Improve That Design: How Aircraft Could Have Been Made Better

[tyrodtom]

What reasons? I just thought the issue had to do with specialized high altitude fighters.

I'm not sure what the projected service ceiling, critical altitude, and combat altitude the XP-54 was expected to fly at, but in practice they had a critical altitude of around 28,500 feet. This isn't much different than the P-51. The P-51's seemed to be able to routinely operate at 31000 feet during combat operations over Europe. I'm not sure how high they flew for B-29 escort.
The problems I can see with the guns are temperature related, as for the radios and instruments, I'm surprised altitude would have much effect. As for engine ignition systems, why would that cause a problem?

One group, squadron, flight, or whatever, of fighters didn't escort the bombers the entire distance, they did it in relays.
Each fighter group would have only been at that high altitude for the part of the mission that were doing the actual escorting, not before the rendezvous with the bombers, and not after they'd turned over the escort duties to another group.

 

[XBe02Drvr]

Each fighter group would have only been at that high altitude for the part of the mission that were doing the actual escorting

Like I said earlier, flying unpressurized at 25K breathing O2 for hours on end is really exhausting and doesn't do good things for your mental acuity. Try KMSP to KMPV nonstop in a plane that only trues out at +/- 200 knots. That's why unpressurized civil aircraft are restricted to FL250 and below, regardless of how much O2 they carry.
Cheers,
Wes

 

[Zipper730]

The guns were temperature related. You needed more heat to the guns to keep them operating. . . .Thin air is less of an insulator than thick air and both radios (which sometimes had 600 volts or more DC running through part of them) and engine ignition systems (thousand of volts) suffered from short circuits and engine cross fired, spark intended for one plug/cylinder jumped to another contact or wire and fired the plug in another cylinder at the wrong time. This caused rough running and loss of power.

I didn't actually think of that, but it does make sense, the current can jump easier if the air acts as an insulator.

This was solved on some engines by pressurizing the magnetos, some engines required special ignition harnesses. The problems were solved but it took time.

When did these efforts begin if I may ask?

One group, squadron, flight, or whatever, of fighters didn't escort the bombers the entire distance, they did it in relays.

Even from Iwo Jima to Japan? In that case they seem to have gone all the way.

R-2800 was already there, and the navy didn't want to deal with another liquid.

Still, couldn't the USAAF have taken over funding? Why didn't the USAAF co-sponsor it early on?

 

[wuzak]

Still, couldn't the USAAF have taken over funding? Why didn't the USAAF co-sponsor it early on?

It is a question of when the H-2470 would have been available in quantity, and would it be better than an R-2800 or V-3420.

So weighing the investment in the H-2470 against spending the money increasing production of existing programs, such as the V-1710, V-1650 or R-2800.

And then you need to fund aircraft designed around it. The XP-54 clearly wasn't going to be it, and there wasn't much, if anything, else.

The XP-54 was a USAAF project that used the H-2470, so there was some support for the engine.

FWIW, the XP-54 first flew in January 1943 and the engine it used was still an experimental version.

 

[GrauGeist]

Just for the record, the Germans were working on pressurized cabins prior to the war and Heinkel had submitted a high-speed bomber design to the RLM in 1940 that incorporated a pressurized cockpit. It was rejected, however, but that concept eventually became the He219 - which did have a pressurized cockpit as well as ejection seats.

 

[swampyankee]

Just for the record, the Germans were working on pressurized cabins prior to the war and Heinkel had submitted a high-speed bomber design to the RLM in 1940 that incorporated a pressurized cockpit. It was rejected, however, but that concept eventually became the He219 - which did have a pressurized cockpit as well as ejection seats.

Just for reference, Germany wasn't unique in this regard: the first flight of the pressurized Boeing 307 was in 1938 (Boeing 307 Stratoliner). Everybody was working on pressurization: the US, the UK, the French, etc.

 

[P-39 Expert]

Just asking, but what would be the effect on a Mustang pilot on a five hour mission escorting bombers to Berlin at 25000' with oxygen but no pressurized cabin? Normal Mustang escort mission.

 

[XBe02Drvr]

Just asking, but what would be the effect on a Mustang pilot on a five hour mission escorting bombers to Berlin at 25000' with oxygen but no pressurized cabin? Normal Mustang escort mission.

I found 5-6 hours at FL250 in the Cessna 210 left me feeling pretty wrung out. And that was with the autopilot doing most of the work. I'm sure flying formation in a stick and rudder airplane, searching overhead for bandits, and weaving to stay with the bombers would have me dreaming wistfully of my rack back in the UK. And it feels SO good to take that mask off when you get down to 10K!
OTOH, the average 8th AF Mustang pilot was a decade younger and most likely more physically fit than I was at the time of my FL adventures.
Cheers
Wes

 

[pinsog]

I found 5-6 hours at FL250 in the Cessna 210 left me feeling pretty wrung out. And that was with the autopilot doing most of the work. I'm sure flying formation in a stick and rudder airplane, searching overhead for bandits, and weaving to stay with the bombers would have me dreaming wistfully of my rack back in the UK. And it feels SO good to take that mask off when you get down to 10K!
OTOH, the average 8th AF Mustang pilot was a decade younger and most likely more physically fit than I was at the time of my FL adventures.
Cheers
Wes

Love the real world perspective some of you guys bring.

 

[Zipper730]

It is a question of when the H-2470 would have been available in quantity, and would it be better than an R-2800 or V-3420.

Well that would be like saying the V-1710 don't need to be built because the R-1820 and R-1820 were built. There was clearly an interest in the USAAF in inlines.

That said, the V-3420 was awesome in power output but it was quite wide and difficult to mount in fighter-aircraft.

And then you need to fund aircraft designed around it. The XP-54 clearly wasn't going to be it, and there wasn't much, if anything, else.

And they didn't have a snowball's chance in hell. It wasn't any faster than current aircraft, if anything, it seemed a step backwards.

That said, it seemed better than the XP-55 and XP-56 in terms of stability: From what I remember those designs both had their share of trouble (at least they were lighter though, and the XP-56 did manage to creatively cool a radial and mount it amidships -- hey, let's look on the bright side); regardless, was there requirements for pressurization on the XP-55 and XP-56?

 

[wuzak]

Well that would be like saying the V-1710 don't need to be built because the R-1820 and R-1820 were built. There was clearly an interest in the USAAF in inlines.

But the V-1710 was in production and in useful aircraft during the war. The H-2470 wasn't.

The V-1710 program predated the existence of the R-1820 and R-1830. The theory of the early 1930s was that air-cooled engines were unsuitable for turbocharging, particularly at high altitudes, where the USAAC wanted their bombers to fly.

That said, the V-3420 was awesome in power output but it was quite wide and difficult to mount in fighter-aircraft.

It was about 4-5" wider than an R-3350, 6 or 7" wider than an R-2800.

And they didn't have a snowball's chance in hell. It wasn't any faster than current aircraft, if anything, it seemed a step backwards.

No, it could not match a P-51, P-47 or P-38.

That said, it seemed better than the XP-55 and XP-56 in terms of stability: From what I remember those designs both had their share of trouble (at least they were lighter though, and the XP-56 did manage to creatively cool a radial and mount it amidships -- hey, let's look on the bright side); regardless, was there requirements for pressurization on the XP-55 and XP-56?

The projected top speed of the XP-56 was 340mph!

The XP-55 actually flew faster, but wasn't the most stable.

Neither the XP-55 or XP-56 had pressurisation.

 

[GrauGeist]

Just for reference, Germany wasn't unique in this regard: the first flight of the pressurized Boeing 307 was in 1938 (Boeing 307 Stratoliner). Everybody was working on pressurization: the US, the UK, the French, etc.

Junkers successfully tested a pressurized cabin with the Ju49 in 1931, the French in 1932 with the Farman 1000 and then in 1937, Lockheed successfully tested a pressurized fuselage with their XC-35.

But I was under the impression that we were discussing pressurized combat aircraft...

 

[Zipper730]

The V-1710 program predated the existence of the R-1820 and R-1830. The theory of the early 1930s was that air-cooled engines were unsuitable for turbocharging, particularly at high altitudes, where the USAAC wanted their bombers to fly.

That said the H-2470 is basically similar in power output to the RR Griffon right?

It was about 4-5" wider than an R-3350, 6 or 7" wider than an R-2800.

At least it was flatter...

The projected top speed of the XP-56 was 340mph!

I thought it was 465...

Neither the XP-55 or XP-56 had pressurisation.

Why did one require and the other not?

 

[Shortround6]

That said the H-2470 is basically similar in power output to the RR Griffon right?

Depends on the Griffon,
A Griffon would have been a V-2240 in American nomenclature.

 

[wuzak]

That said the H-2470 is basically similar in power output to the RR Griffon right?

Similar.

But heavier, longer, taller and much less in production.

I thought it was 465...

465mph was the estimated top speed from the manufacturer. Maybe even the guaranteed top speed.

340mph was the projected (calculated) top speed based on the few flight tests and, possibly, wind tunnel tests. The calculations were done by NACA.

The guaranteed top speed of the XP-54 was, at one stage, 525mph! Its actual top speed was around 400mph, but only with a special finish.

Why did one require and the other not?

Not a clue.

Note that the XP-55 had a single stage V-1710 with no turbo, and the XP-56 had a 2 stage R-2800, but not turbo, so perhaps it was expected that they would not reach teh altitudes requiring pressurisation.

 

[P-39 Expert]

I found 5-6 hours at FL250 in the Cessna 210 left me feeling pretty wrung out. And that was with the autopilot doing most of the work. I'm sure flying formation in a stick and rudder airplane, searching overhead for bandits, and weaving to stay with the bombers would have me dreaming wistfully of my rack back in the UK. And it feels SO good to take that mask off when you get down to 10K!
OTOH, the average 8th AF Mustang pilot was a decade younger and most likely more physically fit than I was at the time of my FL adventures.
Cheers
Wes

What altitude in your Cessna? Oxygen the whole time?

 

[wuzak]

I found 5-6 hours at FL250 in the Cessna 210 left me feeling pretty wrung out. And that was with the autopilot doing most of the work. I'm sure flying formation in a stick and rudder airplane, searching overhead for bandits, and weaving to stay with the bombers would have me dreaming wistfully of my rack back in the UK. And it feels SO good to take that mask off when you get down to 10K!
OTOH, the average 8th AF Mustang pilot was a decade younger and most likely more physically fit than I was at the time of my FL adventures.
Cheers
Wes

What altitude in your Cessna? Oxygen the whole time?

FL250 = 25,000ft from what I understand.

 

[XBe02Drvr]

FL250 = 25,000ft from what I understand.

Affirmative. 25,000 feet indicated altitude with altimeter set at 29.92" Hg, not local surface altimeter setting. Masks go on at 10k, altimeter is reset from local surface value to 29.92 climbing through 18K, and in a puny 300HP piston pounder, it's a long slow slog to FL250. But eastbound it's worth it, as you can generally count on anywhere from 40 to 100+ knots of tailwind. I've seen 350 knots ground speed on the RNAV on a cold winter's night with Aurora B. blazing away off my left wingtip and the distant landscape awash in moonlight. It doesn't get much better than that.
Another advantage to this high altitude flight: a clean airframe like a C210 can glide for nearly a hundred miles (downwind) in case of an engine failure.
Cheers,
Wes

 

[BiffF15]

Anybody who's had a chamber ride can tell you. Above FL 350-360 breathing 100% O2 with an ambient pressure regulator doesn't supply enough partial pressure of oxygen in the blood to stave off hypoxia, so pressure breathing becomes necessary, a very taxing and exhausting exercise. Above approx 450, ambient pressure is not enough to keep the nitrogen in the blood in solution, and it literally "boils" out, resulting in instant death by eruption. If you're going to operate in that altitude range or higher, you need pressurization or a pressure suit, or both.
I've flown a couple hundred hours at FL 250 in a non pressurized turbo 210 Cessna, breathing through nose bags, and let me tell you, though it doesn't feel hard at the time, by the end of the day, you feel like you've been run over by a train.
I can tell you that at 260, I was good for 45 seconds after the mask came off, before the chamber floor came up and kissed my face. And at 370, pressure breathing, I was first in a chamber full of tactical jet aviators to signal "uncle" and have the chamber brought down, after about five minutes. The jet jocks were a little disgruntled that I broke up their little "macho quotient" contest early on.
Cheers,
Wes

Wes,

The 45k you reference above is actually at approx 60k and called Armstrong's Line. The Eagle could get above this easily enough and we were made aware of this during my time in the school house. I know of one now retired 3 star who has been through 75k and and still climbing...

Armstrong limit - Wikipedia

Cheers,
Biff

 

[Zipper730]

BiffF15 and X XBe02Drvr ,

I got a question, and this will probably sound stupid, but I'll ask it anyway: If you're breathing in pressurized oxygen and you lose consciousness, do your lungs inflate and pop? Or something else?