P-61 Endurance

[Zipper730]

I finally found a note I copied at the National Archives yesterday. On Christmas Day 1944, the Northrop rep embedded with the Fifth Service Command reported:

The ships with the extra gas tanks have just enough range for a good combat mission now.

It's not exactly a rave, while the turbochargers were purposely omitted to increase endurance (which makes sense), but if two hours at full throttle was a requirement, I think the turbos might have been the better choice as you'd have more power at altitude, and by flying higher, one would, for the same IAS, fly further (TAS).

Do you know when the requirement for loiter changed to two hours at full throttle?

 

[Shortround6]

I would guess that the change to two hours at full throttle went away pretty quickly as no US aircraft engines were really rated that way, unless max continuous or "normal" power is what is meant by full throttle (it sure wasn't military power).

 

[Zipper730]

I would guess that the change to two hours at full throttle went away pretty quickly as no US aircraft engines were really rated that way, unless max continuous or "normal" power is what is meant by full throttle (it sure wasn't military power).

Were any built that way?

 

[MrSmoothie]

Maybe I missed it, but has anybody mentioned that the first production P-61's did not have provision for drop tanks, but later ones did? I can't remember if drop tanks made it on later A models or not until the B series.

I don't think the "ferry" tank which went into the space occupied by the turret is relevant to the loiter time discussion -- they'd never have flown combat with those installed.

An aside, when I really dug into P-61 history last year I was surprised to learn just how few made it to combat with the top turret. Many, if not most, had no .50's installed, while quite a few in the Pacific had what looked like a turret, but was actually a fixed installation of 4x.50's with a streamlined fairing, the work being done, if I'm not mistaken, in Hawaii before heading out to the final destinations. This fairing is not too hard to spot once you know what to look for -- it's kind of flat on the top. "Moonlight Mickey" and "Lady in the Dark" are two well-known Widows with this non-turret (although model builders persist in using the production rotating turret).

 

[Zipper730]

The original spec called for a 2-hour endurance at full throttle; I hope to be copying the original flight test results later this week...

If you found anything extra, I'm curious when 8 hours loiter time became a requirement. Also, when was the design solidified (by that, I mean the airframe had basically taken on it's final shape, the engine & supercharger was selected, the guns and cannon were placed as intended)?

I'm just wondering when the decision to abandon the turbocharger for the twin-stage supercharger (which was a decision made), and how this compared with loiter time. Looking at the 2 hour full throttle requirement, I'm not sure if the engine could run like that, as emergency power allows only 5 minutes, military power allows 30 minutes, unless normal rated power was to be used.

That said, there is a figure that lists the F4U's maximum endurance at maximum speed as 0.86 hours, or 51 minutes, 36 seconds.

 

[Dana Bell]

Hi Zipper,

Nothing new yet. I'm finding lots of documents on early XP/YP-61 evaluations, but nearly everything is based on Northrop estimates rather than actual flight tests. Later field reports include complaints about speed, altitude, endurance, lack of a functioning turret, and other minor details, but no one was posting actual numbers. This week I'm downtown in the interwar Navy files, but I'll be getting back to the P-61 in mid-August...

Cheers,


Dana

 

[Zipper730]

Nothing new yet. I'm finding lots of documents on early XP/YP-61 evaluations, but nearly everything is based on Northrop estimates rather than actual flight tests.

I still figure that's gotta be useful in some way.

This week I'm downtown in the interwar Navy files, but I'll be getting back to the P-61 in mid-August...

Sounds great.

 

[Zipper730]

This is something I found

The Shrike was a preliminary project by Northrop: I'm not sure if this was the earliest sketches for the P-61, or an earlier concept which inspired the ultimate shape of the P-61 Black-Widow. It clearly had many of the key features

• Twin booms
• 2-engines (which might have been R-2800)
• 3-crew
• A turret

While I'm not sure if the armament called for a 20mm armament off the bat, as this design had 6 guns in the nose.

The chronology seems to follow

• August, 1940
  • General Emmons was briefed on the British development of radar, and that they were working on developing versions that could be carried aboard aircraft
  • British Purchasing Commission announces urgent need for night fighter: Some sources seem to imply an 8 hour time on station here
• October, 1940
  • 10/21: Vladimir Pavlecka was told of the USAAC's need for night fighters
  • 10/22: Pavlecka was given the specifications: He wasn't told exactly how the radar worked, but was told that it assisted detecting fighters at night, and might have been given some basic figures on dimensions, and to keep it in his head as best he could; around this time period, Douglas was developing he A-20 into a night-fighter, and working on the XA-26A for this mission too.
    • The various endurance requirements, whether they were changed by this point, would require a large aircraft and the Shrike was used as a baseline.
    • Crew would be 3, with a pilot, a gunner, and a radar-operator
    • Aircraft would use 2 x R-2800 and a twin-boom configuration
    • Two turrets would be mounted fore and aft with either 2x0.50" or 4x0.50"
    • Weight was estimated to be: 16245 lb. empty, and 22654 lb. loaded
    • Dimensions were estimated to be: 45'6" in length; 66'0" in span, 13'2" in height
• November, 1940
  • 11/14: Fore/aft gun arrangement were deleted; upper and lower turrets (2 x 0.50" apiece) were placed in lieu; an extra crew member was added
  • 11/22: Belly turret deleted, crew reverted back to 3
• December, 1940
  • 12/5: Design was formalized into Northrop Specification 8A (NS-8A).
    • Personal thoughts: Not sure if this was the first specification that included a 2 hr full-throttle requirement, and if 8 hrs was still required at lower power-settings; is unsure if the supercharger selection had been made at this point either.
  • 12/17: Northrop requests a quote for two experimental prototypes
• January, 1941
  • 1/11: After several design changes requested by the USAAC, Northrop signed the contract
    • I suspect that at this point the shape was largely finalized with the exception of the 20mm cannon positions
• March, 1941
  • 3/10: Contract issued for 13 YP-61's
• April, 1941
  • Mockup was ready for inspection
    • 4 x 20mm removed from wings and repositioned under the fuselage
    • Fuel capacity increased from 540 gallons in 2 tanks to 646 gallons in 4 tanks.
• October, 1941
  • Pedestal mount for turrets replace ring-type mount
• December, 1941
  • 12/24: Letter of intent initiated for 100 P-61 aircraft and spares for them
• January, 1942
  • 1/17: 50 more aircraft ordered
• February, 1942
  • 2/12: 410 aircraft ordered; 50 for the RAF under the Lend-Lease program
• May, 1942
  • 5/26: Aircraft makes first flight

 

[Zipper730]

What was the Northrop Shrike designed to do?

 

[Dimlee]

Interesting slides:

 

[pbehn]

Ive just read that P-61 were stationed near my home in 1944 and eventually used against V1s which is a bit of a surprise.

 

[Milosh]

Not the best, size wise.

 

[pbehn]

Not the best, size wise.
View attachment 544961

The Wiki page seems to say they were shooting down V1s from Scorton which is showing off your range taken to extremes.

 

[jalistair]

I read somewhere that the P-61 had over 100 kills, does anyone know anything about these? Were they against bombers, fighters, were there any aces? How did the P-61 handle, was it simply a gun platform with a radar capable of stalking at night or could it dogfight?

 

[fubar57]

According to "P-61 Black Widow Units of World War 2" by Warren Thompson, there were 127 confirmed kills.

 

[jalistair]

According to "P-61 Black Widow Units of World War 2" by Warren Thompson, there were 127 confirmed kills.

Sweet, I wonder though if that was more of a night time stalk and shoot or if it had dogfighting ability. Currently reading "The Last Fighter Pilot" by Don Brown and Jerry Yellin. They mentioned the P-61 a bit. From what they describe in the book the radar system would let them know a plane was there but they couldn't see it per say and would have to stumble around in the dark looking for the plane the radar indicated. Also, it seems the P-61 was used frequently for long range navigation for the P-51 pilots.

 

[Zipper730]

Also, it seems the P-61 was used frequently for long range navigation for the P-51 pilots.

Wait, if it was being used for navigation, that would indicate a daytime use...

 

[fubar57]

Oooooooooor, the P-51s flew at night Makes perfect sense to have a P-61 or other larger aircraft with a navigator to act as escorts for fighters. It was done across the Atlantic as well

 

[BiffF15]

Wait, if it was being used for navigation, that would indicate a daytime use...

I'm guessing here, but if there is an early morning TOT (time over target), then that might drive an early morning departure (still dark) using a P61 as the NAV bird.

 

[pinehilljoe]

Did North American ever propose a P-51N like the F6FN or F4UN? Or once the P-38N was in the pipe no USAAF single place night fighters were pursued?