I agree completely, my point was that it is a sensible choice to put a turbo behind the pilot in a P-47, putting a turbo in the back of a car or bike may work "just" but would be very difficult to drive.
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I agree completely, my point was that it is a sensible choice to put a turbo behind the pilot in a P-47, putting a turbo in the back of a car or bike may work "just" but would be very difficult to drive.I know from some of your previous posts that you are an experienced bike racer. I also know that you know the difference between single stage and two stage superchargers.
I have no first hand knowledge of how a two stage system with a mechanical stage suffers from "lag" in it's turbo auxiliary stage. I would suspect that the throttle response is better than a turbo alone. I have read that the P-38 may have suffered and that there were two methods to get around it. The discredited high rpm, low boost cruise which used more fuel, wore out the engines quicker, over cooled the intake mixture and kept the large GE turbos at low rpm (and a GE turbo is absolutely huge compared to a modern car or bike turbo). or the preferred low rpm, high boost method of cruise, the turbo is spinning thousands of RPM higher, the intake mixture is not puddling in the manifolds and there is a fair amount of boost available to increase power (torque) as the the throttle is opened (or prop control moved?) to accelerate the engine/props.
You also have how the propeller acts as it goes from cruise to high speed. I believe (but could very well be wrong) that the prop is in coarse pitch (or close to it) to give the most speed for a low rpm. when the throttle is opened up and rpm increased the prop should go to a finer pitch as the engine gains rpm and then as the power increases and the speed increase the prop should go back to coarse pitch as high speed is approached?
Most of the people trying to compare modern cars/bikes to WW II engines seem to forget the aircraft engines were operating in rather thin air insead of the "soup" that most cars and bikes operate in. The AIrcraft engine at 20,000ft is only getting about 53% as much "air" (by weight) per cubic ft as the engine at sea level.
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Because all the things it could do were done as well or better by a lashup single made by NAA from the allied parts bin (yes, I know, P-51 is more than that) and by a largely private venture Republic design with a navy engine, it may represent the best the AAC-specified fighters could do, but it was the most mediocre fighter with the most expense, the steepest learning curve and the least development potential.
What this says mostly is that the USAAF succeeded mostly in spite of its procurement process, not because of it.
SIlly the designers back then: they opted to put some distance between engine and turbine so the exhaust gasses can cool a bit, instead of bolting the turbine on the engine block and wait for tubine itself to desintegrate in mid-air due to temperature overload.
by a largely private venture Republic design with a navy engine,
From an engineering/efficiency standpoint, that doesn't make a lot of sense. Turbochargers are "thermal devices", they essentially extract waste power (in the form of heat) from the exhaust to drive the compressor impeller. That is one of their main advantages over mechanical superchargers that consume engine horsepower (and fuel) to drive the compressor. Extending the distance between the engine and turbo, and allowing the exhaust to cool, makes the whole system less efficient. In addition, all that ducting to the turbo is transfering heat to other portions of the aircraft-most likely not a desirable situation.
Would the reason to do that be limited to the metallurgy of the day, or perhaps the turbocharger design (not incorporating cooling) not allowing the turbo to survive at higher temperatures? Modern automotive turbo systems focus on keeping exhaust runs to the turbo short to maximize efficiency. But the materials of today are far from those of the 1940s.
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Dragon dog: "Wow - all those flaws and yet it was a top line (forAAF) Interceptor, escort fighter, fighter bomber, recon (both tactical and high-altitude), air superiority figter. "
Just down the road from me is Mount Farm, used to be home for the USAAF photo recce aircraft. They preferred Spitfires. P-38 was pretty disappointing as a fighter in the 8th. It did fine against enemy planes with a 80mph speed disadvantage in the SWPA, but not in the ETO. That's because it wasn't a top fighter in terms of the state of the art. Your list of roles to illustrate versatility includes four fighter distinctions which do not require versatility. It would fly in the same config for each of them. And as mentioned it wasn't a top camera ship either. Because all the things it could do were done as well or better by a lashup single made by NAA from the allied parts bin (yes, I know, P-51 is more than that) and by a largely private venture Republic design with a navy engine, it may represent the best the AAC-specified fighters could do, but it was the most mediocre fighter with the most expense, the steepest learning curve and the least development potential.
What this says mostly is that the USAAF succeeded mostly in spite of its procurement process, not because of it.
Dragon dog: "Wow - all those flaws and yet it was a top line (forAAF) Interceptor, escort fighter, fighter bomber, recon (both tactical and high-altitude), air superiority figter. "
Just down the road from me is Mount Farm, used to be home for the USAAF photo recce aircraft. They preferred Spitfires. P-38 was pretty disappointing as a fighter in the 8th.
The ETO was not a happy time for P-38 until post March 1944, but after that it was an excellent platform for air to air and air to ground and high altitude - long range recon - and used to the EOW. It could go farther than ay Spit. The preference at Mt. Farm for Spit can be traced to the first deployment of the F-4 all the way to the Mid J F-5
It did fine against enemy planes with a 80mph speed disadvantage in the SWPA, but not in the ETO. That's because it wasn't a top fighter in terms of the state of the art.
See comments above. Operationally the P-38J-15 was a game changer and the -25 with boosted ailerons and dive flaps enabled the 55th and 479th to have spectacular days before converting to Mustangs in Summer 1944.
Your list of roles to illustrate versatility includes four fighter distinctions which do not require versatility. It would fly in the same config for each of them. And as mentioned it wasn't a top camera ship either. Because all the things it could do were done as well or better by a lashup single made by NAA from the allied parts bin (yes, I know, P-51 is more than that) and by a largely private venture Republic design with a navy engine, it may represent the best the AAC-specified fighters could do, but it was the most mediocre fighter with the most expense, the steepest learning curve and the least development potential.
Hmmm, how well did any fighter you have in mind to compare vs P-38 flew well (or at all) on one engine - a nice characteristic in SWP, or accepted a bombardier/Norden sight to lead a FG on a level bombing mission? Or tested for, and capable of, delivering a torpedo or a radar mod w/operator in back seat?
What this says mostly is that the USAAF succeeded mostly in spite of its procurement process, not because of it.
If living close to military airfield confers special expertise, everyone in Kent and East Anglia is a forum guru. I can walk to three former WW2 airfields and on a bicycle could reach well over a dozen.Just down the road from me is Mount Farm, used to be home for the USAAF photo recce aircraft. .
Not all photo reconnaissance was the same.
View attachment 563919
P-38s ( or F series) could (but not always did) carry an array of cameras the single engine planes could not.
Both Cameras and film evolved during WW II.
Dragon dog: "Wow - all those flaws and yet it was a top line (forAAF) Interceptor, escort fighter, fighter bomber, recon (both tactical and high-altitude), air superiority figter. "
Just down the road from me is Mount Farm, used to be home for the USAAF photo recce aircraft. They preferred Spitfires. P-38 was pretty disappointing as a fighter in the 8th. It did fine against enemy planes with a 80mph speed disadvantage in the SWPA, but not in the ETO. That's because it wasn't a top fighter in terms of the state of the art. Your list of roles to illustrate versatility includes four fighter distinctions which do not require versatility. It would fly in the same config for each of them. And as mentioned it wasn't a top camera ship either. Because all the things it could do were done as well or better by a lashup single made by NAA from the allied parts bin (yes, I know, P-51 is more than that) and by a largely private venture Republic design with a navy engine, it may represent the best the AAC-specified fighters could do, but it was the most mediocre fighter with the most expense, the steepest learning curve and the least development potential.
What this says mostly is that the USAAF succeeded mostly in spite of its procurement process, not because of it.
Simply stated - Material Division under leadership of Oliver Echols, did not believe that a two speed-two stage supercharged engine was feasible. In-line engines weren't even considered with enough regard to experiment until Allison passed the 1000 Hp bench testing about the time the RFP for P-38 and P-39 emerged - driven by Kelsey - and as described adequately by Kelsey quotes in Bodie's P-38 work. The Ge Turbo was required at that time to push the P-38 performance envelope above 15,000 feet enough to qualify as a high altitude 'Interceptor'. The P-39 was described by Kelsey as 'the small solution' and never achieved promised capability until the P-63 limped out with the Allison auxiliary second stage - requiring a major redesign to accommodate the engine.
Secondly, the only promising in-line engine manufacturer that's actually developed a reliable supercharged engine was Allison. Allison was underfunded by GM, and starved for R&D funding, but there is no evidence that Allison believed they could develop such an integral 2s/2s engine if given the funding.
As to many references to Kelsey as a visionary, history doesn't support him as ever being an advocate of the P-51 until he was out from under Echols and in ETO operations where the P-38 was under-performing to the P-51B.
General Malin Craig was Army Chief of Staff and retired days before the Germans attacked Poland, not a staunch supporter of AAF vision but also not regarded as a meticulous bean counter looming over Arnold's shoulder regarding approved budgets for R&D. Simply stated again, Arnold drove R&D for AAF while under Malin and basically throughout WWII. Bomber development was number one priority until events in Europe cast doubts of unescorted bombers being able to carry out AWPD-1 to destroy enemy war making capability. Turbo supercharged engines, whether on interceptors or high altitude bombers were central to specifications for new development. The only other alternatives considered were to boost in-line power to continue to raise the ceiling of singles stage engines. The Continental, etc. were attempts that repeatedly failed to drive down weight and volume as well as achieve reliability requirements.
Materiel Command had a miserable record for developing high performance fighters capable of long range escort to support AWPD-1 and -2. Lack of in-line engine development in the US was central to the failures.
No doubt the Mustang was a great fighter and did a number of things very well. But is showed up relatively late in the war (in a high altitude-capable variant anyway), was relatively fragile (at least compared to the '38, '47, Corsair and Hellcat). It had a much lower bomb carrying capability. And of course, one hit anywhere in the cooling system and it wasn't likely to make it home.