# No US-built Merlin: plausible developments?



## tomo pauk (Jun 2, 2012)

For the sake of discussion, what would be the options for the Western air forces without Merlin being produced in the USA? I'm interested in all levels of the developments, from technical (suitable replacements for the Packard Merlin) up to the strategic. Please note that Packard Merlin was used also in the British and Canadian aircraft production.

In this time-line, Packard builds either R-2800 or V-1710 (or some of the derivatives).


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## Edgar Brooks (Jun 2, 2012)

Build R-R factories in the Commonwealth:- Australia, Canada, New Zealand, South Africa, while the USAAF continues to fly its P-51 at sea level.


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## Shortround6 (Jun 2, 2012)

Canada is the only real hope of a Merlin Production line in time to really do anything. 

Australia,New Zealand, South Africa and even India do not have the needed hundreds of small sub contractors needed to support a large engine building program, at least in the first few years of the war. 

Packard built (starting in the middle of 1940), 45 single stage engines in 1941, 7251 single stage and 5 two stage engines in 1942, 12,292 single stage and 2,792 two stage engines in 1943 and 7,171 single stage and 15,798 two stage engines in 1944. 

Packard was a sizable motor car manufacturer, had built aircraft engines before and built the majority of the gasoline engines used in American and British Motor Torpedo Boats. It also had the support of hundreds of subcontractors for nuts, bolts, studs, pump parts, lines, fittings and so on. The majority of the new tooling needed DID not have to brought by ship from another continent. 

Some of the Commonwealth countries did amazing things in WW II as far as production goes but an engine program that completes 1000-2000 engines total by wars end does not compare to a program of over 50,000 engines.


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## davebender (Jun 2, 2012)

Britain would have no choice but to build additional Merlin engine factories elsewhere, probably in England. Resources required to build and operate those factories mean something else gets deleted from British military spending.


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## wuzak (Jun 2, 2012)

Perhaps there is accelerated devlopment of the V-1710 and it gets put into production at Packard.

Perhaps the IV-1430 is pushed more, development taken over by someone with a clue. Packard is one of the production facilities.

Ford's proposed V12 is given backing and starts development - don't know when that will be available.

Did Packard have anything in development themselves?

Maybe the 2A-2775 of 1935 - X-24, 1900hp @ 2800 rpm. Weight 1720lb.

The 1A-5000 X-24 (5000 cubic inches), possibly rated at 3500hp, or the sleeve valve 3A-5000. Perhaps the 2A-5000 H-24 rated to 3000hp. The 1A-5000 weighing 2830lb, the 2A-5000 2750lb.


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## wuzak (Jun 2, 2012)

Double post


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## wuzak (Jun 2, 2012)

Looking at things from another perspective, if Merlins weren't built in the US there would be a rationlising of what gets the available Merlins. 

So, Hurricane production is cut off earlier. Mosquito deliveries are slower. Spitfires are built in fewer numbers, and perhaps the Griffon engine versions pushed forward, that causing delays and cancellations for other Griffon powered models - such as the Fairey Firefly.

Most importantly, there will not be enough Merlins to power Lancasters and Halifaxes. Many Halifaxes ended up with Bristol Hercules engines, only a few Lancasters. Probably in this scenario more Lancasters get Hercules, and if this causes a supply problem then they may look to the US for alternatives - such as the R-2600.

Perhaps Rolls-Royce don't convert the P-51/Mustang with a Merlin 61. Perhaps they do, but since the RAF doesn't need a long range high altitude escort fighter they don't do anything with it. NAA don't do a similar conversion, but seeing RR's performance with the Merlin Mustang, they push Allison (and teh government) for 2 stage V-1710s.


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## Shortround6 (Jun 2, 2012)

wuzak said:


> Perhaps there is accelerated devlopment of the V-1710 and it gets put into production at Packard.



Possible



wuzak said:


> Perhaps the IV-1430 is pushed more, development taken over by someone with a clue. Packard is one of the production facilities.



A very bad choice. The IV-1430 had a number of questionable design features, the real wonder is that it was persisted with so long. There may have been some excuse in 1938-40. To still be fooling with it in 1943-44 means a few somebodies were not paying attention. 



wuzak said:


> Ford's proposed V12 is given backing and starts development - don't know when that will be available.



The Ford V-12 (according to most accounts) isn't "proposed" until Ford had a good look at the plans for the Merlin and perhaps even a sample engine. Ford has little or no background in aircraft engines and little or no background with superchargers. Ford did do an excellent job of making P&W R-2800 engines though. 



wuzak said:


> Did Packard have anything in development themselves?
> 
> Maybe the 2A-2775 of 1935 - X-24, 1900hp @ 2800 rpm. Weight 1720lb.
> 
> The 1A-5000 X-24 (5000 cubic inches), possibly rated at 3500hp, or the sleeve valve 3A-5000. Perhaps the 2A-5000 H-24 rated to 3000hp. The 1A-5000 weighing 2830lb, the 2A-5000 2750lb.



Maybe Packard could have gotten those engines to work in production form or maybe not. They may have been limited in development like the Hispano V-12. For engine of that displacement to be that light leads one to wonder if the structure is strong enough to stand up to higher boost pressures made available by later fuels? Please check the BMEP levels and consider that a Merlin III at 6lb boost was about 180 BMEP as was a "C" series Allison and both the early DB 601 and Jumo 211. later versions of some of these engines had BMEP somewhat over 250.


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## wuzak (Jun 2, 2012)

Shortround6 said:


> A very bad choice. The IV-1430 had a number of questionable design features, the real wonder is that it was persisted with so long. There may have been some excuse in 1938-40. To still be fooling with it in 1943-44 means a few somebodies were not paying attention.



Probably, but it was the Army's baby.

Possibly a better bet would have been in the Lycoming H-2470?




Shortround6 said:


> The Ford V-12 (according to most accounts) isn't "proposed" until Ford had a good look at the plans for the Merlin and perhaps even a sample engine. Ford has little or no background in aircraft engines and little or no background with superchargers. Ford did do an excellent job of making P&W R-2800 engines though.



I only knew that Ford had proposed a V12 aero engine....not the timing.





Shortround6 said:


> Maybe Packard could have gotten those engines to work in production form or maybe not. They may have been limited in development like the Hispano V-12. For engine of that displacement to be that light leads one to wonder if the structure is strong enough to stand up to higher boost pressures made available by later fuels? Please check the BMEP levels and consider that a Merlin III at 6lb boost was about 180 BMEP as was a "C" series Allison and both the early DB 601 and Jumo 211. later versions of some of these engines had BMEP somewhat over 250.



The 2A-2775 maybe a lightweight engine that couldn't have too much development, in the form of boost, at that weight. Still, At 1720lbs dry it would have an installed weight similar to an R-2800 and as much power. And it would have been available sooner. 

The BMEP at 1900hp and 2800rpm is 198psi.

Maybe development during the war sees the 2A-2775 gaining weight as it gains strength. Certainly the rpms are low for the short stroke (5").

The larger 1A-5000 and 2A-5000 made 3000-3500hp in 1939 at weights around 2800lb. The hp/l isn't pushing up there, but the power to weight is good. The document I have (from enginehistory.org) doesn't specify rpms for those two, but if the same rpm is chosen the BMEP is roughly the same (at 3500hp).


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## fastmongrel (Jun 3, 2012)

I like the idea of Packard churning out R2800s these would then power the Typhoon and Tempest, no more Sabre troubles. Doubt if the Lancaster could take the R2800 but wow what a bomber that would have been with 4 turbo R2800s


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## gjs238 (Jun 3, 2012)

Turbocharged V-1710's may supplant some V-1650's.
For example, with no V-1650 powered P-51, P-38's take on a larger role.

Perhaps P-40 production ends earlier in favor of V-1710 powered P-51's.


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## tomo pauk (Jun 3, 2012)

How about P-51 with 2-stage V-1710 (mass production, not just the prototype)? Or, maybe, going for the R-2800 for the plane?

I've made a rough sketch of the turbo-51 (w/ V-1710) a while ago. Prestone oil coolers positioned akin to the P-40, intercooler turbocharger at the back, lower hull. Major shortcoming - external exhaust ducting.


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## Njaco (Jun 3, 2012)

without the Merlin, would more effort be placed on producing jet engines?


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## GregP (Jun 3, 2012)

For the sake of discussion, I’d like to throw out the following. The US Congress contracted for the Allison V-1710 and development started in 1929. They anticipated a high-altitude requirement and developed a turbo-supercharger system for the Allison V-1710. It wasn’t perfect but was exactly what was contracted for. After the prototype P-39 had some issue, they deleted the turbo-supercharger from the aircraft and all subsequent fighters except the P-38.

As a result, all the subsequent fighters except the P-38, while pretty good at low to medium altitude, suffered from lack of high-altitude performance.

Unfortunately, the US Congress owned the design, lock, stock, and barrel. I submit that they should have taken the simple step of appointing an Allison manager for the government and delegating him the authority to oversee improvements to the engine.

Next, he could have asked Allison to pursue a development of the 2-stage, 2-speed supercharger to augment the turbo-superchargers, which were earmarked for the strategic bombers, so they could reach high altitude. We had insufficient quantities of certain metals to allow the number of turbochargers for there to enough for the fighters, according to the war materiel board …but we didn’t need those metals for superchargers.

We still would have needed the time to sort out the issues we found in Europe with the early P-38 deployment. Those issues were the intake manifolds and running on European fuels, with had a much larger percentage of aromatics than did American fuel. Once these were sorted out, the engine problems “went away” and the P-38 had no more difficulties at high altitudes. Most were transferred to the Pacific where they gave yeoman service and were the mount of our two top-scoring Aces, Bong and McGuire.

Meanwhile, if the Allison V-1710 had seen a concerted development effort to field a 2-stage, 2-speed supercharger installation, I feel pretty certain they could have closed in on a good development effort and done it in a reasonable time. In point of fact, the late model Allisons with the auxiliary stage supercharger flew at high altitude very well and made as much power as any high-altitude Merlin. But the auxiliary stage was a dead end in my mind and I am proposing they concentrated instead on an integral unit, such as the Merlin had. Maybe even if we had not built Merlins, we could have consulted with Sit Stanley Hooker on the supercharger design.

I do NOT claim we could have done it exactly quickly, but it could have been done and would have resulted in good things for the V-1710 in time to make a difference in the war.


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## tomo pauk (Jun 3, 2012)

Hi, Greg,
Why do you think that the aux stage (for the V-1710) was a dead end?


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## Balljoint (Jun 3, 2012)

I’m jumping in the deep end as a newbie, but I don’t see this as a hypothetical. The Eighth was flying without the Merlin in 1942. 1930’s doctrine said the bombers could fight their way through and reach the target. The hardly timid RAF found this not to be so, but the US brass persisted.

My suggestion would have been a change in tactics. The bombers were flying at 20.000+ ft and the Allisons ran out of breath at 12,000 ft. So why not bring the bombers down to 10,000 t0 14,000 ft and use P-39s and P-51As for escort? Drop tanks are a low tech problem. And these AC could have been available in reasonable numbers if the ill-conceive A-35 and lend lease planes were switched to escort AC.

Obviously there would have been tradeoffs in range/payload, AAA, rearm/fuel cycle for interceptors etc., but the upside of escort fighters seemingly would more be than offsetting. 

Any thoughts?


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## wuzak (Jun 3, 2012)

The lack of US built Merlins doesn't just affect the P-51.

There were some 50,000+ Packard built Merlins, around 17,000 P-51s (including P-51As) and a few hundred P-40Fs and Ls. The rest went to Lancasters, Mosquitos and Spitfires, and I'm sure one or two other British aircraft.


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## Shortround6 (Jun 3, 2012)

Balljoint said:


> I’m jumping in the deep end as a newbie, but I don’t see this as a hypothetical. The Eighth was flying without the Merlin in 1942. 1930’s doctrine said the bombers could fight their way through and reach the target. The hardly timid RAF found this not to be so, but the US brass persisted.
> 
> My suggestion would have been a change in tactics. The bombers were flying at 20.000+ ft and the Allisons ran out of breath at 12,000 ft. So why not bring the bombers down to 10,000 t0 14,000 ft and use P-39s and P-51As for escort? Drop tanks are a low tech problem. And these AC could have been available in reasonable numbers if the ill-conceive A-35 and lend lease planes were switched to escort AC.
> 
> ...



P-39s are among the shortest range fighters, no good for escort. Drop tanks are for getting _to_ the target/first intercept, internal fuel is for fighting and getting home. 

Bringing the bombers down to 10,000-14,000 ft give the Flak guns a much better chance. A short time of flight for a more accurate fuse timing and a much longer period of time in which the bombers are in range of a particular gun/battery. 

B-17s and B-24s cruised where the FW 190 was beginning to fall off in performance. Cruising below 20,000ft makes the FW 190 even more effective than it was historically.


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## davebender (Jun 3, 2012)

I disagree. 

The Merlin engine had top priority because it powered Spitfires and Lancaster bombers. If the USA doesn't supply Merlin engines then Rolls Royce will be told to concentrate exclusively on Merlin engine production. Development of the Griffin engine and other Rolls Royce projects will sputter to a halt for the duration of the war.


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## Balljoint (Jun 3, 2012)

I don’t differ with you; just saying that without the Merlin it may be a good compromise. I see the bomber effort as initially an air superiority contest requiring fighter escort primarily to destroy LW interceptors and secondarily to protect bombers –though one is a function of the other. Without escort, even Ju-52s were able to stand off and fire rockets at the bomber formations. 

The P-39 was included with regard to availability and the thought that it had perhaps a range of 500 mi. internal fuel. Thus it would be useful over France where the LW would have to defend transportation and provisions for channel defense. This is primarily the time period before the P-51-B was available in reasonable numbers, theP-39 and P-51A, like halitosis, would have been better than no breath at all. But the P-38s and P-47s could also operate in these areas.

Same with Flak. As long as the bombers stayed above the 20 mm stuff, the quantity wouldn’t increase much though the aim and duration over Flak concentrations would somewhat.

Without fighter protection, the 190s and 109s really didn’t need much performance to ravish the bombers. 
My point has to do with tactics to deal with the lack of high altitude, long range escort fighters, which was the situation prior to the arrival of the P-51B. This was a terrible time for the bombers. Perhaps it would have been less so had they come down a bit. From a tactics viewpoint, the bombers set the combat altitude.


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## tyrodtom (Jun 3, 2012)

The USAAF in Europe lost more aircraft to flak, than they did fighters.
Reducing their altitude would make them more likely to take even more damage from their greater threat, flak. Because 10-14 k feet puts the within the range of even medium flak, 37-40mm . More guns shooting, with less of a aiming problem, would offset the ability to protect them from the fighters.


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## wuzak (Jun 3, 2012)

davebender said:


> *Griffon engine versions pushed forward /B]
> 
> I disagree.
> 
> The Merlin engine had top priority because it powered Spitfires and Lancaster bombers. If the USA doesn't supply Merlin engines then Rolls Royce will be told to concentrate exclusively on Merlin engine production. Development of the Griffin engine and other Rolls Royce projects will sputter to a halt for the duration of the war.*


*

While production of the Merlin will take priority, as it did in 1940, the development of the Griffon won't be delayed any more than historically. Production would be the issue.

When these decisions have to be made the Griffon is in initial development, but has been earmarked (from 1939) and modified for use with the Spitfire. The Merlin engined Machester III is just being mooted, while the Merlin Halifax I is about to start production.

I would suggest that bythe time Lancaster production begins the fears over Hercules shortages have been put to rest, and more Lancasters and Halifaxes are so powered - freeing up the Merlins for Spitfires and Mosquitos. Meanwhile, the Griffon Spitfire continues apace.

Also, no reason that the Lancaster can't be adapted to the Griffon sooner, thus giving the Griffon an even higher priority than historically.*


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## GregP (Jun 3, 2012)

I think the aux stage was a dead end because of the weight and length it added. Fine for a bomber or larger aircraft, even though a penalty .... but relatively impossible for a small fighter.


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## wuzak (Jun 3, 2012)

GregP said:


> I think the aux stage was a dead end because of the weight and length it added. Fine for a bomber or larger aircraft, even though a penalty .... but relatively impossible for a small fighter.



It did enable them to keep the standard single stage front section as per turbo installations - at least on some 2 stage versions.


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## parsifal (Jun 3, 2012)

I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.

merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942. A failure to produce the merlin would delay the commencment of the great offensives in 1944, particulalry the air offensives. This would delay the cross channel invasion and allow the Russians time to overrun the whole of Europe. that would probably have had implications for the whole of Europe that would continue to affect us today.

The US built 150000 merlins from 1942 to 1950. You cannot remove that many engines, with a delay of say 1 year and not expect massive impacts on your force structure. Much as this might pain the US forum members, the merlin was one of those critical pieces of kit that could not be ignored in the US victory. The germans had a similar reliance on their DB engines


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## Shortround6 (Jun 3, 2012)

Balljoint said:


> I don’t differ with you; just saying that without the Merlin it may be a good compromise. I see the bomber effort as initially an air superiority contest requiring fighter escort primarily to destroy LW interceptors and secondarily to protect bombers –though one is a function of the other. Without escort, even Ju-52s were able to stand off and fire rockets at the bomber formations.



Do you have a reference for this last bit? 



Balljoint said:


> The P-39 was included with regard to availability and the thought that it had perhaps a range of 500 mi. internal fuel.



I realize that you are new here and I have no idea if what you actually know. I would suggest that there are many technical manuals in the Technical section available for viewing or download. They give a much better idea of the capabilities of some of these aircraft than many print books or websites. However a good website is Zeno's Warbird Video Drive-In - World War 2 airplane videos playing for free live online which has a number of pages from such manuals for mostly American aircraft such as:

http://www.zenoswarbirdvideos.com/Images/P-39/P39SEFC.pdf

and: http://www.zenoswarbirdvideos.com/Images/P-39/P39FOIC.pdf

Granted this version of the P-39 only had 87 gallons of fuel but even with 120 gallons the "range" of a P-39 is not great. For escort duty you can fly on the drop tank/s ( I don't care how big it is) until combat is joined, at which point the tank/s are dropped and you have 120 gallons of internal fuel. USAAF doctrine ( I believe, memory could be going) called for radius of action to figures at 5 minutes of Military power after tanks are jettisoned ( about 11.5 gallons for the late P-39s) and 20 minutes of MAX continous power, even 15 minutes of max con power is worth 27-28 gallons for the P-39. You now have 81 gallons to get home with. A P-39 burns about 0.5-0.66 gallons a minute at it's most economical speed so allowing just 20 minutes reserve to find the airfield and land means another 10-13 gallons that can't be used. Call it 70 gallons to get home and you can't fly at the most economical setting in enemy territory. At 240mph indicated (312mph true) at 15,000ft the P-39 burns 65 gal an hour or about 4.8MPG. 5 minutes at WEP instead of Military power burns an extra 2.5 gallons (12 miles) and an extra 5 minutes at max con power before heading home cost 9 gallons (43 miles). Prevailing winds over Europe are out of the west. A head wind heading home much more often than not. 
How far from the English coast do you want to be when the drop tanks go? 300miles? 200 miles? Less? 



Balljoint said:


> Same with Flak. As long as the bombers stayed above the 20 mm stuff, the quantity wouldn’t increase much though the aim and duration over Flak concentrations would somewhat.



Even if you are above the 37mm stuff you have just radically increased the Flak's effectiveness. Say a German anti-aircraft gun has a max ceiling of 9900meters, it may have an effective ceiling of 8000 meters, effective ceiling is the altitude at which it can track a target and fire a certain amount of shots at it. This ceiling may require the target aircraft to fly directly over the gun and flying several thousand meters to the side could put the target out of effective range ( due to the slant distance). Dropping the target aircraft to 4500-5000meters and the gun can begin firing sooner and keep firing later. It can also fire at targets flying a flight path further to the "sides". If the time fuses have an error of 0.02 of the time of flight cutting the time of flight means "shorts and longs" will actually be much closer to the target. Considering the rate at which shells slow down a 1/3 reduction in altitude may result in 1/2 the time of flight. This also reduces the amount of lead needed further increasing the accuracy. 



Balljoint said:


> Without fighter protection, the 190s and 109s really didn’t need much performance to ravish the bombers.



True but by dropping the bombers AND their escorts into the prime altitude band for the 190 means that the "air superiority contest requiring fighter escort primarily to destroy LW interceptors and secondarily to protect bombers" just shifted somewhat into the Luftwaffe's favor compared to fighting at higher altitudes. The 190s being much more able to deal with allied fighters at 4000-6000 meters than at 7000 meters and above. 



Balljoint said:


> My point has to do with tactics to deal with the lack of high altitude, long range escort fighters, which was the situation prior to the arrival of the P-51B. This was a terrible time for the bombers. Perhaps it would have been less so had they come down a bit. From a tactics viewpoint, the bombers set the combat altitude.



Maybe you are right and maybe you are just trading one means of loosing bombers for other ways.


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## wuzak (Jun 3, 2012)

parsifal said:


> I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.
> 
> merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942.



Had to be made before 1942. The Packard factory had to be built and start supplying engines by then.





parsifal said:


> The US built 150000 merlins from 1942 to 1950. You cannot remove that many engines, with a delay of say 1 year and not expect massive impacts on your force structure. Much as this might pain the US forum members, the merlin was one of those critical pieces of kit that could not be ignored in the US victory.



Packard built 55,000 Merlins - mostly for the British. Continental made a few, but no more than a couple of thousand, and only very late in teh war - they were gearing up to build the IV-1430.

There were 150,000 Merlins built all up.

I thought US production of Merlins finished not long after WW2.


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## Shortround6 (Jun 3, 2012)

parsifal said:


> I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.
> 
> merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942. A failure to produce the merlin would delay the commencment of the great offensives in 1944, particulalry the air offensives. This would delay the cross channel invasion and allow the Russians time to overrun the whole of Europe. that would probably have had implications for the whole of Europe that would continue to affect us today.



I agree with much of what you say except that your timing is off. The Decisions as to what engines to be made were being made in 1940. Packard signs the deal to make Merlin's in Sept 1940, it takes about one year to get the first 2 ceremonial engines onto test stands. It takes until Dec 1941 for production to exceed a dozen a month. Also in Sept 1940 Ford signs deal to make R-2800s and breaks ground on new factory to do so. It takes 13 months to deliver 1st engine, Nov 41 sees 99 engines and by May 42 production hits 500 a month and keeps climbing. Packard had hit 500 engines a month the Month before. Allison had reached 500 engines a month in July of 1941. Studebaker, Buick and Chevrolet started delivering engines in March, April and May of 42 respectively so the "decision" had to made about a year or more earlier. 
Over 2/3s of Merlins made by Packard went to Commonwealth aircraft. While the Merlin may not have been a deal breaker for US forces (depends on view of the Mustang) the loss of that many engines ( or the substitution/delay) of that number of engines to the Allied cause WOULD have very large consequences that cannot be argued/wished away. A one year delay in Packard Merlin Production was worth 7-8000 engines PER year for 1942/43/44 for a total of of around 21-23,000 engines. That is just sliding the 2-42 production to 43 and 43 to 44 and so on.

This makes the decision to go for the Merlin that much easier. 2 reasons.

1st, The US was refusing to build British weapons built to British Specifications but would build weapons/equipment to British orders that US forces could/would use. (No British tank designs and so forth). 

2nd, the Merlin in the summer of 1940 was a proven engine with thousands of MK IIIs made, hundreds of MK Xs and the MK XX ready to go. In the summer of 1940 Allison production had yet to break 100 a month, a total of 8 R-2800s exist. Just over 200 R-2600s were built up until Jan of 1940 and while another 400 had been built by the end of June 1940 they had little time to establish a track record.
The R-1820 and R-1830 were both known quantities but development potential was limited.
Any other US high powered engines existed in quantities under a dozen at best or as "vaporware".


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## Edgar Brooks (Jun 4, 2012)

davebender said:


> I disagree.
> 
> The Merlin engine had top priority because it powered Spitfires and Lancaster bombers. If the USA doesn't supply Merlin engines then Rolls Royce will be told to concentrate exclusively on Merlin engine production. Development of the Griffin engine and other Rolls Royce projects will sputter to a halt for the duration of the war.


No, they wouldn't; the Air Ministry couldn't dictate what a private company's development department did, or didn't, do to that extent. They could refuse to order any new engine, but, if it turns out to be a better product, that would be foolish in the extreme, and Heaven help them if the government found out that they were deliberately holding things back.


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## GregP (Jun 4, 2012)

Parsifal,

The Allison WAS in mass production. We also had a high-altitude system for it.

The decision makers decided to remove that from the popwer system of our fighters by deleting the turbocharger.

Once we identified the issues with the intake system, it took only several months to fix. It took almost a year to realize that European fuels were not teh same mix as American fuels. That took some carburetor adjustments, but was also fixed.


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## davebender (Jun 4, 2012)

That wouldn't surprise me. The USAAF didn't arrive in Europe in large numbers until the war was two thirds over and the Luftwaffe was short on aviation gasoline. 

What do you think would happen if the RAF of 1939 were replaced with the USAAF of 1939?


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## Balljoint (Jun 4, 2012)

Shortround6 said:


> I realize that you are new here and I have no idea if what you actually know.




My interest is broad and tends towards strategy. While I think I have a working knowledge of the aviation it definitely is not the encyclopedic expertise of many on this forum. For the most part I’ve been content to lurk.

My post was intended to tease out one aspect of a larger strategy to test it against greater knowledge – but I thought it might have enough meat as to not waste your time.

I’m sure I had a source for the stand off rocket attack, but the Ju-52 was more an example since many of my resources disappeared during a remodel. I will search though.

And I stand corrected on the P-39; I shouldn’t have dragged it into this issue, i.e. an Allison mustang.

More specifically, the “no Merlin” period from mid1942 until the early 1944 is the period that I’m concerned with. The LW could easily evade the part-way escort. Bomber losses were horrendous. Allison-powered fighter performed well at lower altitude for the Soviets -albeit in tactical roles- and against Oscars in China. The P-51A was an ugly duckling that, with long range tanks could fill a huge gap at lower altitudes.

Actually, I thought that weather would be the main objection. Flak didn’t really track flights but instead filled blocks. Maybe this would change at less height. LW interceptors had to form up at low altitudes so would they gain altitude for the vertical advantage or just come in? 

There are a number of “what if” issues for sure. But when the P-51Bs stared escort duties about Jan 1944 the LW fighter capability was still strong. About May of 44 the allies gained air superiority over Western Europe. What if the P-51A had been on the scene from mid 43 with low altitude but long range escort? Many, many questions, but maybe it would have helped.


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## tyrodtom (Jun 4, 2012)

A Ju-52's service ceiling is 17,000 feet, as low as the daylight formations flew was 22,000, but usually higher. With the Ju-52 top speed being about the same as a allied formations speed and it's altitude being a least a mile lower, I just don't see the possibility of a Ju-52 lobbing rockets at anything but empty sky.


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## Shortround6 (Jun 4, 2012)

GregP said:


> The Allison WAS in mass production.



Please define mass production. In 1940 Allison built/shipped 3 engines in Jan, 7 engines in each of Feb, March and April, 14 engines in May, 30 in June, and 73 in July. 
Allison did deliver 223 engines in Sept when the deal with Packard was signed. First time production hit triple digits. Production fell below 200 per month 3 times by April of 1941 with a high of 400 in Feb. 1941. 
Things got much better after May of 1941. But by that time The Aircraft engine industry was tooling up in massive fashion. The deals with Studebaker, Buick and Chevrolet were already signed in addition to the Packard and Ford deals and more were to come. 




GregP said:


> We also had a high-altitude system for it.
> The decision makers decided to remove that from the popwer system of our fighters by deleting the turbocharger.



The decision makers made that decision because, in their opinion, the 1939 turbo system wasn't ready for either production or squadron service or both. They estimated that waiting for a turbo system that was usable in squadron service would delay the P-40 (see P-37) and perhaps the P-39 by an additional year. Turbo P-40s showing up in the Spring of 1941 instead of non-turbo P-40s the Spring of 1940? Turbo P-39s showing up in Dec of 1941 instead non turbos P-39s in Dec of 1940? It took about 1 year to go from 5th aircraft delivered to the 1000th aircraft delivered for those two models. A little less for the P-40 and a little more for the P-39. 

Much is made of the lack of high altitude capability of American fighters in the Spring/summer of 1942. Not many people consider the effect on the US of being about 2000 fighters shorter than we were at the time of Pearl Harbor and the carry over into the Spring/summer of 1942. Low altitude fighters being better than _NO_ fighters. 

Allison realized the need for a better supercharger in 1938 and started the 2 stage project. But when you are making only 1-2 engines a month and even those are not the same model and trying to expand the factory by an order of magnitude ( or several orders of magnitude) at the same time, certain projects get moved to the back of the stove. 



GregP said:


> Once we identified the issues with the intake system, it took only several months to fix. It took almost a year to realize that European fuels were not teh same mix as American fuels. That took some carburetor adjustments, but was also fixed.



Which problem with the intake? I think there was more than one. 

Anybody with any knowledge of gasoline at all _KNEW_ there was a difference in US gas and British gas in 1940. The specifications could not have been more clear. US Spec fuel _could not_ contain more than 2% aromatics. British Spec fuel could not contain _less than_ 20% aromatics, ten times the US max. Without the aromatics however there is NO rich response (or a very small one), no 100/130 fuel. US fuel Specs were brought into line with the British ones, what the British may have given up I don't know. 

The problem with "European fuel" came later. In an attempt to stretch fuel supplies a higher percentage of heavy compounds were allowed _in all 100/130_ fuel. Not all batches of fuel may have gotten the heavier compounds or gotten them in the same amounts. These heavy compounds showed a greater tendency to condense out (or the fuel, being a bit heavier condensed easier?) at low temperatures and 'puddle' in the intake manifolds. This problem was known/anticipated and Allison was working on a new intake manifold in the late spring or summer of 1943. BY the time P-38s in Europe were actually having difficulties the New manifolds were already designed, flight tested and in production. New engines got the manifolds and old engines were retrofitted in the field with the new manifolds often shipped by air to the units. 
With fuel being made in a number of different refineries and with different amounts of certain compounds allowed or used ( there are over 400 different compounds that can be used in "gasoline", obviously not all at the same time) it is not surprising that a few batches may have come up a little short. I would note that the problems the European P-38s had were also made worse by poor piloting technique. They were being taught to cruise at low boost and high rpm which is not only wrong from a range//endurance standpoint (and against both Allison and Lockheed recommendations) but caused the intake charge temperature to be lower than normal which added to the fuel vaporization problem.

P-38s in warmer theaters may have gotten poorly blended fuel but the warmer temperatures (and lower altitudes) may have kept the vaporization problem to a minimum.

According the "Vees for Victory" ALL Allisons go the new manifolds, P-39s, P-40s, and Allison powered P-51a/A-36s, not just P-38s.


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## tyrodtom (Jun 4, 2012)

davebender said:


> That wouldn't surprise me. The USAAF didn't arrive in Europe in large numbers until the war was two thirds over and the Luftwaffe was short on aviation gasoline.
> 
> What do you think would happen if the RAF of 1939 were replaced with the USAAF of 1939?



That's a bit of exaggeration there dave. If the Luftwaffe was getting short of fuel before the USAAF got there, it would be because they just didn't produce enough, because no one had targeted petrol production to any serious extent up to that time.

In 1939, that would be the USAAC, less than 60 B-17s by the middle of 39, the P-40 first flew in late 38. So a American effort at bombing in 1939 would be B-18s escorted by P-35s and P-36s. That would be a sad exhibition.


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## Shortround6 (Jun 4, 2012)

Balljoint said:


> – but I thought it might have enough meat as to not waste your time.



If you are willing to learn then you are not wasting my time or, I hope, the time of any of the many members who are more knowledgeable than I am. 
We have certainly discussed many subjects with less meat to them  




Balljoint said:


> Actually, I thought that weather would be the main objection. Flak didn’t really track flights but instead filled blocks. Maybe this would change at less height.



Flak did both. If you have hundreds of guns and hundreds of bombers flying over them then you can just point the barrels up and have at it. But every major nation spent a lot of time and money on "predictors/directors" that would track an aircraft target and predict the future location and the time of flight of the shell to get there. They were mechanical analog computers. The Predictor sent signals to the guns that moved pointers on dials, the gunners traversed and elevated the guns until matching pointers lined up with predictor driven ones. One man controlled the traverse and one man the elevation and they never looked at the airplane/s in question, just tried to keep the pointers aligned. The Predictor also sent signals to the automatic fuse setters. The gun crew just stuck the nose of the shell into the fuse setter and automatic jaws aligned the fuse and twisted the timing ring to the correct setting, the crew then removed the shell and loaded it into the Breech in a measured fashion. (predictor figured in a set loading time between setting the fuse and gun firing. 
The lower the time of flight the easier the predictor's "job". Low level attacks took out the predictor because there wasn't enough time to track and get solutions. heavy AA didn't work well below certain heights.


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## Shortround6 (Jun 4, 2012)

wuzak said:


> Probably, but it was the Army's baby.



True but nepotism should only go so far 



wuzak said:


> Possibly a better bet would have been in the Lycoming H-2470?



Possibly but it suffered from some of the same problems as the IV-1430, like the separate cylinders. The Army did try to complicate even further by adding such "features" as a two speed propeller drive which added several hundred pounds of weight. 



wuzak said:


> The 2A-2775 maybe a lightweight engine that couldn't have too much development, in the form of boost, at that weight. Still, At 1720lbs dry it would have an installed weight similar to an R-2800 and as much power. And it would have been available sooner.



It is a mighty big maybe. Consider that the Rolls-Royce Vulture was an X 24 of 2592 cu in (an X-2590 or 2600 in American terms.) that weighed 2450lbs for 2000hp? at 3000rpm. BMEP=203. For Packard to get 1900hp out of a 7% larger engine turning 6.66% slower and yet weighing only 70% as much must mean either that Packard knew a lot more than than R-R about engine building or that the Packard couldn't put out that kind of power for very long (as in service life). 
Also consider that the X-2775 was little more than two short stroke V-1500s running on a common crankshaft and the V-1500 dates from 1924. There were only two and possibly three X-2775s built, the same engine/s were rebuilt into several different configurations.

The 1A-5000 and 2A-5000 were never completed. The poppet valve 5000 series engines were based off the V-2500 cylinder blocks (another 1920s engine) and bore X stroke. 
While the Marine versions in PT boats started at 1200hp and went to 1350 and then 1500hp I would note that these are ground supercharged engines. The supercharger is used to boost performance at ground (sea) level and not for altitude performance. Please subtract about 2% for every 1000ft for altitude performance. Granted a different supercharger and/or gear ratio could improve altitude performance but only at the cost of lower sea level performance. 
Think of them sort of like a Merlin VIII in a Fulmar.


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## tomo pauk (Jun 4, 2012)

Shortround6 said:


> <snip>



This great post should go to myth buster topic, sticky, or something similar. A required read. 

Further on the tread:
What changes for the British production would been undertaken, in order to use the R-2800 or V-1710 (produced by Packard in this time line) in airframes of their origins? Mossie FB with V-1710 (ducks for cover)?


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## wuzak (Jun 4, 2012)

Question: If Packard aren't building Merlins in 1942 is it because Packard or the US Government rejected the request from Rolls-Royce/British Governemnet?

If this is rejected, what of the Tizard mission? Will he take all his goodies (cavity magnitron, jet engine planes, other bits of British technology) back home with him?


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## Balljoint (Jun 4, 2012)

Shortround6 said:


> Do you have a reference for this last bit?


 

The last bit being the ability of JU-52s standing of and launching rockets. No luck on the cite I had in mind but I understand the Ju-52 skepticism. I did find the following at page 208, Masters of the Air by Donald L. Miller;

“That morning, there were more enemy fighters in the air than on the first Schweinfurt mission, and dozens of them were rocket ships: converted twin-engine night fighters, most of them Junkers 88s, capable of launching 250-pound missiles from tubes suspended beneath their wings –called stovepipes by the Germans. These were the rockets that had helped decimate the Hundredth at Munster –fused missiles that streaked towards the bombers and detonated at a predetermined range, creating bursts four times the size of ordinary flak explosions. … The Junkers launched the missiles out of range of the bomber’s guns.”

Certainly a Ju-52 differs from a Ju-88. But even the Ju-88 would not be there in the presence of escort fighters. Of course rockets were used later by German interceptor fighters but only in the face of escort fighters. 

It’s just an opinion, but I suspect that, while overall more bombers were taken by flak than air opposition, if the timing were examined the air losses would be rather larger through early 1944, and thereafter the flak losses would go up sharply. Hitler didn’t want the LW to be a “defensive” weapon. Thus he beefed up the AA to over 13,000 heavy guns while the bombing targets, such as the synthetic fuel plants, became more concentrated.


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## davebender (Jun 4, 2012)

Any aircraft can stand off and launch rockets including passenger aircraft such as the Ju-52 and Boeing 747. But they are hardly ideal for that purpose.


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## Shortround6 (Jun 4, 2012)

davebender said:


> Any aircraft can stand off and launch rockets including passenger aircraft such as the Ju-52 and Boeing 747. But they are hardly ideal for that purpose.



Yep. any aircraft can launch rockets. getting the rockets anywhere near the target aircraft is a whole other story. 

Granted it is wiki but:

Werfer-Granate 21 - Wikipedia, the free encyclopedia

Trying to hit (get rocket to explode within several hundred feet) planes flying several thousand meters higher and flying faster than the Ju 52 would have been like hitting the lottery with your first ticket. It also would have required changing the time fuse to allow for a much much longer flight time. You might want to do a little elementary geometry and try to figure out even the most optimistic flight times to intercept a bomber flying 5000ft higher than the Ju 52 and cruising at 180mph true airspeed.


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## tyrodtom (Jun 4, 2012)

The R4M had a little more range WG-21, it was 1500 meters. Which is about the same as the shortfall of the Ju-52's service ceiling with the very lowest flying formations of daylight bombers. But most of the formations were a great deal higher than 22,000.

Plus I doubt even the R4M had a 1500 meter range when fired straight up, because that is the only way any rocket in the Luftwaffe's inventory had any chance of hitting allied daylight bombers when fired from a Ju-52.


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## Shortround6 (Jun 4, 2012)

Well, the WG-21, in a ground roll, could range to just under 8000 meters when fired at a 45 degree angle. Air at 15,000-20,000ft is about 30-40% thinner so it should range further. If our intrepid JU 52 pilot can get his aircraft to 15,000ft and then pull up 25-30 degrees (With the tubes mounted at 15-20 degrees.) the rockets might just make it to 20,000-22,000ft 12-15 seconds after launch (time fuse modified). Of course in 12 seconds even a slow B-17 has moved over 3000ft so "aiming" is a bit of a problem.  

Of course getting the Ju 52 to 15,000ft with the extra drag of the external tubes is a bit of a problem (mount the tubes inside the fuselage?) as is the 30 degree pull up at max height (almost a guaranteed stall) (solved by internal tubes). 

I can believe a number of aircraft besides the ones listed in Wiki might have carried the big rockets. the JU 52 wasn't one of them.


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## GregP (Jun 4, 2012)

Shortround,

Parsfail said decision about what to produce in 1942 had to be made. They produced 1 engine per month in 1938, 8 engines per month in 1939 … per contract. In 1940, it was up to 300 per month and in 1941 it was 1,100 per month. By 1942, it was 1,400 per month.

Allison went from 94,000 square feet on manufacturing space in 1938 to 1,221,660 square feet in 1940. Allison delivered only 1,143 engines in 1940, when we were not at war, and delivered 6,447 in 1941. That qualifies as mass production in my book. In 1942, they delivered 14,905 engines. Like I said, mass production.

Numbers from Dan Whitney’s Vees for Victory.


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## tyrodtom (Jun 4, 2012)

If you mounted the tubes in the fuselage, what would happen to the fuselage when the rockets fired ?
While the Iron Annie might have been tough, I think that sounds like a one way mission.


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## Shortround6 (Jun 4, 2012)

GregP said:


> Shortround,
> 
> Parsfail said decision about what to produce in 1942 had to be made. They produced 1 engine per month in 1938, 8 engines per month in 1939 … per contract. In 1940, it was up to 300 per month and in 1941 it was 1,100 per month. By 1942, it was 1,400 per month.
> 
> ...



Parsfail was in error, the decision was made in 1940. While Allison had large orders on the books and was doing a fine job of gearing up FOR mass production in the spring/early summer they had not achieved it yet. In 1942 the Allison was in mass production, In 1940 it depends on the month you look at. Another source gives 1149 engines in 1940, a difference of 6 engines isn't worth arguing about. However of those 1143-9 engines 943 of them were delivered in the last 4 months of 1940. It takes time to expand plants and tool up and get rolling, at the actual time in 1940 when the decision to build the Merlin in the US was being made the Allison, while well on it's way was not actually in mass production.


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## Shortround6 (Jun 4, 2012)

tyrodtom said:


> If you mounted the tubes in the fuselage, what would happen to the fuselage when the rockets fired ?
> While the Iron Annie might have been tough, I think that sounds like a one way mission.



Might be a one way mission if the Ju 52 stalls and goes inverted at 15,000f too.

I hope you realize I am joking about the Ju 52  

Very good 1930s transport, lousy bomber interceptor no matter what you stick on/in it.


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## parsifal (Jun 4, 2012)

tyrodtom said:


> That's a bit of exaggeration there dave. If the Luftwaffe was getting short of fuel before the USAAF got there, it would be because they just didn't produce enough, because no one had targeted petrol production to any serious extent up to that time.
> 
> In 1939, that would be the USAAC, less than 60 B-17s by the middle of 39, the P-40 first flew in late 38. So a American effort at bombing in 1939 would be B-18s escorted by P-35s and P-36s. That would be a sad exhibition.



I agree that dave is doing what he does best here, but still, its true that the Germans were in crisis in terms of fuel supplies from quite early in the war. 

The Germans suffered their first fuel crisis in 1942. There are two ways of looking at this....either, as you say the germans didnt produce enough fuel, or, as an alternative way of looking at it, their consumption exceeded what they had planned for. Im not just being cute with the words here....Fuel consumption in 1941 far exceeded expectations, particularly in the East, where logistics created chronic shortages for the germans. In fact the logistics constraints always meant the germans were short on supply in all their distant TOS, like North Africa and the Eastern Front.

Production fell short of demand, because production costs for manufactured fuel were very high....about 10 times the cost per gallon as naturally occurring fuel. The British blockade cut the germans from their traditional overseas supplies, and British bombing, whilst somewhat inneffective, still had an effect on distribution and did include fuel supplies as one of its target priorities (albeit not a primary objective). The germans had hoped to augment their meagre supplies by captured sources, but all wells that were captured were effectively destroyed for the duration. The picture is completed by germany's attrocious attitudes towards its allies. Whereas the allied efforts tried to work to each alliance members' strengths, and compensate for each others weaknesses, the germans from the very beginning treated nations like Rumania and the occupied territories as colonial outposts to be exploited and cheated as much as was humanly possible. The Rumanians returned that treatement in kind. There was never a high level of co-operation in the Axis camp as existed in the Allied camp (though tensions did exist, of course). One result was that the Germans sold armaments to Rumania for inflated prices, and the Rumanians were in no hurry to increase production to meet demand. why would they when Germany was not prepred to pay what that oil was worth to them? 

Explaining why Germany came up short in the supply of oil is more complex than it looks. and trying to attribute the final oil crisis as a result of the 8th AF's precision bombing campaign of 1944-5 is just a partial answer to that equation. it does not explain all the issues


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## gjs238 (Jun 5, 2012)

Could R-2800 2-stage supercharging development have been improved?
While this would not have helped the P-40 or P-51, it could have been interesting to see F4U's in the ETO up high providing escort.
Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.


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## tomo pauk (Jun 5, 2012)

wuzak said:


> Question: If Packard aren't building Merlins in 1942 is it because Packard or the US Government rejected the request from Rolls-Royce/British Governemnet?
> 
> If this is rejected, what of the Tizard mission? Will he take all his goodies (cavity magnitron, jet engine planes, other bits of British technology) back home with him?



Hi,
I'm not questioning/jeopardizing the Tizard mission, just trying to create a discussion about the non-production of the Merlin in the USA and the repercussions of that. In this thread, Packard builds either R-2800 or V-1710 instead.



gjs238 said:


> Could R-2800 2-stage supercharging development have been improved?


Hi,
What kind of improvement you have in mind? The 2-stage R-2800 was one hell of an engine.



> While this *would not have helped* the P-40 or *P-51*, it could have been interesting to see F4U's in the ETO up high providing escort.



Would it be so unreal to up-engine the P-51 with R-2800? 



> Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.



Perhaps the Brits would be better off with single stage R-2800, than the Hercules engines they were using in Beaufighters and heavies? The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat.


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## Shortround6 (Jun 5, 2012)

gjs238 said:


> Could R-2800 2-stage supercharging development have been improved?



I would agree with Tom on this, improved how?

At higher altitudes it had several hundred more HP than a single stage R-2800 and would never have the power of a turbo R-2800. The auxiliary stage took about 350hp to run and if we assume a poor efficiency of 70% that means 245hp is compressing the air and and 105hp is heating it. If you could improve the efficiency to 80% you would only need about 306hp freeing about 44hp on a 1650hp engine but with only 60hp heating the air instead of 105hp the intake charge would be a bit cooler/denser meaning a bit more power. 80% efficiency is about tops for a WW II centrifugal compressor though. Or swap a bit more pressure for a lower efficiency? A few more lbs manifold pressure at 75% E.
That was the attraction of the turbo, using the exhaust gasses to power a turbine to reclaim 300-400hp to drive the supercharger. 



gjs238 said:


> While this would not have helped the P-40 or P-51, it could have been interesting to see F4U's in the ETO up high providing escort.



Interesting yes, but one has to consider that historically the F4U-1 was down a minimum of 350hp compared to a P-47 (at 22,500?) and in later versions the P-47 could have 2280hp at 25,000ft while climbing using water injection while an F4U-1 with water injection could only manage 1600hp at 25,000ft in level flight(P-47 could hold 2200hp in level flight to 30,000ft) at which altitude the F4U-1 might have only 1200hp left. an extra 1000hp (83% more) goes a long, long way in making up for the P-47s extra weight and bulk over the F4U-1. 


gjs238 said:


> Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.



I am not even sure how they could use a single stage R-2800 w/o aircraft design changes. It is far from a plug in replacement for the Hercules. An Early Hercules weighs about 1850lbs dry for 1590hp take off and a max continuous of 1300hp at 14,800ft. A Wright R-2600 "B" series weighs about 1980lbs for 1700hp take off and 1350 max con at 15,000ft. A single stage 2 speed R-2800 went 2300lbs for 2000hp take off and 1450hp max con at 13,000ft. the extra 25% power at take off is going to need a bigger propeller than the Hercules had. The R-2800 is probably going to go 550-650lb dry (no oil) more installed per engine than Hercules. 
Perhaps not a problem on a some planes but sticking an extra 1200-1300lbs in the cowlings of a Beaufighter could prove _very_ interesting to an observer 
Test pilot might describe it differently.


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## Shortround6 (Jun 5, 2012)

tomo pauk said:


> The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat.




???????

Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.

compared the Sabre the R-2800 is down in power (but not as much) while having more drag. Not a good combination for performance even if much more reliable. 

Without the two stage supercharger the R-2800 has the same problem the R-2600 does as a fighter engine, lousy performance at altitude. 1600hp at 13,500 ft in high gear Military power for the version installed in the A-26 bomber and later B-26 bomber, early versions were worse. Like 1500hp at 14,000ft in high gear. Compared to what the Merlin could put out even it's MK XX form the R-2800 single stage is a much better bomber engine than fighter engine.


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## parsifal (Jun 5, 2012)

> Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.



Granted if you assume a single stage supercharger and different fuels, you might be able to explain difference in the power outputs of the two engines. Also concede that at the time of service delivery, the early marks of the Centaurus, as fitted to the Typhoon, were rated at 2250HP. The centauraus during its service career was significantly improved over roughly a two year period. The Bristol Centaurus has 18 cylinders in two rows, and is a sleeve-valved radial air-cooled engine. The first version produced 2,000 bhp, and the most powerful variant produced 3,200 bhp. It was the ultimate Bristol piston engine originally designed for use in Heavy bombers. Over 8,000 were produced. It is difficult to make blanket comparisons between the two engines since both were considerably improved over time. I am not sure why you would want to make assumptions about lower powered superchargers, since the improvements to the supercharger fitted to the centaurus was a major focus of the development program. 

The Centaurus was a sleeve valve radial aircraft engine, an 18-cylinder, two-row design that initially delivered 2250hp but by 1945 delivered over *3,000 hp *under combat conditions using standard wartime high octane rated fuels (I dont know the exact octane rating). This was the rated power output of the engines fitted to the Sea Fury FB11, introduced post war. These aircraft attracted a fine reputation for engine reliability and high engine power outputs. It was one of the largest piston aircraft engines to enter production, and was introduced into service use towards the end of World War II. 

When the R-2800 was introduced in 1939 it was capable of producing *2,000 hp *(1,500 kW). No other air-cooled engine came close to this figure at that time. The type was also noteworthy for its great reliability. 

In 1941 the power output of production models increased to *2,100 hp *(1,600 kW), and to *2,400 hp *(1,800 kW) late in the war. Even more was coaxed from experimental models, with fan-cooled subtypes producing *2,800 hp *(2,100 kW). However experimental versions of the Centaurus also managed to produce up to 3400hp.


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## gjs238 (Jun 5, 2012)

I was thinking if it was possible to improve the development process, not necessarily the end product.
If the 2-stage supercharged R-2800 could be brought into service earlier, perhaps it could mitigate the lack of V-1650's.

However, if turbocharging is really so much better, then perhaps using turbocharged V-1710's and/or other 1-stage supercharged engines for high altitude ops in lieu of the V-1650's is a path to explore.


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## Shortround6 (Jun 5, 2012)

I was going from the point of view of no US production of Merlins in 1940, and trying to substitute R-2800s in the 1940-42 time frame, Hawker was working on the Typhoon in 1937 and flying prototypes of the Tornado and Typhoon before the talks with Americans started and may well have been working on the Centaurus version at the time, R-2800 was giving 1850 hp for take off and promising 2000? British engines were delivering 2000+ and promising even more. Spending time and effort to design installations for the R-2800 in 1940/41 makes little sense as the R-2800 was under powered (at the time) and of higher drag than the Vulture or Sabre. 
R-2800s were used one Version of the Vickers Warwick bomber. 
ALL of these engines, with the exception of the Vulture, made great strides in development and finished the war much more powerful than they started but the decisions as to which one to use in what aircraft in 1941-43 cannot be made on the basis of 1944-45 performance. 

perhaps 2-stage supercharged R-2800s could have substituted in a way for V-1650s but Pratt only delivered 6 two stage R-2800 engines in all of 1941 and 117 in the first 6 months of 1942. They had delivered 98 two stage R-1830s in 1940 and another 507 in 1941. The early R-1830s gave a fair amount of trouble. How much can you speed up the development ( and the P&W two stage needed a lot of room in the airplane for the inter-coolers) vs when does the decision have to be made as to which engine to produce?

Parsifal, I believe the 2000hp version of the R-2800 shows up in 1941 (4 single stage engines built, 2 by East Hartford and 2 by Ford) This is the "B" series engine. the 2100hp "C" series doesn't show up until 1943 in single stage form and 1944 in two stage. Any R-2800s in 1940 and 1941 except for the above mentioned 10 engines and few experimentals are 1850hp "A" series. The even later "CA" series could make 2300hp for take off. All of these are dry (without water) and the addition of water injection and WEP settings ( not always the same thing, P&W rated the engines with water injection. P&W did not assign WEP settings in factory literature) confuses things somewhat. There were a few "D" series engines made for the XP-56 and other pushers? and the F8F Bearcat and F4U-5 used "E" series engines and don't really need to concern us.


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## GregP (Jun 5, 2012)

Shortround,

You are correct in 1940 but, in 1940, we were not at war and the Allison was exactly what was needed. We didn't go to war until December 8th, 1941, and 1942 was just around the corner, and the Allison was in mass production exactly when needed. The first Packard-built Merlin didn't run until August 1941. We STILL WERE NOT AT WAR and the A llison was ramping up nicely.

They didn't ramp up until 1942, and the Allison was in production by then. What it needed was the 2-stage, 2-speed supercharger of the V-1650-3, using the Wright supercharger drive quill instead of the Farman unit of the V-1650-1 Merlin. This could have been achieved rapidly if Congress had simply appopinted an Allison manager authorized to make imp[rovements to the engine. Instead, they clung to the original design most of the way through the war and never delegated imnprovement to anyone. Stupid, really ... and preventable.


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## wuzak (Jun 5, 2012)

GregP said:


> Shortround,
> 
> You are correct in 1940 but, in 1940, we were not at war and the Allison was exactly what was needed. We didn't go to war until December 8th, 1941, and 1942 was just around the corner, and the Allison was in mass production exactly when needed. The first Packard-built Merlin didn't run until August 1941. We STILL WERE NOT AT WAR and ethA llison was ramping up nicely.



Packard production of the Merlin was primarily to give another supply source for the UK. The US government only agreed to it providing there was a proportion (1 in 3) to be supplied to the US.


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## Shortround6 (Jun 6, 2012)

That is pretty much it. The US was not approving production of British designs/weapons unless the US thought they would be able to use them too at a later date. The US had two medium sized radials and 2/3 large radials but only one liquid cooled engine any where close to production or in production so a second one (already proven) would not be hard to find uses for.


Edit. The US and Allison were aware of the limitations of the single speed supercharger on the Allison fairly early. The design of the XP-39E (XP-76)

With the V-1710-47 engine in 1941 shows they were not ignoring the situation. Perhaps not giving the full priority but with 4000 planes ordered at one point certainly not ignoring it. That all 4000 planes were canceled shows that initial hopes/projections were not being met for a number of reasons and faster results were expected elsewhere.


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## tomo pauk (Jun 6, 2012)

Shortround6 said:


> ???????
> 
> Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.
> 
> ...



Hold you horses...err, question marks. I've already said:

_The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat._

That means an, almost, power egg installation (not as much as distributed as in Corsair), and 2-stage R-2800.


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## Shortround6 (Jun 7, 2012)

It could mean that  

Post Hurricane from the Hawker design stand point in practically anything after 1938. 
First flight of a Tornado 6 October 1939 with Vulture engine
First flight of a Typhoon 24 Feb. 1940 with Sabre
First flight of a Tornado 23 October 1941 with a Centaurus. 
First flight of a Tempest 2 September 1942 with Sabre
First flight of a F6F 30 July 1942 with an R-2800. 

Granted the R-2800 two stage shows up somewhat earlier than that but it is a bit late in timing for Hawker to do much with it. 

The Sabre engine was good for 1735Hp at 17,000ft which puts it sort of between the R-2800s power peaks. 1800hp at 15,500ft and 1650hp at 22,000ft. Not so good from around 18,000ft on up but it does have lower drag. 

As a substitute when the Sabre is having trouble? Maybe, but you have to engineer the 'power egg', get them into production, ship them to England, rework the Hawker design to take them and do it before the Sabre troubles are fixed. And if done in quantities of more than a few hundred, figure out where the R-2800s are going to come from.


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## tomo pauk (Jun 7, 2012)

Thanks for the time-line and power figures.



> And if done in quantities of more than a few hundred, figure out where the R-2800s are going to come from.



In this time-line, Packard is not building the Merlins, but something else. R-2800s?


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## Shortround6 (Jun 7, 2012)

The R-2800 is a bit too big and heavy to serve as a substitute Merlin. The US kept 1/3 (at most) of Packard production, some sources say as little as 20%. If Packard doesn't make Merlins that means no Merlin powered P-40s ( not much of a loss) and No Merlin Mustangs ( a much bigger loss) but it also means 36,000-44,000 fewer Merlins for British and Canadian production aircraft. and that is the big loss in this scenario. For existing US engines the R-1820 and R-1830 are too small. The R-3350 is too big and too late. The R-2800 is too big for many applications, It rather leaves the the R-2600 (Hercules replacement in some aircraft and since the Hercules and Merlin both worked on a number of aircraft it might be a small change) and the Allison V-1710, as "plug in" replacements for existing aircraft, at least in a physical size sense.

A Halifax or Lancaster with four R-2800s might be a wondrous airplane but either one with four R-2600s might require a whole lot less redesign. Hurri-bombers with V-1710s might work. 

In 1940-41 the British _NEED_ another source of engines to power the airframes they are already planning to make in 1942-43. They don't need a source of engines that won't be making large quantities of engines until 1943/44 and need new airframes to make use of the larger engines. They already have 4 engines larger than the Merlin in the pipeline themselves.


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## davparlr (Jun 7, 2012)

Could the turbo-supercharged Allison ala P-38 be a successful replacement for the Merlin XX used in the Lancaster and Mosquito? Maybe a bit heavier but probably a better performance at altitude. This would be a similar concept to the turbo-supercharged B-17 and B-24s.


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## Shortround6 (Jun 7, 2012)

Quite possibly. I don't know what the availability of the turbos was however, There may have been a shortage, there may have been no problem supply 40,000 more turbos. 

There is a maintenance issue however. The P-38s often had problems keeping all the exhaust and intake air ducting 'tight' and not leaking. I don't think this was well known (anticipated) in 1940-41 when the engine choice has to be made. 

I would further note that in the summer of 1940 the Allison in production was the long nosed "C" series engine. Just like many other manufacturers Allison had a number of "projects" they were working on which included the much improved "E" (P-39)and "F" (P-38 and high propped P-40) series engines and the two stage supercharger was on the drawing board at the time. Would increasing dependence on the Allison result in more resources being applied to increase development rate or would demands for increased production (even in a satellite/shadow factory) slow development?


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## wuzak (Jun 7, 2012)

There may also be a space issue for installing the turbo and intercooler - especially for the Mosquito.

I believe there was one experimental 2 speed V-1710. Maybe that is the short term solution, as per Merlin.


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## wuzak (Jun 7, 2012)

Also, the Lancaster's Merlins came in a Rolls-Royce developed power egg (not sure who actually made them). Something similar would have to be done for Allisons.


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## Shortround6 (Jun 7, 2012)

There may have been more than one, at least proposed or given a model designation, I am spot reading "Vees for Victory" and one version ("F" series) has cropped up already but not built. The very late war "G" series may well have had a two speed drive on one or more models.


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## gjs238 (Jun 7, 2012)

How feasible are Canadian Merlins?
How feasible is a "big block" version of the Allison? Ala DB 603.


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## Shortround6 (Jun 7, 2012)

Canadian Merlins? Not very feasible. No offence intended but a Canadian Merlin factory would have to be supplied (mostly) with US built machine tools. And hundreds of smaller parts would have to come from hundreds of US suppliers in any case. I don't think any US factory was totally self supplied. Allison actual made a fair amount of it's money in the late 20s and for most of the 30s supplying other US engine companies with crankshaft and rod bearings for instance. 

"Big Block" is a whole new engine and a tougher engineering proposition than the V-3420. Nothing but nuts and bolts in common and a whole new set of vibration problems to deal with.


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## wuzak (Jun 7, 2012)

gjs238 said:


> How feasible are Canadian Merlins?
> How feasible is a "big block" version of the Allison? Ala DB 603.



Do you mean an increased capacity version of the same engine, or do you mean a bigger new engine (as the DB 603 was)?

Not sure how much the bore could be taken out. There may be some room to extend the stroke, but I wouldn't think too much.

Or you could just use the bits from the V-1710 and join them together to make a bigger unit - like the V-3420.


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## Shortround6 (Jun 8, 2012)

A lot of car engines are designed from the start to have some "stretch" built into them so as to get the maximum use from the tooling and casting patterns. A extra 1/2 of block height or bore spacing isn't that big a deal. So a "small" engine weighs 20-30lbs more than a it should if designed tightly ( no extra capacity hiding anywhere) in a 3500-4000lb car. The car is rolling, not flying and the extra weight matters little to top speed or fuel economy, it does matter for acceleration but the percentage is small. 
Aircraft are flying and every pound of extra engine weight is a pound of cargo or fuel NOT carried. There is no real reason NOT to make the largest displacement engine the block/cylinders will support (like marketing in cars). In some countrys the care engines were/are taxed on engine size so being able to offer several engines that fit into different tax categories yet were built with the same tooling made sense. Again, there was no such restriction on aircraft engines. 

Airplane engines are very light for their displacement. AS a general statement it took until the 1950s-60s for even Formula I racing engines to reach the horsepower per pound of good aircraft engines of WW II. Their HP per cu in was obviously much higher


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## davparlr (Jun 8, 2012)

Shortround6 said:


> There is a maintenance issue however. The P-38s often had problems keeping all the exhaust and intake air ducting 'tight' and not leaking. I don't think this was well known (anticipated) in 1940-41 when the engine choice has to be made.



Was this an issue with the B-17/24? Except for the engine type, the turbo-supercharging section should not be significantly different.


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## wuzak (Jun 8, 2012)

The XB-38 was a V-1710 powered B-17, with turbos. The turbo set up remained as per B-17. One of the V-1710s had an exhaust leak causing a fire, damaging the aircrfat. That was fixed, but another exhaust leak caused another fire, this time severe enough that the aircrfat crashed and was destroyed.


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## wuzak (Jun 8, 2012)

I suppose if Packard weren't busy building Merlins they could have helped with development and production of the V-1710.

It seems to me that Allison had a lot going on with the V-1710 and V-3420 with all their myriad variations. Possibly Packard could have had responsibility for building and developing the V-1710 with Allison's guidance.

Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).

Can we expect to see a decent number of Griffons rolling off the line by mid 1943?

What can we use them for? Lancaster? B-17? Mosquito? Lightning?


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## GregP (Jun 8, 2012)

Shortround,

This goes back a couple of pages.

I know of two issue with the intake manifolds: 1) The aor-gas mixture was incompletly atomized. Tjhis was cured by plpacing a turbulator in the manifold. 2) The bands were such that two cylin der on one side got correct mixture, tqwo were rich, and two were lean. This was cured by shaping the trubulator like a hollow cone. When we build up an Allison, we use on late-model intake manifolds, and we have enough for our inventory.

I dispute taht fact taht everyone kn ew about Europen fuels becuase opur wearly planes arrived there jetted for American fuel and sufffered operational issues.

Last, taking the P-38 to "warmer eather" would have no effect. Once above 20,000 feet or so, whether youa re in the tropic or over Great Britian or germany, youa re in about teh same temperatures. The reason the P-38's suffered fewer issue in the pacific was they were running American gasoline and, once they were cured of other issues, they operated just fine. All that happened early in Pacific deployment is that the issues with European gasoline use were never there to stat with, ergo no detonation from excessive aromatics versus the jetting.


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## Shortround6 (Jun 8, 2012)

davparlr said:


> Was this an issue with the B-17/24? Except for the engine type, the turbo-supercharging section should not be significantly different.



It may not be different, I don't know how many problems the B-17 and B-24 had with leaky turbo plumbing but it is a sure bet that it was more than Lancasters and Halifax's had with their Merlin XX engines. This is sort of the point, somewhat over 2/3rds of the Packard engines built wound up in British planes. If Packard doesn't build Merlins what engine choice do the British have in the summer of 1940 to power their planes? An Allison "power egg" with turbo might be made to work but it may have more maintenance issues than the Merlin XX series. 
The Americans didn't have any great demand or need for the Merlin until the Merlin P-51 came along. While the use of the Merlin XX (V-1650-1) in the P-40 was useful and freed up a couple thousand Allisons for other other aircraft it wasn't a big deal for American planners at this time. 

For Wuzak's question:

"Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).

Can we expect to see a decent number of Griffons rolling off the line by mid 1943?"

I would refer people to this paper. http://www.enginehistory.org/References/WWII Eng Production.pdf

Which has figures for the major engine types by factory and by month. Packard figures are broken down by single stage and two stage engines per month. Building Griffons might require a third production line. 
It took until August of 1943 to get decent numbers of two stage engines to come of the line.


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## Shortround6 (Jun 8, 2012)

GregP said:


> I dispute taht fact taht everyone kn ew about Europen fuels becuase opur wearly planes arrived there jetted for American fuel and sufffered operational issues.



We may be getting confused as to which year we are talking about. In 1940 EVERYBODY who mattered knew the fuel was different. One reason the Americans were specifying low aromatic fuel was that the high aromatic fuel tended to dissolve (eat) certain rubber compounds used in American fuel systems. American 100 octane fuel had NO rich mixture response other than what you get going to a rich mixture. American 100 octane fuel was 100 octane running lean and just about 100 octane running rich _ONCE_ the got around to measuring rich response. Now in 1940/early 1941 there were darn few American planes actually being used by the British and certainly no American planes being flown by the Americans in Europe or any other combat theater. British 1940 100 octane fuel with it's 20% (or more) aromatic content, was good for about 115-125 octane ( or performance number) depending on batch. Since in 1939/40 the fuel specification did NOT list a rich mixture number limit as such. As more testing and research went on specifications were written to include the rich mixture response as a measured number and specifications for 100/120, 100/125 (fuel specification AN-F27), and 100/130(fuel specification AN-F28) were quickly written and very quickly superseded each other. the 100/125 may have been an american specification as a number of Allison engines were rated on it. The 100/130 was standardized between the US and the British in fairly short order though. The Americans changing their fuel systems to accommodate the high aromatic fuel. 
There are a number of things that go into fuel and fuel specifications. Fuel has to have a certain number of BTUs per gallon, certain gum and/or residue limits, it is held to certain vapor pressure and evaporation limits not to mention lead limits. There are something over 400 compounds that can be used in aviation gasoline. and different compounds or mixtures of common compounds react differently to the addition of certain other compounds, like lead. Some blends give a very significant increase in octane numbers with addition of small amounts of lead, other blends show only a modest increase with the addition of the same amount of lead. Some blends show a bigger change between lean and rich mixture ratings with the same amount of lead than other blends do. 
In 1940 The written specifications for American and British fuel spelled out the difference in aromatic compound content. By the middle of the war the Waukesha company had delivered hundreds of single cylinder test engines to oil refineries, research labs and government purchasing agencies to help make sure every body was on the same page as far as testing fuel goes. 

Now as more and more high octane fuel was wanted and as supplies of certain compounds changed and as different refining processes were brought online (cat cracked fuel behaves differently than straight run gasoline and straight run can vary depending on the oil field it comes from) the blends or allowable blends were changed to meet the production quotas. It was one of these changes that prompted the development of the Center venturi intake pipe on the Allison. By now it is 1943 and some of the "allowable" blends of 100/130 fuel are not the same as the older 100/125 and 100/130 fuel. Allison knew this and was working on the new manifold before the problem ever cropped up in Europe. It is just that events overlapped. There may have been a few batches of fuel that were less than perfect also. 
The "story" that American fuel was "good" and European (British, what other European nation was supplying fuel for American aircraft in 1943/44)fuel was "bad" needs a rethink. There is little point in "standardizing" fuel between allies if major differences are knowingly allowed. 



GregP said:


> Last, taking the P-38 to "warmer eather" would have no effect. Once above 20,000 feet or so, whether youa re in the tropic or over Great Britian or germany, youa re in about teh same temperatures. The reason the P-38's suffered fewer issue in the pacific was they were running American gasoline and, once they were cured of other issues, they operated just fine. All that happened early in Pacific deployment is that the issues with European gasoline use were never there to stat with, ergo no detonation from excessive aromatics versus the jetting.



You have to go a lot higher than 20,000ft and most air temperature charts do show a difference. There were charts for standard days and "hot days" let alone tropics. Differences could extend well into the 30,000ft range. 
P-38s also suffered problems in other theaters, just not as bad or as widely publicized. 

There were a number of contributing factors, mis-rigged turbo/throttle controls, poor piloting technique, the temperature ( and the planes operating in the tropics seldom spent as much time (several hours at a time) at high altitudes as the European planes), and the change in KNOWN fuel blend. Throw in a couple of 'poor' batches of fuel with a mixture of the 4 listed "factors" and you get the problem coming up a lot. Take away 2 or 3 of those factors, or even ONE, and the scope of the problem changes. 

Late war US fuel use the same high % of aromatics as the British did, especially when you get to things like 100/150 or the post war 115/145 fuel (AN-F-33)


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## tomo pauk (Jun 8, 2012)

Another post as a required reading.


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## Shortround6 (Jun 8, 2012)

Thank you Tomo and others.

I can certainly believe American planes had carburetors adjusted after going overseas. In some cases American units trained on 91 or 91/96 fuel in the states to conserve 100/130 fuel for combat theaters and not only had to adjust carburetors but needed timing changes to change over to the 100/130 fuel. Also a plane "adjusted for Southern California or Texas in Aug or Sept may need adjusting for best performance in England in Nov/Dec. Likewise a plane from Buffalo, New York in Feb might need a bit of adjusting in North Africa or in Darwin. Temperature shifts of 50-80 degrees F would not be uncommon and the equivalent air density change would be several thousand feet. Some units might want to adjust carbs for best performance. 

The questions we have now are not "if" something was done but "why" it was done. And trying to figure out the "correct why" and not legend or "hanger talk".


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## tomo pauk (Jun 8, 2012)

Shortround6 said:


> The R-2800 is a bit too big and heavy to serve as a substitute Merlin.



Thanks for bringing us back to the topic 
Wouldn't it depend upon the airframe that is about to receive the replacement? I can see the Spitfire as being too light for the R-2800, but not the P-51. We can take a look at the soviet examples - they re-engined the Lagg-3 and Yak-3 with the Ash-82, creating the La-5 and Yak-3U. 



> The US kept 1/3 (at most) of Packard production, some sources say as little as 20%. If Packard doesn't make Merlins that means no Merlin powered P-40s ( not much of a loss) and No Merlin Mustangs ( a much bigger loss)



Within a scope of this thread: how feasible is the P-51 with 2-stage V-1710/R-2800, for, say, Big Week to be operating in meaningful numbers (the Packard being second source for the V-1710 or R-2800)?



> but it also means 36,000-44,000 fewer Merlins for British and Canadian production aircraft. and that is the big loss in this scenario. For existing US engines the R-1820 and R-1830 are too small. The R-3350 is too big and too late. The R-2800 is too big for many applications, It rather leaves the the R-2600 (Hercules replacement in some aircraft and since the Hercules and Merlin both worked on a number of aircraft it might be a small change) and the Allison V-1710, as "plug in" replacements for existing aircraft, at least in a physical size sense.
> 
> A Halifax or Lancaster with four R-2800s might be a wondrous airplane but either one with four R-2600s might require a whole lot less redesign. Hurri-bombers with V-1710s might work.



How feasible would be the turbo V-1710s for the British bombers; installation a-la the XB-38? The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes). Beaufighter with V-1710 or single stage R-2800? The Hurricannes loosing the two-speed Merlins, while receiving V-1710s (Merlins go to the heavies)?



> In 1940-41 the British _NEED_ another source of engines to power the airframes they are already planning to make in 1942-43. They don't need a source of engines that won't be making large quantities of engines until 1943/44 and need new airframes to make use of the larger engines. They already have 4 engines larger than the Merlin in the pipeline themselves.



Of course they need the yet another source, and Packard was providing them with meaningful number of engines from 1942 on. Not producing the Merlin, it can produce V-1710 in same quantities (or bigger?). With one of their tasks now made easier, Allison can introduce the 2-stage variant easier/earlier? 
This should not be read as the 'Allison was every inch as good as Merlin' mantra, but something that should inspire the further discussion about the choices for the W. Allies that do not have US-built Merlins in the ww2.


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## krieghund (Jun 8, 2012)

If there wasn't any US production of the Merlin then the US would have probably arrived at this solution a lot earlier without the politics;

The P-51J with the V1710-119


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## wuzak (Jun 8, 2012)

tomo pauk said:


> Thanks for bringing us back to the topic
> Wouldn't it depend upon the airframe that is about to receive the replacement? I can see the Spitfire as being too light for the R-2800, but not the P-51. We can take a look at the soviet examples - they re-engined the Lagg-3 and Yak-3 with the Ash-82, creating the La-5 and Yak-3U.



Not sure that the performance would be there for an R-2800 Mustang.




tomo pauk said:


> How feasible would be the turbo V-1710s for the British bombers; installation a-la the XB-38?



Not very.

The turbo in the XB-38 was mounted in the standard nacelle in the wing, in its original location, not in the V-1710 engine module. The radiators for the V-1710s were in the wing leading edge between the nacelles, and not in the QEC.




tomo pauk said:


> The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes). Beaufighter with V-1710 or single stage R-2800?



V-1710s for Mossie FBs would be possible, but would require changes to suit those particular models. The single sage Allison may not be the best for all FB missions, though, and is definitely not good for PR, NF and B versions.

Most Beaufighters had the Hercules, which wasn't built in the US but had sufficient numbers for what they were being used. No need for the R-2800 here. The number of Merlin models is relatively small - about 600 and, I believe, built before US production of Merlins commences, so no need for a replacement.




tomo pauk said:


> The Hurricannes loosing the two-speed Merlins, while receiving V-1710s (Merlins go to the heavies)?



Maybe Hurricane production is cut earlier in favour of the Typhoon and the R-2800 Tornado (single stage). The latter is an interim fighter until the Centaurus powered Tempest II is ready, but since that arrived very late in the war it is essentially replacing the Hurricane.




tomo pauk said:


> Of course they need the yet another source, and Packard was providing them with meaningful number of engines from 1942 on. Not producing the Merlin, it can produce V-1710 in same quantities (or bigger?). With one of their tasks now made easier, Allison can introduce the 2-stage variant easier/earlier?



Having Packard involved would surely increase the amount of engineers available for development. If Allison assign some areas of development to Packard (like the V-3420) that would free up their own development time for the two stage project.


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## wuzak (Jun 8, 2012)

krieghund said:


> If there wasn't any US production of the Merlin then the US would have probably arrived at this solution a lot earlier without the politics;
> 
> The P-51J with the V1710-119



Why would taht be the case?

Before the P-51 was fitted with a 2 stage Merlin was there any push for a high altitude version from the USAAF?


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## Shortround6 (Jun 8, 2012)

tomo pauk said:


> Thanks for bringing us back to the topic



No problem  

Lets see if I can take these one at a time. 



tomo pauk said:


> Wouldn't it depend upon the airframe that is about to receive the replacement? I can see the Spitfire as being too light for the R-2800, but not the P-51. We can take a look at the soviet examples - they re-engined the Lagg-3 and Yak-3 with the Ash-82, creating the La-5 and Yak-3U.



The Ash-82 was more of a R-2600 sized engine. R-2600 "B" --1980lbs, Ash-82--1984lbs, Hercules XI--1850lbs, R-2800 A series with single stage two speed supercharger 2270lbs, R-2800 with two stage supercharger 2480lbs without inter-coolers and ducts. And that is just for the engines. The R-2800 needs a bigger propeller if you want to get the full benefit. At most times the R-2800 was giving about 15% more power than an R-2600 but also weighed about 15% more, a bit better in the power to frontal area ratio though. Like I said before some planes might not have too much trouble. Wellington with two R-2800s? Lots of room to shift things around to balance the weight. Beaufighter with two R-2800s? you have added over 1/2 ton as far forward as you can go with the weight. Halifax? maybe but while certainly more powerful you have added over a ton to the empty weight and if you use the power you WILL suck down more fuel. You have the power to lift it but you may need to beef up parts of the plane to stand up to the extra weight and power, like heavier landing gear. Possible but no longer a "plug in" replacement. 





tomo pauk said:


> Within a scope of this thread: how feasible is the P-51 with 2-stage V-1710/R-2800, for, say, Big Week to be operating in meaningful numbers (the Packard being second source for the V-1710 or R-2800)?



as far as the R-2800 goes. the Merlin instillation a P-51B/C went about 3246lbs not including fuel system or oil. The R-2800 system in the F6F-3 went 3917. Almost 700lbs more and ALL forward of the front wing spar unlike the P-51 which had several hundred pounds (400-500?) behind the rear spar? P-51 used a 11'2in 4 blade prop. F6F used a 13'2 in 3 blade prop. Unless you use a smaller prop the same thrust line is going to mean a lot of plowed up runways  
using a smaller prop may be a problem, I am not sure how much of the propeller disk in front of the engine really contributes to the thrust. The R-2800 is 52in in diameter or 4 ft 4 in. Merlin is 30 in wide (2ft 6in) and 40 something high but it tapers and is smaller in height at the front than the rear. 
North American may be able to design an R-2800 powered fighter, it may even use the same wing as the P-51, I just don't think much else would be the same. And you can pretty much kiss off long range bomber escort missions. You have a higher drag airplane with a thirstier engine. Not a recipe for long range. Army figured combat radius for bomber escort at 310mph true airspeed at 25,000ft for the cruise portion of the mission profile.

the 2-stage V-1710 is a possibility but it is far in the future in the summer of 1940. 



tomo pauk said:


> How feasible would be the turbo V-1710s for the British bombers; installation a-la the XB-38? The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes). Beaufighter with V-1710 or single stage R-2800? The Hurricannes loosing the two-speed Merlins, while receiving V-1710s (Merlins go to the heavies)?



1. "turbo V-1710s for the British bombers". I have mentioned this before, feasible but at the cost of higher maintenance costs. Power eggs with turbos could be a problem, turbos liked a little distance between the engine and the turbo, longer exhaust duct meant cooler exhaust hitting turbo blades and thus longer life for the turbo.
2. " The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes)". Again feasible but why? without WEP settings Allisons (in historical models) top out at 1325hp for take off. And the engine in the A-36 could only hold 1325hp to 3200ft without going into a WEP setting. Fitting low altitude Allisons to these planes means _really low_ altitudes. No choice of even trying to fly/fight at 10-20,000ft. Fitting higher altitude Allisons means too little power for take-off. 
3. Beaufighter? The Allisons won't give the power for either night fighter missions compared to Merlin XX or Hercules engines and won't give the needed power for strike missions. Weight and balance problems with R-2800s have been mentioned before.
4. Hurricanes? possibly the best choice but again you are really limiting the plane to well under 10,000ft. 





tomo pauk said:


> Of course they need the yet another source, and Packard was providing them with meaningful number of engines from 1942 on. Not producing the Merlin, it can produce V-1710 in same quantities (or bigger?). With one of their tasks now made easier, Allison can introduce the 2-stage variant easier/earlier?


Is Allisons task made easier? or do Allison have to help oversee production in a separate facility for the first few months/year? 
This also skips over the British problem, how much engineering time do they spend on all these alternate engine installations rather than getting the engine they want that will drop into the airframes with little or no engineering time spent?
Substituting R-2600s for Hercules engines might be simpler. It at least solves a big part of the power problem for the 4 engine bombers and thus frees up Merlins for other uses. 



tomo pauk said:


> This should not be read as the 'Allison was every inch as good as Merlin' mantra, but something that should inspire the further discussion about the choices for the W. Allies that do not have US-built Merlins in the ww2.



At times the Allison was every bit as good as the Merlin, unfortunately, the summer of 1940 was not one of those times. In the summer of 1940 the Allison supercharger was as good as the supercharger on the Merlin III and Merlin X, unfortunately the Allison "C" series reduction gear was suspect and the block needed a bit of beefing up. _AND_ Hooker had started his work and the Merlin XX was ready with the improved single stage supercharger. Allison had the improved "E" and "F" series engines in test but not ready for production just yet. you have choice of the Merlin with a somewhat proven track record (several thousand single speed engines built and second generation supercharger having passed tests coupled with two speed drive proven on Merlin X) compared to the promising but unproven Allison. Allison had to rework hundreds of their already delivered "C" series engines at their own expense in 1941 to bring them up to rated power. Building a factory to make "E" and "F" series engines could have been trouble free, it could also have been a disaster.


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## krieghund (Jun 9, 2012)

wuzak said:


> Why would taht be the case?
> 
> Before the P-51 was fitted with a 2 stage Merlin was there any push for a high altitude version from the USAAF?



The push that was there to put the Merlin into the P-51 would be the push to take the USAAF blinkers off and develop the appropriate supercharger the V-1710 which should have been done in the beginning of its development.


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## Edgar Brooks (Jun 9, 2012)

Shortround6 said:


> If Packard doesn't build Merlins what engine choice do the British have in the summer of 1940 to power their planes? .


They use Rolls-Royce engines, which is what they did, anyway. The contract, with Packard, was not signed until September 3rd., 1940, and the first engine was produced in September 1941.


> For Wuzak's question:
> "Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).


It was already thought of, and Packard were given a set of Griffon drawings at the same time as they received those of the Merlin.


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## wuzak (Jun 9, 2012)

Edgar Brooks said:


> It was already thought of, and Packard were given a set of Griffon drawings at the same time as they received those of the Merlin.



But not proceeded with obviously.

Any reason given?


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## Edgar Brooks (Jun 9, 2012)

None that I can find; the "gestation period," for the Griffon was possibly so long that the need for large numbers no longer existed once it was available.


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## Shortround6 (Jun 9, 2012)

Edgar Brooks said:


> They use Rolls-Royce engines, which is what they did, anyway. The contract, with Packard, was not signed until September 3rd., 1940, and the first engine was produced in September 1941.



I am sorry I didn't phrase that better. In the summer of 1940 the British were looking for ANOTHER source of engines that would not come on line until late 1941 or early 1942. Not engines to be delivered in 1940. The Deal was signed with Packard after the deal with Ford America fell through. The question in this thread is what other engine choices were there for this "alternative plant". Or failing this plant what other US engines could have filled in. 

My position is there isn't much choice of engine. 
It has to be an engine that can power first line combat planes 1 1/2 years to 4 (?) years in the future which rules out marginal engines like the Bristol poppet valve engines or more P&W R-1830s. It has to start delivering engines as soon as possible which rules out engines that are still in testing (or in flux, changing specifications of an engine while still tooling up is a sure way to delay deliveries) which, in 1940, rules out things like the Griffon, Sabre or Centaurus. It also has to be an engine the Americans can use or will use. American policy is that they will not allow American factories to tool up for and make weapons, engines and aircraft that the US services cannot/will not use. Should things in England go south (turn pear shaped- insert expression) the Americans don't want to be stuck with factories tooled up to make weapon types the Americans don't want like happened in WW I. It also has to be an engine that will fit into existing (design wise) or planned (near term) British aircraft. This again rules out the Griffon, Sabre, Centaurus. It does no good in 1942 to have a factory spitting out 300 Sabres a month if the Typhoon and the XXX medium bomber both turn out to be crap. It also does no good to be making hundreds of airframes a month if the selected engine is crap. 
So the English have two choices, the Merlin and the Hercules. Merlin is proven and shows a lot of development potential. Hercules shows potential but is unproven and difficult to make. From an American view point they already have a selection of radial engines but only one V-12 and that is just barely coming on line. According to some it has much more potential (NIH at work?)than the Merlin but any other American liquid cooled engines are years away from production. A second liquid cooled V-12 may prove useful to the Americans in the next few years. AS outlined in a previous post only the Wright R-2600 is in a position of offering the right amount of power, in a package of the right size/weight and being built in a numbers at all to be a viable alternative to the Merlin for British aircraft and that is as a Hercules substitute.

Even by process of elimination the Merlin comes out as the only logical choice.


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## Edgar Brooks (Jun 10, 2012)

One item, only occasionally touched on, but of paramount importance, is aircraft balance, aka CofG. It was decided, mid-1940, that fighters needed cannon, to cope with German bombers, and as ground-attack airframes. For the latter task, the Hurricane IIC was seen as the ideal, and, as early as August 1940, its appearance was urgently required. However, the (mere) extra 4" nose length meant that the (also preferred) larger oil tank could not be fitted, since that would have made the nose even longer, and pulled the CoG too far forward. 
Hawker were prepared to consider fitting the Griffon into the Hurricane, but this entailed raking the mainspars forward, to keep the CoG within limits, and the Air Ministry were not prepared to countenance this, telling Cam (who had drawings prepared) to forget it, and concentrate on the Tornado/Typhoon; 29-4-41, the decision was taken that no further development of the Hurricane should take place. To give you an idea how touchy the Hurricane was, on the Mk.I, if it was fitted with the Watts two-blade wooden propeller, armour plate could not be fitted behind the pilot.
The Spitfire IX coped with the Merlin 61 by having lumps of lead fitted near the tail wheel, and shifting the oxygen bottles to the rear; on the Griffon-powered XIV, even more lead was fitted into the fin. Bigger, heavier engines are all very well, but you need bigger, heftier airframes to cope; look at the size/weight of the Typhoon, compared to the Hurricane.


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## rinkol (Jun 10, 2012)

The two stage Merlin also had some major advantages that should be emphasized:

- relative early availability;
- inclusion of an intercooler from the beginning;
- compact layout (at least in comparison with the V-1710s having either the auxiliary stage supercharger or turbosuperchargers).

Even the single stage Merlin, from the XX version, had a two speed supercharger. In comparison with the versions of the V-1710 that were available during the war, this made it a much better choice for bombers such as the Halifax and Lancaster (note that the aforementioned planes would not benefit much from turbosuperchargers).


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## tomo pauk (Jun 10, 2012)

wuzak said:


> Not sure that the performance would be there for an R-2800 Mustang.



Why not? In case the 2-stage R-2800 can be fitted, the resulting plane is far less draggy heavy than the F4U. Sorta heavier more powerful Hayate?




> Not very.
> 
> The turbo in the XB-38 was mounted in the standard nacelle in the wing, in its original location, not in the V-1710 engine module. The radiators for the V-1710s were in the wing leading edge between the nacelles, and not in the QEC.



Thanks. 



> V-1710s for Mossie FBs would be possible, but would require changes to suit those particular models. The single sage Allison may not be the best for all FB missions, though, and is definitely not good for PR, NF and B versions.



Agreed, that's why I'm suggesting FB only, as it would freed up the Merlins for the other uses/verdions on the Mossies.



> Most Beaufighters had the Hercules, which wasn't built in the US but had sufficient numbers for what they were being used. No need for the R-2800 here. The number of Merlin models is relatively small - about 600 and, I believe, built before US production of Merlins commences, so no need for a replacement.



The need for the engines other than Hercules could arose in case the Hercules engines need to be used for the heavies, so 'something' built in the USA could do the task decently.



> Maybe Hurricane production is cut earlier in favour of the Typhoon and the R-2800 Tornado (single stage). The latter is an interim fighter until the Centaurus powered Tempest II is ready, but since that arrived very late in the war it is essentially replacing the Hurricane.



Well, I'd really love to see a 2-stage R-2800 in a Hawker in 1943 



> Having Packard involved would surely increase the amount of engineers available for development. If Allison assign some areas of development to Packard (like the V-3420) that would free up their own development time for the two stage project.



Seem we have differing opinions for this (making job easier for Allison). In case of Packard, that company did have had core manpower, experience in engine manufacturing, and the funding was historically allocated for them anyway (for Merlin production).


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## tomo pauk (Jun 10, 2012)

Shortround6 said:


> The Ash-82 was more of a R-2600 sized engine. R-2600 "B" --1980lbs, Ash-82--1984lbs, Hercules XI--1850lbs, R-2800 A series with single stage two speed supercharger 2270lbs, R-2800 with two stage supercharger 2480lbs without inter-coolers and ducts. And that is just for the engines.
> The R-2800 needs a bigger propeller if you want to get the full benefit. At most times the R-2800 was giving about 15% more power than an R-2600 but also weighed about 15% more, a bit better in the power to frontal area ratio though.



The lighter Ash-82 replaced the lighter M-105; the heavier R-2800 would replace the heavier V-1710. The intercoolers can go to to the place previously occupied by the cooler radiators. 
We can also take a look at the Spitfire, that 'swallowed' far heavier engine (Griffon) without too much trouble.
Thanks again for the numbers.



> Like I said before some planes might not have too much trouble. Wellington with two R-2800s? Lots of room to shift things around to balance the weight. Beaufighter with two R-2800s? you have added over 1/2 ton as far forward as you can go with the weight. Halifax? maybe but while certainly more powerful you have added over a ton to the empty weight and if you use the power you WILL suck down more fuel. You have the power to lift it but you may need to beef up parts of the plane to stand up to the extra weight and power, like heavier landing gear. Possible but no longer a "plug in" replacement.



Fair points.



> as far as the R-2800 goes. the Merlin instillation a P-51B/C went about 3246lbs not including fuel system or oil. The R-2800 system in the F6F-3 went 3917. Almost 700lbs more and ALL forward of the front wing spar unlike the P-51 which had several hundred pounds (400-500?) behind the rear spar? P-51 used a 11'2in 4 blade prop. F6F used a 13'2 in 3 blade prop. Unless you use a smaller prop the same thrust line is going to mean a lot of plowed up runways
> using a smaller prop may be a problem, I am not sure how much of the propeller disk in front of the engine really contributes to the thrust. The R-2800 is 52in in diameter or 4 ft 4 in. Merlin is 30 in wide (2ft 6in) and 40 something high but it tapers and is smaller in height at the front than the rear.



I've already covered the installation of the intercoolers, so they should balance the rest of the powerplant decently. 
As far as the prop goes, P-47 was using the 12,2 ft prop, 4 bladed, early on. NAA can be smart and use the system from the P-47 (extend able gear strut).



> North American may be able to design an R-2800 powered fighter, it may even use the same wing as the P-51, I just don't think much else would be the same. And you can pretty much kiss off long range bomber escort missions. You have a higher drag airplane with a thirstier engine. Not a recipe for long range. Army figured combat radius for bomber escort at 310mph true airspeed at 25,000ft for the cruise portion of the mission profile.



The R-2800 powered P-51 would be far less draggy than F4U, far less weight, with more internal fuel (assuming the disposition of the fixed fuel tanks as it was in 1944), it's able to carry 2 drop tanks from day one (unlike the P-47). Granted that it would be using more fuel than the real Merlin P-51, but also far less than the P-47/F4U.



> the 2-stage V-1710 is a possibility but it is far in the future in the summer of 1940.



Of course, but so is the 2-stage Merlin for the P-51. 



> 1. "turbo V-1710s for the British bombers". I have mentioned this before, feasible but at the cost of higher maintenance costs. Power eggs with turbos could be a problem, turbos liked a little distance between the engine and the turbo, longer exhaust duct meant cooler exhaust hitting turbo blades and thus longer life for the turbo.
> 2. " The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes)". Again feasible but why? without WEP settings Allisons (in historical models) top out at 1325hp for take off. And the engine in the A-36 could only hold 1325hp to 3200ft without going into a WEP setting. Fitting low altitude Allisons to these planes means _really low_ altitudes. No choice of even trying to fly/fight at 10-20,000ft. Fitting higher altitude Allisons means too little power for take-off.
> 3. Beaufighter? The Allisons won't give the power for either night fighter missions compared to Merlin XX or Hercules engines and won't give the needed power for strike missions. Weight and balance problems with R-2800s have been mentioned before.
> 4. Hurricanes? possibly the best choice but again you are really limiting the plane to well under 10,000ft.



1. Well, turbos were many things. Being simple was not amongst them.
2. 1-stage V-1710 for Mossie, why? Because the USA is not building Merlins, so the RAF/MAP need to do some reshufling of those. I was thinking more about the 8.80 SC ratio engines, not the really low level ones.
3. NF job is obvioulsy not for the 1-stage V-1710s. The strike fighter can use the lower weight and lower drag of the inline to make good for the loss of the ~10% of the power, and can also use the WEP (1590 HP at 4500 ft, no ram) for the, well, war emergency 
4. Not really so, with the 8.80 SC ratio engines. That should do up to 15000 ft.



> Is Allisons task made easier? or do Allison have to help oversee production in a separate facility for the first few months/year?


ng 
Packard was not a newcomer into engine business, and the whole US inline story (actually, the V-1710 story) starts receiving more funding, better priority and more government attention (positive, hopefully  )



> This also skips over the British problem, how much engineering time do they spend on all these alternate engine installations rather than getting the engine they want that will drop into the airframes with little or no engineering time spent?



Obviously the British would not re-engine all of their engines, but the designs that would still been serving them good in decent numbers. Using the US engine would free up their engine production for the other designs where such a change would prove troublesome, either from the production or performance standpoint.

Substituting R-2600s for Hercules engines might be simpler. It at least solves a big part of the power problem for the 4 engine bombers and thus frees up Merlins for other uses. 

You mean with Packard-built R-2600s? IIRC Beufighter was tried with R-2600 historically.



> At times the Allison was every bit as good as the Merlin, unfortunately, the summer of 1940 was not one of those times. In the summer of 1940 the Allison supercharger was as good as the supercharger on the Merlin III and Merlin X, unfortunately the Allison "C" series reduction gear was suspect and the block needed a bit of beefing up. _AND_ Hooker had started his work and the Merlin XX was ready with the improved single stage supercharger. Allison had the improved "E" and "F" series engines in test but not ready for production just yet. you have choice of the Merlin with a somewhat proven track record (several thousand single speed engines built and second generation supercharger having passed tests coupled with two speed drive proven on Merlin X) compared to the promising but unproven Allison. Allison had to rework hundreds of their already delivered "C" series engines at their own expense in 1941 to bring them up to rated power. Building a factory to make "E" and "F" series engines could have been trouble free, it could also have been a disaster.



Dang, nothing to dispute here


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## Shortround6 (Jun 10, 2012)

tomo pauk said:


> The lighter Ash-82 replaced the lighter M-105; the heavier R-2800 would replace the heavier V-1710. The intercoolers can go to to the place previously occupied by the cooler radiators.
> We can also take a look at the Spitfire, that 'swallowed' far heavier engine (Griffon) without too much trouble.
> 
> I've already covered the installation of the intercoolers, so they should balance the rest of the powerplant decently.
> As far as the prop goes, P-47 was using the 12,2 ft prop, 4 bladed, early on. NAA can be smart and use the system from the P-47 (extend able gear strut).



The M-105 was actually fairly close to the V-1710 in weight. According to some sources 1268lbs. With the radials there is some shift (small) in the engines center of gravity rearward in relation to the aircraft's center of gravity. The La-5 is about 14cm shorter than a Lagg-3, not a lot but every bit helps. The La-5 was nose heavy enough that armament was limited and we don't have good details on other equipment sights or ballast. P-51 intercooler and radiator were filled with a water/glycol mixture which weighs a lot more than air  Sticking the intercoolers under/behind the pilot gives you a P-47 without the turbo. You don't need the exhaust ducts but you need ducts to carry the intake air from the first stage of the supercharger to the belly mounted intercooler/s and then ducts to bring the intake air back to the engine carburetor/second stage. Intake air inlet needs to be near the 1st stage supercharger section. Cooling air for the intercooler can be brought in from under the engine (F6F or P-47) or from under belly scope but the intercoolers for the R-2800 do not weigh anything like the radiators on the Merlin unless you design and build a air/liquid intercooler for the R-2800 instead of the air/air system that they did use. 

You could use 12'2" props and extending landing gear, But every change from the Allison powered Mustang is more engineering time and more testing. 

Griffon required much larger radiators behind the CG than the Merlin did which helped balance things, plus ballast. 





tomo pauk said:


> The R-2800 powered P-51 would be far less draggy than F4U, far less weight, with more internal fuel (assuming the disposition of the fixed fuel tanks as it was in 1944), it's able to carry 2 drop tanks from day one (unlike the P-47). Granted that it would be using more fuel than the real Merlin P-51, but also far less than the P-47/F4U.



I am not sure where the far less drag is coming from. Yes you have a smaller, lighter wing but moving the intercoolers from behind the engine to the rear/belly of the fuselage may not be a low drag option. We know that a radial P-36 had 22% more drag than P-40 so even if the bigger diameter (and greater appetite for air) R-2800 installation only has 12-15% more drag than the Merlin that will mean a 12-15% higher fuel burn even if you can keep the R-2800 from having to operate at a rich mixture setting. 
A P-51D clean can do 335mph at 25,000ft burning 59 gallons an hour. A Corsair at 21,500 ft and doing 282mph is burning 61.2gallons and hour and at 338mph at 21,500ft is burning 127 gallons an hour. It has to shift into rich mixture to hit this speed. 
A P-47 at 25,000ft clean burns 95 GPH to do 300mph and 145GPH to do 337mph. 





tomo pauk said:


> Of course, but so is the 2-stage Merlin for the P-51.



True, neither one should be a consideration for what engine to pick in 1940. 



tomo pauk said:


> 2. 1-stage V-1710 for Mossie, why? Because the USA is not building Merlins, so the RAF/MAP need to do some reshufling of those. I was thinking more about the 8.80 SC ratio engines, not the really low level ones.
> 3. NF job is obvioulsy not for the 1-stage V-1710s. The strike fighter can use the lower weight and lower drag of the inline to make good for the loss of the ~10% of the power, and can also use the WEP (1590 HP at 4500 ft, no ram) for the, well, war emergency
> 4. Not really so, with the 8.80 SC ratio engines. That should do up to 15000 ft.



The Allisons are are bit late to the game. There are two basic models using 8.80 gears that need to concern us. The F3R (-39) model which was good for 1150hp take-off and 1150hp at 11,700ft, While not in production in 1940 we may assume it was in the planning stages. WER is not approved in US service until Dec 1942 although the British were using high than book pressure much earlier. These engines do not show up in production until the summer of 1941 and are eventually cleared for 1490hp at 4300ft. 
The Merlin XX which was coming into British service in the summer of 1940 and was the Engine that Packard signed to produce was good for 1280-1300hp for take-off and 1240hp at 11,500ft low blower and 1120hp 18,500ft high blower at 12lbs boost. If the British use the higher boost limits for the XX they can get 1480hp at 6,000ft low blower and 1480hp at 12,500ft high blower. The later F4R Allison engine used the P-40 K was strengthened and while rated at 1325hp for take-off and 1150 at 12,000ft it was rated for 1580hp WER at 2500ft. While the beginnings of this version go back a ways it did not enter production until late 1941 and the first P-40K with one does not roll out the factory door until May of 1942. 
Even with 8.80 gears too much power is being given up at all but the lowest altitudes (under 5000ft) to make this a good choice. Coupled with the 10% or so loss of power for take-off (unless over boosting is used) and it really looks less than attractive. 



tomo pauk said:


> Obviously the British would not re-engine all of their engines, but the designs that would still been serving them good in decent numbers. Using the US engine would free up their engine production for the other designs where such a change would prove troublesome, either from the production or performance standpoint.
> 
> Substituting R-2600s for Hercules engines might be simpler. It at least solves a big part of the power problem for the 4 engine bombers and thus frees up Merlins for other uses.
> 
> You mean with Packard-built R-2600s? IIRC Beufighter was tried with R-2600 historically.



I believe there were a few other airframes that got R-2600s on an experimental basis. There was a plan to build Short Stirlings in Canada powered by R-2600s, with two airframes converted. edit> or 4 airframes with 2 flown?<

The R-2600 maybe a viable replacement for the Hercules.

Edit> Later versions of the Merlin XX include the Merlin 21 used in early Mosquitoes, pretty much the same ratings as the XX, The Merlin 23 with 1390hp available for take-off and 1435hp at 11,000ft using 16lbs boost, used in the Mosquito Mosquito I, II, IV, VI, XII and XIII and the Merlin 25 with 1610hp for take off and 1510hp at 9,250ft using 18bs boost used in the Mosquito VI and XIX. Packard versions sometimes varied by 20-30hp but Packard engines include the Merlin 31 and 33 ( a Merlin 23) used in Canadian and Australian Mosquitos. The Merlin 38 used in Lancaster Is and IIs (1400hp take off) and the Merlin 224 225 also used in Lancasters Mosquitoes respectively with 1635hp for take-off and 1680hp at 2500ft in low blower at 18lbs. None of these are two stage engines. 
In 1940 these higher powered versions were in the future and needed 100/130 fuel and engine modifications to reach 18lbs of boost. 12-14lbs boost was achievable with with British 1940 100 octane fuel. 
Perhaps the V-1710 could have been developed to reach these power levels. A two speed supercharger drive would have helped take-off power a lot. It would have been worth an easy 100 hp for the take-off ratings.


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## KiwiBiggles (Jun 11, 2012)

Shortround6 said:


> I am not sure where the far less drag is coming from.



Smaller _laminar flow_ wing, without the ghastly (from an aerodynamic POV) inverted gull-wing of the F4U. I know the 90° wing/fuselage junction of the F4U is very efficient, but the P-51 is quite slab-sided anyway, so its interference drag at the root would be quite low. The drag coming off that kink in the F4U wing would swamp any gains at the root. I think the fuel consumption figures you quote bear this out.


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## tomo pauk (Jun 11, 2012)

Plenty of good points, SR6, thanks 



Shortround6 said:


> The M-105 was actually fairly close to the V-1710 in weight. According to some sources 1268lbs. With the radials there is some shift (small) in the engines center of gravity rearward in relation to the aircraft's center of gravity. The La-5 is about 14cm shorter than a Lagg-3, not a lot but every bit helps. The La-5 was nose heavy enough that armament was limited and we don't have good details on other equipment sights or ballast.



The armament of the La-5 was of bigger weight than of Lagg-3: 2 cannons vs. 1 cannon 2 LMGs. With installation of the heavier engine, the 2 HMGs are also out from the plain P-51.



> P-51 intercooler and radiator were filled with a water/glycol mixture which weighs a lot more than air  Sticking the intercoolers under/behind the pilot gives you a P-47 without the turbo. You don't need the exhaust ducts but you need ducts to carry the intake air from the first stage of the supercharger to the belly mounted intercooler/s and then ducts to bring the intake air back to the engine carburetor/second stage.



Merlin P-51 needed to cool the both the engine and intercooler via the aft belly radiator, so the fuselage changes were undertaken in order to provide for that. This time around, the air ducts would be installed to feed the inter cooler radiators.
Agree about air being of lower weight than the water/glycol mix 



> Intake air inlet needs to be near the 1st stage supercharger section. Cooling air for the intercooler can be brought in from under the engine (F6F or P-47) or from under belly scope but the intercoolers for the R-2800 do not weigh anything like the radiators on the Merlin unless you design and build a air/liquid intercooler for the R-2800 instead of the air/air system that they did use.



No quarrels about that. 



> You could use 12'2" props and extending landing gear, But every change from the Allison powered Mustang is more engineering time and more testing.



Agreed again. We could note the Merlin Mustang was delayed also, airframes waiting for the engines. In this time line, the R-2800s being produced by yet another capable manufacturer such a hiccup is less likely to happen (not likely at all?).



> Griffon required much larger radiators behind the CG than the Merlin did which helped balance things, plus ballast.


 
No free lunch, even for the redoubtable Spitfire 
The radiators at the Griffon spitfires were mounted far more in front than it was case for the P-51. Circa twice as close to the CoG, Spit XII/XIV vs. P-51B-K.



> I am not sure where the far less drag is coming from. Yes you have a smaller, lighter wing but moving the intercoolers from behind the engine to the rear/belly of the fuselage may not be a low drag option.



The wing is still of the laminar flow type, of smaller profile and area. The Merredith effect is still there. So the drag reduction is no problem, P-51 vs. F4U.



> We know that a radial P-36 had 22% more drag than P-40 so even if the bigger diameter (and greater appetite for air) R-2800 installation only has 12-15% more drag than the Merlin that will mean a 12-15% higher fuel burn even if you can keep the R-2800 from having to operate at a rich mixture setting.
> A P-51D clean can do 335mph at 25,000ft burning 59 gallons an hour. A Corsair at 21,500 ft and doing 282mph is burning 61.2gallons and hour and at 338mph at 21,500ft is burning 127 gallons an hour. It has to shift into rich mixture to hit this speed.
> A P-47 at 25,000ft clean burns 95 GPH to do 300mph and 145GPH to do 337mph.



Thanks for the figures.
The R-2800 P-51 will have to use the 2x110 gals drop tanks (instead of more common 75 gals), and the range after those are dropped would be less (vs. Merlin P-51, same int. fuel). 

For the rest of the post - later, really got to go to bed


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## Shortround6 (Jun 11, 2012)

tomo pauk said:


> The wing is still of the laminar flow type, of smaller profile and area. The Merredith effect is still there. So the drag reduction is no problem, P-51 vs. F4U.



The laminar flow is debatable, you will get people arguing both sides. The wing is smaller in profile and area ( and not fabric covered . Meredith effect may take some work. You need a good heat source for the Meredith effect to really work. A V-1650-3 Merlin had a total cooling requirement of 777hp being dissipated by the radiator/oil cooler and inter cooler I believe. 120hp of that is from the intercooler. Granted the intercooler of the R-2800 may be trying to get rid of more heat than the Merlin's intercooler radiator but even at 200hp worth of heat (a WAG) it may not be worth the bulk of the duct. In theory it can be done but theory and practice seemed pretty far apart. Getting exhaust thrust to work on radial engines takes a bit of work also. It is a trade off between thrust and drag. the highest thrust for a radial engine will use an individual stack for each cylinder but that also means the highest drag although it also may be the lightest exhaust system. The F4U-1 and F6F-3 did not use exhaust thrust although later models did. 

Another problem with the Fat-51 is the extra weight, even _if,if,if,if_ you can get the CG right (reposition the wing?) you have added over 700lbs (minimum) to the empty weight of the plane which went from 7325-7580lbs (with fuselage tank?) "B""C" basic weight (empty +trapped oil + guns + pyrotechnics) this is going to mean higher take-off and landing speeds and without beefing up the structure, some bent airplanes in combat. The P-51 was good for 8 "G"S at 8000lbs. any increase lowered the allowable "G" limit. at 9,000lbs it is good for 7.11 "G"s the Fat-51 is over 10,000lbs with 4 guns and normal wing tanks. 6.4 "G"s. and at 10,500lbs ( rear tank full even if you can get the CG to work for combat) and you are down to 6.09 "G"s. there is a 50% safety factor but it has gone from 12 "G's to just over 9 at this point. The bigger engine and prop may require a larger tail and on it goes and goes. The Fat-51 will weigh with 110 gallon tanks what a Merlin-51 would weigh with the next size tanks. 

Don't be too tired to work, stay safe.


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## tomo pauk (Jun 12, 2012)

Thanks 

All this debate, or my trying to 'engineer' the P-51 around something other than Merlin points at the fact that Merlin Mustang was a such an outstanding airplane - with R-2800 'shoehorned' on it, it looses the endurance (at least that); with 2 stage V-1710 (as those mounted at P-63A, so early-mid 1944 time frame) the performance at 20000-35000 ft is not that great as with Merlin.

Some other questions: in case the RAF is really lacking the engines for their heavy bombers, how about introducing Liberator in the night bomber units (British-built heavies assume more the task of ASV, to balance this out)? Maybe the (X)B-28 gets produced, despite being only a twin? The 2-stage Packard Merlins are available for the RAF only in 1944, so the 2-stage V-1710s are used in that year?


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## wuzak (Jun 12, 2012)

tomo pauk said:


> Some other questions: in case the RAF is really lacking the engines for their heavy bombers, how about introducing Liberator in the night bomber units (British-built heavies assume more the task of ASV, to balance this out)? Maybe the (X)B-28 gets produced, despite being only a twin? The 2-stage Packard Merlins are available for the RAF only in 1944, so the 2-stage V-1710s are used in that year?



What time frame are you talking?

The Liberator had more range than the British heavies, especially when bomb bay fuel tanks could be used as large bomb loads were not required.

On the other hand it lacked the bomb bay flexibility that the Halifax and Lancaster offered, and could not carry the larger bombs (ie the 4000lb HC "cookie") that BC favoured from 1943.

When would the XB-28 have appeared?


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## Glider (Jun 12, 2012)

tomo pauk said:


> Thanks
> 
> Some other questions: in case the RAF is really lacking the engines for their heavy bombers?


If the RAF ran out of Merlin engines for the Lancaster there was the Lancaster II with Hercules.


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## Shortround6 (Jun 12, 2012)

If you can stick R-2600s into a Short Stirling you can stick them in a Halifax or even a Lancaster, may not help performance but shouldn't hurt it too bad either. 

probably wouldn't do much for the Mosquito though


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## wuzak (Jun 12, 2012)

Shortround6 said:


> If you can stick R-2600s into a Short Stirling you can stick them in a Halifax or even a Lancaster, may not help performance but shouldn't hurt it too bad either.
> 
> probably wouldn't do much for the Mosquito though


 

No, it wouldn't.

But for each Lanc or Halifax with Merlins you get 2 Mossies and 4 Spitfires....


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## tomo pauk (Jun 13, 2012)

2 Mossies _or_ 4 Spitfires? 
Seem like Packard building the R-2600s (so the British can use those in bombers), and no P-63 (P-51 gets 2 stage V-1710s instead) is 'our' best bet for non-US Merlin scenario



wuzak said:


> What time frame are you talking?
> 
> The Liberator had more range than the British heavies, especially when bomb bay fuel tanks could be used as large bomb loads were not required.
> 
> ...



Time frame from Spring of 1943 on.

Do we know what was a possible bomb 'layout' of the B-24s (bomb sizes x bomb count)?

The XB-28 first flew on 26th April 1942, so the B-28 in service maybe from Autumn 1943?


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## gjs238 (Jun 13, 2012)

So if Packard ended up building R-2600's, what would the US do with it's 1/3 of the engines?


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## tomo pauk (Jun 14, 2012)

Okay, I'll bite 
There would not be any surplus of the R-2600s for the US needs, but the R-3350 will gain more or/and earlier some extra resources, plus manpower to iron out the bugs?


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## Shortround6 (Jun 14, 2012)

Wright seemed to have problem sharing responsibility with licensee companies. P&W tended to get along much better with theirs but NONE of the P W licensee plants did ANY development work on the engines. They did come up with new ways of making the parts though. last Packard air cooled radial was the Diesel about 1930-31. 
The R-3350 went through almost a total revamp between the early models of the late 30s and even the the ones used in the first B-29s (which still needed a lot of work). Wright also did major redesigns of the R-1820 and the R-2600.


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## tomo pauk (Jun 19, 2012)

Thanks for the response.

In a time frame where the Packard builds R-2800s 'stead of V-1650s: how much of the influence upon the arrival of the C-series R-2800s did have the delivery of the six Sundstrand center-less grinders to the British (to aid on the Centaurus production, IIRC)? With R-2800 seen as the main production effort, maybe those are diverted later/never, so the C-series is built earlier; Hawker's fighters also getting those?


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## Shortround6 (Jun 19, 2012)

the time delay I have read about is 6 weeks (?). The Sundstrand center-less grinders were to bail Napiers out on the Sabre. Annoying to P&W and pointing out that machine tools were in limited supply but not so limited that entire programs had to be reshuffled or new versions of planes designed. Even if the Grinders had not been "borrowed" a new batch could have been delivered before an R-2800 powered Typhoon could have been designed, built, test flown, and the retooling done at the Typhoon factories. 

The Centaurus was almost 17% bigger than the R-2800. Good as the R-2800 was it was going to be hard pressed to make up that displacement difference in the later Hawker aircraft.


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## tomo pauk (Jun 20, 2012)

Thanks to point me towards the right delivery place.
As good the Centaurus was, it was not in service for the ww2. The 2-stage C-series R-2800 (like the one powering the F4U-4) was every bit as good as the Centaurus of 1945; displacement difference percentage is far lower than at DB-601/605 vs. Merlin, for example. 
As for 'designing a Typhoon with R-2800', they already have had something very much like that (Tornado + early Centaurus):

http://i37.photobucket.com/albums/e68/GTwiner/ALT%20RAN%20FAA/CentTornado.jpg


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## Shortround6 (Jun 20, 2012)

True but if they decided to scrape the Sabre (and reassign the engineers and draftsmen) the Centaurus might be as good an alternative as trying to use the R-2800. 
From Wiki, take as you will:

"The first Tempest Mk.II, LA602, flew on 28 June 1943 powered by a Centaurus IV (2,520 hp/1,879 kW) driving a four-blade propeller"

" This was followed by the second, LA607, which was completed with the enlarged dorsal fin and first flew on 18 September 1943"

"Orders had been placed as early as September 1942 for 500 Tempest Mk.IIs to be built by Gloster"

At some point it was decided that ALL Tempest IIs would be _tropicalized._

"in 1943, because of priority being given to the Typhoon, a production contract of 330 Tempest Mk.IIs was allocated instead to Bristol, while Hawker were to build 1,800. This switch delayed production even more"

"The first Tempest II was rolled off the line on 4 October 1944"

Apparently it didn't enjoy the highest priority


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## Jugman (Jun 28, 2012)

GregP said:


> For the sake of discussion, I’d like to throw out the following. The US Congress contracted for the Allison V-1710 and development started in 1929. They anticipated a high-altitude requirement and developed a turbo-supercharger system for the Allison V-1710. It wasn’t perfect but was exactly what was contracted for. After the prototype P-39 had some issue, they deleted the turbo-supercharger from the aircraft and all subsequent fighters except the P-38.



So you have a contract number for this very elusive contract. The first contract I know of is BuAer contract No. 17952 for one "GV-1710-2" (Allison model VG1710) dated June 28, 1930. All following contracts are either USN, USAAC/USAAF, or foreign in origin.

WRT turbos. There were two *PRODUCTION* fighters (P-43 and P-47) and virtually all of the fifty and sixty series fighter, as well as the P-71, did or were to have them. There were several USN fighters with them as well.



> Unfortunately, the US Congress owned the design, lock, stock, and barrel. I submit that they should have taken the simple step of appointing an Allison manager for the government and delegating him the authority to oversee improvements to the engine.



Do you have any proof to backup this claim? If this were even remotely true there would be a huge paper trail. Yet all the authoritative sources I have ever seen make no mention of this highly peculiar and rather bizarre arrangement. 




> We still would have needed the time to sort out the issues we found in Europe with the early P-38 deployment. Those issues were the intake manifolds and running on European fuels, with had a much larger percentage of aromatics than did American fuel. Once these were sorted out, the engine problems “went away” and the P-38 had no more difficulties at high altitudes. Most were transferred to the Pacific where they gave yeoman service and were the mount of our two top-scoring Aces, Bong and McGuire.



Not according to the AAF "Pilot's Information file" or several NACA documents (NACA WR-E-164 for example). The assertion that the various fuel issues (fuel condensing in the intake manifold, poor TEL distribution between cylinders and spark plug fouling) were caused by Eurapean fuel or climate are smiply fales. These issues were noted months before any P-38s were operational in the UK. Furthermore corrective measures (the "Madame Queen" intake pipe being the major one) were introduced about the time the P-38J became operational. Before the P-38J these issues were considered relatively minor nuisances. Existing engine were to be retrofitted only at overhaul and not immediately. Obviously retrofitting aircraft in Europe first would have alleviated much of the in theater difficulties.


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