P-61 Performance (6 Viewers)

[MIflyer]

I recall immediately one, the first Me 262 Mossie encounter.

First, the 262 was terrible at turning, at least by fighter standards. It had a control stick that unfolded to give the pilot more leverage for the ailerons.

Second, not that long ago I read something a pilot flying a restored Mossie said: It was not good at turning.

 

[SaparotRob]

First, the 262 was terrible at turning, at least by fighter standards. It had a control stick that unfolded to give the pilot more leverage for the ailerons.

Second, not that long ago I read something a pilot flying a restored Mossie said: It was not good at turning.

Okay. So we have two famous fighters, neither especially good at turning, dueling with each other. The Mossie still used evasive maneuvers to get away.

 

[ThomasP]

FWIW if my info is correct

re Mosquito turn ability

The Mossi F & NF Mk II were stressed for 6g (I think) design & 8g ultimate, the F & NF versions having strength mods vs the bomber variants which were 5g design & 7.5g ultimate.

The Me262A had 6g design max (I think ?), not sure what the ultimate load factor was. (If anyone has different info please let me know.)

However, the wing loading for the Me262A (clean) was around 50% higher than the Mossi F/NF Mk II (clean) - at about 60 lb/ft2 vs 40 lb/ft2 respectively - so even if the practical pilot-limited g loads were the same the Mossi should have been able to easily out turn the Me262A (and later heavier variants) at low to medium speeds - medium being in the 250 - 300 mph IAS range which covers the Mossi's Vmax at any(?) altitude.

I think the above is correct, but if anyone has conflicting info please let me know.

 

[GregP]

According to modern pilots who have flown the Mosquito, it is a very neat airpalne, but will never be mistaken for a fighter by anyone flying it. ANY single-engine fighter will out-turn it and most are faster. The real problem for defense against a Mosquito was high cruise speed. If you weren't at just the right place at just the right time, it was hard to catch. But if you DID catch it, it wasn't going to evade very well against a faster, better-turning, well-armed attacker.

Turns out, history says it was hard for defenders to be in the right place at the right time.

 

[Jugman]

Reflecting on this some more, the P-61's tip speed (860 fps) with 12'2" propellers was pretty normal. It's not like the screaming 903-963 fps of the P-38 or the 964 fps for the B-25. Unlike the P-47 that lost 16-22mph when fitted with 4 bladed version of the B-26's propeller.

 

[ThomasP]

FWIW

The P-61A-1 & A-5 used the same engines as the F6F and would have had the same limits, which was 2550 rpm (I think) in service at the higher altitude.

My understanding is that the limit on the P-61A-10's R-2800-65W engine output at the higher altitude was the IHP (Indicated Horse Power) that would have been generated at 2700 rpm, said IHP being proportional to the stresses generated inside the engine on the pistons, crankshaft, supercharger, etc.

As an example, when the Merlin XX was putting out 1440 BHP with +16 lbs boost at 11,000 ft in high gear, but the engine was generating 1750 IHP, with about 300 HP being absorbed by the supercharger.

In low gear the Merlin XX's respective BHP/IHP was 1470/1700 at +14 lbs boost at 6,750 ft, with about 215 HP being absorbed by the supercharger..

This limit with the Merlin XX-23 resulted in the Merlin 24/25. As note above, the Merlin XX-23 at 1440-1470 BHP were limited by the internal stresses to about 1750 IHP using 130 grade, and while switching to 150 grade reduced the chance and frequency of detonation at that output, increasing the BHP/IHP caused various mechanical breakage issues. After various strength mods the Merlin 24/25 could reliably handle upto 1640 BHP at +18 lbs boost with 130 grade, and upto 1800 BHP at +25 lbs boost using 150 grade without blowing up right away. At +25 lbs boost the Merlin 24/25 was putting out 1790 BHP at 3,750 ft in high gear, with about 2170 IHP - the supercharger absorbing around 370 HP.

I think most of the Merlin 24/24 strength mods were incorporated in some of the Merlin 60 series and later as well.

I think this is correct.

 

[Juha3]

First, the 262 was terrible at turning, at least by fighter standards. It had a control stick that unfolded to give the pilot more leverage for the ailerons.

Second, not that long ago I read something a pilot flying a restored Mossie said: It was not good at turning.

Well, the Mossie wasn't exactly a dogfighter, but that engagement at least began at high speed and high altitude—the Mossie pilot reacted in the standard way upon spotting an aircraft approaching rapidly: full throttle and climbing. They were already at a high altitude, as photo-recon (PR) aircraft typically were. And the 262's turning capability at high altitude and high speeds wasn't actually that terrible.
And yes, Mossie pilots tended to avoid day combat with single-engine LW fighters, even if Bob Braham claimed two day victories over Fw 190s he was eventually shot down by a 190 pilot from the JG 1.

 

[MIflyer]

Kit Carson described a combat with a Me-262 that had come out to attack a PBY that was rescuing some downed aircrew. The P-51 could easily outturn a 262, but the 262 could fly around a circle so much faster that it basically cancelled out the ability of the Mustang to turn tighter and get its guns pointed in front of the 262.

Similarly, the P-61 was described as the USAAF's "most maneuverable fighter" but that was in terms of turning ability. The P-61 could out turn almost anything once it was established in the turn but its roll rate was not all that great, so was it truly "most maneuverable"? Depends on the circumstances.

 

[hermankeil]

Regarding the P-61's maneuverability, in the 1960s I knew a P-61 pilot, Wilfred Bachle. He told me that he once got into a friendly dogfight with, as I recall 4 Marine Corsairs, and cleaned their clocks.

 

[Tom Fey]

 

[MIflyer]

Regarding the P-61's maneuverability, in the 1960s I knew a P-61 pilot, Wilfred Bachle. He told me that he once got into a friendly dogfight with, as I recall 4 Marine Corsairs, and cleaned their clocks.

In an article in what I think was Wings/Airpower the the 1970's a WW2 P-61 test pilot was quoted saying that with that airplane and a full 3 man crew with an operational top turret he thought he could take on any four WW2 prop driven fighters and beat them.

 

[MrSmoothie]

It was Air Classics, March 1971. First issue I ever saw, i was 11— and still have it. I have a PDF of the article, I'll try to attach it

 

[MrSmoothie]

Great article!

 

[MIflyer]

The odd thing about the P-61 was that it was designed for not only night fighting, including not only multiple crew positions with good visibility, special provisions for radar as a designed in feature rather than an add-on, and very heavy armament - but also extreme maneuverability for an aircraft of that size.

Read about any WW2 night fighting and you see that such maneuverability was not very useful. At night "dogfighting" is nonexistent. You have to stalk your prey carefully to prevent losing it on the radar scope, get into position, and BLAM! If an airplane saw you coming and tried to evade you then that probably was the end of that combat. It is true that Mossies would lure German night fighters in by acting like a bomber and then turning in a circle to come in from behind the other fighter but that does not require much maneuverability - which the Mossie did not have, anyway. After all, the Ju-88, BF-110G, Do217, and He 219 were almost certainly even less maneuverable than the Mossie and a single engined Wild Sau fighter did not have radar with which to reacquire the target if it broke away. And I can hardly think of a better way to lose control of an aircraft at night than to be horsing it around in tight turns.

One article talked about the P-61 being designed to put down its flaps, throttle back, and "float" over London all night awaiting for interception opportunities, able to turn on a dime but I don't know of anyone who actually did that. In reality they raced around the sky following the ground radar directions.

If the people at Northrop really knew what night fighting was going to be like, would they have designed their Black Widow the same way? I really doubt it. The P-38M probably was a better night fighter, or would have been except for the fact that the poor radar operator was crammed in there so tight he was of little or no use at aiding in visual scans. The Swordfish P-38 designed to investigate the compressibility problem was a better two seat design but that was hardly something that could have been done as a Depot mod. Comparing the P-38M and P-61, the units in the field found them of being of about equal effectiveness, with the P-61 having the edge due to better crew coordination.

The P-82 almost certainly would have been far and away the best nightfighter of WW2, even if it had not had vastly superior performance. The radar operator as well as the pilot had a great view.