SOH P-61 project

[fliger747]

The fighter guys weren't that much impressed by the "fighter handling" but certainly much better than a similar sized B-25. I'll look in my R2800 book and see if there is anything special about the A & B model installations. The C version had an elaborate turbocharger setup, housed in the hefty bulge on the bottom of the nacelle. I'll look at what info there is on the roll rates at speed, but a four second roll is considered very good for the era. Lot of inertia there! I don't recall the P-38 being capable of a three second roll. Will research this.

Currently the CH and oil temps might be a bit on the high side. There is existing an instrumented 2 D cockpit that is handy for monitoring engine parameters etc, in addition to the AFSD utility.

I did have a copy of the POH, but think I scrubbed it from my computer recently.

Cheers: T

[fliger747]

The P-61 A and B used the very common R2800-10/65 (used in the Hellcat). The difference between the -10and -65 was in the ignition system. To model the P61 C version a big change in the nacelle countours would be necessary.

The -10/65 engines were a R2800 B series. To/Combat and Military power was 2000 hp at SL, max of 60" at 2700 RPM. At 22,500 ft 1650 HP @ 2700 RPM, 53-54" MP. The differences in output between the two appear to be very slight. (Table 53. p 381 hunnert thou) The aux blower was shifted out of neutral at 5000 ft, and to high blower at about 18,500 ft. (Graph 46, page 381, Hunnert Thou)


P-61 roll rate varied from 20 deg/sec at 100 mph to 50 deg/second at 320 mph IAS with a 90 lb control force. By contrast the P-38 topped out at 77 deg/sec at a very small range around 290 mph IAS. At 110 mph it was about 30 deg/sec and 400 mph about 47 deg/sec.

Pilots commented that for it's size manuverability was "suprisingly good". However as a fighter its manuverability was fair to (mostly) poor in the 1944 Fighter conference "flyoff".

Takeoff distances were very substantial, 1650 ft at 25,500 lbs to 2450 ft at 32,000 lbs, hard surface, no wind. VMCA varied from about 120 mph at lighter weights to 140 mph at higher weights.

Cheers: T

[fliger747]

The 10W/65W engines put out a max power of about 2230 HP at SL with water/meth injection) and had all blower shifts when wet at slightly lower (2000-4000') altitudes. Have to sniff elsewhere to find out how much extra boost was useable in WEP. Note that the engine is able to use a more (best power) stochemetric fuel/air ratio than mil power which uses extra fuel flow for cooling. So higher MP is not the only reason for the power increase.

T

[N2056]

Here's my pic-o-the-night

Work continues on the Gunner's seat. Now I have seat back tubing, and I added in the start of the gun sight assembly.

Attachment 15068

[BananaBob]

Nice work bro!

[N2056]

Thanks Bob. It sure is good to see you back in the game!

[fliger747]

With Water Methanol Anti Detonation Injection it appears at SL that max MP went from 54 to 60 ".

Tanks were good for 20 mins or so of flow.

T.

[Cag40Navy]

Wow flinger, you could make a book with all that info.

[Whitehawk]

VMCA varied from about 120 mph at lighter weights to 140 mph at higher weights.

Hey Fliger is this from America's Hundred Thousand? Only reference I've found to VMCA so far is in the re-printed AFM which mentions the aircraft 'can be controlled down to its normal stalling speed (gear and flaps up) of 100 mph IAS' Not doubting your source rather I'm trying to build as full a picture of handling the P-61B as I can so I know what I'm looking for in the testing, there's a lot of conflicting information out there lol!

[fliger747]

The VMCA value is from Hunner't Thou (p-387). A lot of the compiled handling notes are from the 1944 Fighter Conference, which had service and industry test pilots and tech reps there to evaluate both US and captured aircraft. The purpose was of course to try to find out what did work well and point towards future directions in aircraft development. Ther is also several pages of info on the P-61 series in the book "Us Experimental and Prototype Aircraft Projects, 1939-1945".

Data on the R2800 series comes from the Book "R2800, P&W's dependeable Masterpiece". Published by SAE.

The VMCA value given seems quite reasonable and about par with most other powerful twin engine aircraft of the era. Similar to the P-38 and F7F. Stall and spin were very gentle and recovery quite easy. Though the aircraft had sloppy roll control at slow speeds, the gentle slow flight manners rated it fairly good marks in this area. Even modern GA twin aircraft have a fairly high "blue line", as opposed to the certification of transport category aircraft which have much more stringent requirements.

Cheers: T

[fliger747]

Attached is engine data for the R2800-10

Cheers: T

[warchild]

Fliger!! Your awesome.. The next three days sees me starting on the Stearman and an A-10, but this weekend will be specifically for the Widow.. I'll put all your data into the flight model then and we'll see what we can come up with.. I believe the exact engine we're building is the R-6800-25S with a unique 2 stage supercharger ( which is gonna drive me nuts if i cant figure it out ) and producing 2500 hp..

All the Painters are on board. I'm still waiting to hear from Snuffy in regards to his modeling the radar operators station..

For painters.. The UV Maps arent done yet, so just hang in there with us for a lil while more.. If you can, I'd like to ask that when you get the UV maps that you work in a 4096x4096 format, reducing it to 2048x2048 for the release.. That will give us the best looking paints we can get, while not cutting too deeply into the frame rates.... Jankees has been the most vociferous and active in getting the ball rolling, so just like crashaz is managing the model team, i'd like jan to manage the texture team.. He's got a ton of great paints and there's plenty to go around..

It's been a hell of a week over the last three days for me. I've helped birth an A-7 and moved county state and national organizations one more step towards developing peer support crisis intervention teams aimed at supporting civilian victims on local scales.. I'm tired ::LOL::.. I'm gonna go rest for the night but will be back in the morning..

Jankees, i have your email and will reply to it first thing in the morning when ive gotten enough rest to think clearly..

Pam

[warchild]

Here's my pic-o-the-night

Work continues on the Gunner's seat. Now I have seat back tubing, and I added in the start of the gun sight assembly.

Attachment 15068

Thats looking outstanding Those curves aent easy to get..

[warchild]

With Water Methanol Anti Detonation Injection it appears at SL that max MP went from 54 to 60 ".

Tanks were good for 20 mins or so of flow.

T.

60?? 370 knots here we come ::LOL::

[N2056]

The seat got some padding. The gun sight is next...

Attachment 15149