P-61 alternatives

[MikeMeech]

Were any USAAF studies or prototypes made of trying to fit the APS-4 radar into a single place fighter like the P-51 or P-47, similar to the deployment in the F4U-4N or F6F-3N. The P-38M was late to the War.

Hi

Well if the P-61 is unavailable then the USAAF may well have asked the British for more Beaufighters, such as the 414th, 415th, 416th and 417th NF squadrons of the 12th Air Force used in the Middle-East, equipped from June-August 1943. Or maybe asked for Mosquitos from the British. Both these types were also used for night-interdiction as well as night fighting.

Mike

 

[pinehilljoe]

the reason I'm curious if studies were done for the P-47 is the P-61's relatively low speed.

 

[jmcalli2]

The night fighter version of the Douglass A20 Havoc known as the P70 might have been fitted with PW R-2800 engines. With 18% more power and less drag due to the smaller diameter engines it should have a decent performance. I suspect 350mph. Fitting navy two stage supercharger engines even more. The A26 Invader seems a good candidate as well.

The Germans tried radar on the Me 109 and Fw 190. The pilot could tell range and approximately who far up/down left/right the target was but they found staring into an abstract oscilloscope destroyed his precious night vision. I really don't know how the USN got around this. The radar would have to be so good the pilot didn't need night vision.

The difference in diameter is 2.2 inches.

 

[jmcalli2]

J jmcalli2

How were interdictions done at night?

It's been a while since I read it. Wish I remember where I read

it. A quick google search found this site; Beware the Black Widow | History | Air & Space Magazine
I've included a screenshot also.

 

[MiTasol]

The difference in diameter is 2.2 inches.

And you would need to redesign the nacelle to reduce the frontal area - probably not going to help because the MLG pretty much fills the nacelle.

I do like the idea of the twin Pratts with 2 stage blowers but then again I prefer working on Pratts and the sound of them.

 

[pbehn]

We used to put lightly exposed radiographic film over the screen to darken it but it only partly solves the issue, I could still see a green line for hours after finishing work every time I shut my eyes.

BiffF15 Having been "disturbed" recently by Typhoons on exercise Crimson Warrior which always involved flights at night, how does the pilot use a head up display at night, doesn't it eliminate the use of eyes to see anything outside of the plane? From what I know and have experienced about human night vision, it is better than most people think it is because very few people use it. As I understand it, it takes 20-30 minutes for eyes to become used to very low light and only a seconds use of artificial light to take you back to needing that 20-30 minutes again. For a while when I was training, I had to develop macro photographs that had to be developed under minimum safelight conditions (no red light as you see in the movies). To be honest it was easier to literally learn to do it with your eyes closed, like a truly blind person, than wait the 20 minutes needed for your eyes to pick up what little could be seen.

 

[BiffF15]

BiffF15 Having been "disturbed" recently by Typhoons on exercise Crimson Warrior which always involved flights at night, how does the pilot use a head up display at night, doesn't it eliminate the use of eyes to see anything outside of the plane? From what I know and have experienced about human night vision, it is better than most people think it is because very few people use it. As I understand it, it takes 20-30 minutes for eyes to become used to very low light and only a seconds use of artificial light to take you back to needing that 20-30 minutes again. For a while when I was training, I had to develop macro photographs that had to be developed under minimum safelight conditions (no red light as you see in the movies). To be honest it was easier to literally learn to do it with your eyes closed, like a truly blind person, than wait the 20 minutes needed for your eyes to pick up what little could be seen.

pbehn,

Prior to wearing NVG's we would just turn it down, along with all the interior lights, and acclimate. When NVG's came out, we would turn off all interior lights, turn the HUD down super low, and get fairly decent use out of the goggles. I didn't care for the NVGs as they were heavy, and if not well focused, would give me unbelievable eyeball headaches. Or they would come off during heavy maneuvering and would smash into your dangly bits with a lot of force... While wearing them we would look around the HUD, and if we needed to look through it would look under the NVGs. They sit far enough away from your eyes that its easy.

The NVGs had some good uses and not so good ones. Good ones were long range visual pick ups with the right conditions, of other fighters. Or doing rejoins on the tanker (although it looked like a spaceship at times). You could probably land without any exterior lights if there was enough zodiacal light (star light) or a little of the man made type. Bad ones were seeing two lights, one brighter than the other, and assuming that the dimmer was further away (not always the case). Annoying weight, could come off, and were a pain in the arse.

What I can't answer is how the Helmet Mounted Sights integrate, if at all. If a jet carries a Pod of some sort (or IRSTS) it could probably be integrated. We also have data link now, and that is incorporated into the Helmet. If forced to fly with one or the other, I would take the helmet. When i flew with NVGs I got to the point were I only pulled them on when getting close to other guys.

Long winded answer, hope that covers it.

Cheers,
Biff

PS: Realize I leave a lot of stuff out to prevent some info from being compromised.

 

[Shortround6]

There was a reason the P-61 was as big as it was. Aside from carrying the turret it was supposed to stay in the air for a certain number of hours.

The A-20 is a much smaller airplane,

The P-61 carried 646 US gallons of fuel internal to feed it's two stage, supercharged navy style engines. Normal fuel capacity of an A-20 was 400 gallons in the wings. Yes on the later models it could use fuel tank/s in the upper bomb bay. But then the later P-61s got drop tanks. Some got a fuel tank in place of the turret (?).

P-61 put the intercooler intakes and carb intakes in the wing just outboard of the nacelles, which is where the outer wing tanks are on an A-20.

P-61 wing area, 664 sq ft
A-20 wing area 464 sq ft.
Beaufighter.......502 sq ft
Mosquito...........454 sq ft.

The US got both reverse lend lease Beaufighters and Mosquitos to use as Night fighters while waiting for the P-61.
Perhaps a good reason why they weren't interested in single engine fighter lash-ups. Or spending a lot of time redesigning the A-20 to take bigger engines, not to mention the A-26 first flew in the summer of 1942.

 

[Koopernic]

The difference in diameter is 2.2 inches.

2.2 inches is a 5% reduction in diameter results in a 10% reduction in frontal area and therefore 10% less drag. It is substantial.
Then there is the 18% to 30% increase in power In addition to options such as water injection and two stage superchargers.

 

[Shortround6]

R-2800-65s as used in the P-61A's and later aircraft were about 550lbs heavier each than the R-2600s used in the A-20s.
This does NOT include the weight of the intercoolers, the ducting or the larger propellers. It does not include the weight of the oil coolers and the oil and/or any other "accessories".

The 2nd A-26 prototype, ordered in June of of 1941, was to be a night fighter version.

four 20mm in the belly pod. This plane used single stage, two speed engines.

Going backwards and trying to install the heavier 2 stage engines in the older A-20 airframe was not going to happen in my opinion. Granted the A-26 program slipped (rather badly) but going back and redoing so much of the A-20 means a much later introduction of the A-26.

 

[jmcalli2]

2.2 inches is a 5% reduction in diameter results in a 10% reduction in frontal area and therefore 10% less drag. It is substantial.
Then there is the 18% to 30% increase in power In addition to options such as water injection and two stage superchargers.

When you use the diameters to calculate the area it is a 8% difference.

You also have to take into account that the A-20 was a generation behind the

P-61 in aerodynamics. Remember the A-26 used R-2800s but also had much better aerodynamics as a next generation design, yet managed only 42MPH more, 317mph to 359MPH on 800 more HP; hardly competition for the P-61's 366 to 430MPH. In fact, a version of the A-26 was evaluated as a night fighter and rejected in favor of the P-61.

 

[Milosh]

Why do you keep mentioning performance for an a/c that never saw combat?

The first P-61C aircraft was accepted by the USAAF in July of 1945. However, the war in the Pacific ended before any P-61Cs could see combat. The forty-first and last P-61C-1-NO was accepted on January 28, 1946. At least thirteen more were completed by Northrop but were scrapped before they could be delivered to the USAAF. Northrop records show an additional 400 P-61Cs with 1945 serial numbers to have been on order, with blocks 5 and 10 being at least in the planning stages.

 

[Dana Bell]

I think the oft-quoted figures touting P-61 performance are slightly off. AAF Manual 45-59-1 Security Classification and Selected Data on AAF Aircraft and Equipment dated August 1945 was, itself, formerly classified Confidential. Page 23 describes the P-61A and P-61B with the unclassified max speed as "Over 375 mph." Critically, the classified max speed is listed as 363 mph 15,000 feet (formerly Restricted). What matters to me is that the P-61 was the only aircraft in the document to list a classified max speed lower than the unclassified max speed.

Another note explains that the P-61C will have the CH-5 turbo-supercharger for high altitude performance. No projected high speed is listed, but internal memos note that the P-61C's actual high speeds were dismally below projections.

Cheers,



Dana

 

[jmcalli2]

Why do you keep mentioning performance for an a/c that never saw combat?

The first P-61C aircraft was accepted by the USAAF in July of 1945. However, the war in the Pacific ended before any P-61Cs could see combat. The forty-first and last P-61C-1-NO was accepted on January 28, 1946. At least thirteen more were completed by Northrop but were scrapped before they could be delivered to the USAAF. Northrop records show an additional 400 P-61Cs with 1945 serial numbers to have been on order, with blocks 5 and 10 being at least in the planning stages.

Maybe because the other guy was talking about an A-20 with R-2800s, a plane that never existed.

 

[MiTasol]

When you use the diameters to calculate the area it is a 8% difference.

And if you cannot slim nacelle because of the MLG and other things that hide there then the reduction in area is zero.

 

[MiTasol]

AAF Manual 45-59-1 Security Classification and Selected Data on AAF Aircraft and Equipment dated August 1945

Hi Dana
Interesting sounding document but I can find no trace of it using Dogpile
Is it available on line that you know of?
Mi

 

[Dana Bell]

Hi Mi,

No such luck - it's in the T2 section, formerly classified, bulky reports section of RG18 (CDF 1943-45) at the National Archives. I suspect there are copies at Maxwell too, but I've not looked there.

Cheers,



Dana

 

[jmcalli2]

I think the oft-quoted figures touting P-61 performance are slightly off. AAF Manual 45-59-1 Security Classification and Selected Data on AAF Aircraft and Equipment dated August 1945 was, itself, formerly classified Confidential. Page 23 describes the P-61A and P-61B with the unclassified max speed as "Over 375 mph." Critically, the classified max speed is listed as 363 mph 15,000 feet (formerly Restricted). What matters to me is that the P-61 was the only aircraft in the document to list a classified max speed lower than the unclassified max speed.

Another note explains that the P-61C will have the CH-5 turbo-supercharger for high altitude performance. No projected high speed is listed, but internal memos note that the P-61C's actual high speeds were dismally below projections.

Cheers,



Dana

Maybe this will help on the P-61C:
Northrop P-61C Black Widow

 

[Koopernic]

When you use the diameters to calculate the area it is a 8% difference.

You also have to take into account that the A-20 was a generation behind the View attachment 601986P-61 in aerodynamics. Remember the A-26 used R-2800s but also had much better aerodynamics as a next generation design, yet managed only 42MPH more, 317mph to 359MPH on 800 more HP; hardly competition for the P-61's 366 to 430MPH. In fact, a version of the A-26 was evaluated as a night fighter and rejected in favour of the P-61.

The P-61 had two stage intercooled superchargers (originally developed for the US Navy) while the A-26 had single stage superchargers. Latter version of the A26 managed over 400mph. The superior speed of the P-61 over the A26 comes almost certinly down mainly to the P-61 being able to maintain power to higher altitude. The altitude of maximum speed suggests this (16000ft versus 20,000ft).

The R-2800 appears to be about 300lbs heavier than the R-2600 but I suggest it is within the capacity of the A20 to handle especially as the bomb bay would not be used.

 

[jmcalli2]

The P-61 had two stage intercooled superchargers (originally developed for the US Navy) while the A-26 had single stage superchargers. Latter version of the A26 managed over 400mph. The superior speed of the P-61 over the A26 comes almost certinly down mainly to the P-61 being able to maintain power to higher altitude. The altitude of maximum speed suggests this (16000ft versus 20,000ft).

The R-2800 appears to be about 300lbs heavier than the R-2600 but I suggest it is within the capacity of the A20 to handle especially as the bomb bay would not be used.

Do you have a source for 400mph A-26? I've never seen it over 370.
Later versions of the P-61 were at 430mph.
And 370 is amazing at the altitudes it was designed to fly at, under 15,000.
The P-61 was designed for 15-20,000+ altitudes, thus the supercharger differences.

However, my point was replying to the idea that an A-20 with R-2800 engines would be better than the P-61. I just used the A-26 as an example of a more advanced aircraft (than the A-20) using those engines being roughly equal or slightly inferior to the P-61; therefore, the less advanced A-20 would not likely perform better. If it would, why build the A-26 at all?

I'm a fan of all three aircraft. Only the A-26 was still in combat 20 years after its first flight.