P-61 Performance (1 Viewer)

[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.

Tirns out, history says it was hard for defenders to be in the right palce 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 outrun 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.