P-40 what-if

[Clay_Allison]

I was thinking about the P-40 and the reasons it wa considered a stopgap at best. What if, though, the P-40 had been reengined, not with the Merlin (as in the P-40F) but with the RR Griffon (if it had been turned over to an American comany for development when it was de-prioritized). Would that have worked?

 

[davebender]

It would be 1943 before a Griffon powered P-40 entered operational service. By then there are better choices available. Heck you could produce a Griffon powered P-51 during early 1943.

 

[Clay_Allison]

The first Griffon engine was run in 1933, I think that it would have been available before Jan 1942 if we had wanted it.

 

[claidemore]

Rolls Royce had started developing the R version engine in 1933 (Schnieder Trophy R engine), but that project was shelved. Actual Griffon development started in 1939.

The first Spitfire with a Griffon (RG 2SM) flew in November 1941, the first operational ones in October 42 (Griffon III).

 

[davebender]

There's our benchmark for availability.

The P-51 (a British financed project) was flying during 1941. Why not specify that it should use a Packard built RR Griffon engine rather the the Allison? It also could be operational around October 1942, entering mass production ILO the P-47.

 

[claidemore]

There's our benchmark for availability.

The P-51 (a British financed project) was flying during 1941. Why not specify that it should use a Packard built RR Griffon engine rather the the Allison? It also could be operational around October 1942, entering mass production ILO the P-47.

Probably because the Allison was available right there in the USA, already operational, and the P51 was doing +400mph with it, which made it the fastest plane at low alt in its class at that time. Kind of a "if it works don't fix it" scenario.
They only switched the P51 to a Merlin because of the experiment done with it by RAE, which showed such dramatic improvement that it could not be ignored. Had they done a similar experiment with a Griffon, they might have used it instead, except that the Merlin had already been proven in combat and in volume production, while the Griffon was still being put out in low numbers at a low rate of production.

 

[davebender]

The same reason it was used in the P-38, P-39 and P-40. But if we're going through the trouble of manufacturing the Griffon engine in the USA then it should power the P-51 rather then the less capable P-40.

 

[BombTaxi]

It would not have been worth manufacturing the Griffon in the USA though - as claidemore points out, it was an untried design. The Merlin was a combat-proven design which gave the Mustang best-in-class performance. Why sacrifice that advantage for an engine which offered little at the time but a host of unknowns in terms of life, ease of maintenance and overall impact on performance? From the point of view of the original British purchasing mission that commissioned the Mustang, there were some thousands of technicians in the RAF who were well used to working with the Merlin, and production facilities which could provide considerable operational as well as technical expertise to US plants. The Griffon would throw away those huge advantages.

 

[Marshall_Stack]

They only switched the P51 to a Merlin because of the experiment done with it by RAE, which showed such dramatic improvement that it could not be ignored.

I have read that the USAAF was also experimenting with the Merlin P-51 at the same time as the British.


Didn't the Griffon have more "room to grow" than the Merlin?

 

[Colin1]

Rolls-Royce
did in fact carry out a design study on a Griffon 61-engined Mustang. For some reason they chose a mid-engined configuration over the proven successful conventional layout.
They arrived at the somewhat obvious conclusion that a major redesign would have been necessary and that this would have required major redesign once again if the engine, in later marks, became longer.
The Griffon Mustang was never built although Mustang AM148 was earmarked for a Griffon installation. They did get as far as a mock-up with the cockpit moved forward and other necessary changes.
A Griffon 57 did eventually see Mustang duty in P-51D N7715C as a racer based in Idaho Falls. It was in the conventional position driving a modified de Havilland 6-bladed contra-prop screw.

The attachment, though a racer, gives a reasonable idea on how it may have looked in service

 

[davebender]

Nobody is going to discontinue the RR Merlin. That would be insane. But you could certainly make an argument for having Allison manufacture the RR Griffon or Merlin ILO their own design.

 

[MikeGazdik]

Here is a current Griffon engined Stang, I saw it in 07 in Columbus, Ohio. Well actually I drooled on it.

 

[Clay_Allison]

It would not have been worth manufacturing the Griffon in the USA though - as claidemore points out, it was an untried design. The Merlin was a combat-proven design which gave the Mustang best-in-class performance. Why sacrifice that advantage for an engine which offered little at the time but a host of unknowns in terms of life, ease of maintenance and overall impact on performance? From the point of view of the original British purchasing mission that commissioned the Mustang, there were some thousands of technicians in the RAF who were well used to working with the Merlin, and production facilities which could provide considerable operational as well as technical expertise to US plants. The Griffon would throw away those huge advantages.

For the potential of developing its' many design features and making a leap forward in technology.

 

[davebender]

That potential needs to be recognized before someone pours millions into research development. Frankly I'm not convinced the U.S. Army Air Corps knew what a good liquid cooled aircraft engine looked like. Which is strange considering that American air cooled radial engines were cutting edge.

 

[drgondog]

It would not have been worth manufacturing the Griffon in the USA though - as claidemore points out, it was an untried design. The Merlin was a combat-proven design which gave the Mustang best-in-class performance. Why sacrifice that advantage for an engine which offered little at the time but a host of unknowns in terms of life, ease of maintenance and overall impact on performance? From the point of view of the original British purchasing mission that commissioned the Mustang, there were some thousands of technicians in the RAF who were well used to working with the Merlin, and production facilities which could provide considerable operational as well as technical expertise to US plants. The Griffon would throw away those huge advantages.

Pretty good summary - for both sides of the pond for a critical resource.

Another question which I don't have answer to, is what was the specific fuel consumption of Griffon vs the 1650-1, 3 and 7. If it was less, then the truly great advantage of the 51 (extreme range with high perfromance) is somewhat mitigated.

 

[claidemore]

According to AFDU the Griffon engined Spitfire Mk XIV used 1 1/4 times as much fuel as the Merlin engined Spitfire Mk IX. (10-15 gallons per hour more than Mk VIII.)

Not sure how that would equate to the P51 airframe, but a guestimate of 20-25% decrease in range would seem reasonable.

 

[drgondog]

According to AFDU the Griffon engined Spitfire Mk XIV used 1 1/4 times as much fuel as the Merlin engined Spitfire Mk IX. (10-15 gallons per hour more than Mk VIII.)

Not sure how that would equate to the P51 airframe, but a guestimate of 20-25% decrease in range would seem reasonable.

If the 10-15 gal/hr was at cruise settings it would have a corresponding impact on combat radius - I suspect your 25% number would be about right.

That would have had a huge impact on effectiveness in first half of 1944 going deep to Stettin, Berin, Leipzig and Munich.

 

[BombTaxi]

For the potential of developing its' many design features and making a leap forward in technology.

Agreed we know now, with the gift of hindsight, that the Griffon had huge potential. But the USAAF didn't know that in 1942, and 20000ft above Germany, in combat with the LW was never going to be the place to try and find out...

Interesting info about the fuel consumption - thanks guys. I hadn't realised just how dramatic the effect of the Griffon could be in that respect.

 

[davebender]

20000ft above Germany, in combat with the LW was never going to be the place to try and find out...

I agree. However that happens a lot during wartime. Sherman tank crew going into battle for the first time thought they had the best tank on the battlefield. Then they encountered the Panther tank. The P-38 fighter aircraft was realistically tested for the first time at 30,000 feet over Germany. That didn't go over too well either. The Luftwaffe attempted to use the Me-110 fighter-bomber as a long range bomber escort during 1940. The B-17 was such a bad dude that it could bomb Germany during the daytime without a fighter escort. Or so they thought.....

 

[BombTaxi]

True, there was much learned in combat, although I personally tend to see much of it coming from mistaken doctrine or lack of foresight (said, of course, with the priceless and inexcusable benefit of hindsight). It was not something anyone would want to do by choice though, when a working solution was already on hand.

Slightly OT, your final comment about the B-17 reminds me of something I read while doing a bit of research for a model of an RAF Fortress I that I hope to build soon. Apparently, the USAAF warned the RAF that the B-17C was not sufficiently armed to operate unescorted over Germany, and that altitude alone would not save it. They were right - the RAF suffered horrible problems with mechanical failures and crew capability issues due to high altitude flight, and the LW got fighters up high enough to intercept and destroy several aircraft. The RAF abandoned the type after less than 50 sorties and concentrated on night bombing instead.

Fast foward a year or so, and the 8th AF arrives with newer, admittedly more heavily armed B-17s and... repeats the folly again, although in a slightly different manner. Strange how some lessons can be unlearned isn't it?