Dec 13, 2017)

wuzak said:


> Don't forget the Lancaster and Mosquito.


I wasn't Wuzak but at the time that the Merlin was being developed the Mosquito didn't exist. The Manchester became the Lancaster when the Vulture programme was suspended but this took some very quick work in Avro, the Lancaster very nearly did not go into production, similarly the Halifax was not originally ordered with Merlins, that was changed earlier on though. Behind the timeline posted above is the failure of the Vulture and chronic problems with the Sabre. The UK went from planning to phase out the Merlin to making the MErlin the main engine on most front line bombers and fighters.


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## pbehn (Dec 13, 2017)

tomo pauk said:


> Merlin also powered the 1st Halifaxes, and it turned the Whitley into an useful bomber. Plus, Tornado/Typhoon was ill suited to replace the Battle, that was a long range bomber, nor they could do any of night fighting well. Merlin-powered Fulmar was no great performer, but it got it's job done..


I was discussing the situation when the Merlin was first designed. If anyone in Rolls Royce had been told that 150,000 would be made they would probably have fainted, but then they would have designed an engine made slightly differently.

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## tomo pauk (Dec 13, 2017)

pbehn said:


> I wasn't Wuzak but at the time that the Merlin was being developed the Mosquito didn't exist. The Manchester became the Lancaster when the Vulture programme was suspended but this took some very quick work in Avro, the Lancaster very nearly did not go into production, similarly the Halifax was not originally ordered with Merlins, that was changed earlier on though. Behind the timeline posted above is the failure of the Vulture and chronic problems with the Sabre. The UK went from planning to phase out the Merlin to making the MErlin the main engine on most front line bombers and fighters.



Problems with Vulture and Sabre didn't have anything to do with Merlin being produced in three (four?) factories in the UK, plus a deal with Ford, then Packard to produce it under license - and that was happening already by mid-1940.


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## pbehn (Dec 13, 2017)

tomo pauk said:


> Problems with Vulture and Sabre didn0t have anything to do with Merlin being produced in three (four?) factories in the UK, plus a deal with Ford, then Packard to produce it under license - and that was happening already by mid-1940.


The Typhoon prototype had already been delayed by then, the Halifax had already had its engines re specified in 1937.

from wiki
During July 1937, Handley Page was instructed that the HP56 should be redesigned to utilise a four engine arrangement as opposed to the original twin engine configuration; by this point, the Vulture had already been suffering from reliability and performance problems.[3] The rival Avro 679 proceeded into service as the Avro Manchester, which was powered by a pair of Vulture engines, but was only built in a limited quantity due to the type suffering substantially from engine-related difficulties.[_citation needed_] The redesign increased the wingspan from 88 ft (27 m) to 99 ft (30 m) and added 13,000 pounds (5,900 kg) of weight.[3] In September 1937, the use of four Rolls-Royce Merlin engines were specified by the Ministry; according to aviation author Phillip J. R. Moyes, the redesign to adopt the four Merlin engine configuration had been "much against the company's wishes".[3]


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## tomo pauk (Dec 13, 2017)

I hear what you are saying.
However, IMO, there is quite a long distance between statement '_The UK went from planning to phase out the Merlin to making the MErlin the main engine on most front line bombers and fighters_' and '_The Typhoon prototype had already been delayed by then, the Halifax had already had its engines re specified in 1937_.' I'd like to know who said that UK was planning to phase out Merlin, and in what year.
The Air Ministry of the UK knew before the war that they will eventually phase out the Merlin, but with commitment to mass production much before BoB, that phasing out was not a matter of months, but years.

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## Shortround6 (Dec 13, 2017)

Tomo is correct. The Merlin fell into a most useful size/catagory of engine. The only other large piston engine engine to be made in larger numbers was the P & W R-1830. 
The Allison, Merlin, DB 600/1 and Jumo 211 all being similar in size, weight and power in the late 30s. 
Most radial engine makers were trying for 1000-1300hp at the time. Engines like the R-2600 and R-2800 were sort of the exception. 

The British were in a bit of bind, They had a bunch of 800-1000hp engines which were too small to do the jobs wanted (even in 1938-39) and the "super" engines (1800-2000hp) were too far in the future. Only other medium engine was the Hercules and a discreet veil will be pulled over it's suitability for mass production in the late 30s, as well as the suitability of the 3 super engines. 

I would also note that the Merlin was being made by the hundreds when the Allison was only a bit better than tool room samples. 
14 engines delivered in 1938 and 46 in 1939. They did build 1175 in 1940.


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## pbehn (Dec 13, 2017)

tomo pauk said:


> I hear what you are saying.
> However, IMO, there is quite a long distance between statement '_The UK went from planning to phase out the Merlin to making the MErlin the main engine on most front line bombers and fighters_' and '_The Typhoon prototype had already been delayed by then, the Halifax had already had its engines re specified in 1937_.' I'd like to know who said that UK was planning to phase out Merlin, and in what year.
> The Air Ministry of the UK knew before the war that they will eventually phase out the Merlin, but with commitment to mass production much before BoB, that phasing out was not a matter of months, but years.


The Manchester was to have Vulture engines, which it did, replaced by the Lancaster with the Merlin.
The Halifax was to have Sabre engines, redesigned with the Merlin
Along with the Stirling no UK heavy bomber was originally due to have Merlin engines, 
The Hurricane was only seen as a stop gap, the Typhoon Tornado were to replace it. 
In 1940 the Mosquito was a design project as was the Mustang.


Prior to war being declared the Merlin had no future in long term planning but the failure of other engines declaration of war quickly changed things. The UK was obviously planning to phase out the Merlin because in 1937 all its new designs used other types. In 1939 a total 1960 Tornados were ordered only 1 flew. The Typhoon was delayed due to problems with the Sabre engine then pushed into service too quickly. The Merlin factories you describe in UK would certainly have been making Vultures and possibly Sabres if they could have been proved to work, they were financed by the UK government. This is a different issue to my original point that the Merlin was designed in peacetime for orders of 100s for the Defiant Battle Spitfire and Hurricane.


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## pbehn (Dec 13, 2017)

Shortround6 said:


> Tomo is correct. The Merlin fell into a most useful size/catagory of engine. The only other large piston engine engine to be made in larger numbers was the P & W R-1830.
> The Allison, Merlin, DB 600/1 and Jumo 211 all being similar in size, weight and power in the late 30s.
> Most radial engine makers were trying for 1000-1300hp at the time. Engines like the R-2600 and R-2800 were sort of the exception.
> 
> ...


My point was the production figures the Merlin was built around, if Rolls Royce had known that they were designing an engine that would be produced in 150,000 units they would have designed it in a different way, as car manufacturers they were and are high cost/ low volume it only passed producing 4000 cars per year in 2015. Allison made 1175 engines in 1940, what was the size of the order because at that time the P40 was one of the few US planes in the game and at the time the USA was not actually at war.

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## Shortround6 (Dec 13, 2017)

pbehn said:


> Allison made 1175 engines in 1940, what was the size of the order because at that time the P40 was one of the few US planes in the game and at the time the USA was not actually at war.



Of those 1175 engines, 833 went to the British (British had taken over ex French orders in addition to their own) 342 went to the Americans.

Americans had ordered over 837 in June of 1939. They deferred some deliveries of both engines and airframes to speed up the delivers to the British.

Point is that the Allison, despite being started in 1930, was in terms of production, a later engine than the Merlin. Allison had 3 factories, #1 was little more than an experimental shop. #2 was in started 1936 and dedicated May 30th 1937 with an production capacity of 100 engines a YEAR (perhaps only one shift?).
#3 broke ground on May 30th 1939 with a planned capacity of 75 engines a month. Plant #3 was to comprise 390,000 sq ft. By June 1943 Allison was using over 3 million sq ft of plant area and this does not include the sub contractors. 

Please note that all was NOT smooth sailing. They redesigned the crankshaft in March 1940 and then the lubrication system in April 1940 in order to solve connecting rod bearing failures. Until already produced engines could be brought back to the factory and reworked they were derated to 950hp. 

Please note that RR was getting the Merlin XX into production at this time which may also explain the US interest in the Merlin engine just a few months later.

I would also point out that the Allison was also an interim engine. Army projects being designed around the Continental 1430 engine, the P&W X1800 and the Wright R-2160 Tornado in 1938-41. Unfortunately for the Army these all crapped out worse than any of the British engines.


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## wuzak (Dec 13, 2017)

pbehn said:


> The Manchester was to have Vulture engines, which it did, replaced by the Lancaster with the Merlin.
> The Halifax was to have Sabre engines, redesigned with the Merlin
> Along with the Stirling no UK heavy bomber was originally due to have Merlin engines,
> The Hurricane was only seen as a stop gap, the Typhoon Tornado were to replace it.
> In 1940 the Mosquito was a design project as was the Mustang.



Yes, the Manchester was designed around the Vulture. Other Manchester versions were to have the Sabre or the Centaurus.
The HP.56 was supposed to have the Vulture. None were built. HP lobbied to change to the 4 engine HP.57 Halifax, which was designed for the Merlin from the outset.
Note that at that time the Vulture was early in its development life. 

The Hurricane was not seen as a stop gap. It was the front line fighter, development starting in 1934. The Typhoon/Tornado development was started in 1938 and was intended to replace the Hurricane and Spitfire. It was not uncommon for the RAF/Air Ministry to look for a successor to an aircraft just entering service.

The Lancaster program came together as quickly as it did because Rolls-Royce had developed the power egg for the Beaufighter.

Note that the Griffon was a supplement to the Merlin, not a replacement. The Griffon may well have dropped off the production list in 1940/41 if someone hadn't figured out that it could fit in a Spitfire.

This is a list of prototype or production aircraft using the Merlin that were developed before 1940 and flew before, or during 1940.
Armstrong Whitworth Whitley
Boulton Paul Defiant
Bristol Beaufighter II
Fairey Barracuda
Fairey Battle
Fairey Fulmar
Fairey P.4/34
Handley Page Halifax
Hawker Henley
Hawker Hotspur
Hawker Hurricane
Supermarine Type 322
Supermarine Spitfire
Vickers Wellington Mk II and Mk VI

Note also that one of the compeitoprs to the Hawker Typhoon/Tornado were the Supermarine Type 324/325/327, which was to use, as first choice, two Merlins.


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## pbehn (Dec 14, 2017)

The Merlin was designed in peace time as a private venture. Other RR engines like the Kestrel sold 4,750 units while the Peregrine sold 300. Other successful designs between the wars like Bristols Mercury sold 20,000. There was simply no basis for designing or modifying an engine for production of 150,000 units especially since Rolls Royce themselves were working on its replacement. Things moved increasingly quickly as war loomed and contingencies were made, factories built etc but things really changed in 1939 when war was a fact. They changed still further in 1940 when France fell after the RAF lost a lot of Hurricanes there. Then the Battle of Britain started and the Ministry of aircraft production was formed. Despite a massive increase in production losses to all causes meant front line strength rose slightly. This combined with Lancaster and Halifax production starting meant a huge and uncertain rise in the need for Merlin engines, and a panic in case a factory was hit.


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## wuzak (Dec 14, 2017)

pbehn said:


> The Merlin was designed in peace time as a private venture. Other RR engines like the Kestrel sold 4,750 units while the Peregrine sold 300. Other successful designs between the wars like Bristols Mercury sold 20,000. There was simply no basis for designing or modifying an engine for production of 150,000 units especially since Rolls Royce themselves were working on its replacement. Things moved increasingly quickly as war loomed and contingencies were made, factories built etc but things really changed in 1939 when war was a fact. They changed still further in 1940 when France fell after the RAF lost a lot of Hurricanes there. Then the Battle of Britain started and the Ministry of aircraft production was formed. Despite a massive increase in production losses to all causes meant front line strength rose slightly. This combined with Lancaster and Halifax production starting meant a huge and uncertain rise in the need for Merlin engines, and a panic in case a factory was hit.



The Vulture was not a replacement for the Merlin - they were in two different power classes.

The Griffon was not a replacement for the Merlin. It was a supplement, originally intended for naval aircraft. Its design only started in 1938.

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## pbehn (Dec 14, 2017)

wuzak said:


> The Vulture was not a replacement for the Merlin - they were in two different power classes.
> 
> The Griffon was not a replacement for the Merlin. It was a supplement, originally intended for naval aircraft. Its design only started in 1938.


The Spitfire and Hurricane were to be replaced by the Typhoon/Tornado that is no Merlins in fighters All heavy bombers were originally specified with engines other than the Merlin. All the cases quoted where other uses were found were as a result of the Sabre and Vulture running into problems.

At the time of the Merlins original design no one could have foreseen a situation where the Merlin could have the same power output as the Vulture but that is approximately what happened with the de rating of the Vulture and the introduction of the Merlin XX. That was my original point.


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## Shortround6 (Dec 14, 2017)

That may be true but that is the case in many other nations. Most engines of the early to mid 30s were considered too small by even 1940. 
However most of the replacements failed. Some more spectacularly than others. Also France was knocked out of the race early and Italy didn't have the engineering capacity to bring any of the large engines to production status (at least in reliable form). 

A lot depended on fuel and in the 1935-38 time period a lot of companies/designers were trying to design engines that would make big power on 87 octane fuel. Some were working with 100 octane (but not 100/120 let alone 100/130) and a lot of the engine designs reflect that. Without the ability to use high boost they were left with either large displacement or high rpm or a combination, lots of cylinders for displacement and small cylinders for High RPM. 

Once the fuel supports more than 6-8bs of boost (and the 7-8lb level needed small cylinders and/or sleeve valves) a lot of these complicated engines lost their appeal. 
The problems with vibration, lubrication and heat dissipation were vastly underestimated with most of these engines. 
Even the Merlin XX as originally produced was not a substitute for the Vulture. That took uprating that depended on better fuel.


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## pbehn (Dec 14, 2017)

Shortround6 said:


> That may be true but that is the case in many other nations. Most engines of the early to mid 30s were considered too small by even 1940.
> However most of the replacements failed. Some more spectacularly than others. Also France was knocked out of the race early and Italy didn't have the engineering capacity to bring any of the large engines to production status (at least in reliable form).
> 
> A lot depended on fuel and in the 1935-38 time period a lot of companies/designers were trying to design engines that would make big power on 87 octane fuel. Some were working with 100 octane (but not 100/120 let alone 100/130) and a lot of the engine designs reflect that. Without the ability to use high boost they were left with either large displacement or high rpm or a combination, lots of cylinders for displacement and small cylinders for High RPM.
> ...


I am sure there is a library of books on the situation political, military and technical on the situation as it developed between 1936 and 1940. Even on Wikipedia there is a change on almost all types in this period. For me I believe that the performance of the "Racing Merlin" in the "Speed Spitfire" pointed another way. That is that it is the volume of gas/fuel mixture that is important not the swept volume of the engine. There were changes to the Merlin engine block as it developed but they were of little importance compared to the developments in fuels and supercharging. None of this could or was foreseen at the start of the Merlin programme, for an engine in that period to be developed and used for a front line fighter (Hornet) more than a decade later was unprecedented.


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## wuzak (Dec 14, 2017)

The changes to the Merlin block were of high importance,as they allowed greater reliability and the strength to cope with boost levels.

And while it is true that the air flow was important, there is only so much boost an engine can take without combustion issues. Then the engine's rpm has to be increased to keep up with the airflow requirements, and this too had its natural limits (and why crankshafts and rods, for example, were evolved).


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## pbehn (Dec 14, 2017)

wuzak said:


> The changes to the Merlin block were of high importance,as they allowed greater reliability and the strength to cope with boost levels.
> 
> And while it is true that the air flow was important, there is only so much boost an engine can take without combustion issues. Then the engine's rpm has to be increased to keep up with the airflow requirements, and this too had its natural limits (and why crankshafts and rods, for example, were evolved).


That again was my point, the changes to the engine block were for reliability, the ability to develop more power was from fuel and supercharger improvements. This was an ongoing issue in engine development. A few decades later 1.5 Litre turbo engines would be developing 1,350 BHP in formula1 However that was just in qualification, a maximum of 6 minutes running time.


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## Shortround6 (Dec 14, 2017)

The Speed Spitfire and the Racing Merlin used one of Rod Bank's special "brews" but the ability to run at 1600hp for ten hours on the test stand pointed to the fact that should better fuel become available the basic Merlin engine could handle a much higher power level than was being used in service engines without extensive work ( something that could not be said for some other engines). This must have been some comfort (or provided some breathing room) as the replacement engines stumbled and fell. 
Again I am not picking on the British. 
The two American hyper engines depended on high rpm to try to make up for small displacement. The Continental was enlarged to 1430 cu in (still too small) and the Lycoming company gave up and stuck two engines together to make a 2470 cu in 24 cylinder engine. The Wright Tornado use 42 cylinders to get 2160 cu in but went to 4150 rpm for peak power. The small cylinders kept the piston speed down but still????? 
Many US aircraft projects had to switch from engine to engine as these "wonder" engines slid down the slope of Thomas Crapper's device.


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## pbehn (Dec 14, 2017)

Shortround6 said:


> The Speed Spitfire and the Racing Merlin used one of Rod Bank's special "brews" but the ability to run at 1600hp for ten hours on the test stand pointed to the fact that should better fuel become available the basic Merlin engine could handle a much higher power level than was being used in service engines without extensive work ( something that could not be said for some other engines). This must have been some comfort (or provided some breathing room) as the replacement engines stumbled and fell.
> Again I am not picking on the British.
> The two American hyper engines depended on high rpm to try to make up for small displacement. The Continental was enlarged to 1430 cu in (still too small) and the Lycoming company gave up and stuck two engines together to make a 2470 cu in 24 cylinder engine. The Wright Tornado use 42 cylinders to get 2160 cu in but went to 4150 rpm for peak power. The small cylinders kept the piston speed down but still?????
> Many US aircraft projects had to switch from engine to engine as these "wonder" engines slid down the slope of Thomas Crapper's device.


I didn't suggest that you were picking on the British, I wouldn't because I have read your posts for a long time. I remember in when Honda were trying to develop a 500cc four stroke racer to compete with the two strokes they had a V4 eight valve per cylinder that revved to 22,000 RPM and an engineer said "It is OK getting the engine to rev up to that speed but the problem is getting it to produce power". In some respects the tuning a supercharged engine runs counter to the technology and science of conventionally aspirated engines.

Honda NR500 - Wikipedia


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## wuzak (Dec 14, 2017)

pbehn said:


> My point was the production figures the Merlin was built around, if Rolls Royce had known that they were designing an engine that would be produced in 150,000 units they would have designed it in a different way, as car manufacturers they were and are high cost/ low volume it only passed producing 4000 cars per year in 2015.



When the Merlin was initially designed it was for British military aircraft, At that time (early '30s) there wasn't going to be a huge market for aero engines.

The Vulture, Peregrine and Griffon, all of which made production, were designed along much the same principles as the Merlin.

They were not designed with any more consideration for quantity production. 

Factories were being built for the Merlin. Licence production suppliers were sought for the Merlin.

Changing these in favour of the Vulture or Sabre would not be a simple thing to do, and it would certainly cost many months of production.

As far as I know, no additional facilities were sought or obtained for the Vulture or Sabre.


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## pbehn (Dec 14, 2017)

wuzak said:


> When the Merlin was initially designed it was for British military aircraft, At that time (early '30s) there wasn't going to be a huge market for aero engines.
> 
> The Vulture, Peregrine and Griffon, all of which made production, were designed along much the same principles as the Merlin.
> 
> ...


As far as I know it was the other way around, if it wasn't the other way around then the whole Typhoon Tornado Manchester programme makes no sense. The Vulture and Sabre were supposed to replace the Merlin but couldn't so the Merlin was developed further. No additional facilities were sought for either engine because they didn't deliver, they were both de rated at the start, the Vulture in service and the Sabre in its prototype version. That is purely in power output, the comparison in reliability was another issue.


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## Shortround6 (Dec 14, 2017)

I would note that at the time. late 1930s, many aircraft engines exceeded the _power to weight ratio _of many car racing engines. 

For instance the Mercedes 1939 Grand Prix engine was a 3 liter (181 cubic in) engine that made 485hp at 7,500rpm but weighed 603lbs. 
It used two stage supercharging at 2.31 Atm manifold pressure and the fuel was 86% methanol, 4.45 nitrobenzol 8.8%acetone and 0.8% sulphuric ether. 

Granted there is some economy of scale but most large aircraft engines were in a pretty high state of "tune" considering their weight.


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## pbehn (Dec 14, 2017)

Shortround6 said:


> I would note that at the time. late 1930s, many aircraft engines exceeded the _power to weight ratio _of many car racing engines.
> 
> For instance the Mercedes 1939 Grand Prix engine was a 3 liter (181 cubic in) engine that made 485hp at 7,500rpm but weighed 603lbs.
> It used two stage supercharging at 2.31 Atm manifold pressure and the fuel was 86% methanol, 4.45 nitrobenzol 8.8%acetone and 0.8% sulphuric ether.
> ...


I agree, which is why producing 150,000 F1 engines was a considerable achievement considering they were used in aircraft and needed a major overhaul after 250 hours, that is more than a Grand Prix season.

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## EKB (Dec 20, 2017)

Re: Rolls Royce Merlin XX / Merlin 45 / Packard V-1650-1 / Allison V-1710-81/85

A P-40F with a Packard Merlin XX engine was heavy, at about 8,500 lbs. for take-off. The Kittyhawk II with British spec changes weighed about 9,000 lbs. with a normal service load. Either way the rate of climb was poor and service ceiling was below 35,000 feet during U.S. and U.K. government trials.

That does not read like a missed opportunity.

In any case a Mustang with a Merlin XX would have been heavier still, and would not have climbed higher than a P-39N, P-40N or P-51A.

The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation with the Merlin 45 engine. This airplane easily out-climbed a standard production model with a Merlin XX. Hurricane P3157 (Merlin 45) climbed to 20,000 feet in 7.1 minutes, compared to a best time of 8.5 minutes by Hurricane Z3564 (Merlin XX). The take-off weights were 6,685 lbs. (P3157) and 7,397 lbs. (Z3564).

The Merlin 45 weighed less, consumed less fuel, had fewer moving parts, and returned a lower build and maintenance cost than the Merlin XX. It’s no surprise that the RAF made the Merlin 40 series standard for Spitfires until the 60 series was available.

The Allison engine held a big advantage at forward airstrips because of the down draft carburetor, with the air scoop being on top of the engine nacelle. The RAF Desert Air Force and USAAF reported that the V-1710 ran dependably with the air cleaner removed, for the purpose of increasing power.

The Merlin used an updraft carburetor setup that ingested dirt and sand like a vacuum cleaner. Taking out the air cleaner was attempted, but doing so ruined the Merlin quickly. The engine nacelles of many RAF planes were retrofitted with tropical air intakes but the Kittyhawk II was not one of them.

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## Shortround6 (Dec 20, 2017)

EKB said:


> The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation with the Merlin 45 engine. This airplane easily out-climbed a standard production model with a Merlin XX. Hurricane P3157 (Merlin 45) climbed to 20,000 feet in 7.1 minutes, compared to a best time of 8.5 minutes by Hurricane Z3564 (Merlin XX). The take-off weights were 6,685 lbs. (P3157) and 7,397 lbs. (Z3564).


Well something doesn't smell right about this. 
According to most sources the difference in weight between the Merlin 45 and the Merlin XX was about 25-30lbs not 700lbs. Hurricane Z3564 was used for a number of tests but it was a IIb with 12 machineguns. 
Was Hurricane P3157 similarly equipped? (roughly 200lbs for the extra 4 guns and ammo over a MK IIa) 
One book claims a 490lb difference between a IIa and IIb just at empty weight (tare) without guns installed and both would have Merlin XX engines. 

In Fact Hurricane P3157 seems to be a Hurricane I from Gloster's first production block of 500 aircraft. Not saying it wasn't later used for test purposes but 
something seems a bit dodgy comparing these two aircraft.

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## tomo pauk (Dec 20, 2017)

Yeah, let's not miss a chance to trash Merlins, even if the figures don't exactly prove the point.



EKB said:


> Re: Rolls Royce Merlin XX / Merlin 45 / Packard V-1650-1 / Allison V-1710-81/85
> 
> A P-40F with a Packard Merlin XX engine was heavy, at about 8,500 lbs. for take-off. The Kittyhawk II with British spec changes weighed about 9,000 lbs. with a normal service load. Either way the rate of climb was poor and service ceiling was below 35,000 feet during U.S. and U.K. government trials.



Basic weights (includes radios and 6 guns, but no ammo, pilot, fuel and oil), 'clean' A/C, data from 'America's hundred thousand', lbs:
-P-40F: 7089
-P-40K: 6880;
So the -F is ~3% heavier empty.
Engine power at 20000 ft, no ram: 840 HP for the -K, 1060 for the -F. The -F has ~25% more power there, it's power is better from 6000 ft above. 



> That does not read like a missed opportunity.
> 
> In any case a Mustang with a Merlin XX would have been heavier still, and would not have climbed higher than a P-39N, P-40N or P-51A.



Cram 180 gals of fuel on the P-39N and P-40N, full ammo, additional oil, and then see how good they will climb. The engine installed on the P-51A, P-39N and P-40N will have power deficit of 150 HP at 20000 ft vs. Merlin 20/28/V-1650-1, and was running late vs. V-1650 by almost a year. Any vs. Merlin XX by two and half years.



> The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation with the Merlin 45 engine. This airplane easily out-climbed a standard production model with a Merlin XX. Hurricane P3157 (Merlin 45) climbed to 20,000 feet in 7.1 minutes, compared to a best time of 8.5 minutes by Hurricane Z3564 (Merlin XX). The take-off weights were 6,685 lbs. (P3157) and 7,397 lbs. (Z3564).
> 
> The Merlin 45 weighed less, consumed less fuel, had fewer moving parts, and returned a lower build and maintenance cost than the Merlin XX. It’s no surprise that the RAF made the Merlin 40 series standard for Spitfires until the 60 series was available.



Merlin 45 for the Americans is the moot point - they don't have it in production.
The decison to use Merlin 45 on Spitfires have had much to do with realities of war-time production (Merlin 20 series went to bombers in huge quantities, plus at the Hurricane), as well as timing, since Hurricane needed any help it can get to cancel the performance gap vs Bf 109E in 1940. Thus Spitfire got Merlin XII, and later 40 series.



> The Allison engine held a big advantage at forward airstrips because of the down draft carburetor, with the air scoop being on top of the engine nacelle. The RAF Desert Air Force and USAAF reported that the V-1710 ran dependably with the air cleaner removed, for the purpose of increasing power.
> 
> The Merlin used an updraft carburetor setup that ingested dirt and sand like a vacuum cleaner. Taking out the air cleaner was attempted, but doing so ruined the Merlin quickly. The engine nacelles of many RAF planes were retrofitted with tropical air intakes but the Kittyhawk II was not one of them.



The Merlin Mustangs need to be deployed in Britain. Allison Mustangs don't have the altitude performance to challenge Luftwaffe avbove 15000 ft, until the 2-stage engine is available.

added: 
Merlin 45: 1385 lbs, 
V-1650-1 (= Merlin 28): 1520 lbs

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## EKB (Dec 20, 2017)

tomo pauk said:


> Yeah, let's not miss a chance to trash Merlins, even if the figures don't exactly prove the point.
> 
> 
> 
> ...




Except that the P-40K was not equipped with the V-1710-81. A better comparison would be a Merlin 32 Seafire or Merlin 50M Spitfire with same take-off weight as P-40K.


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## EKB (Dec 20, 2017)

tomo pauk said:


> The Merlin Mustangs need to be deployed in Britain. Allison Mustangs don't have the altitude performance to challenge Luftwaffe avbove 15000 ft.



But they would not be better off with Merlin XX Mustangs, a plane that would not climb higher but would most definitely use more fuel and weigh more than a P-51A.


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## tomo pauk (Dec 20, 2017)

EKB said:


> Except that the P-40K was not equipped with the V-1710-81. A better comparison would be a Merlin 32 Seafire or Merlin 50M Spitfire with same take-off weight as P-40K.



Choice between V-1710-81 or -73 does not chage anything weight-wise.
Comparing any Spitfire with any P-40 does not add anything to this thread IMO.



EKB said:


> But they would not be better off with Merlin XX Mustangs, a plane that would not climb higher but would most definitely use more fuel and weigh more than a P-51A.



Let's see. 
For max cruise setting, auto lean mixture: V-1650-1 used 53 gph at 16000 ft, auto-lean, making 758 HP; the V-1710-81 used 63 gph at 16600 ft, 760 HP. Or, the V-1710-81 will use almost 20% more fuel for same gain. 
Military power, auto-rich: V-1650-1 used 120 gph for 1120 HP at 18500 ft; the V-1710-81 used 135 gph for 1125 HP at 15000 ft.

Granted, the Mustang with V-1650-1 would've been heavier than the P-51A, but it would've also be faster above 10000 ft, would've offered superior range, while being available many months earlier.


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## Greyman (Dec 20, 2017)

Shortround6 said:


> Well something doesn't smell right about this.
> According to most sources the difference in weight between the Merlin 45 and the Merlin XX was about 25-30lbs not 700lbs. Hurricane Z3564 was used for a number of tests but it was a IIb with 12 machineguns.
> Was Hurricane P3157 similarly equipped? (roughly 200lbs for the extra 4 guns and ammo over a MK IIa)
> One book claims a 490lb difference between a IIa and IIb just at empty weight (tare) without guns installed and both would have Merlin XX engines.
> ...



I have a copy of the test in question and P3157 appears to be a standard Mk.I (Rotol prop).

"_The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation ..._"

Brought into question by who, would be my question. The A&AEE would know how much weight would effect the Hurrie's climb:

Hurrie I L.2026 (Merlin III, Rotol) - 6,315 lb - 20,000 feet in 8.35 min
Hurrie I L.2026 (Merlin III, Rotol) - 6,750 lb - 20,000 feet in 9.75 min

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## EKB (Dec 20, 2017)

Shortround6 said:


> Well something doesn't smell right about this.
> According to most sources the difference in weight between the Merlin 45 and the Merlin XX was about 25-30lbs not 700lbs. Hurricane Z3564 was used for a number of tests but it was a IIb with 12 machineguns.
> Was Hurricane P3157 similarly equipped? (roughly 200lbs for the extra 4 guns and ammo over a MK IIa)
> One book claims a 490lb difference between a IIa and IIb just at empty weight (tare) without guns installed and both would have Merlin XX engines.



P3157 was not a Hurricane II.


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## EKB (Dec 20, 2017)

tomo pauk said:


> Let's see.
> For max cruise setting, auto lean mixture: V-1650-1 used 53 gph at 16000 ft, auto-lean, making 758 HP; the V-1710-81 used 63 gph at 16600 ft, 760 HP. Or, the V-1710-81 will use almost 20% more fuel for same gain.
> 
> Military power, auto-rich: V-1650-1 used 120 gph for 1120 HP at 18500 ft; the V-1710-81 used 135 gph for 1125 HP at 15000 ft.
> ...




What is your source for all these numbers?


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## tomo pauk (Dec 20, 2017)

EKB said:


> P3157 was not a Hurricane II.



It could be much better if you'd post more data about that particular Hurricane, eg. state of protection installed, guns, ammo, prop etc.



EKB said:


> What is your source for all these numbers?


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## EKB (Dec 20, 2017)

tomo pauk said:


> It could be much better if you'd post more data about that particular Hurricane, eg. state of protection installed, guns, ammo, prop etc.



A&AEE test aircraft were converted from one version to another on a regular basis. Knowing the engine type and take-off weight is more useful, along with drag items attached.

I get your point about avgas economy at certain max settings, but the operators manuals that you posted also states that minimum specific fuel consumption is lower for the Allison engine.


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## tomo pauk (Dec 20, 2017)

EKB said:


> A&AEE test aircraft were converted from one version to another on a regular basis. Knowing the engine type and take-off weight is more useful, along with drag items attached.



Knowing the number & type of guns, ammo or ballast for it, protection is important, so we can level the playing field in regard with rate of climb. Aircarft A that has 8 guns will climb faster than otherwise similar aircraft B that has 12 guns.



> I get your point about avgas economy at certain max settings, but the operators manuals that you posted also states that minimum specific fuel consumption is lower for the Allison engine.



I must 1st correct myself, the V-1650-1 used as much fuel as the V-1710-81 on max cruise AL setting - 63 gph (52 imp gals per hour).
As for the lower spec consumption of the V-1710 in low power regimes - yes, sounds great, but I dont't think any Allied aircraft will be using 500 HP when flying over German-held Europe in 1942-44.


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## EKB (Dec 20, 2017)

tomo pauk said:


> I must 1st correct myself, the V-1650-1 used as much fuel as the V-1710-81 on max cruise AL setting - 63 gph (52 imp gals per hour).
> As for the lower spec consumption of the V-1710 in low power regimes - yes, sounds great, but I dont't think any Allied aircraft will be using 500 HP when flying over German-held Europe in 1942-44.



If the plane was low on fuel then throttling back to reach home base seems like a better alternative vs. taking a bath in the North Sea or parachuting into the arms of Stalag guards.


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## tomo pauk (Dec 20, 2017)

EKB said:


> If the plane was low on fuel then throttling back to reach home base seems like a better alternative vs. taking a bath in the North Sea or parachuting into the arms of Stalag guards.



There was a thing called 'mission planing' that was supposed to account for abilities and limitations of a particular piece of military hardware. The planing can tailor bombing raids for targets that are within the combat radius of the escort force. Planning _cannot_ improve aircraft's altitude performance.
The P-51B-K, much heavier, with even thirstier Merlin aboard was good for 460 miles of radius with internal 180 gals + two 75 gal tanks (and 700 miles with fuselage tank filled), with reserves and accounted for climb, with fuel for 20 min of combat. All while cruising at 300+ mph true at 25000 ft. 460 miles from East Anglia = Rostock-Brunswick-Stuttgart line = plenty of German factories to bomb.

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## pbehn (Dec 20, 2017)

tomo pauk said:


> There was a thing called 'mission planing' that was supposed to account for abilities and limitations of a particular piece of military hardware. The planing can tailor bombing raids for targets that are within the combat radius of the escort force. Planning _cannot_ improve aircraft's altitude performance.
> The P-51B-K, much heavier, with even thirstier Merlin aboard was good for 460 miles of radius with internal 180 gals + two 75 gal tanks (and 700 miles with fuselage tank filled), with reserves and accounted for climb, with fuel for 20 min of combat. All while cruising at 300+ mph true at 25000 ft. 460 miles from East Anglia = Rostock-Brunswick-Stuttgart line = plenty of German factories to bomb.


Planning is based on estimates, if anything was estimated incorrectly or things changed mid operation then the contingency may be insufficient. Within the planning was (for example) 15 minutes combat but LW pilots didn't give a cheery wave after 15 minutes.


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## tomo pauk (Dec 20, 2017)

pbehn said:


> Planning is based on estimates, if anything was estimated incorrectly or things changed mid operation then the contingency may be insufficient. Within the planning was (for example) 15 minutes combat but LW pilots didn't give a cheery wave after 15 minutes.



We can take a look on that from German side. 
It is Spring/early Summer of 1943 in the ETO. WAllies have 3 short ranged fighter (mostly Spitfires, some P-47s), 1 long ranged (P-51 with Merlin), and two 4-engined bomber for each fighter LW can muster west from Berlin, and between Pyrenees and Norway. Stripping the escorts from bombers is out of question west from Ardennes due to Spitfires and P-47s. After that, LW can decide: 
-all against escorts?
-all against bombers?
-a combination?
Either of 3 cases has drawbacks. Case 1 means both fighter forces trade losses, while bombers remain unmolested. Case 2 means that interceptors might be hacked by escorts. Case 3 represents dividing of forces, ie. it is against the 'concentration of forces' mantra. The 15-20 min duration of combat is equaly applicable to LW.
We might also look at the inability of fighters based in France to effectively contribute vs, bombing raid incoming over the North Sea, or inability of fighters located in Norway, Denmark and Northern Germany vs. the raid incoming over France - further problems for the LW.


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## pbehn (Dec 20, 2017)

I was just stating reasons a plane may be short on fuel,


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## EKB (Dec 29, 2017)

Lost in this discussion is that the Merlin 20 series was not regarded as a high altitude engine in the RAF.

That is why Mosquito bombers with Merlin 21/25s were ultimately consigned to low altitude air strikes. The engines simply did not give enough performance for high altitude missions, during which the loss rate was higher than acceptable.

With a normal combat load the service ceiling of a Mosquito IV or Mosquito VI was about 30,000 feet, or about the same as a Whirlwind I or Mustang I used by the RAF Army Co-operation Command.


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## tomo pauk (Dec 29, 2017)

EKB said:


> Lost in this discussion is that the Merlin 20 series was not regarded as a high altitude engine in the RAF.
> 
> That is why Mosquito bombers with Merlin 21/25s were ultimately consigned to low altitude air strikes. The engines simply did not give enough performance for high altitude missions, during which the loss rate was higher than acceptable.
> 
> With a normal combat load the service ceiling of a Mosquito IV or Mosquito VI was about 30,000 feet, or about the same as a Whirlwind I or Mustang I used by the RAF Army Co-operation Command.



Still on the anti-Merlin crusade??
RAF couldn't wait to install Merlin 20 in the Hurricane in order to cancel out Bf 109E performance advantage. Spitfire III was the best-performing of the line until Mk.VII/VIII/IX emerged. 
And why stating out faulty data? Service ceiling of Mossies with 20s series Merlins was 33000 ft at max weight (includes the 4000 cookie on board), and 34000 ft on mean weight. Reason to why Mosquitoes were better used in low level bombing has everything to do with bombing accuracy.
Service ceiling of the Hurricane I was in the ballpark of 33000 ft, vs. 37000 ft for the Hurricane IIa (8 .303s).


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## pbehn (Dec 29, 2017)

I thought bomber cruising height was also governed by the height vapour trails form and persist.


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## GregP (Dec 29, 2017)

I show a Merlin XX at 1,280 HP for takeoff and 1,480 HP/3000/6,000 ft and 12,250 ft.
I show the Merlin 45 at 1,480 HP at 12,250 ft.

The only difference I see is the Merlin XX had a single-stage, 2-speed S/C and the Merlin 45 had a single-stage, 1-speed S/C. They SHOULD have been very close in performance up until the single-speed unit started losing a bit before the 2-speed unit. Not sure what altitude that would be, but they cannot be 700 pounds apart due to addition/deletion of a couple of gears.

In fact, the Merlin 45 was a version of the Merlin XX. I believe they used the same block, but could be mistaken there as I haven't seen it definitively stated other than that the 45 was a version of the XX, implying same basic engine.


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## tomo pauk (Dec 29, 2017)

Very roughly, the Merlin 45 is kinda Merlin XX with deleted 'items' (low supercharger gear and necessary clutch & gear changing mechanism). Benefit is lower weight (10%, give or take) and shorter length, plus it is easier to produce. Shortcoming is less power between Sl and 5000-10000 (depending on ram effect available), along with being available some 6 months later than the Merlin 20.


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## pbehn (Dec 29, 2017)

The Merlin 21 and 25 were Merlin 20 (XX) and 24 engines with coolant flow reversed to suit the Mosquito wing radiator.


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## Greyman (Dec 29, 2017)

Data Sheet info (service ceilings at max/mean weights):

*Beaufighter I *(Herc III)
28,900 max
30,000 mean

*Beaufighter II* (Merlin XX)
30,800 max
32,600 mean


*Defiant I* (Merlin III)
28,400 max
31,000 mean

*Defiant II *(Merlin XX)
32,900 max
34,000 mean


*Hurricane I *(Merlin III)
32,500 max
33,500 mean

*Hurricane IIa *(Merlin XX)
37,000 max
37,500 mean


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## EKB (Dec 29, 2017)

tomo pauk said:


> And why stating out faulty data? Service ceiling of Mossies with 20s series Merlins was 33000 ft at max weight (includes the 4000 cookie on board), and 34000 ft on mean weight.




What is the serial number of that Mosquito? Your data does not agree with British government testing.

For starters, I found only one Mosquito with Merlin 20 series engines that actually completed climbing trials at the A&AEE. And the report was dated from September 1943.

At the lightest load recorded, Mosquito FB VI - HJ679 had a service ceiling of only 29,800 feet (take-off weight 21,020 lbs). With weight increased to 21,985 lbs. the service ceiling fell to 29,100 feet. Merlin 25 engines.

A&AEE climbing trials were terminated for Mosquito II - W4052, because the Merlin 21 engines kept cutting out above 24,000 feet.


Other planes tested by the A&AEE included:

Mosquito II - W4076 (Merlin 21). Speed checks up to 25,000 feet. No climbing trials.

Mosquito II - W4096 (Merlin 21). Speed checks up to 24,000 feet. No climbing trials.

Mosquito IV - DK290 (Merlin 21). Speed checks up to 24,000 feet. No climbing trials.

Mosquito VI - HX809 (Merlin 25). Speed checks up to 18,000 feet. No climbing trials.

Mosquito XX - KB328 (Merlin 31). Speed checks up to 28,000 feet. No climbing trials.
This was a Canadian-built Mosquito IV with Packard version of Merlin 21s.





tomo pauk said:


> Reason to why Mosquitoes were better used in low level bombing has everything to do with bombing accuracy.




Not according to pilots who returned from those missions.


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## Shortround6 (Dec 29, 2017)

I believe, but could very well be wrong, that there was a difference between the crankcases of the two engines. The area at the back of the crankcase being different to accommodate the two speed drive for the supercharger?
This means, if I am correct, that a production line tooled up for production of Merlin X engines could be switched over to Merlin XX's pretty easily while a line making Merlin IIIs or XIIs could not. But they could make Merlin 45s with less trouble. 
There seems to be an intermediate section between the crankcase proper and the supercharger which is where a number of "accessories" are located, like magnetos, starter motors,, generators and some odd pumps (hydraulic, vacuum etc) perhaps it is the tooling for this section which is different? 
This may also be the difference between Packard engines and British engines as Packard used a different supercharger drive/shift mechanism. 
The Merlin XX and 45 used the same supercharger (at least internal and front cover/inlet) 

The main point, which we are loosing sight of, is that the Merlin XX made 1175hp at 20,500ft compared to the 840-850hp (?) the early Allison made at the same/similar altitude, which would obviously affect the performance at 20,000ft and above.
The Merlin 61 was rated at 1390hp at 23,500ft which really explains the difference between an Allison Mustang and a Merlin Mustang.

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## tomo pauk (Dec 29, 2017)

EKB said:


> What is the serial number of that Mosquito? Your data does not agree with British government testing.
> 
> For starters, I found only one Mosquito with Merlin 20 series engines that actually completed climbing trials at the A&AEE. And the report was dated from September 1943.
> ...



Data sheets:
-one
-two
-three
Each of whom state service (not absolute, that is higher) ceiling of 33000-34000 ft, depending on the weight. The 2-speed variants of the Merlin 30s series not differing from 20 series in power vs. altitude.



> Not according to pilots who returned from those missions.



Not the case if you can't state so many hundreds of after action reports that prove your point.


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## tomo pauk (Dec 29, 2017)

Shortround6 said:


> ...
> The main point, which we are loosing sight of, is that the Merlin XX made 1175hp at 20,500ft compared to the 840-850hp (?) the early Allison made at the same/similar altitude, which would obviously affect the performance at 20,000ft and above.
> The Merlin 61 was rated at 1390hp at 23,500ft which really explains the difference between an Allison Mustang and a Merlin Mustang.



If I'm not mistaking it badly, the power figure of 1175 HP at 20500 ft is from provisional charts/tables? It can be seen, however, on the Hurricane IIa data sheet. The power chart (here) shows 1175 HP at 17500 ft, or 1060 HP at 20000 ft, the Packard Merlin table giving the similar power vs. height value (1120 HP at 18500 ft; unfortunately listed under 'with ram' coulmn, instead of under 'without ram').






Merlin 60/61/62 (we can se how the Merlin 61 was utter crap):

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## EKB (Dec 29, 2017)

Greyman said:


> Data Sheet info (service ceilings at max/mean weights):
> 
> *Beaufighter I *(Herc III)
> 28,900 max
> ...




Specific airplanes that went through climbing trials with a similar take-off weight:


*P-39N No. 42-4400*
(Allison V-1710-85)
auw 7,274 lbs.
38,500 ft (service ceiling)

*P-40N No. 42-9987*
(Allison V-1710-81)
auw 7,413 lbs.
38,200 ft (service ceiling)

*Hurricane II No. Z3564*
(Rolls Royce Merlin XX)
auw 7,397 lbs.
35,900 ft (service ceiling)

*Spitfire XII No. DP845*
(Rolls Royce Griffon VI)
Clipped Wings
auw 7,320 lbs.
37,300 ft (service ceiling)

*Seafire III No. LR765*
(Rolls Royce Merlin 50)
auw 7,100 lbs.
35,600 ft (service ceiling)


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## pbehn (Dec 29, 2017)

The high altitude performance of a FB Mosquito is about as relevant as a Stukas. The first Mosquitos in service were PR types which were quite obviously high altitude planes.


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## Shortround6 (Dec 29, 2017)

I would note that trying to compare the service ceiling different aircraft to determine how good or bad the engine was ignores several other factors. 
Two of which are lift and drag. to show how these can screw things up the Spitfire with a Merlin III had a higher ceiling than than Hurricane with a Merlin III
same engine even if the weights were only a few hundred pounds apart. Hurricane had a slightly larger wing, 258 sq ft vs 242 and should have had more lift. (air foils were NOT the same) but the higher drag sucked up more of the power. 

I would also be a bit suspicious of the P-39 and P-40 as those are abnormally low weights for them. The P-40 for example having only four guns with 235rpg. Fuel load is unspecified but as this was sort of a prototype of the P-40N (plane was actually a P-40K) the forward wing tank may not be present. The engine may or may not have an electric starter.(first few hundred P-40Ns did not) and they used a much smaller battery than the planes with electric starters.


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## wuzak (Dec 29, 2017)

EKB said:


> *Seafire III No. LR765*
> (Rolls Royce Merlin 50)
> auw 7,100 lbs.
> 35,600 ft (service ceiling)



Note that the Merlin 50 had the same 10.25" supercharger impeller as the XX, but ran a lower speed ratio than the XX in FS gear - 9:0:1 vs 9:49:1.

That means that the XX has higher altitude capability than the Merlin 50.

The Merlin 50 has to balance low altitude performance vs altitude performance. The XX had less of a compromise due to the low gear.


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## EKB (Dec 30, 2017)

Shortround6 said:


> I would also be a bit suspicious of the P-39 and P-40 as those are abnormally low weights for them. The P-40 for example having only four guns with 235rpg. Fuel load is unspecified but as this was sort of a prototype of the P-40N (plane was actually a P-40K) the forward wing tank may not be present. The engine may or may not have an electric starter.(first few hundred P-40Ns did not) and they used a much smaller battery than the planes with electric starters.





Type of wing guns has nothing to do with engine performance.

You seem suspicious of any facts that run afoul of this ongoing Merlin XX what-if fantasy.

No P-51s were built with the Packard Merlin XX because the P-40F did not exactly deliver thrills.

Many, if not most, British made aircraft evaluated by the A&AEE were prototypes.

Results from specific government tests are more helpful than generic figures that are claimed to be
estimates from the makers.

Engine graphs are interesting and also a red flag when the data does not correlate with flight testing.


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## EKB (Dec 30, 2017)

wuzak said:


> Note that the Merlin 50 had the same 10.25" supercharger impeller as the XX, but ran a lower speed ratio than the XX in FS gear - 9:0:1 vs 9:49:1.
> 
> That means that the XX has higher altitude capability than the Merlin 50.
> 
> The Merlin 50 has to balance low altitude performance vs altitude performance. The XX had less of a compromise due to the low gear.




Seafires tended to be slower than Spitfires with the same engine, but if loaded weight were adjusted there was no significant change in ceiling if going from a Merlin 50 to a standard Spit Five engine:

*Spitfire VC No. AA873*
(Rolls Royce Merlin 45)
auw 6,917 lbs.
36,400 ft (service ceiling)

*Spitfire VC No. AA878*
(Rolls Royce Merlin 45)
auw 6,965 lbs.
36,500 ft (service ceiling)


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## tomo pauk (Dec 30, 2017)

Service ceiling:
P-40E: 30600 ft
P-40F: 34300 ft

Speed at 20000 ft:
P-40E: ~320 mph
P-40F: 350-360 mph

All despite the P-40F was heavier by 300 lbs. Thus it looks to me that there was improvement once the V-1650-1 was installed on the P-40. The P-40F predate the 6-gun, compete-fuel version of the P-40N by a year. That was credited with 325-340 mph at 20000 ft, and service ceiling of 31000 ft


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## wuzak (Dec 30, 2017)

EKB said:


> Seafires tended to be slower than Spitfires with the same engine, but if loaded weight were adjusted there was no significant change in ceiling if going from a Merlin 50 to a standard Spit Five engine:
> 
> *Spitfire VC No. AA873*
> (Rolls Royce Merlin 45)
> ...



The Merlin 45 had the same supercharger impeller and gear ratio as the 50. They had the same power ratings.

The Merlin 46 had a larger supercharger and had a higher ceiling in the Spitfire.


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## wuzak (Dec 30, 2017)

EKB said:


> No P-51s were built with the Packard Merlin XX because the P-40F did not exactly deliver thrills.



Rolls-Royce seriously considered installing a Merlin XX into a Mustang I at the time they were doing the Mustang X conversion. The conclusion was that the Merlin 61 gave much better performance and that making the Merlin XX version would be a dilution of effort for a much smaller performance improvement.

The Merlin 61 had been in testing for a while and the Spitfire IX was entering production when the discussions on the Mustang X were being held. The Spitfire IX was entering service about the time the Mustang X was being converted and its first flight.

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## wuzak (Dec 30, 2017)

tomo pauk said:


> Service ceiling:
> P-40E: 30600 ft
> P-40F: 34300 ft
> 
> ...



You mean to say the contemporary P-40 had a lower ceiling than the Spitfire V?


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## tomo pauk (Dec 30, 2017)

wuzak said:


> You mean to say the contemporary P-40 had a lower ceiling than the Spitfire V?



That is no wonder.


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## pbehn (Dec 30, 2017)

tomo pauk said:


> That is no wonder.


It wasn't until this thread started, my head hurts.


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## Shortround6 (Dec 30, 2017)

EKB said:


> Type of wing guns has nothing to do with engine performance.
> 
> You seem suspicious of any facts that run afoul of this ongoing Merlin XX what-if fantasy.
> 
> No P-51s were built with the Packard Merlin XX because the P-40F did not exactly deliver thrills.



You are correct, type of wing guns has little to with engine performance
*however * _*weight *_of the guns (and ammo) has a very noticeable and measurable affect on performance of the *aircraft. *

Ceiling is a measure of_ aircraft _performance not _engine_ performance. 

Strip enough weight out of an aircraft and you can increase the ceiling by thousands of feet with no change to the engine.
And that is what your examples of the P-39 and P-40 are doing, running hundreds hundreds of pounds lighter than the normal combat versions.
They only built about 200 of the light weight P-40Ns and after they were in service the units operating them often installed the electric starters and bigger batteries, they often added the forward fuel tank back in too, finding the 120 gallons of internal fuel too limiting. Likewise the lightweight P-39s with only 87 US gallons were found to be to limited in service and retrofit kits were issued to bring them back up to the standard 120 gallons. 

I happen to like facts but I Like my facts applied equally and not cherry picked. The P-40F did deliver some thrills. at altitudes over 20,000ft it was 30-40mph faster than a P-40E. The P-40N _prototype _you quote figures for is not only 1000lbs lighter than a standard P-40F with Merlin it it is almost 800-900lbs lighter than vast majority of P-40Ns. 

I actually think that the Merlin XX in the Mustang was not that great an Idea as the amount of time and effort to get it to work is not worth the result, not so much in performance but in the sense that you just have to do it all over again (and build new jigs and fixtures) to get the two stage engine in the Mustang. 
The difference in timing being around 1/2 a year.

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## tomo pauk (Dec 31, 2017)

Think it would've been fair to note that installation of the V-1710 (and V-1650-1 for that matter) on the P-39/40/51 was better than it was the case with 1-stage Merlins installed on Hurricanes and Spitfires, due to having a better carb and less draggy exhausts, that were probably also less restrictive. Better carb, once installed on the Spitfire, gave 10 mph. So once at 30000 ft and above, benefits of better installation should be outweighting the benefits of several HP extra the particular engine can provide.



Shortround6 said:


> ...
> I actually think that the Merlin XX in the Mustang was not that great an Idea as the amount of time and effort to get it to work is not worth the result, not so much in performance but in the sense that you just have to do it all over again (and build new jigs and fixtures) to get the two stage engine in the Mustang.
> The difference in timing being around 1/2 a year.



Depends on when the project is started. If the V-1650-1 powered Mustang is produced instead of the A-36 that would meant the USAF has a viable LR fighter for the ETO by Spring of 1943. Leaves plenty of time to escort bombers over Germany, saving 8th bombers and giving the LW bloody nose.


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## wuzak (Dec 31, 2017)

tomo pauk said:


> Depends on when the project is started. If the V-1650-1 powered Mustang is produced instead of the A-36 that would meant the USAF has a viable LR fighter for the ETO by Spring of 1943. Leaves plenty of time to escort bombers over Germany, saving 8th bombers and giving the LW bloody nose.



The discussion for installing the V-1650-1/Merlin 28 in the Mustang occurred at the same time as the discussions about installing the Merlin 61.

So, having a P-51/V-1650-1 program would have had to run concurrently with the P-51/V-1650-3 program. 

The advantage is that the V-1650-1 was in production, so airframes wouldn't be waiting for engines.

The disadvantage is that there are two programs, one of which would have priority and delay the other. If the P-51/V-1650-3 had priority the P-51/V-1650-1 would be delayed such that it was available no earlier, and possibly later, which would be a waste of effort. If the P-51/V-1650-1 had priority the P-51/V-1650-3 would be delayed and wouldn't have been available when it historically was.

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## drgondog (Dec 31, 2017)

Tomo - I have formed an opinion after many years of diving into the 1941 era NAA/Packard/AAF Mat'l Command web and doubt that that any action save BPC having the foresight to stipulate a Packard Merlin 28 be part of the Contract back in April 1940. A scenario that works for me is that every key agency involved peered into a crystal ball - in 1940/41 and foresaw that the "Bombers will Not always get through" and that a beer truck runs over Oliver Echols in early 1940 so that he does not persist in breathing air and hating NAA for going 'behind his back'.

Along with that branch in history, BPC funds a separate four ship build of NA-73X, devoting two to a separate Merlin XX/28 airframe/engine subset which would drive the initial lower cowl/carb design plus radiator plus even dropping the wing to clean up lines. This also probably drives a lot of complexity into Schmeud's world of driving a project completion to first flight. In my mind the completion of NA-73X prototype marks the very first possible date for engineering work on the two Merlin NA-73X to proceed in the Experimental shop. They would probably achieve completion in mid 1941 in time for flight tests, in same timeframe as NA-73.

Extrapolating the alternate reality, with Echols dead, MC may have an open mind and test the Merlin version in late 1941 and love it. At the same time news of the emerging Merlin 60 series as well as details would be exchanged with Packard to evaluate the new supercharger, as history shows us. (NOTE - the 1650-3 production with new supercharger "Wright" design change first contemplated Feb 1942 is still the Critical Milestone for the P-51B).

AAF-MC says "Wow" and NAA Mustang priority increases to "2" one year earlier and Packard gets more subcontractor resources to accelerate production of first, the 28/1650-1, then second the 61/1650-3. The changes to be made must also include dropping the wing to better fair the lower cowl.

This sets the stage for the NA-73X/Merlin to incorporate the many changes made in parallel for production NA-73/83 beginning in ~ April, 1941 (Still need funding that the A-36 got in April, 1942) to tool for a.) mass production set up of the new airframe w/1650-1 including dive brakes while finishing NA-83/-91, b.) procure funds for NA-101 due to brilliant senior level staff officer to Arnold (for clout) several months earlier as news of the high altitude performance of the Merlin 60 series emerges from RR with no knowledge of the forthcoming 8th AF loss rate escalating in another year beginning with Blitz Week July 943.

The Potential benefit is that the wing of the Army Air Force that could care less about strategic bombardment but very much cared for tactical airpower gets a production A-36/1650-1 months ahead of both the A-36 and P-51A.The Allison line is done in June, 1942. A further benefit is possible earlier discovery of yaw instability pointing to the requirement for the Dorsal Fin and reverse boost for rudder by 12 months. 

The P-51B, however does NOT get delivered earlier because there is no certainty, even with new priorities that Packard receives in this perfect world, can tool fast enough for the new 1650-3. The tooling and production line preparation will be completed earlier, the first production airframe will be completed sooner if authority granted before first flight test (sans surprises due to flight tests of Radiator and Duct changes that only surfaced after XP-51B first flights - which was delayed because Packard was 30+ days late with first 1650-3). 

Only a steady supply of Merlin 61s diverted from RR and shipped to US (at sacrifice of Spit IX - fat chance) could accelerate the delivery of complete P-51B-1-NA airframes.

With that scenario, the engineering hours devoted to A-36/P-51A after April 1942 (miraculously available to NAA in 1941 under this scenario) may be available to contract and develop NA-105/XP-51F six to seven months earlier.


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## EKB (Jan 1, 2018)

Shortround6 said:


> You are correct, type of wing guns has little to with engine performance
> however weight of the guns (and ammo) has a very noticeable and measurable affect on performance of the aircraft.
> 
> Ceiling is a measure of aircraft performance not engine performance.
> ...




I was talking about engine performance vs. a given loaded weight. I'm not here to argue about shortcomings of using four vs. six guns on the P-40N. And besides, the P-51B went into battle with four guns.

If you don't want to cherry pick, then show us some proof that a P-40F out-climbed a P-40N with the same loaded weight and surface attachments. Otherwise you don't practice what you preach.

It should be obvious by now that a Merlin 45 Spitfire ballasted to 7,400 lbs. would not have a service ceiling anywhere near 38,200 feet but P-40N - 42-9987 did, according to Wright Field tests. The Merlin XX gave essentially the same high flying performance as a Merlin 45, and that was the point in case you didn't get it the first time.




Shortround6 said:


> I actually think that the Merlin XX in the Mustang was not that great an Idea as the amount of time and effort to get it to work is not worth the result




We agree.


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## EKB (Jan 1, 2018)

pbehn said:


> The high altitude performance of a FB Mosquito is about as relevant as a Stukas. The first Mosquitos in service were PR types which were quite obviously high altitude planes.




Mosquito I - W4050, the first hand-built prototype, was a feather weight at 16,770 lbs. when tested at the A&AEE. At that time the service ceiling was 33,900 feet with Merlin 21 engines. No data about time to climb, up to specific heights. Apparently the climbing test of serial W4050 was not finished, possibly for the same reason as serial W4052.

At any rate the results would have been immaterial because the operational load ballooned considerably. Typical all-up weights for the nine Mosquito PR 1s were 18,050 lbs. as normal, and 19,310 lbs. for two aircraft in the long-range configuration. This is according to Martin Sharp who worked at de Havillands.

He cited Victor Ricketts of the PRU, who said that 24,000 feet was the common transit height for a Mosquito PR 1 on those early missions. Pictures were usually taken from 22,000 feet or below, depending on cloud cover.


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## Shortround6 (Jan 1, 2018)

You are cherry picking which P-40N. _Strange_ how later tests at higher weights (8300lbs take off) show a service ceiling of 31,000ft even though the plane burned off enough fuel to get under 8100lbs. Climb at 31,000ft being 100ft per minute and at 25,000ft it was 760fpm, both at 3000rpm and full throttle. 

test of a P-40F with a take-off weight of 8450lbs has a climb of 1000fpm at 25,000ft, 530fpm at 30,000ft and 100fm at 34,000ft. 
All done at 2850rpm, not 3000 rpm (max continuous Or 30 minute rating and not military) 
Yes the P-40F had probably burned off several hundred pounds of fuel also. 

The P-40F was supposed to climb from sea level to 30,000ft in 21 minutes. Chart for the P-40N-5 shows 27.5 minutes. 

That is how to compare different engines, try to use the same airframe at as close a weight as you can find. 
The British in a seperate test of the P-40F got about 300ft more service ceiling but took 21.8 minutes to get to 30,000ft which is certainly close enough. 

A few British tests show better numbers for the P-40N but then they were testing lighter versions, 7900lbs or under. 
You may not care about the reduction in guns but one test of the light weight P-40N had it weighing 900lbs less than a P-40E, due in part to the elimination of fo the forward fuel tank 100imp gallons instead of 125 imp gallons. change in type of fuel tank (non-metallic), 33% reduction in oil capacity. Elimination of vacuum system, only blind flying instrument left was an electric bank and turn indicator. Electric starter taken out, electric trim tab motor removed. much simplified radio installation. The change in wheel size and material (magnesium ) and the change to aluminum radiators and oil coolers helped and did not degrade operational capabilities like many of the other changes.

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## drgondog (Jan 1, 2018)

EKB said:


> I was talking about engine performance vs. a given loaded weight. I'm not here to argue about shortcomings of using four vs. six guns on the P-40N. And besides, the P-51B went into battle with four guns.
> 
> If you don't want to cherry pick, then show us some proof that a P-40F out-climbed a P-40N with the same loaded weight and surface attachments. Otherwise you don't practice what you preach.
> 
> ...



The P-40F out performs the P-40N-5 in just about every category.

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## EKB (Jan 3, 2018)

Shortround6 said:


> You are cherry picking which P-40N. _Strange_ how later tests at higher weights (8300lbs take off) show a service ceiling of 31,000ft even though the plane burned off enough fuel to get under 8100lbs. Climb at 31,000ft being 100ft per minute and at 25,000ft it was 760fpm, both at 3000rpm and full throttle.
> 
> test of a P-40F with a take-off weight of 8450lbs has a climb of 1000fpm at 25,000ft, 530fpm at 30,000ft and 100fm at 34,000ft.
> All done at 2850rpm, not 3000 rpm (max continuous Or 30 minute rating and not military)
> ...




Well I figured you might pick this low hanging fruit, but you have missed a few cherries:

P-51A-1 No. 43-6007 also had a V-1710-81 engine, yet the service ceiling was 35,100 feet on 8,000 lb.

Clearly, something was amiss with P-40N-5 No. 42-105241 at 8,300 lb. because the service ceiling was 4,000 feet lower.

The B-7 wing racks and center line rack with braces put on the P-40N-5 caused some drag, but not that much!

I am no doctor of physics, but I know that 300 lbs. and a different wing shape will not cause a 4,000 ft. drop in ceiling, but a motor down on power would.

Another hint is the lack of War Emergency Power readings for speed and climb on P-40N-5 No. 42-105241. Odd because the P-40N-1 was tested at WEP one year earlier.

There is no explanation for that in the report, but if the engine in the P-40N-5 worked properly then why was it not tested at full power?


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## wuzak (Jan 3, 2018)

EKB said:


> Well I figured you might pick this low hanging fruit, but you have missed a few cherries:
> 
> P-51A-1 No. 43-6007 also had a V-1710-81 engine, yet the service ceiling was 35,100 feet on 8,000 lb.
> 
> ...



P-51A-1 No. 43-6007 had a high speed of 408mph at 17,500ft at military rated power - 1,125hp (415mph @ 10,400ft @ 1,480hp).

P-40N-5 No. 42-105241 had a high speed of 350mph @ 16,400ft at 1,110hp.
P-40N. No. 42-9987 had a high speed of 378mph @ 10,550ft @ 1,480hp and 371mph @ 17,300ft @ 1,125hp at a weight of 7,413lb.

At 7,413lb 42-9987 had a service ceiling of 38,200ft. The advantage of nearly 1,000lb less weight (~11%).

Which suggests that the P-51 had much lower drag than the P-40. Which would account for the difference in ceiling and general performance.


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## EKB (Jan 3, 2018)

wuzak said:


> P-51A-1 No. 43-6007 had a high speed of 408mph at 17,500ft at military rated power - 1,125hp (415mph @ 10,400ft @ 1,480hp).
> 
> P-40N-5 No. 42-105241 had a high speed of 350mph @ 16,400ft at 1,110hp.
> P-40N. No. 42-9987 had a high speed of 378mph @ 10,550ft @ 1,480hp and 371mph @ 17,300ft @ 1,125hp at a weight of 7,413lb.
> ...




That doesn’t track because of a similar difference in drag with the Spitfire and Hurricane.
The variation in ceiling was less than 1,000 feet, not 4,000 feet.


*Spitfire I - N3171 *
Merlin III
auw 6,050 lb.
h/s 354 mph
s/c 34,700 ft.

*Hurricane I - L2026*
Merlin III
auw 6,316 lb.
h/s 316 mph
s/c 33,750 ft.


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## tomo pauk (Jan 3, 2018)

EKB said:


> That doesn’t track because of a similar difference in drag with the Spitfire and Hurricane.
> The variation in ceiling was less than 1,000 feet, not 4,000 feet.
> 
> 
> ...



Hurricane is draggier by a large margin, and almost 300 lbs heavier.

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## Shortround6 (Jan 3, 2018)

The faster plane (with the same engine) will have a higher ceiling for several reason. 
One, as already mentioned is the lower drag. At the same or similar speed the aircraft will have more power left to climb with. 
Two. the faster plane will have more ram effect going to the carburetor, meaning it is making more power at a given altitude above FTH than the slower plane.
Three, for planes using ejector exhausts the higher speed plane gets more benefit from the same thrust because the exhaust gas velocity is a closer match to the planes exhaust (and actually there is more thrust due to the higher ram increasing the actual charge weight). 

For the Hurricane vs SPitfire comparison look a little deeper. The engine had a nominal rating of 1030hp at 16,250 at 6 1/4lbs without RAM yet due to RAM effect it could hold the needed manifold pressure to 17,750ft in a 6,316lb Hurricane and 17,200ft in a 6,750lb Hurricane Please note that the extra weight knocked about 1000ft off the _estimated ceiling. _

On the Spitfire the engine could hold 6+ pounds to 18,900 feet in one example. And there is part of the answer, The Spitfire, with it's higher speed, is always going to have more RAM effect (more power in the cylinders) and more exhaust thrust an any altitude over these FTH _unless _it slows down to the Hurricanes speed. 

Likewise the nominal altitude for the V-1710-81 was 14,600-15,500ft(?, sources differ) yet the critical altitude in level flight for the P-51A with that engine was 17,500ft. In the stripped P-40N it was 17,200ft and in more normally equipped P-40 it was 16,200ft in one test. Something seems just a little too good about that stripper P-40N? When the British tested one it was 27mph slower at 17,000ft???? bad engine???

By the time you get the Allison powered planes to 30,000ft you are down to a bit over 600hp and individual aircraft and engines can show significant differences which is why. even in 1940, The British figured that a 500fpm climb rate ceiling was needed for even small formation flying and 1000fpm was about the minimum for combat.

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## Peter Gunn (Jan 3, 2018)

drgondog said:


> Tomo - I have formed an opinion after many years of diving into the 1941 era NAA/Packard/AAF Mat'l Command web and doubt that that any action save BPC having the foresight to stipulate a Packard Merlin 28 be part of the Contract back in April 1940. A scenario that works for me is that every key agency involved peered into a crystal ball - in 1940/41 and foresaw that the "Bombers will Not always get through" and that a beer truck runs over Oliver Echols in early 1940 so that he does not persist in breathing air and hating NAA for going 'behind his back'.
> 
> Along with that branch in history, BPC funds a separate four ship build of NA-73X, devoting two to a separate Merlin XX/28 airframe/engine subset which would drive the initial lower cowl/carb design plus radiator plus even dropping the wing to clean up lines. This also probably drives a lot of complexity into Schmeud's world of driving a project completion to first flight. In my mind the completion of NA-73X prototype marks the very first possible date for engineering work on the two Merlin NA-73X to proceed in the Experimental shop. They would probably achieve completion in mid 1941 in time for flight tests, in same timeframe as NA-73.
> 
> ...




So what you're saying in this incredibly simple scenario ( which by the way, I fail to comprehend why it didn't go down this way in reality ) is that the we will not get a Mustang with -B performance into action any sooner but the possibility of getting a scorcher type P-51F about the time the -D was coming on line instead? Or is the headache I'm battling today totally muddling up what I'm reading? ( Which is entirely possible. )


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## EKB (Jan 3, 2018)

Shortround6 said:


> The faster plane (with the same engine) will have a higher ceiling for several reason.
> One, as already mentioned is the lower drag. At the same or similar speed the aircraft will have more power left to climb with.
> Two. the faster plane will have more ram effect going to the carburetor, meaning it is making more power at a given altitude above FTH than the slower plane.
> Three, for planes using ejector exhausts the higher speed plane gets more benefit from the same thrust because the exhaust gas velocity is a closer match to the planes exhaust (and actually there is more thrust due to the higher ram increasing the actual charge weight).
> ...




This overlooks other Wright Field trials that stated a P-40 lost just 600 feet of service ceiling from adding 271 lbs.
(Re: P-40D - 40-362 and P-40E - 40-384 with V-1710-39 engines).

It does not make sense that a P-40 in good condition would lose 7,200 feet of service ceiling from adding 
887 lbs. (Re: P-40N - 42-9987 and P-40N - 42-105241 with V-1710-81 engines).

Add to that, No. 42-105241 was a fighter but it wasn’t tested at max power. Clearly the engine was not tip-top,
or some other important piece of information was omitted from the return.


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## EKB (Jan 3, 2018)

Shortround6 said:


> The faster plane (with the same engine) will have a higher ceiling for several reason. One, as already mentioned is the lower drag.



I understand, but you have to accept that some airplanes were simply down on performance.

For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).


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## tomo pauk (Jan 3, 2018)

EKB said:


> I understand, but you have to accept that some airplanes were simply down on performance.
> 
> For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).



Yay, crusade is on - it is not just that Merlin is crap (never mind the 2000 HP figure), but Spitfire is, too.
It does not matter that Fw 190 with 1.56 ata boost (= 1950 PS) was good for 370 mph, nor it does not matter that oh so good Fw 190D-9 was about as good as Spit with 2000 HP, but while using 2100 HP provided by series engine that used MW 50. The another oh so good fighter, Bf 109K-4, also can't do it with either 1800 or 2000 HP.

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## pbehn (Jan 3, 2018)

Why did the allies persist with the Spitfire and P51 when the P 40 was obviously the way ahead? Or did I read things wrong again?

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## Shortround6 (Jan 3, 2018)

EKB said:


> Add to that, No. 42-105241 was a fighter but it wasn’t tested at max power. Clearly the engine was not tip-top,
> or some other important piece of information was omitted from the return.



It was tested at full military power. 

If you are running an Allison at 3000rpm and 44.5in MAP (or anything close depending on model) you are running at full Military power. 

WEP or WER was only available _below _*FTH *and have nothing to do with service ceiling or speed or climb at altitudes above FTH.

Purpose of the test was to get data for range charts. Stressing the engine and possibly having to delay tests while waiting for replacement engine or aircraft wouldn't have been smart. 

Please note that *any *flight that used WEP/WER required notation in the log books and this could result in more frequent spark plug changes and extra checks for metal in the oil and depending on number of times and length of time at WEP it could shorten time before overhaul.

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## drgondog (Jan 3, 2018)

Peter Gunn said:


> So what you're saying in this incredibly simple scenario ( which by the way, I fail to comprehend why it didn't go down this way in reality ) is that the we will not get a Mustang with -B performance into action any sooner but the possibility of getting a scorcher type P-51F about the time the -D was coming on line instead? Or is the headache I'm battling today totally muddling up what I'm reading? ( Which is entirely possible. )



The problem with the F was that there was no 'Interceptor' buy and the F/G had no internal fuselage tank. To add it and extend the range, while maintaining the stress allowables, the airframe needed a complete 'structural re-do' ------------> which led to P-51H

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## pbehn (Jan 3, 2018)

EKB said:


> I understand, but you have to accept that some airplanes were simply down on performance.
> 
> For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).


EKB, you are obviously well informed but you are not as well informed as the people making the decisions in WW2. It is an historical fact that the Hurricane was inferior to the P 40 which were inferior to the Spitfire. That is why they were used how they were used. The limitations of Allison engine aircraft be they P40s or Mustang Mk 1s at altitudes over 15,000ft were known when they were ordered by the purchasing commission. Those Mustang Mk Is were optimised for performance below 15,000ft and served well until the end of the war. In 1944 The P51 was without peer as a long range escort, although the P47N was arriving. The Tempest was the dogs dangly bits as a low level air superiority fighter and the Spitfire retained its role as the interceptor of choice to defend the UK at any altitude. Pilots have an historical preference for the planes they flew for natural reasons, they had lived to tell the tale flying those planes so they may be more than a little biased. In 1944 the Spitfire was for air superiority at all altitudes the P 51 for bomber escort, the Tempest for air superiority over the battle fields after D Day, the P 40 didn't figure in anyones calculations for front line combat after the early days in North Africa.

That is not at all to disparage what the P 40 did historically, like the Hurricane it achieved a lot when there were no other alternatives.

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## Greyman (Jan 4, 2018)

tomo pauk said:


> Yay, crusade is on - it is not just that Merlin is crap (never mind the 2000 HP figure), but Spitfire is, too.



I think he was pointing out that JL165 was down on performance (compared to other Mk.IX examples tested), not the Spitfire as a whole.


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## wuzak (Jan 4, 2018)

Greyman said:


> I think he was pointing out that JL165 was down on performance (compared to other Mk.IX examples tested), not the Spitfire as a whole.



Maybe if any Spitfire IX could do 390mph at sea level.


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## tomo pauk (Jan 4, 2018)

Greyman said:


> I think he was pointing out that JL165 was down on performance (compared to other Mk.IX examples tested), not the Spitfire as a whole.



Nah. It is agenda.


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## Peter Gunn (Jan 4, 2018)

drgondog said:


> The problem with the F was that there was no 'Interceptor' buy and the F/G had no internal fuselage tank. To add it and extend the range, while maintaining the stress allowables, the airframe needed a complete 'structural re-do' ------------> which led to P-51H



Mein Gott, I just realized you answered a similar question late last year regarding all the development marques of the Mustang, among them the F/G interceptor and the long range tank issue, structure redesign with end result P-51H.

I apologize for my short memory and greatly appreciate you patience, thank you.


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## drgondog (Jan 4, 2018)

Peter Gunn said:


> Mein Gott, I just realized you answered a similar question late last year regarding all the development marques of the Mustang, among them the F/G interceptor and the long range tank issue, structure redesign with end result P-51H.
> 
> I apologize for my short memory and greatly appreciate you patience, thank you.


It was a 'forgettable' dissertation..


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## Peter Gunn (Jan 4, 2018)

tomo pauk said:


> Nah. It is agenda.



I must admit, much of this P-40 discussion has left me scratching my head. By January 1944 I'd think it was rather academic what the P-40 could do, it was already living on borrowed time and then some.


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## Peter Gunn (Jan 4, 2018)

drgondog said:


> It was a 'forgettable' dissertation..



For a dyed in the wool Mustang lover such as myself it's an unforgivable travesty. I go to penalty box two minutes... feel shame.

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## Shortround6 (Jan 4, 2018)

Peter Gunn said:


> I must admit, much of this P-40 discussion has left me scratching my head. By January 1944 I'd think it was rather academic what the P-40 could do, it was already living on borrowed time and then some.


Well, it wasn't doing too bad for an airframe that first flew in May of 1935. Not all aircraft have the same amount of "stretch".


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## Peter Gunn (Jan 4, 2018)

Shortround6 said:


> Well, it wasn't doing too bad for an airframe that first flew in May of 1935. Not all aircraft have the same amount of "stretch".



True, but then again... 

OK, that might be a bit off track...


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## tomo pauk (Jan 4, 2018)

Indeed, the XP-40Q pointed to what kind of the performance can be 'bought' with up to-date engine. The P-40 always rolled and dived well, most of the times well armed, all while it was sturdy,

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## Peter Gunn (Jan 4, 2018)

tomo pauk said:


> Indeed, the XP-40Q pointed to what kind of the performance can be 'bought' with up to-date engine. The P-40 always rolled and dived well, most of the times well armed, all while it was sturdy,



No real argument from me really, I agree totally, but I wouldn't make it my personal first choice going into front line combat in January 1944.


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## Shortround6 (Jan 4, 2018)

Peter Gunn said:


> True, but then again...
> 
> OK, that might be a bit off track...


this is streeeeeetch.





which can be traced back to

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## Peter Gunn (Jan 4, 2018)

One might argue that's more "bloat" than "stretch", this however...

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## EKB (Jan 12, 2018)

Shortround6 said:


> It was tested at full military power.
> 
> If you are running an Allison at 3000rpm and 44.5in MAP (or anything close depending on model) you are running at full Military power.
> 
> ...


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## EKB (Jan 12, 2018)

Greyman said:


> I think he was pointing out that JL165 was down on performance (compared to other Mk.IX examples tested), not the Spitfire as a whole.




Exactly. One serial did not define the whole series.

There was a wide variety of results when Spitfires, Seafires and other fighters were performance checked with the same 
engine specs. What is average or normal depends on which data is used as a baseline.


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## EKB (Jan 12, 2018)

tomo pauk said:


> Yay, crusade is on - it is not just that Merlin is crap (never mind the 2000 HP figure), but Spitfire is, too.
> It does not matter that Fw 190 with 1.56 ata boost (= 1950 PS) was good for 370 mph, nor it does not matter that oh so good Fw 190D-9 was about as good as Spit with 2000 HP, but while using 2100 HP provided by series engine that used MW 50. The another oh so good fighter, Bf 109K-4, also can't do it with either 1800 or 2000 HP.




You are the only member to use the word "crap" in this discussion.




tomo pauk said:


> It does not matter that Fw 190 with 1.56 ata boost (= 1950 PS) was good for 370 mph, nor it does not matter that oh so good Fw 190D-9 was about as good as Spit with 2000 HP, but while using 2100 HP provided by series engine that used MW 50. The another oh so good fighter, Bf 109K-4, also can't do it with either 1800 or 2000 HP.






tomo pauk said:


> Nah. It is agenda.




At least one FW-190 (USAAF No. EB-104) was taken prisoner and brought to Wright Field. Obviously not factory fresh, but good enough to return 415 mph at 22,000 feet and 340 mph at sea level.

The BMW-801D radial engine was limited to about 1,750 hp because methanol injection and nitrous oxide were not tested. Max rate of climb was pretty good at 4,000 ft/min, even though the Focke-Wulf was about 1,150 lbs. heavier for climbing trials when compared to Spitfire JL165. We'll never know how much better EB-104 might have been with emergency boost.

And yes, let's never mind about the Merlin 66 having 2,000 hp at lower altitudes. Spitfire IX No. JL165 did not break 389 mph at any height or power setting, by A&AEE accounting.

Surely you must have noticed all this. Presumably you decided to argue about it anyway because that’s your agenda.


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## tomo pauk (Jan 12, 2018)

EKB said:


> ...
> At least one FW-190 (USAAF No. EB-104) was taken prisoner and brought to Wright Field. Obviously not factory fresh, but good enough to return 415 mph at 22,000 feet and 340 mph at sea level.
> 
> The BMW-801D radial engine was limited to about 1,750 hp because methanol injection and nitrous oxide were not tested. Max rate of climb was pretty good at 4,000 ft/min, even though the Focke-Wulf was about 1,150 lbs. heavier for climbing trials when compared to Spitfire JL165. We'll never know how much better EB-104 might have been with emergency boost.
> ...



We actually do know how fast the Fw 190As were on 'emergency boost'. The Fw 190A-5 making 580 km/h (360 mph) at SL with 1880 PS: link
Fw 190A-8 on emergency boost - again ~580 km/h: link
Methanol injection on BMW 801? Germans tested it and decided it is bad idea. Nitrous oxide at SL???
If you have probem with LJ165, there is plenty of other Spitfire IX specimen making 400-410+ mph (eg. here), and if Merlin Spitfire is not enough, there were Griffon Spitfires around.
Sorry for naming things as they are.


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