P-39 "Airacobra"
A fantastic start to the air racing study. The Airacobras are quick, hold energy, and have decent power to weight for their match maker allowing them to build back speed quickly after sharp turns. They are capable of extremely tight turns, fully using the "Plan A" or "Points to Point" race strategy. However they are prone to overheating quickly.
P-400
AEC:
Starting with the P-400, it may technically be the slowest of the group but its the first of the American low tiers to feature a turbo super charger, making it one of the fastest 2.0 fighters in the study. Its exhaust vents are tiny, so while they may not prevent the plane from overheating entirely, at least they don't add to the overall parasitic drag on the airframe. I noticed around the fourth AEC test that when switching from military power to full WEP I momentarily got a boost in thrust before it quickly tapered off. Historically due to how western countries incorporated variable pitch propellers on its planes the propeller is not changing its pitch directly but is instead using a governor and oil pressure to make the change. So when I slam the throttle full forward the engines rpm spikes before the propeller pitch governor can catch up and adjust the pitch angle for a constant safe engine rpm. This results in a moment of high thrust. This quirk of the Airacobra is too small to be usable in turns for AEC but it does open up significant time saving for MEC tests.
MEC:
It took a bit of work to find a combination of MEC controls that worked best for the P-400. With the engine rpm "full throttle spike" in mind I tried to find a setting where I could abuse that behavior without destroying the aircraft. I first tried 90% pitch and 20% cooling and this allowed for "infi-wep" or WEP without the concern of overheating. The temperature numbers stayed nice and yellow the entire time, barely moving a few degrees over the course of the lap. So with that test secured that gives me room to play with the exhaust vents a bit to shave off more seconds right? Well I certainly tried. Dipping below 20% always made the engine overheat somewhere around the major chicane or the last hairpin, forcing me to dump the vents and lose any minor time savings I had. If you are going to race this plane just use the above mentioned controls.
P-39N-0
AEC:
A significant improvement over the P-400. Its better T:W allows it to maintain 300+ mph for the whole race and it maintains the good energy retention of the P-400. Generally speaking as aircraft near their top speeds the force of the air over their tail surfaces force the nose of the aircraft more and more downwards. With most aircraft the leveling off entirely with the horizon line but with the P-39 family they all sit around -2 to -4 AOA over the duration of the race. This isn't bad, it just throws me off a bit as I'm racing. On average the P-39N-0 fully overheats at H3 (hairpin 3) or Hagen forcing the pilot into a cycle of switching between military power and 103% WEP. Anything more than 103% and the engine overheats too much and too quickly for WEP to be useful.
MEC:
On tests using anything more than 90% prop pitch the engine would overheat far too quickly and would still flash red even with the vents fully open. I tried a number of combinations but ultimately landed on 90% prop pitch and a special regiment for cooling. With that prop pitch % I could close up the exhaust vents fully and only start overheating around H3 where I would then slowly open the vents more and more. Starting with 20%, that would make the numbers go down in color to orange but then moments later (even on the cooler numbers) it would overheat again. So I'd open the vents up to 30% and by then I had reached the final stretch and stowed everything again for maximum aerodynamic efficiency.
P-39Q-5
AEC:
A straight downgrade over the N-0 It moves its wing guns into gun pods rather than keeping them in the wings. This alone would cause a significant amount of parasitic drag on the airframe. It still maintains all of the overheating problems of the earlier mentions but now its exhaust flaps are slightly larger. At least it still maintains the good energy retention of this airframe.
MEC:
Using what I learned from the N-0 I started the first test out at 90% prop pitch and 20% radiator but no matter what I always ran into overheating problems. Even opening the vents to 100% was not enough by itself to cool the engine down, despite being the same engine with the same ratings as the N-0. Bringing prop pitch down to 85% would temporarily fix the problem but trying to move on from 85% prop pitch and 100% radiator post first overheat would be a death sentence for this engine.
P-39Q-25
AEC:
Overheats in about the same place as the Q-5 (around H3). With the addition of an extra propeller blade it does accelerate faster however its top speed is unchanged. So with the already good energy retention and the slightly better thrust I'm able to stay in the 290-310 mph range which is far far better than the Q-5. Still is an overall downgrade compared to the N-0.
MEC:
The P-39Q-25 can "infi-wep" at 90% prop pitch and 20% radiator. Any attempts to improve upon this result in the engine overheating and the pilot being stuck in an overheat cycle, thus ruining any attempts to save time by using less radiator. At least the airframe is consistent and easily predictable.
Planes in game but not tested:
P-39K-1: I don't have it, and none of my friends have it. It's considered a predecessor to the N-0 but I wouldn't expect it to be any faster.
Porkryshkins P-39N-0: I don't have it, and none of my friends have it. It's also no different from the N-0 already tested, so anything learned with that airframe can be said about this plane as well as they are exactly the same.
P-39Q-15:I don't have it nor does anyone I know.
Fun Facts!:
The P-400 was only ever an early export option for lend lease nations.
So its weird that its only ever seen in the American tech tree.
Britain had 80 before they switched to the "Airacobra 1" otherwise known as the P-39C and 200 P-400s were sent to the USSR after Pearl Harbor.
The P-39Q was the dedicated ground attack variant of the P-39 with many of them featuring some combination of increased armor, increased fuel, and added pylons for bombs and rockets.
They also replaced the .30 cal wing machine gun with a .50 cal machine gun pod.
The Q-15 was further reinforced over the previous Qs.
Some Soviet pilots preferred having the wing mounted guns of their lend lease planes removed as they tended to have a difficult time aiming them effectively on moving ground targets.
This change would have affected all aspects of the aircraft's flight envelope making it lighter, potentially turn tighter and perform faster than all p39's that came before it.
It would be nice if this was reflected in game.
Some German aircraft have the option to switch out nose cannons or wing cannons, or omit them entirely, why can't the Airacobras be the same?
The Airacobra saw limited time in air racing post war, the two most famous P-39's in racing were "Cobra 1" piloted by Jack Woolhams and "Cobra 2" piloted by Tex Johnston.
Cobra 2 would go on to win the 1946 Thompson Trophy race, beating out other race modified aircraft with its 2000 horsepower monster engine.
There were a number of historical P-39's in racing but it's hard to find any information regarding them outside of what wikipedia can provide.
It would be interesting to test the Airabonita, should that ever come to the game ever.
It was a naval version of the Airacobra, its aft sections were strengthened to handle carrier landings and it used a conventional tail wheel.
It had its T9 replaced by a .50 cal machine gun and 2 nose mounted .30 cals.
Since it was an experimental version of the P-39E it had a significantly worse engine, comparable to the P-400.
But it would be the lightest in the P-39 family and that could be a serious competitor in the rank 1 races.
If you wish to read more about the P-39 and its historical performance the book "Bell Aircraft" By A J Pelletier has been archived on the Internet archive.
Pages 25-41 are only about the P-39.