XP-39 and the Claims

[P-39 Expert]

I was one of the participants in the 1970s P-39 tumbling study. And yes it was totally an unofficial and unfunded test. But now everyone involved is either retired or passed on, so no one can get in trouble, but it can be good lesson on how sometimes historic research gets done. At the time I was an aerodynamics engineer at Beech Aircraft involved in new aircraft development and as part of my job I did both flight testing and wind tunnel testing including many spin tunnel tests at Langley. I studied aviation history both as a hobby and to gain knowledge and data for my vocation of engineering. A friend of mine, who was also an aeronautical engineer and history buff, had been doing research on the P-39 stories of tumbling. He had gone thru the old Wright Field reports and noted that they had seen no tendency of the aircraft to tumble, but he also noted that the flight testing was all done with an equivalent full mass of ammunition in the nose and full fuel. He had interviewed several P-39 combat veterans and they had indicated to him that the tumbling occurred on the return from combat missions when the ammunition had been expended and fuel burned off. He asked me if I had at looked at the NACA P-39 spin tunnel test data? I told him yes, but only from the point of view of the effect of the door opening and of the pilot escape path. But I also informed him I had a spin tunnel test to do at NASA Langley in a few weeks and would ask see the P-39 test data while I was there. My NASA friends pulled the P-39 test file for me and the NACA spin tunnel test had been done at a request from the AAF which called out the test requirements. The AAF had only requested testing at full gross weight and that was all that was done. There was no sign of tumbling seen. Now one has to remember that in WWII the Langley tunnels were running 7 days a week, three shifts a day, so there was little time was for exploring outside the formal test request. During a coffee break in the spin tunnel conference room, I brought up the P-39 tumbling. The NASA engineers got interested and also read the file. Now in the 1970's, the offices, hallways, and conference room in the spin tunnel building all had old spin tunnel models hanging from the ceilings. Now it just so happened one of the models hanging in the conference room was the P-39. Also Jim Bowman, head of the spin tunnel at that time was in on the coffee break and mentioned that in WWII he had been an apprentice in the model shop where the P-39 model was constructed. Well as you probably know engineers and wind tunnel technicians are nothing but over aged little boys, thus a plan was formed to refurbish the P-39 model and test it in those other flight conditions. Of course this was all done on lunch hours and coffee breaks! A few check points were made at the gross weight loadings which repeated the original WWII tests. The model was then reballasted to simulate no nose ammunition and low fuel and retested. And with this loading the P-39 model would sometimes tumble.

Excellent first hand information, thanks for posting. It was also said that no tumbling was possible during normal flight or landing even with nose ammo expended. The plane needed to stall at a high AOA at near vertical. Did your test verify that? Thanks again.

 

[P-39 Expert]

As I read through this the one over riding thought about the XP-39 is that it was not a very good fighter as built. Kelsey wrote the specs but he was very disappointed in the performance and room for growth into a viable high altitude capable Pursuit aircraft. It was "the Small Solution' compared to the XP-38. It was always cursed with marginal stability, short range and crappy altitude performance (Allison issue, however).

Bell just never did develop either experimental or production aircraft considered better than average (except by 1943 VVS standards) - nobody even claims that either the X-1 or X-1A were 'great'. That changed with Bell Helicopter due largely to Bart Kelley post WWII.

Disagree with you on the crappy altitude performance.

The N model (produced Dec '42-April '43) had a service ceiling of 38,500', a combat ceiling (1000fpm) of 31000' and a climb rate of 2650fpm at 20000'. Most other contemporary (late '42-early '43) fighters climbed at only about 2000fpm at 20000' including the P-38F/G, P-47 (not even in combat yet), P-51A, Hellcat (not even in combat yet), Corsair, Typhoon, FW190 and Zero. The Me109G could climb with the P-39N and of course the Spitfire IX outclimbed everything in the sky. None of these planes (except P-51A) was considered a low altitude plane.

Despite going all the way through the Q model designation, there were really only two production P-39 models: D/F/K/L with the earlier Allison models -35 and -63 with the 8.8 supercharger gears and the later M/N/Q with the later (late '42) Allison -83 and -85 with the higher rated 9.6 gears. Airframes were the same, differences included propellers, reduction gears, armament, radios and (different models of the Allison) engines. Of the 9500+ P-39s built, over 7000 had the higher rated 9.6 geared engines from late '42.

The earlier D/F/K/L models with the 8.8 engines were low/medium altitude planes but could match the N model in climb if their weight was reduced from standard 7650# to around 7200# which was easily done by removing the .30 caliber wing guns (200#) and the extreme nose armor plate (100#) and a few other unnecessary items. But, in their standard configurations at 7650# they had a very difficult time reaching high altitude (over 20000') with their ubiquitous 110gal drop tanks. Reduce the weight to 7200# and that restriction goes away.

 

[wuzak]

Wuzak,

While the normal cruise of a P-51 was about 275 mph, a P-51 didn't have to speed up to cruise with a Mosquito. Mostly the 275 mph cruise speed of the P-51 was to allow it to zig-zag above the bombers to it could stay with them. A P-51D/K had a range of 1100 miles at a speed of 395 mph at 2400 rpm according to the 1944 pilot's manual charts from this forum. Of course, that was not the optimum range for the P-51D/K, but it COULD do it. The 275 mph was the best bomber escort cruise. Heck, it can go 1,500 miles at 370 mph at 2,500 rpm with 269 gallons of fuel on board.

Watton was covered with a thin layer of snow as they took off at 0920 in NS569. Prior arrangements were made to rendezvous at 0925 with four P-51s from 20th FG at 18,000 feet over Cromer. They would provide escort to Stettin and return.

The Mosquito met the fighter escort as planned; but now heavily loaded with l,000 gallons of fuel, flew at a severe speed disadvantage. Geary attempted to maintain economical cruising speed but outpaced the P-51s and was forced to throttle-back to continue flying formation with them. The Mustangs had long-range drop tanks and were also fully loaded. Once involved with enemy action, they would jettison their tanks, and therefore, were attempting to conserve and obtain maximum range from their fuel supply. This exacerbated the problem. It was a very-long flight to the Polish border, and on three occasions Geary throttled-back and did not receive the mileage planned.

German Jet Encounters

I have doubts that a P-51 could cruise at 370mph for 1,500miles. Looking at the manual, it says 1,040 miles at that cruise condition. 1,600 miles could be achieved with 419 USG of fuel.

The PR.XVI could carry 760 UKG (912 USG) internally and 100 UKG (120 USG) in wing fairing (drop) tanks. A total of 860 UKG (1,032 USG). A PR.XVI could go a long way, especially at best economical speed.

The typical Mosquito wasn't going to do that. Normal cruise was about 295 mph and could go to 325 mph and later 360 mph or so. Yes, it could go faster, but not at cruise speed. Anything over 340 mph was getting into shorter ranges unless you had a specific type, like maybe a 1945 NF. Mk 30. It COULD cruise at 364 mph at 27,500 ft, but max speed was 397 mph at best altitude and the range at 360 mph wasn't all that great. There really weren't all that many Mosquitos that could hit much more than low 400 mph.

I didn't say a "typical" Mosquito. I said a PR.XVI Mosquito, which can carry a shit load of fuel without drop tanks.

Low 400mph range, fully loaded, for B and PR Mosquitoes.

The point is that the PR.XVI could carry the bulk of its fuel in the regular tanks and in bomb bay auxiliary tanks.

The F Mk. II could hit 358 mph. The NF Mk. XV could hit 408 mph or so. The B Mk. IX could hit right at 405 mph. The FB Mk. VI could hit 368 mph or so. The IV could hit 367 - 380 mph depending on the exhaust stub. The PR Mk. XVI could hit 401 mph. These are all maximum speeds in FS gear and optimum altitudes. Any MS gear speed was 15 - 20 mph slower. Yes, it was a fast, amazing airplane, particularly when cruising into hostile airspace, but not faster than a P-51 if the P-51 wanted to fly that fast.

The F.II and FB.VI had single stage engines. The fighters/fighter/bombers also suffered more drag due to the flat windscreen, so were slower than the equivalent bomber version.

The NF.XV had extended wing tips for high altitude operation, but they never went into service. And there were only a handful of them built.

 

[BiffF15]

Hi Biff,

By "not babying the Allisons," I mean Steve was sometimes pulling 55"+ MAP. Not always, of course, but I'm assuming when they went vertical on the way up from less-than-high airspeed. The P-38 will outclimb the P-51 at lower altitudes, but not likely from low-but-identical airspeeds. I rather doubt the P-51's were babying their Merlins, either when looping from airshow airspeeds. Neither was either type using even full military power in the airshow clip. After all, they weren't exactly flying with 145 performance number fuel. I doubt if anyone in the formation was pulling more than about 1,000 - 1,100 hp.

As for the comment about what it doesn't show (not yours, Biff), what it clearly tells me is the dissimilar aircraft have no problems flying formation. Our fighters cruise to airshows and other public displays together routinely in formation, and they don't have any trouble. We have even had a P-47, P-38, and P-51 information with an F-22, and THEY didn't have any trouble with it, either.




In fact, I have never heard any of our pilots, speakers, or visitors say they had any trouble flying in formation with another aircraft type. Not sure where the notion they would have trouble staying in formation with dissimilar aircraft would even come from.

I'm sure they wouldn't do it for extended periods unless there was a reason to do so, but the capability is certainly there. Liquid-cooled inline fighters would probably have trouble flying for extended periods at 185 mph (plug fouling), but the radials would have little difficulty cruising at 250 - 280 mph except for the extra fuel consumption. They certainly have the ability to cruise with one another for some time, should the need arise, regardless of altitude, unless you happen to be right at the altitude where a supercharger in one of the birds changes gears automatically.

I'd place a bet that Biff flew formation in an F-15 with something other than another F-15 at some point.

Mal H, THANK YOU for posting!

Greg,

Good info, which leads me to more questions surprisingly enough! If pulling 55' of MAP is pushing the engines (today's fuels), then what is the normal range on an Allison or Merlin? Does your guys (POF) P38 have the turbos operating?

The comment about dissimilar formation flying alludes to what's called wingman consideration. I would bet the the P38 can loop at a lower speed than the Mustangs, therefore the 38 pilot must fly his aircraft inside the Mustangs parameters (above his min loop airspeed) when going over the top (looping). The 38 has centerline thrust with both engines operating and a thicker wing allowing for a slower loop than the Mustang (guess on my part).

In addition to making sure your "flight" has enough speed to accomplish a maneuver, you may have to add some additional speed / power to insure your wingmen are going fast enough to have good flying quality for their respective planes. Too mushy on the stick adds danger and looks bad. Too fast and wingys can't keep up (get spit out on outside of turn).

I have flown close with F111, F16, F18, F4, KC135, KC10, B1, RC26, Mig29, F14 and I'm sure others (while in the Eagle). First time was at Red Flag as a wingman in the Eagle. I got split from my flight lead and was a RTB. Flowed into one of the arrival corridors, and spot a pair of F111s. I'm thinking great, one of them is a flight lead and I will join up and go back with them (lowers the odds I will screw up the arrival or go to the wrong runway). Well I form up with them and they pass me the lead. WTF! So I lead them back, checking out their plane the whole way (had not been up close to one) thinking they wanted me to lead so they don't screw it up! Hah. I needed to lead it because my overhead (360 overhead in civilian speak) was smaller and faster, which would get all three of us on the ground that much faster (pattern gets very busy during a Red Flag recovery). We were told we could/ should do this (much more efficient) but had, up to this point, not done anything the first time without having been instructed in it.

And I still had to face the debrief to answer how I got split from my lead (Jobu). Those were some fun days.

Cheers,
Biff

 

[GregP]

Hi Biff!

WWII engines are surprisingly reliable. I worked the Planes of Fame airshows for more than 10 years and we generally flew three days (Fri, Sat, Sun) with something like 65 - 70 sorties per day. We had a VERY low rate of problems. Did we have issues? Sure.

Figure 50 sorties per day for 3 days to be conservative. That's 150 sorties per airshow for 10 years. 1500 sorties. I recall 1) one Corsair that couldn't get one wing to fold down, 2) a flat tire, 3) A Grumman F3F that backfired during landing and blew the crankcase gaskets out (dropped oil everywhere), and 4) a couple of aborted takeoffs due to a rough engine. That's around 5 aborts in 1500 sorties, or about 0.3% aborts. Pretty good! I might have missed a few more, but not many. So, these engines are NOT fragile.

Typically, they use some decent power for takeoff / Initial climb, and then throttle back for economy. The government isn't paying for fuel. Steve Hinton told me he doesn't shy away from using 2,000 Hp on takeoff in a Bearcat or other R-2800 aircraft, but not for extended periods. A clip below shows him doing some aerobatics in a Tigercat. Listen and tell me he's not running the R-2800s above cruise power!



In our P-38, we are not running the turbos. They are installed but non-operational. I know of only one P-38 currently running the turbos at this time, but I suppose there could be more than one. I don't keep up with the current population's configurations too often except for knowing most of the Allisons rather intimately. All but one or two are flying Joe Yancey engines. The Red Bull units is flying Allisons from Bud Wheeler. In a stock P-38, the little scoop on the side of the boom near the trailing edge is the turbocharger air intake . Since the Planes of Fame ins't running the turbos, they have that blocked off and the carburetor intake feeds from the center of the boom-front airscoop intake. The outer two boom-front air intake sections feed the oil coolers as expected.

As for the Allison operation in the P-38, the "normal" military max was about 1100 HP / 2600 rpm at sea level AND at 30,000 feet, 57" MAP. Steve might pull that or close to it briefly during a vertical climb for maybe 5 - 10 seconds or so and then throttle back on the way down because there isn't any reason to rawhide the engines unnecessarily. Then again, he might leave power in it all the way around. I have not flown a fighter through a vertical maneuver and don't know for sure. I have ridden in a P-51 through a loop / roll, but confess I wasn't watching the throttle at the time. Power WAS added for the loop, but we also got some airspeed from a slight dive to start. These aircraft normally cruise at economy settings and only throttle up for takeoff and airshow maneuvers to keep them safe on vertical lines. Mostly, they don't fly aerobatics. I'd say most flights might see a 3 - 4 G break or two, possibly more Gs than that, but very few flights actually see much in the way of aerobatics. Usually, that is for airshows and maybe the occasional dogfight with a friend. If you fly a private fighter as a civilian, I'm sure the temptation to play is occasionally overwhelming. Maybe you can expand on that a bit. Our museum pilots generally fly these aircraft to not stress the engines / airframes too much and not use excessive fuel without a good reason. An airshow aerobatic demo is one good reason, and they DO practice enough to maintain safety and a low-altitude waiver when they do airshow aero.

Below is an example of an airshow crash at Biggin Hill when the P-63 pilot didn't throttle up to do a safe vertical maneuver. He basically pulled up from low-cruise power, stalled or maybe just torqued around at the top with low airspeed. He had plenty of power on tap but didn't use it, and did sort of a lazy semi-spin into the ground.



To be safe, you need the proper speed and power setting for the maneuver you are doing. But you are a fighter pilot and rather obviously KNOW that. I doubt you'd try a vertical maneuver in an F-15 without adding some thrust to keep airspeed. Maybe you can expand a bit on airshow F-15 power settings for vertical maneuvers from level flight.

 

[BiffF15]

Hi Biff!

WWII engines are surprisingly reliable. I worked the Planes of Fame airshows for more than 10 years and we generally flew three days (Fri, Sat, Sun) with something like 65 - 70 sorties per day. We had a VERY low rate of problems. Did we have issues? Sure.

Figure 50 sorties per day for 3 days to be conservative. That's 150 sorties per airshow for 10 years. 1500 sorties. I recall 1) one Corsair that couldn't get one wing to fold down, 2) a flat tire, 3) A Grumman F3F that backfired during landing and blew the crankcase gaskets out (dropped oil everywhere), and 4) a couple of aborted takeoffs due to a rough engine. That's around 5 aborts in 1500 sorties, or about 0.3% aborts. Pretty good! I might have missed a few more, but not many. So, these engines are NOT fragile.

Typically, they use some decent power for takeoff / Initial climb, and then throttle back for economy. The government isn't paying for fuel. Steve Hinton told me he doesn't shy away from using 2,000 Hp on takeoff in a Bearcat or other R-2800 aircraft, but not for extended periods. A clip below shows him doing some aerobatics in a Tigercat. Listen and tell me he's not running the R-2800s above cruise power!



In our P-38, we are not running the turbos. Thye are installed but non-operational. I know of only one P-38 currently running the turbos at this time, but I suppose there coupld be more than one. In a stock P-38, the little scoop on the side of the boom near the trailing edge is the turbocharger air intake . Since we aren't running the turbos, we have that blocked off and the carburetor intake feeds from the center of the boom-front airscoop intake. The outer two boom-front air intake sections feed the oil coolers.

As for the Allison operation in the P-38, the "normal" military max was about 1100 HP / 2600 rpm at sea level AND at 30,000 feet, 57" MAP. Steve might pull that or close to it briefly during a vertical climb for maybe 5 - 10 seconds or so and then throttle back on the way down because there isn't any reason to rawhide the engines unnecessarily. Then again, he might leave power in it all the way around. I have not flown a fighter through a vertical maneuver and don't know for sure. I have ridden in a P-51 through a loop / roll, but confess I wasn't watching the throttle at the time. Power WAS added for the loop, but we also got some airspeed from a slight dive to start. These aircraft normally cruise at economy settings and only throttle up for takeoff and airshow maneuvers to keep them safe on vertical lines. Mostly, they don't fly aerobatics. I'd say most flights might see a 3 - 4 G break or two, possibly more Gs than that, but very few flights actually see much in the way of aerobatics. Usually, that is for airshows and maybe the occasional dogfight with a friend. If you fly a private fighter as a civilian, I'm sure the temptation to play is occasionally overwhelming. Maybe you can expand on that a bit. Our museum pilots generally fly these aircraft to not stress the engines / airframes too much and not use excessive fuel without a good reason. An airshow aerobatic demo is one good reason, and they DO practice enough to maintain safety and a low-altitude waiver when they do airshow aero.

Below is an example of an airshow crash at Biggin Hill when the P-63 pilot didn't throttle up to do a safe vertical maneuver. He basically pulled up from low-cruise power, stalled or maybe just torqued around at the top with low airspeed. He had plenty of power on tap but didn't use it, and did sort of a lazy semi-spin into the ground.



To be safe, you need the proper speed and power setting for the maneuver you are doing. But you are a fighter pilot and rather obviously KNOW that. I doubt you'd try a vertical maneuver in an F-15 without adding some thrust to keep airspeed. Maybe you can expand a bit on airshow F-15 power settings for vertical maneuvers from level flight.

Greg,

In the T38 we would use military power / 500kts and 10k above you to do a loop. IIRC we were at about 250 going over the top. In burner it would loop in about 3500-4000' and have about 200-230 over the top. Lots more buffet as you pulled a good bit harder. In the Eagle at airshows the vertical climb was done in full burner and max deflection (or close to it) aileron rolls. It would go straight up to about 20k (from sea level) before you had to pull over the top (at as low as 200kts or so). Do that climb without the aileron rolls and you could go up into the 40's. I did it, rolled out at 43000 and accelerated thru the Mach. Lots of drag when doing full lateral rolls. If at a lower fuel weight and no external tanks you could go over the top with as low as 200 kts. Looping is a much cleaner maneuver than going over the top. One is done for fun, the other to win a fight.

There was no pushing the engines in the Eagle. You used AB (afterburner) when required. You could go full AB on takeoff and not pull it out until fuel dictated, and the motors would shrug it off. FADECs are PFM (pure effing magic).

The POF has some great maintenance with that low of an abort rate! What I meant about pushing the motors was, is there a band that's used under normal circumstances, say 30-50 MAP, and for other times they are pushed higher? Lookin for actual numbers if you have them.

Cheers,
Biff

 

[GregP]

Thanks, Biff!

When "social distancing" is over, I'll ask Steve about the Allison and Merlin numbers for normal flying.

 

[Mal H]

Excellent first hand information, thanks for posting. It was also said that no tumbling was possible during normal flight or landing even with nose ammo expended. The plane needed to stall at a high AOA at near vertical. Did your test verify that? Thanks again.

It has been too many years gone by and I do not remember the exact flight conditions from which we saw tumbling. But in the spin tunnel the aircraft starts out at 90 degrees angle of attack and decreases down until it reaches a spin (or in this case tumble) or if not flys out.

 

[Venturi]

Great info. Thanks Mal, Biff, GregP and others who have great first hand experience.

I suspect that the MAP chosen in "power needed" situations is due to the fuel used, is that right Greg? 55" or so for the Allison at 3000 with 100 PN to avoid detonation?

I have a question / statement re 8.8 gear s/c P-39. Is there any evidence these a/c used greater than 100PN fuel? If so, what PN fuel did they have access to? I have a reason for asking...

 

[Shortround6]

Is there any evidence these a/c used greater than 100PN fuel

Little, if any, 150 or 115-145 fuel showed up in the Pacific, at least until the last few months of the war.

Unfortunately nobody was keeping really good records of 100PN fuel in the early part of the war. Or even most of the war.

When the US switched to "100" fuel it was 100 octane (the PN scale didn't exist yet) and since the US specified not more than 2% aromatics a lot of the US fuel was 100/98-99 to 100/100+ when later tested. This was in 1939-40. The British 100 "octane" during the BoB was 100/115 to 100/120 depending on batch, Until the PN scale was invented there was no way to test it or rate it. There may have been an interim 100/125 fuel, at least several Allisons were rated on it. The US and British got together and came up with a specification for a common fuel with a rating of 100/130, By the end of 1942, beginning of 1943 they were on their 3RD specification for 100/130 PN fuel, each different specification had different limits for allowable quantities of lead and some other changes like amounts of certain kinds of aromatic compounds and volatility ( how well the fuel evaporates at low temperatures). But all three were known as 100/130 fuel and since by 1942/43 there was no other kind of 100/--- fuel in use anywhere many reports just use 100 as a shorthand for the 100/130 fuel.

I have no doubt that many P-39s with 8.80 gears ran on 100/130 in both the Pacific and in NA and Italy.

 

[GregP]

There is a nice story of detonation with Allisons early in their deployment to Europe. It was eventually traced to the difference in aromatics in gasoline. Basically, the Allisons were jetted at the factory using U.S. fuel (2% aromatics) and were thus improperly jetted for the British fuel (20% aromatics). It took a short while for this to be "discovered." When it was found, the issue was rather quickly corrected, resulting in better-running Allisons in Europe. After that, the issue never resurfaced.

By the time Merlins were being built in the U.S.A., the aromatic thing was past, and they were never mis-jetted from the factories.

There were a number of early "stumbling blocks" to U.S. mission in the ETO. They were eventually all ironed out. All sides had stumbling blocks and we have had many threads about it. The Germans ironed out theirs in the Spanish Civil War. The British started out the war flying in Vic formation, and didn't switch to finger-four until later when the advantages of it became obvious. So, we tried things our way at first and found out for ourselves what worked and what didn't, just as the other air forces had.

 

[wuzak]

So British fuel was to blame for problems with the Allison early in the war and failures in late model P-38s late in the war?

 

[Venturi]

What failures in the late P-38 are you referring to, wuzak?

 

[wuzak]

Arrival of the newer P-38J to fill in behind the P-38H was supposed to help, but did not help enough. The J model's enlarged radiators were trouble-prone. Improperly blended British fuel exacerbated the problems: Anti-knock lead compounds literally seethed out and became separated in the Allison's induction system at extreme low temperatures. This could cause detonation and rapid engine failure, especially at the high power settings demanded for combat.

Why the P-38 Flunked in Europe

 

[varsity07840]

Disagree with you on the crappy altitude performance.

The N model (produced Dec '42-April '43) had a service ceiling of 38,500', a combat ceiling (1000fpm) of 31000' and a climb rate of 2650fpm at 20000'. Most other contemporary (late '42-early '43) fighters climbed at only about 2000fpm at 20000' including the P-38F/G, P-47 (not even in combat yet), P-51A, Hellcat (not even in combat yet), Corsair, Typhoon, FW190 and Zero. The Me109G could climb with the P-39N and of course the Spitfire IX outclimbed everything in the sky. None of these planes (except P-51A) was considered a low altitude plane.

Despite going all the way through the Q model designation, there were really only two production P-39 models: D/F/K/L with the earlier Allison models -35 and -63 with the 8.8 supercharger gears and the later M/N/Q with the later (late '42) Allison -83 and -85 with the higher rated 9.6 gears. Airframes were the same, differences included propellers, reduction gears, armament, radios and (different models of the Allison) engines. Of the 9500+ P-39s built, over 7000 had the higher rated 9.6 geared engines from late '42.

The earlier D/F/K/L models with the 8.8 engines were low/medium altitude planes but could match the N model in climb if their weight was reduced from standard 7650# to around 7200# which was easily done by removing the .30 caliber wing guns (200#) and the extreme nose armor plate (100#) and a few other unnecessary items. But, in their standard configurations at 7650# they had a very difficult time reaching high altitude (over 20000') with their ubiquitous 110gal drop tanks. Reduce the weight to 7200# and that restriction goes away.

Climb rate aside, what was the max speed of the P-39N vs. the P-47D, P-51B/D/K, P-38J/L at the altitudes required for bomber escort? What was the P-39N's radius of action after getting to escort altitude? With regard to weight savings on earlier models, given the P-39's poor air to air armament, one would think that removal of the 37mm gun the archaic sychronised .50s and the would be the first step. But that wasn't possible because the aircraft was designed around nose armament particularly the cannon. Removal would affect the cg, just the way expended ammo did. Removal of the nose guns on the P-40 caused no such problems. So, what you would end up with is two slow firing .50 cal guns and a cannon that was totally unsuited for fighter vs fighter combat. Yes, the Russians made good use of the P-39 in that configuration, but I doubt if you could have found an American pilot of that era who would prefer to fight with that type of armament.

 

[varsity07840]

There is a nice story of detonation with Allisons early in their deployment to Europe. It was eventually traced to the difference in aromatics in gasoline. Basically, the Allisons were jetted at the factory using U.S. fuel (2% aromatics) and were thus improperly jetted for the British fuel (20% aromatics). It took a short while for this to be "discovered." When it was found, the issue was rather quickly corrected, resulting in better-running Allisons in Europe. After that, the issue never resurfaced.

By the time Merlins were being built in the U.S.A., the aromatic thing was past, and they were never mis-jetted from the factories.

There were a number of early "stumbling blocks" to U.S. mission in the ETO. They were eventually all ironed out. All sides had stumbling blocks and we have had many threads about it. The Germans ironed out theirs in the Spanish Civil War. The British started out the war flying in Vic formation, and didn't switch to finger-four until later when the advantages of it became obvious. So, we tried things our way at first and found out for ourselves what worked and what didn't, just as the other air forces had.

Packard started building V-1650-1s in 1941, and V-1650-3 powered P-51Bs were in production in 1943, well before the P-38s problems with fuel, among other things, came to light. The aromatic thing was not past. It hadn't been discovered yet. The V-1650 didn't have a problem with British fuel to begin with and apparently either did the R-1820, R-1830 and R-2800, all of which were pre war designs when the use of British fuel was not even considered. It was solely an Allison problem. The suggestion that some sort of lesson was learned from the Allison problems and applied to V-1650 production doesn't add up.

 

[Shortround6]

Why the P-38 Flunked in Europe

It would be nice if that explanation was the right one but there is a lot wrong just in that short excerpt.

Did the "new" radiators cause trouble or was it the new intercoolers?
Back to blaming the "British" fuel? Every refinery that made fuel made it in batches depending on what material were available and sometimes made several different batches in the same week. The fuel could actually be one of hundreds of different blends. There may have been bad fuel, it may have been available in England at the time, now try to trace it to a British Refinery.
"Anti-knock lead compounds" there are a lot of anti-knock compounds used in fuel, like the up to 20 % aromatics, none of them are lead. Lead is an anti-knock compound but it is singular, not plural and was limited by specification to 4.6 cc per US gallon.

I didn't read through the whole link to see if the author mentioned misrigged turbo and throttle controls or pilots not being taught the methods for cruising that BOTH Lockheed and Allison recommended.

 

[wuzak]

Just using it as an example of where British fuel was blamed for engine failures.

 

[GregP]

Never said British fuels were to blame for late-model P-38 issues, Wayne, and you damned well know it. We've had this conversation before. The early P-38's had issues with the intake that was fixed with the turbulator-venturi inside the intake. They had issues with the 20% aromatic fuels. The fix took some 6+ months to iron out because the issue wasn't recognized at first. They had issues with the cockpit heater. The fix was a simple electric heater in the cockpit. And we had issues with training. That took experience and not flying into a combat zone with the engines at low cruise and the gunsights cold. They never DID fix the low critical Mach number.

You really need to stop trying to put words in other people's mouths, at least mine. If I'm trying to say something, I'll say it. If you want to say something, say it and take credit for it, but don't attribute it to me, OK?

As for when we made Merlins, the XP-51B didn't fly until Nov 1942 and the P-51B/C wasn't in production until after that. Meanwhile, the Merlins that were built here were built to British specifications until the USAAC/F started acquiring the P-51B/C. The P-51As didn't cause any issues at home because we were flying U.S. gasoline and didn't see the issue at all. There were many issues with making Merlins in the U.S.A., but the aromatic fuel thing wasn't really one of them. The Merlin issues were largely with transferring production and associated drawings ... normal start-up things for a new factory tooling up for an existing design.

 

[BiffF15]

I need a refresher on the P38 in ETO problems and timeline. I know it's been discussed in here before, does anyone have a link?

Cheers,
Biff