P-61 alternatives

Thumpalumpacus · Mar 21, 2021

FLYBOYJ said:
If you didn't have to add additional equipment, the first solution would be adding ballast before a structural mod.

Not being too conversant with the equipment weights, I'd think that extending the rear of the nacelle to accommodate the RIO -- and perhaps a larger radar than the pod-mount carried by the P-38M -- I was thinking that a plug installed forward of the cockpit to put the weight of guns and/or ammo would serve to counterbalance.

Then again, we could simply take advice about the P-39 and move the radio?

Bottom line is that if this project is taken in hand in early 1942, I don't doubt that by mid-1943 a flying solution could hit the assembly lines and be issued to squadrons for work-ups.

FLYBOYJ · Mar 21, 2021

Thumpalumpacus said:
Not being too conversant with the equipment weights, I'd think that extending the rear of the nacelle to accommodate the RIO -- and perhaps a larger radar than the pod-mount carried by the P-38M -- I was thinking that a plug installed forward of the cockpit to put the weight of guns and/or ammo would serve to counterbalance.

Again, if you're adding more equipment, yes - to stop and do a re-design (engineering, tooling, production phase in) is too much work and time consuming if can add a few pounds of ballast to achieve the same goal.

Thumpalumpacus said:
Then again, we could simply take advice about the P-39 and move the radio?

LOL - yea, just make sure the CG goes forward!

Thumpalumpacus · Mar 21, 2021

It'd definitely take some time no matter what solution was chosen, not just for the redesigns (preferably minor, perhaps more than minor being required), but also for a testing regime before operational capability is acquired.

At any rate, I suspect it was doable had the need been present (to nit at another thread, if the Me-264 had started haggling New York, or something, for instance). As it was, our need for night-fighters wasn't as pressing as the Brits, which is why theirs were pegging out better, I imagine.

FLYBOYJ · Mar 21, 2021

Thumpalumpacus said:
It'd definitely take some time no matter what solution was chosen.

The additional equipment maybe, adding ballast to support the CG, not. Ballast installations are simple to do and in most cases can be done within hours (if less).

Thumpalumpacus · Mar 21, 2021

FLYBOYJ said:
The additional equipment maybe, adding ballast to support the CG, not. Ballast installations are simple to do and in most cases can be done within hours (if less).

I'm assuming additional equipment/structure in order to give the radar operator a better crew-position behind the pilot -- extending the nacelle a couple of feet aft, and giving the RIO the room for screens and life-support equipment; and perhaps relocating the radar into the nacelle (under/behind the RIO, or between him and pilot?) in order to clear the way for guns relocated to the underside to avoid flash-blindness.

I sure wouldn't want to do a Quasimodo on my backseater for a six-hour mission like the -M would require.

Admittedly a longer development time, but still, I think 16-18 months (if started in, say, Jan 42) giving the US a competitive night-fighter by summer of 43.

I'm not sure how much extra room any -38 had in the nose for ballast (given ammo load-out) to compensate for these mods, so I'm being conservative. But I think even being conservative, we could have made a good nightfighter from that airframe by mid-1943 had the need been demanding.

There's a few ways to skin this cat, I think.

wuzak · Mar 21, 2021

Quick and easy way to get a RIO in a P-38

Snautzer01 said:

BiffF15 · Mar 21, 2021

wuzak said:
Quick and easy way to get a RIO in a P-38

Is that a recce bird (note window)? Also has the long range navaid antenna.

wuzak · Mar 21, 2021

BiffF15 said:
Is that a recce bird (note window)?

Yes.

GrauGeist · Mar 21, 2021

Typically, the SCR-720 was mounted in the nose.

Thumpalumpacus said:
I'm assuming additional equipment/structure in order to give the radar operator a better crew-position behind the pilot -- extending the nacelle a couple of feet aft, and giving the RIO the room for screens and life-support equipment; and perhaps relocating the radar into the nacelle (under/behind the RIO, or between him and pilot?) in order to clear the way for guns relocated to the underside to avoid flash-blindness.

I sure wouldn't want to do a Quasimodo on my backseater for a six-hour mission like the -M would require.

Admittedly a longer development time, but still, I think 16-18 months (if started in, say, Jan 42) giving the US a competitive night-fighter by summer of 43.

I'm not sure how much extra room any -38 had in the nose for ballast (given ammo load-out) to compensate for these mods, so I'm being conservative. But I think even being conservative, we could have made a good nightfighter from that airframe by mid-1943 had the need been demanding.

There's a few ways to skin this cat, I think.

If you're going to go to all that trouble, than perhaps look to the XP-58. It had a good start but was plagued with engine development issues that ended up shelving the project towards war's end.

MiTasol · Mar 21, 2021

Structural mods involve design, stress analysis, aerodynamics, punches and dies, form blocks and other tooling, jigs, training, etc etc etc
Moving heavy components like the battery and oil tank(s) etc and adding ballast are always the preferred options

Thumpalumpacus · Mar 21, 2021

wuzak said:
Quick and easy way to get a RIO in a P-38

... and you can drop him off on your way home. I like it!

Thumpalumpacus · Mar 21, 2021

GrauGeist said:
Typically, the SCR-720 was mounted in the nose.

MiTasol said:
Structural mods involve design, aerodynamics, punches and dies, form blocks and other tooling, jigs, training, etc etc etc
Moving heavy components like the battery and oil tank(s) etc and adding ballast are always the preferred options

I'm learning a lot in this discussion. That's always cool.

MiTasol · Mar 21, 2021

Thumpalumpacus said:
I'd think that extending the rear of the nacelle to accommodate the RIO -- and --- I was thinking that a plug installed forward of the cockpit to put the weight of guns and/or ammo would serve to counterbalance.

You now have a much larger keel surface area which will try and keep the aircraft flying in a straight line so will need bigger elevators and rudders which means extending the nose for balance which means...... It is not as simple as it first sounds.

Thumpalumpacus · Mar 21, 2021

GrauGeist said:
If you're going to go to all that trouble, than perhaps look to the XP-58. It had a good start but was plagued with engine development issues that ended up shelving the project towards war's end.

I guess that's essentially my solution, without the engine swap. Say with mounting the radar and the crewman you add 4-500 lbs, without changing the engines with all that entails. What is that in terms of airspeed, do you know? I'd guess you lose thirty or forty MPH, which still gets you an improvement over either of the bomber conversions mentioned.

MiTasol · Mar 21, 2021

Thumpalumpacus said:
I'm learning a lot in this discussion. That's always cool.

That is one of the reasons I hang out here when I have spare time. There are so many here who know so much more that I do and who are willing to share it.

Thumpalumpacus · Mar 21, 2021

MiTasol said:
You now have a much larger keel surface area which will try and keep the aircraft flying in a straight line so will need bigger elevators and rudders which means extending the nose for balance which means...... It is not as simple as it first sounds.

Yeah, I was thinking the nose would have to be extended a little. I get that the rudders need to be larger, for yaw stability. So long as the platform is stable enough for night-shoots it should be okay, no?

I may be underthinking this. I appreciate y'all humoring me.

GrauGeist · Mar 21, 2021

Thumpalumpacus said:
I guess that's essentially my solution, without the engine swap. Say with mounting the radar and the crewman you add 4-500 lbs, without changing the engines with all that entails. What is that in terms of airspeed, do you know? I'd guess you lose thirty or forty MPH, which still gets you an improvement over either of the bomber conversions mentioned.

*when* the Allison V-3420s were working properly, it was able to attain a max. speed over 435mph.
Wince we're in sort of a "what-if" zone here, I'd suggest fitting it with R-2800s from the start. Also stop wasting time by trying to equip it with any and every sort of rifle/cannon that's in the Army's inventory - go for a brace of 20mm cannon.
There should be enough room in the nose for the SCR-720 radar and enough room in back for the crewman to operate the radar equipment.
I'm even thinking that the two defensive turrets may not be nessecary...

Thumpalumpacus · Mar 21, 2021

GrauGeist said:
*when* the Allison V-3420s were working properly, it was able to attain a max. speed over 435mph.
Wince we're in sort of a "what-if" zone here, I'd suggest fitting it with R-2800s from the start. Also stop wasting time by trying to equip it with any and every sort of rifle/cannon that's in the Army's inventory - go for a brace of 20mm cannon.
There should be enough room in the nose for the SCR-720 radar and enough room in back for the crewman to operate the radar equipment.
I'm even thinking that the two defensive turrets may not be nessecary...

Yeah, I'm thinking no defensive armament, and no engine swaps. For a night fighter, I'd like 4x20mm under the hood. Same 1710s, no guns pointing the wrong way, and accept the lower speed -- still in the high 300s -- as that will get the job done anyway.

What I'm thinking would certainly require redesigning the nacelle, but done right, you should be able to do that without too much fuss elsewhere. Larger rudders -- or dorsal fillets? -- to tamp down yaw from the extra length.

XP-58 is certainly more than what I'm imagining. Too much superstructure, and new engines to boot.

Shortround6 · Mar 21, 2021

Thumpalumpacus said:
Yeah, I was thinking the nose would have to be extended a little. I get that the rudders need to be larger, for yaw stability. So long as the platform is stable enough for night-shoots it should be okay, no?

I may be underthinking this. I appreciate y'all humoring me.

The Problem is that the P-38M used radar that didn't exist in 1942. let alone when work started on the P-61.

The SCR-520 radar went about 477lbs. It was replaced by the SCR-720 radar.
The P-38M used the same radar as the Corsair and F6F used in the wing mounted pods.

The parabolic dish on the SCR-520 was 30in in diameter. see The Pacific War Online Encyclopedia: SCR-520 Airborne Radar

Good radars got smaller rather quickly but the small radars aren't going to show up until sometime in 1943.

Thumpalumpacus · Mar 21, 2021

Shortround6 said:
The Problem is that the P-38M used radar that didn't exist in 1942. let alone when work started on the P-61.
View attachment 616877
The SCR-520 radar went about 477lbs. It was replaced by the SCR-720 radar.
The P-38M used the same radar as the Corsair and F6F used in the wing mounted pods.

The parabolic dish on the SCR-520 was 30in in diameter. see The Pacific War Online Encyclopedia: SCR-520 Airborne Radar

Good radars got smaller rather quickly but the small radars aren't going to show up until sometime in 1943.

Anyone know the cross-sectional dimensions of the P-38 nacelle?

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