MiTasol
1st Lieutenant
Interesting report that
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Where in the world do you get the notion that I said the aircraft was designed for the US forces?I think you have the wrong end of the stick on several items - the most glaring being that the Mustang was designed for the RAF - NOT the USAAC
It really was should you wish to read the aircrafts history. The Army Co-operation role included keeping enemy aircraft off their backs, FW 190 for instance, read about the Dieppe raid. The introduction of the 190 caused the British much concern and were anxious to get the -51 so as to counter it, to the extent that they considered building the -51 in the UK, part of that worry was when the Spitfire IX might reach operational status.It really wasn't. Certainly no more than the P-40 or P-39 were designed as "Army Co-operation" aircraft.
And if it was the case, it would have been unlikely that the Mustang would have changed from the 8.8:1 supercharger gear to the 9.6:1, which was aimed at better altitude performance.
It really was should you wish to read the aircrafts history. The Army Co-operation role included keeping enemy aircraft off their backs, FW 190 for instance, read about the Dieppe raid. The introduction of the 190 caused the British much concern and were anxious to get the -51 so as to counter it, to the extent that they considered building the -51 in the UK, part of that worry was when the Spitfire IX might reach operational status.
The supercharger ratio change would have been a performance enhancement, but doesn't change the fact that the aircraft's raison d'être was Army Co-0peration as the British called it. Airborne attacks on the troops were not made from high altitude, Stuka etc were the trouble.
The V-1710 engines in the Mustang Mk.I aircraft "as delivered" did not have an automatic boost control. On the V-1710 engines on the Mustang Mk.IA, they were initially fitted with a Delco-Remy or later a Claudel Hobson automatic boost control, however these proved troublesome and prevented the engines from developing the required level of "over-boost" required, when combined with the modifications (cropping) conducted on the supercharger vanes to improve performance below 10,000ft. (Sources: Various AIR and AVIA files held in UK Archives relating to Mustang Aircraft, Air Ministry Mustang Mk.I and Mk.IA Pilots Notes, Erection and Maintenance Manuals AP Series, original diaries, personal papers, original service documents and interviews with surviving RAF aircrew and groundcrew who flew and maintained Mustang Mk.I, Mk.IA, Mk.II aircraft in RAF service 1942 to 1945.)
The Allison had significant problems in its tubocharged version. The list of excuses for its problems is endless but the fact is it was found wanting at crunch time.Love to hear of the significant problems.
The Allison was the preferred engine by those doing low level Rhubarb type missions because it provided greater range through better fuel economy and was more robust, being better able to endure abuse, so good in fact that they removed the boost control in order to increase manifold pressure. When the Merlin production line started the USAAC operating in Africa put forward a proposal (have a copy) to keep the Allison powered version in production because of its superior qualities in the low level role. The Merlins forte was its high altitude capability. The better economy of the Allison was due to its ability to run at very low RPM that the Merlin was unable to match.
On what page does he make that statement?
People tend to forget that the Mustang was originally designed as an Army Co-operation aircraft ie low level operations, for which the Allison was the perfect choice.
Was that in any plane other than the P-38.?The Allison had significant problems in its tubocharged version. The list of excuses for its problems is endless but the fact is it was found wanting at crunch time.
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Fortunately not.Was that in any plane other than the P-38.?
Did the P-38 have problems or issues with its turbo system throughout the war. Or did they just have troubles making it work at the wars beginning.?Fortunately not.
The Allison did well at low level but that was a limited niche. I would also point out that he Merlin 32 was optimized for low altitude and it out performed the contemporary Allison used in the A-36.
The P-38 was thrown off the job of high altitude escort in the ETO because of all the problems suffered during the winter of 1943 to 1944. The 8th AF replaced the P-38s in 3 fighter groups with P-51s in July 1944 with the remaining group lasting until September before it received P-51s.Did the P-38 have problems or issues with its turbo system throughout the war. Or did they just have troubles making it work at the wars beginning.?
Thank Yiou
It really wasn't. Certainly no more than the P-40 or P-39 were designed as "Army Co-operation" aircraft
It really was. The British wanted NAA to build P-40's for the Army Cooperation role but NAA said we could build a better aircraft than the P-40. The RAF had an Army Cooperation Command, along with Bomber Command, Fighter Command, and Coastal Command, the AC Command was disbanded on 31st March 1943. The RAF used the Allison aircraft primarily for tactical reconnaissance, low level fighter and ground attack (Army Cooperation - close support fighter to our US friends). From "FROM ARMY CO-OPERATION TO FIGHTER RECONNAISSANCE – DEVELOPMENTS 1939-1945" by Peter Elliott.Army cooperation is what it could do, not what it was designed for.
From "Mustang" by Robert Grinsell,The Curtiss Tomahawk, however, was available and in 1941 the re-equipment of fourteen squadrons began. Serviceability proved to be poor, due to engine problems, and at the start of 1942 the decision was made to reequip with the Mustang.
The Allison-engined Mustang I proved to be a very capable reconaissance fighter – fast and a stable platform for photography – and it eventually equipped all the home-based AC (Army Cooperation) squadrons. Unlike the Tomahawk, however, the Mustang was not able to take vertical photographs.
Engines.......................................................................................HorsepowerThe initial RAF unit to receive the Mustang I was 26 Squadron based at Gatwick, which took delivery of one of the new aircraft from Speke in January 1942. By March, the Mustang began to appear in the inventories of several other Army Co-operation units whose main task was to support the British army in training exercises up and down the length of Britain in preparation for future combat operations on the European mainland. Due to the fact that the Mustang was essentially in training, and no current need existed for it as a fighter interceptor, delivery of it to the various units was slow and several experimental modifications were evaluated. The one which was to have not only a major impact on the air supremacy of the Allied Forces in later years, but one which may have also played a major role in determining the overall outcome of World War II, was the installation of the Rolls-Royce Merlin powerplant into four Mustang ls. The success of these aircraft convinced the U.S. Government to place an order for two Packard-built Merlin powered prototypes, designated XP-78 (North American designation NA-101). These aircraft were to provide the basis for the later model P-51B model of the Mustang which offered long-range high-altitude bomber escort and interceptor capabilities.
The first combat operations in which the Mustang was used as an offensive weapon occurred on 10 May, 1942, when a single aircraft of 26 Squadron took off from Gatwick on a reconnaissance sortie to the French coast. The pilot photographed parked Luftwaffe aircraft at Berck airfield and then swung his Mustang around for a strafing pass at the various vehicles and supplies lined up along the outskirts of the field. On his way home, the pilot sighted a supply train and again banked his aircraft to attack. In less than two hours the Mustang was back at Gatwick, but it had set the stage for almost continuous Mustang "reconnaissance and destroy" (called "Popular" by the RAF) sorties into German-held French territory. The first known casualty of a Mustang occurred two months later when, in ]uly, 1941, 26 Squadron reported the loss of aircraft AG 415 during a strafing mission near Le Touquet, France.
With the combat worthiness of the Mustang I being proven daily, the RAF decided to expand its role and during the late summer and early fall of 1941 assigned the aircraft to Coastal Command duties which included the escort of slower more cumbersome anti-shipping bomber aircraft, and in low-altitude fighter interception sorties against wave-top flying Fw 190s which were carrying out deep interdiction raids against British coastal harbors and ports. In addition, the Mustang units were assigned to "Seek-and-Destroy" sorties over the coast of France to strafe specific targets such as trains, transport convoys and military installations.
It really was. The British wanted NAA to build P-40's for the Army Cooperation role but NAA said we could build a better aircraft than the P-40. The RAF had an Army Cooperation Command, along with Bomber Command, Fighter Command, and Coastal Command, the AC Command was disbanded on 31st March 1943. The RAF used the Allison aircraft primarily for tactical reconnaissance, low level fighter and ground attack (Army Cooperation - close support fighter to our US friends). From "FROM ARMY CO-OPERATION TO FIGHTER RECONNAISSANCE – DEVELOPMENTS 1939-1945" by Peter Elliott.
The Curtiss Tomahawk, however, was available and in 1941 the re-equipment of fourteen squadrons began. Serviceability proved to be poor, due to engine problems, and at the start of 1942 the decision was made to reequip with the Mustang.
The Allison-engined Mustang I proved to be a very capable reconaissance fighter – fast and a stable platform for photography – and it eventually equipped all the home-based AC (Army Cooperation) squadrons. Unlike the Tomahawk, however, the Mustang was not able to take vertical photographs.
This is wrong in my opinion, before any Mustang Mk Is were delivered the UK was technically bankrupt and Lease lend kicked in, the British were only going to get what the USA didnt want. By the time any Mustang Is were issued to squadrons at Gatwick the USA was at war with Japan and Germany. That changed the whole game. The P-40 was tried in tactical recon and couldnt do it. It could work in N Africa, that 21 miles of water and the defences beyond it changed the whole game.From "Mustang" by Robert Grinsell,
Engines.......................................................................................Horsepower
.................................................Supercharger Ratio.....T/O......At Rated Alt........Rated Altitude
Mustang I......1710-39..........................8.8...................1150.............1150.......................11,800
Mustang II.....1710-81.........................9.6....................1200.............1125.......................14,600
A-36.................1710 -87........................7.48.................1325.............1325..........................2,500
All supercharger impellers are 9.5 inches diameter
The cropping of the impellor was a RAF developed modification and was applied to all the Allison V-1710 engines proposed to be installed in operational RAF Mustang Mk.I, Mk.IA and Mk.II aircraft. It was on the list of modifications that the RAF had that had to be performed on a Mustang to be considered fit for operational flying. The effect of the cropping of the impellor was to improve engine performance below approximately 8,000ft and particularly enhance it in the zero to 4,000ft range. The RAF had sought technical advice on the modification from Rolls-Royce and a number of other aviation engine specialists in the UK.First time that I have heard of the V-1710's impeller being cropped.
The Merlin 45M had its impeller cropped to 9.5 inches - the same size as the regular V-1710 impeller.
As noted, a Merlin supercharger was mounted remotely to an Allison and basically performed the same. However the supercharger failed shortly into the test, the exact cause was never confirmed but the speculation was that by being remote it wasn't kept up to same temperatures that it would have it was directly mounted to the crankcase.
Early aircraft engines used brass floats to control the fuel level in the carburetor – rising to stop fuel flow, sinking to allow fuel in. If the floars weren't properly soldered shut or developed leaks in service, they would sink and fuel would flow overflow the carb. With an updraft carb, the excess fuel simply falls to the ground. With a downdraft carb, it usually flows somewhere bad – into the intake flooding the engine, over the red hot exhaust causing fires, etc.
The American auto industry, with engines like the flat head v-8, were making better downdraft carbs. And let's not forget Allison is a subsidiary of GMC, an automotive company.
Aside: Peregrine and Vulture, RR latest 2 engines pre-War and the post war Merlin 130s were downdraft. Downdraft is a better configuration, but sometimes you have to stick with what is working.
The engineers at Allison developed very sophisticated intake manifolds that "rammed" air into the cylinders at optimum rpm.
The engine was also developed for turbocharging. The combination of the 2 meant the camshaft timing was fairly mild allowing the engine to run smoothly at less than 50% power, again allowing it to be more economical.
As you might recall from high school chemistry, it takes a huge amount of energy to boil water*. RR engineers used this fact by allowing very limited, very local boiling in their engines around the exhaust valves. Once mixed with coolant in the engine, the water vapour is return to water again but the mixture is very hot. As the mixture is very hot, you need a smaller radiator because there is greater temperature difference with outside air. So, Merlin gets away with less than ½ the cooling water of the Allison.
It's also why you can't turbocharge a Merlin – the exhaust is running so close to thermal limits that the extra heat from restricting exhaust exit melts the head.
Early P-38s issue was Lockheed didn't anticipate flying for extended periods of time at high altitude. The decision to use the outer wing leading edge as an intercooler appeared to be stroke of genius. But unfortunately, in conditions that 8th AF found themselves in, planes were flying at cruise speed for hours in -30° cold. And the load on the turbocharger wasn't enough to have them creating enough warm air to justify the intercooling but there was no way to limit it. The carb/engine on the Allison wasn't designed for operating in that environment for extended periods.
I do wonder why Allison/GE never pushed for a turbocharged Allison Mustang. If you remove the fuselage tank, there would be room for the turbo. Routing of intake and exhaust wouldn't be any different from Thunderbolt in concept.
NAA did a design & engineering study on the Allison Mustang to look at putting a turbo supercharged engine onto it, and the changes required to accommodate the engine, all the associated plumbing, increased cooling requirements meant that it was not a modification, it was going to require a whole new fuselage structure to accommodate it. Combined with the increased fuel consumption, they then had to look where to put the additional fuel, which then got into a circular argument about what else in the design had to be moved to make room for more fuel, then where what had been moved to make room for more fuel tanakge, where that would go.......... Already, in terms of size and engineering requirements, the option of using a R-R Merlin, either manufactured in the UK or the USA made a better option as the changes required in the initial considerations looked to be simpler to implement as modifications to the existing airframe rather than a total re-work and redesign - with all that was associated with that in terms of new tooling if it went into production..I do wonder why Allison/GE never pushed for a turbocharged Allison Mustang. If you remove the fuselage tank, there would be room for the turbo. Routing of intake and exhaust wouldn't be any different from Thunderbolt in concept.
Regards the Allison in the P-51
Could the Merlin 2-Stage have been mated to the Allison without much fanfare.?
If that WAS possible, would the P-51 have the same gas mileage with the Allison as the Merlin.
Could Allison have kept up with the demand for Allison motors, in a P-51 from 1944 onward.?
Thank You
The V-1710 project began May 7, 1929 and from the very outset it was intended to be a 1000ph engine compatible with turbosupercharing and fuel injection. The first contract for A V-1710 was signed by the Navy on Jun 26, 1930 for one 750hp with a 8.25" supercharger running at 8:1 and a 3:2 reduction gear. The first Army engine contract is dated January 5, 1933. This model was specified as 750hp engine with the understanding that a 1000hp is the desired power. This contract was also first one state that the engine needs to be compatible with turbosupercharing and fuel injection. The contract for the V-1710-4 airship engine wasn't signed until January 24, 1933.I dispute the claim that the V-1710 was developed for use with turbochargers.
It was first designed as an airship engine, which did not have a supercharger at all - but was reversible in flight. That last bit made changing from RH to LG rotation somewhat easier.
I don't believe Allison ever tested the V-1710 with a turbocharger on a test stand until after the Bell XFM and Curtiss XP-37 had flown. If it had been developed with turbocharging in mind I would have thought it would have been fitted with the turbo for running on the test stand.
It was the purpose to which the aircraft were put. The RAF had a Fighter Command and an Army Cooperation Command, although Army Command ceased to exist on 31 March 1943 the Allison Mustang was still performing Army Cooperation work up until VE day by the only Allison squadron remaining, 26 Squadron. From memory all, bar perhaps one or two squadrons, the Allison Mustangs went to Army Cooperation Command. All Merlin aircraft went to Fighter Command. Once again, remember the Mustang was designed, developed at the behest of the RAF to fulfill a RAF requirement - Army Cooperation, the only US involvement was giving permission to NAA to devote the resorces and to supply the aircraft. Beyond that the US had absolutely no interest in the aircraft, it was not for some time that the US understood what a jewel was hiding in the woods.I would dearly love to see some actual "proof" that the P-40 or the Mustang I were designed for army co-operation