Mustang Mk IA Photo

[ColFord]

I could list the multiple AIR, AVIA and other files held in the UK Archives as my sources, and the long, long list of RAF and Commonwealth Air Forces personnel who flew and maintained them. But unfortunately as the full set of detailed sources and information involves other researchers who have spent many years on this subject and are in the process of finalising the publication of their work as a commercial publication, I have limitations on what I can share at this time.

Also I made no statement about the RAF's engine modifications being used by Allison or the USAAF. I noted that RAF provided reports on what they were doing with the Allison engines in their service to increase service performance. What USAAF and Allison did or did not do with the information contained in those reports is not something I have focussed on.

 

[MIflyer]

The V-1710 did not have a manifold pressure regulator before the version used in the P-40M. The regulator also was included in the later P-38's where it caused problems since it tended to fight the turbo regulator. In at least some F-5 recon aircraft the manifold pressure regulator was removed since it interfered with the smooth flight needed for photography.

The V-1710's used in the Mustang Mk I and Mk IA (V-1710-39) military power rating was 1150 HP at 11,700 ft, with 44.6 in MAP and War Emergency power of 1490 hp at 4300 ft with 56 in MAP. Supercharger gear ratio is 8.8:1

The A-36A's engine (V-1710-87) was rated at Military Power of 1325 hp at 2500 ft and War Emergency power of 1500 hp at 5400 ft with 52 in MAP. Supercharger gear ratio is 7.48:1

The P-51A's V-1710-81 engine was rated at 1125 hp at 15,500 ft and 44.5 in MAP and War Emergency power of 1410 hp at 9500 ft and 57 in MAP. Supercharger gear ratio is 9.60:1 Obviously the P-51A was set up for better high altitude performance than the others.

Note that the P-51A is quoted as having basically the same top speed as a Spit IV at 20,000 ft, although the Spit IX's top speed came a bit higher.

I'd be interested in hearing how the RAF souped up the V-1710 for the Mustang! But you can see that the single stage supercharged V-1710 could really put out the power at low altitudes.

 

[ColFord]

Extract from a USAAF report dated August 1943 utilising information provided by the RAF on their use of Mustang Mk.I and Mk.IA aircraft and some basic information on state of modification at that time of engines in RAF use - although touched on very lightly. The list of engine modifications required for operational status Allison engined Mustangs in RAF service, comprised over 50 different modifications, including specific modifications to the supercharger impellor and a number of ancilliaries. In developing these modifications, the RAF made good use of a number of specialist firms in the UK, including ROOTES, who had even then and still have quite a degree of experience and success in supercharging a wide range of engines. The RAF continued its program of refining and improving the performance and life they were getting out of the Allison engines in the Mustangs until late 1944. SO a number of the performance figures quotes in the USAAF report below, were exceeded by later RAF modifications.

Performance of the Mustang I and IA

32. The record of the Mustang I is excellent. The pilots all like to fly it and its success has been due to its reliability, simplicity and the fact that it is faster than any contemporary aircraft at low and medium altitudes.

33. This aircraft is powered with the Allison 1710-39 engine having a rated power of 1150 H.P. at 3000 R.P.M. and 44" Hg. at 12,000 ft. The engine was originally equipped with an automatic boost control limiting the manifold pressure at the lower altitudes to 44". The British remove this so as to get the vastly increased performance at lower altitudes thru the judicious use of over-boost. As has been mentioned before, they have had exceptionally good service out of these engines and due to its smoothness at low RPM's, they
are able to operate it so as to obtain a remarkably low fuel consumption giving them an operational range greater than any single engine fighter they possess (the fact that the Merlin engine will not run well below 1600 prevents them from obtaining an equivalent low fuel consumption and therefore limits its usefulness for similar operations).

34. Actual combat has proven that the aircraft can run away from anything the Germans have. It's only inferior points are that it can't climb as well as the ME-109 and FW-190 and that at the slower speeds of close combat it loses effectiveness of aileron control and therefore has a poor rate of roll – but its turning radius with a slight amount of flap is shorter than either of the German aircraft.

35. In view of the British experience, it is felt that we have a plane excellently fitted and suited for long range, low altitude daylight intrusion and for a medium altitude escort fighter to accompany our medium bombers. It must be realized that an aircraft will fulfil the conditions for a medium bombardment escort fighter might not be completely suitable for a long range intruder due to the inability on the part of the engine to run at the exceptionally low R.P.M. necessary for such long range operation. This is also assuming an operation which will allow a major portion of such missions to be made over waters where interception would be unlikely, such as from North Africa or the Mediterranean Islands to the mainland.

36. In view of the British operation and the fact that we have an approved war emergency rating on the 1710-39 engine of 56", it is suggested that immediate steps be taken to remove the automatic boost controls from our P-51 airplanes in this theatre and that the instrument dials be marked with the proper lights. The British have operated at full throttle at sea level (72" Hg) for as much as 20 min. at a time without hurting the engines. According to them, the Allison is averaging 1500 hours between bearing failures as compared to 500 to 600 hours for the Merlin. The Allison, they have found, will drag them home even with the bearing ruined.

37. It is suggested that the Allison powered P-51A may lend itself better to a combination low altitude fighter-intruder and a medium bombardment escorter than will the Merlin powered P-51B due to the inherent difficulty of operating the Merlin engine at the low RPM's necessary for a low fuel consumption. It is felt that definite engineering and flight information should be secured in these two aircraft immediately.

CHARLES F BORN Brigadier General, CSC, Asst Chief of Staff, A-3.

 

[tomo pauk]

I could list the multiple AIR, AVIA and other files held in the UK Archives as my sources, and the long, long list of RAF and Commonwealth Air Forces personnel who flew and maintained them. But unfortunately as the full set of detailed sources and information involves other researchers who have spent many years on this subject and are in the process of finalising the publication of their work as a commercial publication, I have limitations on what I can share at this time.

Hmm - that means you have put down claims, but there is nothing to back them up here.

Also I made no statement about the RAF's engine modifications being used by Allison or the USAAF. I noted that RAF provided reports on what they were doing with the Allison engines in their service to increase service performance. What USAAF and Allison did or did not do with the information contained in those reports is not something I have focussed on.

Okay, I've misunderstood you on that part.

Extract from a USAAF report dated August 1943 utilising information provided by the RAF on their use of Mustang Mk.I and Mk.IA aircraft and some basic information on state of modification at that time of engines in RAF use - although touched on very lightly. The list of engine modifications required for operational status Allison engined Mustangs in RAF service, comprised over 50 different modifications, including specific modifications to the supercharger impellor and a number of ancilliaries. In developing these modifications, the RAF made good use of a number of specialist firms in the UK, including ROOTES, who had even then and still have quite a degree of experience and success in supercharging a wide range of engines. The RAF continued its program of refining and improving the performance and life they were getting out of the Allison engines in the Mustangs until late 1944. SO a number of the performance figures quotes in the USAAF report below, were exceeded by later RAF modifications.
...

Removing or installing manifold pressure regulator had nothing to do with supercharger impeller. I don't think that Rootes-type or Rootes-designed superchargers were used on any aero engine of ww2.
We also know that way before 1943 people were over-boosting their V-1710s, from AVG on. That is without input of RAF.
Again - I respect that you are not willing to share your research on an open forum, but making claims usualy requires backing them with data in order for people to accept the said claims.

 

[XBe02Drvr]

I don't think that Rootes-type or Rootes-designed superchargers were used on any aero engine of ww2.

But that doesn't mean Rootes consultation help couldn't have gone into the RAF modification effort.
Cheers,
Wes

 

[tomo pauk]

But that doesn't mean Rootes consultation help couldn't have gone into the RAF modification effort.
Cheers,
Wes

I don't think that anybody can prove a negative - 'someone didn't do something'. Hence the 'burden of proof' is on the side that made a positive claim: 'someone did do something'. So I'll wait for an actual proof that Rootes improved/modified the V-1710's supercharger on RAF's Mustangs.

 

[MIflyer]

The RAF did crop the Supercharger impellers of Spit V to improve low altitude performance and enable it to better handle the FW-190. They also clipped the wing tips to improve the roll rate. Spit pilots reported that was the hottest of all the Spits at low altitude.

Farnborough and NAA worked to improve the roll rate of the Mustang with new ailerons. Capt Winkle Brown reported that the Farnborough aileron had a slightly higher roll rate than the one adopted by NAA for the later aircraft. These were incorporated starting with the B model and perhaps before that.

The RAF also messed with the supercharger controls of the Typhoon to get better low altitude performance to intercept low altitude FW-190 fighter bomber attacks and that was one reason for the poor reliability of the Sabre engine.

 

[tomo pauk]

The RAF did crop the Supercharger impellers of Spit V to improve low altitude performance and enable it to better handle the FW-190. They also clipped the wing tips to improve the roll rate. Spit pilots reported that was the hottest of all the Spits at low altitude.

Rolls Royce did the 'cropping', actually they designed and produced a whole smaller supercharger.

The RAF also messed with the supercharger controls of the Typhoon to get better low altitude performance to intercept low altitude FW-190 fighter bomber attacks and that was one reason for the poor reliability of the Sabre engine.

Sabre was already excellent at low altitude. Poor reliability of Sabre engine was due to Napier's inability to produce sleeves that would last more than 20 hours. Situation much improved 1st by using sleeves from made by Bristol (those lasted 120+ hours by mid war), and 2nd by urgent import of specific machine tools from the USA.

 

[MIflyer]

Recently read a book by a RAF Typhoon and Tempest pilot. That and numerous other personal accounts I've read led me to conclude that there was nothing wrong with the Typhoon that could not have been fixed by removing that beautiful bubble canopy used on the later models and sticking a P-47 under it. The Typhoon was a killer when it came to ditching, and given the engine problems that was a real concern; there was also nothing the pilot seemed to be able to do about it in terms of landing technique. They assumed it was that big radiator up front that made each water landing A Voyage to the Bottom of the Sea, but in reality it was the wing design. In marked contrast the Tempest ditched nicely, eliminating the need for getting the RN involved in training pilots to become submariners..

The author of the book I read most recently said that most of the problems with the Sabre was due to Napier farming our parts to companies that normally did not build engines. Supposedly, when they started making those parts in-house late in the war reliability improved. but it still sounded none too good, even with the Tempest.

Good point: Although LF Spit V's were called "Clipped, Cropped and Clapped," given that you could not yank the "accessory" section off a Merlin as you could do with the V-1710, I would guess that making an LF variant of the engine would require rather more than swapping out one part.

 

[wuzak]

In developing these modifications, the RAF made good use of a number of specialist firms in the UK, including ROOTES, who had even then and still have quite a degree of experience and success in supercharging a wide range of engines.

Don't confuse Rootes, a conglomerate of British car manufacturers at the time, with Roots, the American developer and manufacturer of Roots type positive displacement pumps.

Rootes built aircraft in a shadow factory, including the Handley-Page Halifax, and military vehicles based on their commercial vehicles.

Roots' expertise lay with the pump they designed, and not with centrifugal type superchargers. Not sure how much their expertise would have assisted the aero engine manufacturers.

Initially, the V-1710 supercharger was designed by General Electric. At some stage early in production, supercharger development was taken in-house at Allison.