Early Mustangs-performance/experience?

[tomo pauk]

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.

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).

 

[drgondog]

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.

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

 

[tomo pauk]

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?

 

[bobbysocks]

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.

 

[bobbysocks]

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

86th Fighter-Bomber Group

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

 

[drgondog]

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.

 

[wuzak]

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.

 

[tomo pauk]

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.

 

[pbehn]

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.

 

[tomo pauk]

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.

 

[pbehn]

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.

 

[Shortround6]

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?

 

[wuzak]

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?

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.

 

[tomo pauk]

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.

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?

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.

 

[drgondog]

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.

 

[tomo pauk]

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

 

[Shortround6]

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?

 

[MIflyer]

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.

 

[tomo pauk]

...
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.

 

[Shortround6]

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.