Improve That Design: How Aircraft Could Have Been Made Better

[nuuumannn]

WEP isn't much use if you can't use in the tropics or dessert conditions

No, the P-39N gives you notoriously bad digestion straight after the main course.

Not only that, but according to the reports on the 'N model under trial conditions is the following statement; "Airplane does not meet Air Corps cooling requirements at any of these powers."

Here: Memorandum Report on P-39N-1, A.C. No. 42-4400 (wwiiaircraftperformance.org)

 

[pbehn]

I think we have another groundhog infestation?

 

[P-39 Expert]

So if all this was true why didn't at happen Expert, why did the US leave their most valuable A6M killer back in the states or used it for secondary roles when quite clearly it would have turned the tide in the Pacific?.

The 1942 P-39s (D/F/K/L) were very overweight for the power available (V-1710-35/63) and had a hard time cruising over 18000ft with the ever-present drop tank. Almost every combat with the A6M2 Zero or Ki-43 Oscar began with the Japanese planes making a firing pass from above. Not fun. At all. Those 1942 P-39s did fight the Japanese planes to a draw despite inexperienced pilots because they were about 40mph faster and had armor protection. But pilots hated them (along with the P-40) because they had to give the Japanese the first punch, and intercepting high flying Japanese bombers (18000-22000ft) was an iffy proposition.

The decision had already been made by the AAF brass that the war would be fought with turbocharged P-38 Lightnings and P-47 Thunderbolts. Problem was they didn't have enough of them yet until the P-38F/G got into combat in very late 1942 and the P-47C in April 1943. The P-39 and P-40 would be exported under lend-lease to our allies or used for training by the AAF.

By November 1942 the -85 engine with the 9.6 supercharger gears was in the P-39N which was the best performing model of the P-39 series. It was faster under 20000ft and would outclimb and out turn both the early P-38F/G and the P-47C/D. It dived better than the P-38 and had about the same endurance as the P-47. Ceiling was competitive with both. And the P-39 was inexpensive compared to the ultra-expensive Lightnings and Thunderbolts. But the AAF had four fighters in production and the Merlin P-51 was being put into production too.

The P-39 (and P-40) would have benefitted from the two stage -93 engine that was in production in April 1943. But the field was crowded and the decision had been made to emphasize the turbo P-38 and P-47.

 

[nuuumannn]

As I pointed out, at the time of those trials in August 1942, frontline P-39 units were using the 'D model, not the 'N model. And despite the P-39N's obvious advantages compared to the earlier models, by 1944, when the P-39N has reached the frontline and had been equipping for around a year, the P-38, P-47 and P-51 were the AAF's primary fighters across both the PTO and ETO. That the P-39 remained in service beyond 1943 was down to the numbers game - the AAF needed fighters and the P-39 was available, warts 'n all. If the AAF could have equipped all its P-39 units with any of the other fighters it probably would have. They offered significant advantages over their enemies the P-39 did not possess.

 

[Shortround6]

You have about 3 things going on in late 1942, maybe more.

1, the change to the 9.60 supercharger gears on the single speed/single stage Allison. These are not magic, they do improve altitude performance by about 4,000ft. (What plane powered by the older engines could do at 13,500 it could now do at 17,500) which is not enough to make the P-40 and P-39 effective fighters at 20,000ft and above unless they lost a LOT of weight.
2. The US was late to party when it came to overboosting engines. A lot of testing was going on, some squadrons were overboosting in the field. Officially The US did not approve over boosting until Dec of 1942 (after the tests of the P-39N).
3. It took the US about 3 to 6 months to get a fighter from the factory door to an operational combat unit overseas. In the case of the P-39N the first ones rolled out the door in Nov 1942, They showed up in North Africa in April (?) of 1943 and at Henderson field in June of 1943. Shipping space arrangements and allocations of aircraft were often made before the actual planes rolled out the door.

Decisions as to which planes to send where in the first part of 1943 were made before the test flights of the P-39N. And the test flights using WEP settings in the P-39N showed some serious problems. THE USAAF and Allison called for a max cooling temperature of 250 degrees F or 121 degrees C .

We may well consider that P-39 use the Soviet union was quite different due to the Soviets acceptance of lower service life between overhauls and the usually colder temperatures the engines were operating in. You could get hot temperatures in southern Russia in the summer but lets face it, The P-39N was overheating using WEP in Buffalo New York in Oct and barely exceeding the allowable in limit in November.

Correction from Wuzak

 

[wuzak]

3. It took the US about 3 to 6 months to get a fighter from the factory door to an operational combat unit overseas. In the case of the P-39N the first ones rolled out the door in Nov 1942, They showed up in North Africa in April (?) of 1943 and at Henderson field in June of 1942.

Either that was a type or Henderson Field was using a time machine.

 

[wuzak]

The P-39 (and P-40) would have benefitted from the two stage -93 engine that was in production in April 1943. But the field was crowded and the decision had been made to emphasize the turbo P-38 and P-47.

In production and available in meaningful numbers are two different things.

In any case, Bell was working on the P-63 to use the 2 stage engine.

 

[BiffF15]

Back to how aircraft could be made better....

F4U Corsair: floorboards under cockpit and some seat adjustments so somebody shorter than a 75th percentile male would fit properly

Single-engine fighters in general: Standardize on cockpit layout. Bluntly, it's not exactly rocket science to have the instruments and controls in similar locations on different aircraft.

P-38: Put generators on both engines (the aircraft had Curtiss Electric propellers. It needed electricity to fly)

SwampYankee,

I can't help but agree that all three of your points are good. However, point number 2 has always dumbfounded me. It would have made transition from one to the next much easier and safer.

Cheers,
Biff

 

[swampyankee]

SwampYankee,

I can't help but agree that all three of your points are good. However, point number 2 has always dumbfounded me. It would have made transition from one to the next much easier and safer.

Cheers,
Biff

Thank you.

Panel design is something where, I think, the NACA, USAAC/USAAF and USN could have actually agreed on in the early 1930s. A lot of the panel designs looked like something a drunken frat boy puked up after a hard night of drinking.

 

[Shortround6]

In production and available in meaningful numbers are two different things.

In any case, Bell was working on the P-63 to use the 2 stage engine.

It took until the fall of 1943 to clear the 2 stage engine for WEP ratings. This including things like the new keystone piston rings.

Without the WEP/water injection the V-1710-93 engine was rated at 1180hp at 21,000ft
which is about 200hp less at 2,500ft lower than the Merlin 61 of spring/summer of 1942, one year earlier.

First P-63s built with the engine flew under restrictions until the engine was cleared.

 

[BiffF15]

Thank you.

Panel design is something where, I think, the NACA, USAAC/USAAF and USN could have actually agreed on in the early 1930s. A lot of the panel designs looked like something a drunken frat boy puked up after a hard night of drinking.

I have attached the cockpit panel of the mighty T-37 Tweet. This nightmare was in use into the 2000's. Plane was designed for day visual flight rules and morphed into a full Instrument Flight Rules (IFR) jet. Oh, and it held very little fuel. But at least it was loud, and the A/C sucked...

Cheers,
Biff

 

[GregP]

One of the big improvement they COULD have made to the F6F was to remove the dihedral from the outer wing panels. The decision was not to interrupt production to make the F6F roll much better. Instead, they developed the F8F Bearcat while producting the F6F-5. The F6F-6 was the fastest Hellcat, but they only built 2 of them ...

 

[special ed]

A friend flew the AT-37 in VN. All sorts of interesting experiences in combat.

 

[BiffF15]

A friend flew the AT-37 in VN. All sorts of interesting experiences in combat.

He probably flew the A-37 Dragonfly, with different engines and a whole lot more capabilities. Panel still sucked I'm sure...

 

[GregP]

Panel DID suck, but the performance was nothing short of spectacular if you compare it with a standard T-37 dog whistle. One engine made thrust and the other one just made noise. Still, you could at least go up and spin one of them.

Here's one of them:

 

[special ed]

From time to time while he was still in his career he would call and I'd listen to war stories. Before he retired, I asked him if it turned out as well as he hoped at the start. He said, " listen Ed, I get up and look outside and it's a beautiful day. I call ops and ask for a plane. (He was flying F-16s then). I go down check out, get in the bird they fueled, and go flying. It's great and they pay me to do it."

 

[P-39 Expert]

I wasn't doing it the hard way, I was using the Pilot's Operating Handbook, which the REAL pilots would have been using, and which YOU should be using, too.

My P-39N POH says full internal fuel is 87 gallons. Could be that later P-39Ns had 120 gal, I won't look it up, but I thought the P-39Q-5 was the one with full internal tanks restored after they had been reduced to 87 gallons. Maybe I disremember and maybe you do. If they DID have 120 gallons, you had 32 more gallons, which would last for 133 more miles at fast cruise, 67 more miles combat range because you have to fly back. Still isn't very impressive and isn't likely to get that way ... they are long out of service and there isn't much chance of them doing better in another war. All P-39s up to the 167th N model had the normal 120 gallons. Fuel was reduced for the Russians. Kits were available to restore the full 120 gallons. The POH numbers speak for themselves.

The F6F Hellcat was the best fighter, in terms of enemy aircraft shot down, in the Pacific, so I won't really bother with analyzing it; go look at the POH. It stands upon merit. The fact that is WAS the best at shooting down enemy aircraft is no doubt due to the US Navy holding off approving the F4U for carrier operations until the British embarrassed them by approving it for their own carriers, forcing the Navy to "save face" and ALSO use it that way. As a result, the early Corsairs were used from ground bases by the Marines and weren't living in the target-rich environment of a front-line WWII U.S. carrier fighter in the Pacific. In point of fact, the Corsair was also a VERY good fighter and would have held its own or even have been the best had it been deployed at the same time to carriers. Again, it stands upon earned merits. My purpose is not to denigrate the Hellcat or Corsair, both were excellent planes for carrier operations. Performance of the P-39N was as good as those planes and it was available before both of them.

The P-39 has no such merits in U.S. or British service and thus should be looked at with some scrutiny since it had short-range and didn't prove very good at air comat in U.S. or British service. Now, had we been fighting ourselves over, say, Nebraska, where targets were close and there was gound under the belly, it might have been fine. It wasn't over water at longer ranges. About the ground part, the P-39 didn't do very well in Europe where there WAS ground under the belly. In the ETO, it was removed from service by the British and sent to obscrure low-priority fronts, like North Africa and the Med, where it ALSO didn't do very well. It did OK in Russian service, but that isn't my country and it didn't do well for us. P-39 had 20% more fuel than a Spitfire. British P-39s were another subject, they were the reason the 1942 models were so heavy. Okay in Russian service? Just okay? Half their top aces flew the P-39 and they only received less than 5000 of them.

And, if you use a 110-gallon drop tank, you drop it before combat, so all the extra fuel is dependent upon NOT finding combat. If you are flying P-39s, you are, or SHOULD be, based close to your targets or you won't get there and back. At least with the P-51 in Europe, if they dropped tanks, there was enough range to fight combat and get home even if they DID abandon escort to make it home. Drop tank rules apply to every plane that carries them, if you find combat before your drop tank fuel is used, then the rest is wasted.

You are beating a dead horse, guy, and it isn't going to get any better. And it's time you admitted that there is a lot you don't know about the P-39.

Answers above.

 

[P-39 Expert]

Are you saying the P-39 went into combat with the 110gal drop tank still attached?

P39FOIC.pdf (zenoswarbirdvideos.com)
P39TOCLC.pdf (zenoswarbirdvideos.com)

Like any plane that carries a drop tank, it was dropped just prior to combat.

 

[Milosh]

Like any plane that carries a drop tank, it was dropped just prior to combat.

Did it have enough fuel to get home then?
I suggest you look at the charts in the links posted.

 

[P-39 Expert]

It also tends to gloss over details.

If you want to use 95% of the gross weight for the performance, fine use it.
BUT make sure the plane you are comparing to is also at 95% and not 100-102% That's how the AAF (and British) tested their planes. Full of fuel, but the quoted weight in the test was the average weight of the plane for that particular flight.
The P-39N will still beat the F6F-3, just not by as much.

Lets also consider than some of the P-39Ns (the early ones) were delivered with 87 gallon fuel tanks. There was no just fill them up with 120 gallons internal fuel for certain missions.
Later P-39Ns got the 120 gallon fuel tanks restored and some of the ones in the field were refitted. Kits were available to restore the full 120 gallons of internal fuel.
Part of the reason for this was to get rid of the weight of the self sealing fuel cells holding the last 33 gallons.
You also don't "just" add drop tanks and presto-chango get quite the boost in range you are calculating. Just adding the 75 gallon tank cost the P-39Q 2-5 gallons in climb to height. Adding another 210-225lbs might cost a few more gallons just for the climb. The manual says it took 34 gallons to climb to 25000ft, an additional 900lbs took another 5 minutes. A full 110gal drop tank weighed 750lbs. While spending the extra 5 gallons climbing the plane is still moving forward at 170mph IAS (255mph TAS at 25000ft). Not much range differential at all.

and then we have the HUGE problem of the P-39 having no combat power rating at 20,000ft. It doesn't even have a full military power rating. Sure you can run it at 3000rpm but the supercharger will NOT supply even the 44.5in of MAP for military power. The engine can only make about 880-885 hp at 3000rpm. This is the big reason it has such good range at 20,000ft.
The engine isn't making any power. Even worse at 25,000ft. On that paltry horsepower the P-39 still did 385mph and climbed at 2650fpm at 20000ft. At 25000ft it did 370mph and climbed at 1950fpm. For 1943 the speed is good but the climb is excellent. Look at the P-39/F6F chart.

It doesn't matter how much fuel you can strap underneath. What matters is trying to fight on internal fuel (minus warm up and take-off) and then how much fuel is left in the internal tanks for the trip home. You don't fight with drop tanks attached ( well the Japanese did but..........) Drop tank rules are the same for all planes. If the tank must be dropped before all fuel is expended then that fuel is wasted.

At 25,000ft the P-39 has about 725hp available running at 3000rpm and wide open throttle. 370mph and 1950fpm climb. Real good for 1943.

I would also like to see the Flight operation instruction chart for the P-39 with the 110 gallon tank attached. Me too.

P-39Q-1 with the gun pods could only do 267mph true at 25,000ft with the tank attached at 2600rpm and wide open throttle. Why add the external gun pods? Compared to the 4 .30s they only provided 50% more firepower but weighed 86% more. The plane already had a 37mm cannon and two .50cal MGs. Just like reducing the internal fuel, it seems like every modification made by the AAF was detrimental. Delete the wing guns altogether and use the additional performance.

I would like to know how or why the F6F-3 used up 45 gallons getting to 5,000ft. Corsair with basically the same engine only used up 22 gallons to take-off and climb to 5,000ft with a gross weight of 14,200lbs. The 45 gallon number wasn't used in USN range computations. USN just used "20 min for warm up, 20 min for takeoff and climb etc." I used the 45 gallons from the P-47 manual manual since they both had R-2800 engines. Was trying to compare the F6F if used for a land mission instead of a carrier mission. As always I enjoy our conversations. Thanks.

See above.