USAAF procurment system in WW2

[Shortround6]

That may be true and I am in no position to argue that it wasn't, and have no wish to.

The thing is that the Spitfire (at least until the shooting started for the US) would NOT have been accepted as an American aircraft because it didn't meet the the US standard "G" load specification. Once a few thousand had been used in combat without breaking and with the US short of fighters in Europe we did accept around 600 into service but that was a number of years after the Spitfire first flew.

What I was trying to point out was that there was a 'list' of 'standard' specifications that designs had to adhere to that were NOT listed in individual invitations to submit bids/designs because they were pretty much a given.

 

[GregP]

Never said there was "so much room inside" Shortround. I said the XP-39 had a turbo system and it did.

If it had been allowed to mature, the solution might well have been NACA ducts for inflow and out flow, I can't say because it was dropped. The Allison V-1710 didn't and doesn't need a huge radiator ... it needs a lot of oil cooling (the Allison requires more oil cooling than the Merlin, but less radiator), an intercooler in the case of a turbo, and the turbo system itself, all of which were installed in the XP-39. There are any number of ways to fix the drag problem, but someone has to be willing to pay the bill to research it and fix it. If the customer isn't willing the easiest and cheapest way to fix a turbo installation is to delete it ... no more turbo problem at the expense of all that nice-to-have boost.

The "what if" of the P-39 turbo installation can be argued forever to no end ... but it COULD have been made to work. In real life, they eliminated it and created a low-altitude aircraft. When you (figuratively you, not literally you, Shortround ... none of this is aimed at you) do that knowingly, don't complain about the altitude performance later when it bites you. You reap what you sew in this case and we did.

They fixed the turbo installation in the P-38 and eliminated the intake manifold issue, too, and the radiators on the side of the P-38 boombs aren't huge drag penalties, the P-38 had no trouble exceeding 400 mph even on lower-horsepower early V-1710 engines. Of course, a larger airframe, like the P-63, would have been nice to have early-on, too. It was a pretty good performer in its own right but we had planes as good or slightly better in service by the time it came along. Ergo we only bought a few.

In the relative scheme of things, the US procurement system didn't perform poorly. It procured the P-38, P-39, P-40, P-47, P-51, P-61, and P-63. The only real mistake in there was the P-39 and the weakness in that aircraft was caused by the USAAC themselves. Not too bad a record for all the decisions and issues they faced. All in all, I'd say the procurement system worked quite well given the pressures and timframe of WWII. In the case of the P-40, they elected not to continue with P-40 development as illustrated by the XP-40Q series of aircraft, but the planes they bought instead were pretty good aircraft and probably had more development potential than the P-40 ... development potential that was mostly never tapped since the war ended and we fell in love with jet engines. 10 years after WWII was over, only the Reserves / National Guard were flying piston singles with the exception of the Skyraider and some liaison aircraft. All the rest were jets or turboprops.

 

[vikingBerserker]

That's called an "Unsolicited Proposal." It's still done today, this is one of the more recent ones that are known.

Wow, that one surprised me!

 

[wuzak]

The turbo was not exactly inside the XP-39....

i wonder if they didn't have teh requirement for the big 37mm cannon if they could have moved the cockpit forward a little, and freed up space for the turbo and other bits and pieces?

 

[Shortround6]

The P-39 was trying to put a quart in a pint pot. A bare B-2/3 turbo weighs 135lbs so, while not extremely heavy, does require a bit of planning as to where it goes. Throw in the requirements for the exhaust pipes, combustion air, inter cooler air and cooling air for the turbo and the volume for the system goes up a lot more than the weight. A lot

The bulk of the turbo was inside the P-39, what is sticking out in the picture were the 4 exhaust pipes and the turbine, turbine cap and cooling scoop for the turbine.

B-3 turbo upside down;

only about 1/4 of the turbo is outside the plane.

The installation could have been cleaned up and refined but the later two attempts at mock ups on a P-39D caused speed reductions of 45mph for the 'saddle back' and 40mph for the 'pod' according to one book. Altitude/conditions not given. even if the speed reduction was reduced to 30mph at medium altitudes that turns a P-39D with belly shackles but no tank into a 320mph airplane at 13,000ft. Granted it would have been a lot zippier at higher altitudes than the non-turbo model but there is no free lunch.

 

[GregP]

Actually I had a free lunch today, but I wasn't desigining an airplane or trying to fix the XP-39.

I should have paid and eaten at a better restaurant.

 

[parsifal]

That may be true and I am in no position to argue that it wasn't, and have no wish to.

The thing is that the Spitfire (at least until the shooting started for the US) would NOT have been accepted as an American aircraft because it didn't meet the the US standard "G" load specification. Once a few thousand had been used in combat without breaking and with the US short of fighters in Europe we did accept around 600 into service but that was a number of years after the Spitfire first flew.

What I was trying to point out was that there was a 'list' of 'standard' specifications that designs had to adhere to that were NOT listed in individual invitations to submit bids/designs because they were pretty much a given.

This suggests the US had some issues with the Spit before circumstances more or less forced them ionto the situation of using it.....if they had issues with the Spit, they must have turned themselves inside out over the Mossie they also used.

 

[Shortround6]

I don't think they had an "issue" with it other than it not meeting (in peace time) some of the US basic requirements they they applied to ALL aircraft, rightly or wrongly.

British had a number of requirements that they applied to ALL new aircraft at the time too. Like the max allowable tire pressure to prevent rutting the grass fields. Which leads to some large tires that were harder to hide inside the aircraft. British may have been a bit more restrictive on things like field length, even on large bombers.

The stressing of aircraft was only a few years old in the 1930s. Quite a number of WW I aircraft suffered structural failures in flight as did some aircraft in the 1920s and a few racing planes in the early 30s. Different countries adopted different "standards" to try to prevent this without really knowing what was actually needed for service. More of a "what will it need in service and what is a decent added safety factor". Just to keep things interesting the US Navy had a few requirements the US Army did not have

 

[Glider]

This suggests the US had some issues with the Spit before circumstances more or less forced them ionto the situation of using it.....if they had issues with the Spit, they must have turned themselves inside out over the Mossie they also used.

Maybe that's why the USAAF officially considered the Mossie to be unsuitable as a night bomber or night fighter.