GregP
Major
Speaking of high speeds and Oscars in the same sentence isn't something I usually contemplate ...
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CORSNING
Tech Sergeant
I apologize kool kitty, I meant to answer this earlier and got side tracked. With the wing guns and armament remove, maneuverability would have increased. The maximum roll rate would have stayed the same, however acceleration into the roll would have increased. Also, weight savings is performance added.
FLYBOYJ
"THE GREAT GAZOO"
That's a pilot problem and should have been addressed during training. If a pilot can't adjust to changes in CG due to load out (providing the CG is within limits) then they shouldn't be flying in combat.
BTW, you load just about any aircraft "nose light" (or tail heavy) it will be easier to spin - stick and rudder 101.
Shortround6
Major General
P-39s weren't supposed to fly with empty ammo containers/boxes in the nose unless carrying ballast. That suggests a plane that was a little close to the CG limit even in normal flight.
GregP
Major
Thye did a study some 10 - 15 years after the war and found the P-39 was past the rear CG limit when the ammunition was empty. Up until then, all of their testing was done at simulated full ammunition loads. During that aft CG test, the P-39 DID "tumble and roll" in the wind tunnel.
I think if has been posted in here before, but I can't recall the thread it was posted in.
I think if has been posted in here before, but I can't recall the thread it was posted in.
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kool kitty89
Senior Master Sergeant
The other problem was that the P-39's flat spin was irrecoverable at any altitude under some conditions. (I believe it was only under nose-light circumstances, but I'm not positive)
I wonder if the NACA's recommendation of lengthening the tail in the prototype contributed to those issues. (with the limited length of the extension shaft, you couldn't really make the nose any longer without repositioning the engine and entire cockpit with it)
I wonder if the NACA's recommendation of lengthening the tail in the prototype contributed to those issues. (with the limited length of the extension shaft, you couldn't really make the nose any longer without repositioning the engine and entire cockpit with it)
FLYBOYJ
"THE GREAT GAZOO"
I believe the flight manual says not to spin the aircraft to begin with
GregP
Major
... unless you're in it at the time.
Nylon letdown over the guys you just bombed or straffed isn't a recipe for continued good health.
Nylon letdown over the guys you just bombed or straffed isn't a recipe for continued good health.
P-39 Expert
Non-Expert
If you mean the P-40Q with the mechanical two stage engine, it would have benefited the P-39 also. An E model V-1710 for the P-39 with mechanical second stage was developed in parallel with the F model for the P-40Q. Same engines, only difference was the remote reduction gear for the E model. Then both the P-40 and P-39 would have had high altitude capability by mid '43.
Shortround6
Major General
I think you just speed up the time line by about 6-9 months.
At least one of the P-40-Qs had more than one engine. In fact the first one went through several engines and 2nd may well have flown with Both F27 and F28 engines. Or the first had it's engine rebuilt/modified at least twice and was updated to model specs when rebuilt.
In Mid 1943 the two stage Allison was good for about 1150hp at 20,000ft despite making well over 1800hp at sea level and that is just not enough in planes weighing close to 9000lbs.
At least one of the P-40-Qs had more than one engine. In fact the first one went through several engines and 2nd may well have flown with Both F27 and F28 engines. Or the first had it's engine rebuilt/modified at least twice and was updated to model specs when rebuilt.
In Mid 1943 the two stage Allison was good for about 1150hp at 20,000ft despite making well over 1800hp at sea level and that is just not enough in planes weighing close to 9000lbs.
Agree with that.
Even such V-1710s would've much improve the performance of P39s (in case they can fit at the 1st plac, I won't bet my house on it) and P-40s, even when compared with P-39N and P-40N.
P-39 Expert
Non-Expert
The V-1710-93 (Allison model E-11) actually made 1180HP at 21500'. The contemporary V1710-85 powering the P-39N made about 900HP at the same altitude. That extra 280HP represents a 31% increase. A normal P-39N weighed 7650#, add the second stage and a four blade propeller and it's still under 8000#.
P-39 Expert
Non-Expert
They got the two stage Allison into a modified P-39D resulting in the experimental -E. They moved the coolant tank up between the engine and the pilot and put the second stage where the coolant tank had been (same as P-63). The size of the area that held the second stage was exactly the same size on the P-39 an the P-63. Just a little internal rearranging.
Shortround6
Major General
Great, another nickel rocket, left out the oil system needed, left out the bigger cooling system, left out the water injection system, left-out the water/alcohol.
How long is the V-1710-93 going make it's higher power without all that "stuff" , a few minutes? Weight is about 8250lbs, my mistake on the 9000lbs (although that is the weight of the P-40Q)
I like the modified bit. Wingspan went from 34ft to 35ft 10in, wing area went from 213 sq ft to 236 sq ft, fuselage was lengthened by 1.75FT. new tail surfaces were tried on all three examples. The XP-39E (at least one of them, went 6936lbs empty and 8918lbs gross weight.
How many of these changes were needed to strictly get the engine in I don't know. How many were done to try to fix/improve other parts of the P-39s performance I don't know. On the P-39, to use the full power of the -93 engine you have to add the water injection system and find someplace to stick the water tank (25 gallons on the P-63) you also need to find the space for the larger oil system, which went from 60lbs (empty) on the early P-39s to about 135lbs on a P-63.
If you are going to use a fluid coupling to drive the auxiliary supercharger and use engine oil as the fluid then you need bigger oil coolers and bigger oil tanks and so on.
You are not going to cool an 1100-1200hp engine at 20-22,000ft with a radiator sized to cool a 900hp engine at those altitudes.
P-39 Expert
Non-Expert
V-1710 will make military power (1280HP at 21500') for 5 minutes. Without water injection or an intercooler there would be no WEP. P-38F/G didn't have WEP and an early P-63 would do 390mph at 30000' before water injection (no WEP). Still a huge performance increase even without WEP.
The P-39D-2, K and L used the 1325HP engine (same T/O HP as -93) and cooled adequately.
The P-39D-2, K and L used the 1325HP engine (same T/O HP as -93) and cooled adequately.
Shortround6
Major General
To get adequate cooling (something P-39s generally skated on the thin edge of) you DO NOT plan on using the power to the propeller as your cooling load but rather the total power developed in the cylinders. This takes into account both Friction and the power needed to drive the supercharger.
Once you have your cooling load you figure how many pounds of air per minute you need going through the radiator matrix and at what temperature.
Density of air obviously changes with altitude as does temperature. At around 21,000ft you need twice the cubic feet of air per minute to get the same pounds of air as you get at sea level. Yes the air is colder but mass of the air is more important than the temperature.
Your two stage Allison might cool just fine using standard P-39 radiators and oil coolers just as long as you don't exceed the standard P-39 power ratings at either low level (no WEP) or high level (no 1180hp at 21,500ft?). At which point there isn't much reason to try to stick the the two stage supercharger in the plane is there?
Please look at the difference in the radiators/intercooler on MK V Spitfire and a MK IX to see the difference in cooling required and please note the Griffon powered ones got even bigger.
The WEP will certainly be there for the V-1710 without water injection or intercooler (provided the historical cooling system) - many times called 'WEP (or WER) dry', contrary to the WER with ADI that was called 'WEP (or WER) wet'.
For the 2-stage V-1710s:
Boost at 'WEP dry' was between 52 (or 54?) and 61 in Hg, 5 min duration, max power 1425 HP (vs. 1325 HP military power, at 52 (54?) in Hg). Boost at 'WEP wet' was for 10 minutes max, between 54 and 75 in Hg, max power to 1825 HP. All max power figures listed are attained at sea level.
P-38D (as all the P-38s) was already with intercooler, yet there was no wer.
The fluid coupling was increasing the cooling loads on the oil system, there was a reason why the oil system on the P-63 was much bigger and heavier than on the P-39. So without a substantial increase of size & capacity of both cooling systems (coolant and oil) the P-39s will go through engines like a baby through the diapers.
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P-39 Expert
Non-Expert
P-39 manual shows 9.4gal oil with 15.8gal overload, P-63 manual shows 9.6gal/13.7gal overload. Pretty much the same.
Shortround6
Major General
Please try to compare oil needed/used for normal flying (combat) for a 120-126 gallon fuel capacity and ignore max capacity oil used for ferrying with max drop tanks.
With the "normal" fuel supply the two stage engine only needed a few extra gallons but they were in the fluid coupling and in the larger oil cooler and not just sitting in the oil tank.
P-63 used the size inlets they did because Bell engineers were stupid?
Or because the engine needed more cooling air?
P-39 inlets
With the "normal" fuel supply the two stage engine only needed a few extra gallons but they were in the fluid coupling and in the larger oil cooler and not just sitting in the oil tank.
P-63 used the size inlets they did because Bell engineers were stupid?
Or because the engine needed more cooling air?
P-39 inlets
