P-61 Performance

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MIflyer

Captain
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May 30, 2011
Cape Canaveral
Barrett has mentioned the questionable performance of the P-61. I recently obtained a copy of the P-61 Pilot's Training Manual. Note what it says:

P-61 Flight Manual9.png


Not that it says the P-61 "edged out" the P-70 in speed at all altitudes. This is not a ringing endorsement. The P-70 was a modified A-20, the aircraft being made available because they were supposed to be the turbosupercharged version of the airplane, a program that was canceled because a turbo failure caused a crash (of course I am not sure anything ever equipped with a GE turbo did not have a prototype crash). So the aircraft did not have turbos added and became P-70's, most of which were used for training in Florida. The P-70 was at best a minimally capable night fighter, not really being fast enough or fast climbing enough for the job, and being only lightly armed. It was built only in small numbers and its limitations in the Solomans Islands campaign led to a local adaptation, a P-38F being equipped with radar. And except for climb and altitude performance the P-61 seemingly was only a little better than the P-70. The P-38M was found by the combat users to be better than the P-61 in terms of performance but no more effective overall since the guy in the back seat running the radar apparantly was almost useless for aiding in spotting targets visually.

Now, the P-61C, which was equipped with tubosuperchargers liek the P-47 rather then the P-61A and P-61B engines which were like the F4U and F6F, was a much faster airplane, exceeding the performance of just about every other WW2 night fighter. But it was effectively a postwar airplane, by which time a radar equipped P-82C probably would have proved to be far superior.

P-38nghtFtr-1.jpg


Lockheed P-38M.jpg
Screenshot 2024-11-23 at 16-09-07 P-70 at DuckDuckGo.png
Screenshot 2024-11-23 at 16-04-35 Northrop P-61C Black Widow National Museum of the United Sta...png
 
The performance differences are significant. What is questionable about it?
P-70 speed peaks near 15000 ft - 306 mph TAS with 2300 RPM, at 27000 lbs, climb rate at this height ~450 ft/min ( combat power ), ~1130 ft/min initial
P-61 A/B speed peaks at 20000 ft - 346 mph TAS with 2550 RPM, 30000 lbs. (At this height, P-70 is 290 mph). Initial climb 29000 lbs 2560 ft/min, still climbing 1900 ft/min at 15000 ft.

I don't have data for the P-61C, other than prop diameter was increased by 6 inches.
 
re war-time P-61 maximum speeds

Somewhere on the internet (I think) there are flight test reports on the P-61A and B. I do not remember for sure if they were on the net (if so I did not download them) or if I ran across them in hard copy, but I have a summary of the results in my notes.

Performance tests of the P-61A Airplane
Memo Report No. Eng-47-1796-A
26 August 1944

Standard production P-61A-1-NO but fitted with R-2800-65W engines, tested with/without turret installation
TOGWs were 29,240/27.600 lbs

Vmax___________Altitude_____Engine Setting
363/365 mph____22,500 ft____Normal power (2550 rpm at 49.5"Hg)
360/363 mph____21,600 ft____Military power (2700 rpm at 53"Hg)
369/372 mph____17,600 ft____WEP (2700 rpm at 60"Hg with ADI)

The speeds were run through the full standard correction process.
 
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There was a multi part article in the old Wings/Airpower magazine. The first hand accounts of pilots if I remember basically said they loved the plane, but it just wasn't fast enough. I'll try and dig it out of my files and scan.
 
There was a multi part article in the old Wings/Airpower magazine. The first hand accounts of pilots if I remember basically said they loved the plane, but it just wasn't fast enough. I'll try and dig it out of my files and scan.
I remember that article. I said the handling was great, the firepower was awesome. EVERYTHING except top speed was superior. It was apparently VERY maneuverable with respect to most single-engine fighters, too, and could hold it's own in a dogfight, even against respectable opposition. Also, since it had only small ailerons combined with spoilers, the high-speed (think a downhill line) roll response was light and better than many single-seaters. That is, it didn't "heavy up" and get slower with speed.

Many very good properties for a not-so-well known airplane.
 
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I recall an article by a test pilot that said with a good crew and the turret installed a P-61 could take on any four WW2 prop driven fighters. And the official USAAF history says that the P-61 was the service's "most maneuverable fighter." I think that one on one in daylight between a P-61 and an FW-190 would favor the Black Widow, unlike the Mosquito. The C model redressed the speed problem, but it was too late for WW2. I think the P-61 would have been great for Korea in both night interception and interdiction but they were gone by then.
 
I remember that article. I said the handling was great, the firepower was awesome. EVERYTHING except top speed was superior. It was apparently VERY maneuverable with respect to most single-engine fighters, too, and could hold it's own in a dogfight, even against respectable opposition. Also, sine it had only small ailerons combine with spoilers, the high-speed (think a downhill line) roll response was light and better than many single-seaters. That is, it didn't "heavy up" and get slower with speed.

Many very good properties for a not-so-well known airplane.
I had time to dig through my boxes and look for the old issues of Wings and Airpower issues. There was an account of a fly off between the P-61 and Mosquito, the author interviewed Colonel Kratz and said he could out turn the Mosquito, and over took it, but he was convinced the Brits were holding back on the speed so no Mosquitos were diverted to the USAAF. Very good series of articles. Around PDF page 7 is the description of the fly off between the P-61 and Mosquito. Copyright by Sentry books, 1976

I keep hoping one of the Wings/Airpower CDs of all the issues will pop up on eBay; to buy them from the current vendor they are pricey, $100/decade of magazines or 120 issues (which at $1.20 an issue I guess its not that bad. My favorite part of the magazine was all the first hand accounts.
 

Attachments

  • P-61 pt 2 Dec 1976.pdf
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I have no doubt that a P-61 could out turn a Mossie. I do not recall reading of a Mossie crew using a tight turn as an escape maneuver against a fighter.
Not as an escape technique perhaps but definitely as an intercept technique with Monica tail warning radar.

"The two centimetric squadrons were also equipped with the
MONICA tail warning radar which, in the bomber support context,
was used in the 'Whiting Manoeuvre'. Here, if a bogey was detected
astern, it was allowed to approach within 5,000 feet whereupon the
pilot would swing his aircraft through 360º in an attempt to get behind
the potential target. If successful, use of the 'Whiting Manoeuvre'
would reacquire the hostile on radar and allow the navigator to bring
his pilot within range for a visual identification. MONICA was widely
used throughout No 100 Gp's fighter arm and the Group is thought to
have fielded the Mks IIIE (100 produced), IV (specifically for AI Mk
X equipped aircraft), VI (96 produced) and VIII (again for AI Mk X
aircraft) variants."


See p33 onwards.
 
You guys outa look what former member, writer historian Dana Bell had to say about the p-61 including the so called fly off.
Search his name here on this board...
 

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