On big American fighters

[BiffF15]

Thanks Tomo!

 

[tomo pauk]

...
Rearranging fuel placement could have addressed the CoG issues and possibly expanded internal fuel tankage too.

Balancing out the removal of a fixed weight with the weight of a consumable should be a tricky business? Once the fuel is consumed the aircraft would became too nose-heavy?

Still yes, with as well as the turbo worked on the P-47 this isn't all that attractive of an argument, more academic curiosity. (the P-47J's cowling+fan configruation is a more compelling topic on that aircraft anyway -including reduced drag increasing range -especially at high speed cruise -a fan cooled F4U would have been interesting for similar reasons)

Always loved the XP-47J
The non-turbo R-2800 should need two things for greater real capability. One is the use of individual exhaust stacks, along the lines of the XP-42, where such stacks were tested for the R-1830 already during the winter of 1941/42. Second might be the dedicated ram air intake(s), like what was eventually used on the F4U-4 and -5.

This too. Worth noting that the P-51A could manage 415 MPH at 10,400 ft at 1480 HP WER, though the Merlin 20 series in high gear should make similar power a bit higher up. (not sure when they raised boost limits on the V-1650-1, though)

The V-1650-1 was giving the same power as the P-51A's engine 4000 ft higher, and 6000 ft higher than the P-51's engine - that might be the main appeal?

Though another thing on the turbo-less P-38, even aside from recognizing the intercooler problems, allocating resources to properly engineer the export Lighting models (with or without counter-rotation) and thus showing the genuine advantages of that configuration would have been really significant. Plus, the British may have actually accepted them for service. (should have been a better plane than the P-39 and P-40 in most regards) If counter-rotating engines really did give a noticeable performance boost, that might have sold the British over the parts commonality with P-40s. (still, half the engines could have been compatible, though that would mean switching from C series to F series engines to follow P-40 trends)

The P-38 was much more appealing to the USAF than to the RAF, IMO. The Spitfire V was about as fast as the P-38s that have had 1150 HP; the Spitfire VIII/IX was every bit as fast as the contemporary P-38. The USAF, on the other hand, it was either P-38, or P-39/40. Those two were not that good above 15000 ft, while lacking in combat radius (especially the P-39, that received only scathing remarks from Gen Kenney of the 5th AF), a crucial asset of the P-38.
The main thing that would stood as an obstacle for the RAF to have any P-38s might be the low availability of them, though.

 

[Shortround6]

Couple of points..

If we're talking single stage R-2800 than yes, definitely a bad idea, but the fact that P&W had fairly good high-alt capable supercharged engines early-war is a big deal.

A lot depend on when you are talking about. P W built six two stage supercharged R-2800s in 1941. They Built 1070 in 1942 and 670 of those were built in the last 3 months of 1942. The two stage engines are "B" series engines and P W built TWO single stage "B" engines in 1941. P W and Ford did build a lot of single stage "B" series engines rather quickly in 1942. Ford never built a two stage engine. They built 532 P-47s in 1942. Engines completed and on loading docks or in transit are certainly not engines installed in aircraft at factories so engines completed are always going to be ahead of aircraft completed.

You either start the design of the P-47 in the summer/fall of 1940 with the navy two stage engine or you start with the turbo, and then you stick with what you started with, switching from one version to the other could delay actual service introduction by months. In Dec of 1940 the Navy had accepted just 22 F4Fs with two stage superchargers and there were teething troubles with those.

On the Export P-322s, The French and British went with the same rotation engines against Lockheed's advice because they wanted common engines with P-40s they were ordering. Please remember that that the Allison factory was around 600 miles by rail to the closest big east coast port (no big highway system at the time) and then over 3500 miles by sea to Liverpool let alone to France. Nobody was flying trans-Atlantic freight like they would be in just a few more years ( first 200 dive flap sets going to England where lost when the C-54 carrying them was mistaken for a FW 200 and shot down).

 

[drgondog]

P-38 Development, Testing, Training
They did experiment with different airfoil sections with a modified P-38E, but I'm not sure if any of those actually addressed the center of lift problems at critical mach. (there was also the buffeting issue cause by the wing/body interface, but that was solved with smooth wing fillets)

The 'Thinner' wing on the test bed yielded some small benefit - but not worth wholesale adaption

It was more than just the thick airfoil too, since the nose-down pitch issue was rather specific to the P-38. (and not blanked controlls like most high speed controll loss, but super heavy ones due to airflow and center of lift shifting and boosted elevators technically being able to overcome this, but not without easily overstressing the airframe -namely ripping off the tail -same risk you'd run if using the trim tabs to pull out)

All 'standard' airfoils with max T/C near 25% experienced 'tuck' issues moving through critical mach and pushing the aerodynamic center aft - creating a negative Moment about the a.c. The airspeed for critical Mach was lower for fat airfoils like the NACA 23016 (P-38) vs the thinner airfoils of the Spitfire. The P-47D introduced the same dive flap at ~ 30% chord as the P-38 which solved the problem for the P-47. The P-51 NACA/NAA 45-100 airfoil had maximum T/C of about 40% which in effect achieved a lower velocity gradient from the nose of the airfoil to the thickest part of the wing - then coupled with the delayed shock wave formation and movement of the a.c., the 51 never really developed a 'nose down Tuck' in dive.

Still, the crash of the XP-38 delayed discovery of those compressibility problems. The P-47B was still having serious terminal dive control issues too and might have had that delayed a bit longer if things hadn't gone as favorably.

That said, the dive-flap solution seems like it could have been reasonably applied as a stop-gap measure early on even with the assumption that a proper solution was later possible. (dive flaps/breaks capable of operating at high speeds might have still taken time to properly engineer, granted, but still a fairly straightforward concept ... ideal placement so they both slowed the plane down AND affected center of lift positively would be more significant though -I'm not sure those flaps DID the latter, but I'd gotten the impression they were designed to do so)

The dive flap for the P-38 was tested successfully in early 1943. The first field kits were inexplicably delayed until late fall - and the first shipment of 200 was shot down by RAF pilot who thought the AAF C-54 was a Fw 200. The entire purpose of the flap was to delay the almost instantaneous transition from fast level cruise in the .55-.60M to MCr at .65M when pushed over into a dive from 28000 to 30000 feet. It delayed the acceleration and if low enough prevented the shock wave from forming..depending on altitude. The location at 30% chord had the effect of delaying the full blown transition of the shock wave - enough to avoid a severe nose down pitching moment and enabling the pilot to pull out of the dive.

Besides that, having dive breaks is good for fighter-bomber capabilities and potentially in air to air combat.

Maneuver flaps yes - dive flaps no - for air to air combat.. energy is life, dive brakes are useful but extremely limited in use for a fighter other than dive bombing. The maneuver flap increased lift Coefficient but brings the drag penalty with it. Better get what you are shooting at or you bleed too much airspeed.

This is better than what I was thinking with the P-47's case in addressing early dive problems. Serious problems encountered on the initial prototype before any series production would be really significant. (more similar to what the P-39 experienced -for better or worse)

Though another thing on the turbo-less P-38, even aside from recognizing the intercooler problems, allocating resources to properly engineer the export Lighting models (with or without counter-rotation) and thus showing the genuine advantages of that configuration would have been really significant. Plus, the British may have actually accepted them for service. (should have been a better plane than the P-39 and P-40 in most regards) If counter-rotating engines really did give a noticeable performance boost, that might have sold the British over the parts commonality with P-40s. (still, half the engines could have been compatible, though that would mean switching from C series to F series engines to follow P-40 trends)

The export version of the P-38, like everything through the early F's, were simply not ready for combat - although I agree that the 'modified' P-322 to the F-15 combat capability should have been more interesting but the Brits never had one in their hands. They cancelled the Mark II based on probably 2x cost over the Mustang Mk I and sorry performance for the issues they spotted while testing the 322. Remember the P-51 was flying combat missions by the time the 3rd P-322 arrived in the UK, was much less expensive, half the cost of maintaining, half the cost of operation and performance leaned to the Mark I
.

 

[kool kitty89]

Balancing out the removal of a fixed weight with the weight of a consumable should be a tricky business? Once the fuel is consumed the aircraft would became too nose-heavy?

Yes, the P-39 and P-51 both suffered from that (P-39 became nose-light and tended to spin badly when nose guns were expended, and P-51 with the rear fuselage tank was unstable while full). Shifting the entire cockpit back might have made more sense on the whole though ... most of that gets into a totally different (if similar in concept) P-47. Or something much sloer to the F4U without the Navy-specific requirements. (including landing performance -though the F4U was marginal for carriers there too in some respects)

I suppose I was mostly just comparing the Republic design philosophy to Vought's given similar engine configurations.


Though thinking specifically on the real-world P-47, I wonder if the structure really wouldn't allow a pair of more F4U/P-38 style belly pylons arranged to either side of the wing roots spaced far enough apart to allow 2 bombs or tanks to be carried. Granted, that's nix the big conformal or flat tanks, but enough space to carry a pair of 75 or 108 (maybe 150/166 gallon) drop tanks would be a big deal and possibly reduce the drag (and certainly the roll rate) limits of bombs/tanks on the outer pylons.

The V-1650-1 was giving the same power as the P-51A's engine 4000 ft higher, and 6000 ft higher than the P-51's engine - that might be the main appeal?

Well yes. I never meant to say the V-1650-1 wouldn't be an attractive choice for the early P-51. There's pretty much no question those engines would be better used in the P-51 than P-40s or Canadian Hurricanes they went into instead. (though probably better in P-40s than hurricanes ... allocating Allisons to hurricanes adapted for that engine would have been an interesting international compromise there, again that's tricky political stuff but ... as it was, they WERE going to be American Engines in British/Commonwealth planes either way)

The P-38 was much more appealing to the USAF than to the RAF, IMO. The Spitfire V was about as fast as the P-38s that have had 1150 HP; the Spitfire VIII/IX was every bit as fast as the contemporary P-38. The USAF, on the other hand, it was either P-38, or P-39/40. Those two were not that good above 15000 ft, while lacking in combat radius (especially the P-39, that received only scathing remarks from Gen Kenney of the 5th AF), a crucial asset of the P-38.
The main thing that would stood as an obstacle for the RAF to have any P-38s might be the low availability of them, though.

The P-39D really should have compared more favorably with the Spit V at low alt (or Spit V LF) once WER was raised, but with the original millitary power ratings, yes it'd be pretty poor compared to the spit aside from dive and a moderate advantage in range. (P-40 had more of a range advantage -at least without a drop tank, or especially carrying bombs) For air to air combat I really find it hard to believe the P-40 was favored over the P39 with the exception of more forgiving stall characteristics ... well, perhaps armament.

P-38 would have been interesting as a long-range fighter/fighter-bomber prior to the Mustang reaching production, less attractive afterward. And in theory, without turbos (and good intake/exhaust configurations) should have had advantages over the Spitfire V in climb/dive/level speed (and some trade-offs in maneuverability -P-38s having interesting/useful turn/high speed stall characterstics ... polar opposite of the P-39 in that area). Roll rate would be the weak point.

The P-38H received again newer engines, the inter-cooler was the same, unfortunately. The engines were rated for 1425 HP (boost of 54 in Hg) up to 22000 ft, both for take off and military power of now 15 minutes of duration, when using 100/130 grade fuel. It is my understanding that fuel of higher octane rating allowed for greater boost and hence power, since the charge will less likely to detonate than with lower octane fuel. The 'war emergency rating' was established, 1600 HP up to 7000 ft, for 5 minutes.

There was certaily a feedback, either from stateside tests, or from theaters, or from both, that engine is having problems, and manifold intake (tubing connecting supercharger with cylinders) is to blame. The fuel was condensing from spray in to droplets. Allison was testing a new intake manifold already in 1943, it was used from early 1944 on.

The intercoolers of greater capacity were introduced with P-38J, before the new intake is introduced. The new inter-coolers aggravated the problems, if the 'low boost/high rpm' setting was used for cruise - the charge will now cool too much, much more fuel droplets will form, the TEL (fuel additive that upped the octane number) will separate from the fuel, and the engine will be wrecked by detonation.
Apart from the intake issue, the cure was to use the 'high boost/low rpm setting on cruise, so the charge will be more heated, and the charge will be less prone to forming the droplets.
Engines on the P-38J were doing up to 1600 HP up to 25000 ft, and were successfully tested for up to 2000 HP on 100/150 grade fuel.

Might a water injection system have been a quicker engineering fix than intercooler and manifold improvements? Or might that have also worsened the consensation/separation issues? (since the separation was more a cruise issue and not WEP/WER/MIL power issue -when water injection might be used- that seems unlikely though)

 

[tomo pauk]

...
Though thinking specifically on the real-world P-47, I wonder if the structure really wouldn't allow a pair of more F4U/P-38 style belly pylons arranged to either side of the wing roots spaced far enough apart to allow 2 bombs or tanks to be carried. Granted, that's nix the big conformal or flat tanks, but enough space to carry a pair of 75 or 108 (maybe 150/166 gallon) drop tanks would be a big deal and possibly reduce the drag (and certainly the roll rate) limits of bombs/tanks on the outer pylons.

Re. conformal tanks - the Far East AF Service command experimented with a 70 gal form-fitting belly slipper tank, August 1944. They also tested the 42 gal fuel tank under pilot. Those experiments were too late to matter - the P-47s already received the increase of 65 gals for the main tank, and was able to carry 3 drop tanks by then. The increased take off weight would mean introduction of new heavier-ply tires also, that was deemed as 'impractical' back then.
The conformal self-sealing fuel tanks were also designed for the P-63 (64 us gals). Spitfires 'slipper' tanks were also interesting, not sure whether any of them were self sealing - info, please

P-38 would have been interesting as a long-range fighter/fighter-bomber prior to the Mustang reaching production, less attractive afterward. And in theory, without turbos (and good intake/exhaust configurations) should have had advantages over the Spitfire V in climb/dive/level speed (and some trade-offs in maneuverability -P-38s having interesting/useful turn/high speed stall characterstics ... polar opposite of the P-39 in that area). Roll rate would be the weak point.

IMO the P-38 was more capable than P-51 as a fighter bomber. With 4 additional racks, it was capable to carry 2 x 165 gal DTs and 4 x 500 lbs bombs.
Spitfire (any) was a better diver than any P-38, though. The Spitfire V should also climb better.

Might a water injection system have been a quicker engineering fix than intercooler and manifold improvements? Or might that have also worsened the consensation/separation issues? (since the separation was more a cruise issue and not WEP/WER/MIL power issue -when water injection might be used- that seems unlikely though)

The better inter-coolers were installed some time before the water injection was used on the (2-stage) V-1710. WI would make sense IMO with all P-38s, allowing for greater boost/power up until about 25000 ft. The (X)P-38K was to use both better inter-coolers and WI (and a bigger prop, that was the undoing).

 

[Shortround6]

I suppose I was mostly just comparing the Republic design philosophy to Vought's given similar engine configurations.

Trouble is they weren't similar, Corsair had 1650hp at 22,800ft to 24,350 depending on RAM (and 21,200ft on climb) while the P-47 had 2000hp at 25,000ft and up to 27,800ft (with ram in level flight).
21% more power 2-3,000ft higher up.

Though thinking specifically on the real-world P-47, I wonder if the structure really wouldn't allow a pair of more F4U/P-38 style belly pylons arranged to either side of the wing roots spaced far enough apart to allow 2 bombs or tanks to be carried. Granted, that's nix the big conformal or flat tanks, but enough space to carry a pair of 75 or 108 (maybe 150/166 gallon) drop tanks would be a big deal and possibly reduce the drag (and certainly the roll rate) limits of bombs/tanks on the outer pylons.

Well yes. I never meant to say the V-1650-1 wouldn't be an attractive choice for the early P-51. There's pretty much no question those engines would be better used in the P-51 than P-40s or Canadian Hurricanes they went into instead. (though probably better in P-40s than hurricanes ... allocating Allisons to hurricanes adapted for that engine would have been an interesting international compromise there, again that's tricky political stuff but ... as it was, they WERE going to be American Engines in British/Commonwealth planes either way)

You run into a timing problem, especially for the Hurricanes. The Canadians built 166 Hurricanes with Merlin IIIs shipped from England before switching to the Packard Merlin 28 29. Sticking in lower powered Allison engines would have made them even less useful. Please remember that the WER ratings for US engines weren't approved until the summer/fall of 1942 and production planners do not use power levels used by individual squadrons in the field as guides to what engines to order. We know that the Allison could be over boosted quite nicely in 1942, the production planners did NOT in 1941 when allocations of engines and production were being made for 1942.

(P-40 had more of a range advantage -at least without a drop tank, or especially carrying bombs) For air to air combat I really find it hard to believe the P-40 was favored over the P39 with the exception of more forgiving stall characteristics ... well, perhaps armament.

P-40 might have had a slight edge in practical altitude performance.

 

[tomo pauk]

What was the opinion of the LW fighter pilots about P-47 might be read here (thanks, Stona, once more). The intercepted radio transmissions read eg. 'The swine (Thunderbolts) have spotted us, curse them', or 'The everpresent menace of Thunderbolts caused the greatest disturbance'; 'Achtung Thunderbolts Kommt!'; 'I am not coming; there are Thunderbolts with them'.
This is from August/September 1943, ie. when the quick dirty combat capable drop tanks were installed on the 8th AF P-47s. The turbocharged R-2800s enabled the performance 'surplus' above 20000 ft for the P-47 to represent a real threat for the LW of second half of 1943. The turbo-less P-47 would probably be in the ballpark wit the F4U, and Corsair was not able to outpace the captured Fw-190 at any altitude during the US tests.

 

[GregP]

Hi FLyboyJ,

If they could have fixed the low critical Mach number, then things would have gotten better even if they didn't fix anything else. Today we could make it have a higher crictical Mach number, but with the information avialable at the time, I'm not sure they even knew what to do to start with.

I don't have a timeline of what we ("we" meaning the Allied design community) knew and when, aerodynamics-wise. A LOT of things were known, but we discovered a lot between 1945 and 1949 when we were experimenting with early jets, too. That knowledge would certainly have helped in 1943, but exactly what was known and exactly when it was known isn't clear to me. Since they were trying "fixes," perhaps they were unaware that the wing was too thick and perhaps they were unaware of other things, too, and were simply trying fixes as they were thought up.

It would have been interesting, for instance, to see a P-38 with an all-moving horizontal tailplane instead of a stabilator and an elevator. Another tack they might have tried, at least with models, would be to note the P-51 airfoil was better at high speeds. So make a model with no change other than a switch in airfoil and see what happens in the wind tunnel.

They also might have DONE this to no effect, and I simply am not aware of the tests.

This is a what if, after all.

Update:

According to people who were there at the time, the "troublesome British fuel" is NOT a myth at all. It was real. In fact, it wasn't even troublesome, it was just a different blend of aromatics, not a different performance number. U.S. Fuel had 2% max aromatics and British fuel of the same performance number had not less than 20% aromatics, meaning the engines developed in the U.S.A. were not jetted correctly for British fuels.

I never said British fuel was BAD, I siad we had some difficulties with it. Not suprisingly, we also had some difficulties with British engines and aircraft sent over here for testing ... as they were misjetted for U.S. fuel.

Once you know, you can correct and there is no more issue.

That is accordiing to Tony Levier who was a very regular visitor at the museum before his passing, not according to me. If there was anyone in the world qualified to sound off on the issue, it was the pilot sent to the UK by Lockheed to address the P-38 issues. Rather obviously, I wasn't there. People who frequent(ed) the museum include(d) Bud Mahurin, Tony Levier, Clay Lacy,Pete Law, Bruce Boland, Bob Cardenas, and a host a test pilots other than Steve Hinton alone.

I am frequently taken to task in here for passing along their thoughts, but I believe them since they were there and were involved in DOING it at the time. "The guys" included some rather distiinguished aviators.

According to Tony, the U.S. fuels were less than 2% aromatics.

British fuels were not less than 20% aromatics. They switched from 87 Octane to 100 Octane in Battle of Britain or just before. Early British 100-Octne fuels were usually 115 – 125 Octane because they didn't know how to exactly control it. There was a short-lived 100/125 spec, superseded by the 100/130 spec.

US oil was not as "good" as Romanian oil, and the US had to invest in expensive boosting systems. This turned out to have benefits as the US started developing higher Octane fuel through boosting agents earlier than Germany. American gasoline was typically 130 to 150 Octane and could deliver more power by boosting the supercharger pressure.

By early 1943 there was a shortage of certain compounds that forced a change to the 100/130 spec allowing more heavier compounds. It was this fuel that caused havoc with the P-38's in Europe by the simple fact that the Allisons wre jetted in Indianapolis, Indiana, U.S.A., not London or anywhere else in the UK.

Once this was discovered, the issue was very short-lived and did not raise it's head again during the war. Also, once the issue went away, there were no more fuel "gremlins" to talk about and they could get on with the more important things.

Too bad they never solved the low critical Mach number of the P-38, but they DID fix the cockpit heater, add hydraulic ailerons, add maneuver flap settings, and dive recovery "flaps."

They probably SHOULD have concentrated some effort on arming the P-36 and adding fuel/power. It might have been a very good idea versus the P-40. Once the turbo was removed from the P-39 they never got it back as Ben Kelsey wanted, and should have simply abandoned it for types better suited to the altitudes at which they were fighting in Europe.

Our hindsight is a luxury they didn't have in 1942 - 1942. In the end, they did OK with the decisions they made, and we are still living with the results. I retrospect, I'm glad they made decisions as well as they did in WWII, despite everything going on in the world.

 

[Shortround6]

You just won't give in on the "British" fuel thing will you.

It is two different things. In 1940 there were TWO different 100 octane fuels. The difference in aromatics being well known.
By 1943 you are at least 3 if not 4 Fuel specifications removed from the 1940 fuels, both British and American as they were issuing joint specifications.

BTW there is NO "US oil" as Pennsylvania crude is different than Texas crude and both are different from California crude and so on. Pennsylvania crude yielded gasoline of about 38-40 octane from a straight run while California crude yielded gasoline of about 70 octane using the same refining process. They blew up/wrecked a LOT of engines in WW I figuring out the difference. Of course all they KNEW was which oil field the fuel came from. The octane scale wasn't invented until 8 years or so later.

British fuel in 1940 was 100/115 to 100/120 NOT because they didn't know how to control it but because they couldn't measure it. The "octane" scale doesn't go above 100. No if's, ands or buts, it doesn't go above 100. Using 100 octane plus 1cc lead and 100 octane plus 5cc lead was not only cumbersome but didn't work very well. The difference between 5 cc and 6 cc of lead is much less difference than the difference between 1cc and 2 ccs of lead. S.D. Heron helped develop the Performance Number scale which is much more liner than the octane scale. Once they could accurately measure the differences between batches of fuel they could control it. Somewhat a difference in semantics but you can't 'control' what you cannot measure.
By 1943 the only 100/100, less than 2% aromatic fuel left was in some obscure fuel dumps, lost in the system. It sure wasn't being used in ANY front line aircraft or for testing.

There are several books available that were written by S.D. Heron but he died in 1965 and so was never available to give talks at the Planes of Fame Air Museum and thus gain the 'credibility' some people desire.

The facts that S.D. Heron helped design engines in WW I (research in air cooled cylinders) and RAF 8, a 14 cylinder radial, developed what is known as the Heron cylinder head. The RAF 8 was later turned into the Armstrong Siddeley Jaguar (Heron had left by that time due to disagreements with management), worked for Curtiss for a short time. He helped develop the sodium cooled exhaust valve and then worked for the Ethyl Corporation until well into the 1950s.

Now, I would say 'he was there and was involved with doing it at the time.' He was NOT a distinguished aviator but without him many distinguished aviator would not have been.

There are writers and researchers who put together the threads, stories of many people to get a good idea of a particular event or series of events. Sometimes only one story or view point gives a skewed view.

If "jetting" would solve the the problem of "British" fuel in the fall of 1943 why was Allison working on a new intake manifold in the spring of 1943? Why was the new manifold made standard on ALL Allisons, not just P-38s.

Why would the the engines be "jetted" for a different fuel in 1943 when the US and British had been using a common fuel specification/s for well over a year (maybe two)?

Batches of fuel could vary quite a bit from one batch to the next, especially if different base stocks (crude from different fields) were used and depending on refining methods. Like straight run or catalytic cracked gasoline. Throw in the different 'additives' and there could be dozens if not hundreds of slightly different blends that could meet the specification. The specification was a performance specification, not a mixture specification of recipe. As long as the fuel blend acted like 100/130 reference fuel and had the required vapor pressure, evaporation temperatures and other criteria it passed. As an example the early 100/130 could contain NOT MORE THAN 3CC of lead per gallon. It didn't HAVE to contain 3CCs, but it could NOT have more. A later spec went to 4CCs per gallon and an even later one went to 4.6CCs per gallon. It was one of these later specifications that caused the problem and it wasn't the lead. It was the type and quantity of the aromatics that were allowed to be used. There are something like 12-16 different basic aromatics and who knows how many compounds/combinations.

Allison was well aware of a problem the new fuel spec might cause and was working on the problem months before it happened in Europe and it had nothing to do with a difference in jetting needed between England and Indiana.

There was a jetting/ignition timing problem that came up a few times when engines that were supposed to go to US training commands and run on 91 octane fuel were sent to Europe instead and run on 100/130without being modified. There were directives in place that were supposed to stop that from happening but it did. The engines didn't blow up, they just ran poorly and failed to give full power.

They probably SHOULD have concentrated some effort on arming the P-36 and adding fuel/power. It might have been a very good idea versus the P-40.

A very good idea that simply needed the laws of physics repealed. The P-40 prototype was developed to a point ( needed several tries) that it had 22% less drag than a P-36. Getting enough power into the P-36 or reducing it's drag at that point in time was simply not going to happen. Especially if you add weight and drag from extra guns and extra weight from more fuel. (P-36 and early P-40s carried the same amount of fuel).

Other numbers from test flights.
P-36 at 15,000ft needed 845hp ( full throttle) to go 290.5mph.
XP-40 at 15,000ft needed 800hp ( part throttle) to go 314.5mph.
XP-40 at 15,000ft needed 900hp ( part throttle) to go 319mph.
P-40B at 15,000ft at wide open throttle was 352 mph at 1090 bhp at 3000 rpm.
P-40B at 15,000ft at cruise was 286 mph at 600 bhp at 2200 rpm.

I have no idea how much help the P-40 was getting from exhaust thrust, the P-36 was getting darn little. Of course the P-40 at a cruise setting of 600hp wasn't getting a whole lot either.

You need around 1450hp with no increase in drag for the radial R-1830 powered P-36 to go as fast as the P-40B.

P W did get a radial powered P-40 up to 386mph in the fall of 1942 (over 3 years late) but they did it at 22-23,000ft where the air is thinner (less drag) and using a two stage supercharger and using exhaust thrust (and no guns).

 

[GregP]

Hi Shortround,

Actually, it isn't a case of giving in or being stubborn. The guys who were there and were tasked with showing the air crews how the problems had been overcome stated such in speeches at the museum. I think Tony Levier would KNOW, don't you. I also believe Pete Law, who knows more about aircraft piston engines than anybody in here. He has over 20 Reno wins as the engine guy, still consults for the Lockheed Skunk Works, and is as much of a walking authority as there is about aviation piston engines. His credentials are impeccable. So are Tony's.

As for my own feelings about British fuel, I have none. I wasn't there.

Joe Yancey has Allison factory documents describing the problem (after it was found), Tony Levier said the same, and many different P-38 pilots over the years have described a "love-hate" relationship with the P-38. They describe the early engine issues and how it was so much better after the fixes had been accomplished. They guys who left the P-38 before the fixes were in place never DID like the aircraft and still don't today.

I KNOW the intake manifolds had turbulators installed in them to correct the rich-lean issue with the four 3-cylinder manifolds on the Allison since I worked at an Allison shop for two years, and that type of manifoild is all we used for aero engines. They are very easy to tell apart when seen beside each other. I KNOW they added an electric cabin heater. I KNOW they got some twin-engine training for the Lightning pilots on proper engine operations. And I very strongly suspect the fuel issue was there since several very notable people who were there and dealt with it have said so.

You might recall that Tony Levier didn't work for Allison, he worked for Lockheed. I doubt he'd have gone out of his way to help Allison but also don't really know. I also doubt he'd lie about it. I don't suspect him of lying about anyuthing else related to the war or flying and I don't supect this either.

Apparently you do or at least discount him, and that's fine. I am not aiming any posts at you, Shortround. Take it or leave it.

About any subject, if someone's mind is made up and they aren't interested in hearing anything else, that's just fine. I'm sure it can be investigated, but there would have to be some documentation still existing to prove it. I have no idea if there still is any. Lack of it doesn't mean it didn't happen, it means we have no first-hand evidence. After 70 years, I think there are a LOT of things about WWII that lack any currently-existing evidence. Despite our best efforts, documents get lost. There are Motorla technical documents that we developed in the mid-1980's, that I have copies of in my files (and authored some) ... and you cannot find them today. That was 40 years after WWII.

Just as stubborn as you feel me to be, it seems exactly the opposite from my point of view, when I have first-hand statements of something from people who were there versus things I see about the same subject in this forum. I can say the same about other subjects we have disagreed about in here. On any given day we have anywhere from five to 15 P-51's at Chino, and the pilots talk rather freely and friendly if you ask them. The Museum operate three P-51's, two P-51S and one P-5A. Some of the stuff I read in here just generates laughs from the real-life pilots. Most of them had fathers who flew them in WWII.

A forum is fun only for me and I've tried to shared some collected data on aerial victores in a format that is actually useful to someone who is interested in the subject. I have tried to share some drawings. So far, I mostly get flak. This is starting to not be fun.

So if you don't want to believe something, don't. If you don't want to entertain discussion, don't. Either way it's fine. But if all you want to do is post personal jibes, then why not just refrain? I honestly do not believe I have posted any jibes at you in a LONG time.

In actuality, I don't care about the British fuel issue more than just in passing. But if you're going to discuss it, you might as well hear what the people who were there say. In a few short years, there probably won't be any of them around anymore. That will be a sad day since the people who still maintain interest will have no choice but to read about it somehwere as the vets will all be gone.

Actual recollections of guys who were there need to appear somewhere or else we're stuck with interpretations by people who never even TALKED with people who were there. Then all we will have is revisionist history written by people who interpret the events of WWII from the pespective of a modern person ... and WWII was NOT fought by modern people. It was fought by people who embraced the attitudes of the time and had motivations WAY different from someone today.

I think I'm outta' here for awhile.

Cheers to everyone.

 

[GrauGeist]

Greg, you might be surprised to find that folks here on the forum have direct contact with pilots and other personnel who had a direct connection to WWII also.

While my Uncle Bill was ship-board in WWII, he later became a pilot for the Navy, flying jets until he was lost in Vietnam. My Great Uncle James started his time with the USAAC in the late 1930's and finished with the USAF in the late 1940's. Both of my Mom's older brothers signed up with the USN on 8 December, 1941 and retired as career Chiefs (during WWII, one was a submariner, other other aboard destroyers and was a "frogman" - both PTO).

I was taught to fly by a large gang of WWII characters, all friends of the family: a USMC Corsair pilot, an ETO P-47 pilot and a Luftwaffe pilot to name a few. My checkride was with a B-29 pilot. All knew very well what they were doing, gave very thorough instructions and offered extremely sound advice.

This does not include all the other guys that served in other branches and specialties: and all greater men than I.

The point being, there is a vast wealth of information being shared on the forums, a good deal of it coming right from the source...it's nice that you get to deal with those that were there and they share info with you, but some of us have access to first-hand info, too.

 

[kool kitty89]

Re. conformal tanks - the Far East AF Service command experimented with a 70 gal form-fitting belly slipper tank, August 1944. They also tested the 42 gal fuel tank under pilot. Those experiments were too late to matter - the P-47s already received the increase of 65 gals for the main tank, and was able to carry 3 drop tanks by then. The increased take off weight would mean introduction of new heavier-ply tires also, that was deemed as 'impractical' back then.
The conformal self-sealing fuel tanks were also designed for the P-63 (64 us gals). Spitfires 'slipper' tanks were also interesting, not sure whether any of them were self sealing - info, please

When I mentioned conformal tanks, I was actually thinking of the unpressurized conformal tub-shaped ferry tanks used early in the war. The P-47 had access to 200 gallon tanks fairly early, they just weren't capable of operating above 10,000 ft.

IMO the P-38 was more capable than P-51 as a fighter bomber. With 4 additional racks, it was capable to carry 2 x 165 gal DTs and 4 x 500 lbs bombs.
Spitfire (any) was a better diver than any P-38, though. The Spitfire V should also climb better.

The P-51's advantage there would be cost, so logistics for per unit bombload, cost of each plain (maintenence included) and logistics of pilots needed (and survivability) would all come into play.

Tough call there ... but with value of the pilot being high on the list, it'd lean towards the P-38. (and aside from turbo/intercooler related engine failures, it should fare better survivability wise than a P-40, P-51, or P-39 ... maybe even advantages over a P-47 in that regard)

The better inter-coolers were installed some time before the water injection was used on the (2-stage) V-1710. WI would make sense IMO with all P-38s, allowing for greater boost/power up until about 25000 ft. The (X)P-38K was to use both better inter-coolers and WI (and a bigger prop, that was the undoing).

Water injection was empoyed on the 2-stage allisons in leu of ANY intercooling, much like the early 2-stage units used on Pratt and Whitney radials. It was a simpler quick fix than actually developing an intercooler arrangement.

You run into a timing problem, especially for the Hurricanes. The Canadians built 166 Hurricanes with Merlin IIIs shipped from England before switching to the Packard Merlin 28 29. Sticking in lower powered Allison engines would have made them even less useful. Please remember that the WER ratings for US engines weren't approved until the summer/fall of 1942 and production planners do not use power levels used by individual squadrons in the field as guides to what engines to order. We know that the Allison could be over boosted quite nicely in 1942, the production planners did NOT in 1941 when allocations of engines and production were being made for 1942.

Hmm perhaps. If only looking at aircraft going to Brit/Commonwealth units, it's still useful for the planners to consider all the aircraft being ordered (Hurricanes, Warhawks, Mustangs) and manage allocation/distribution of resources accordingly. Overboosting/WER would have been a bonus after the fact, but potentially sacrificing hurricane performance in favor of Warhawk/Mustang performance would be the more serious initial consideration.

Grantedm with NA not even offering a V-1650-1 powered variant (unlike Curtiss) there's that issue to overcome first. (I'd imagine they'd have had trouble managing to even get ahold of an engine to test with given problems with engine procurement for the XP-51 due to wartime priority)

P-40 might have had a slight edge in practical altitude performance.

You mean due to more RAM power and wing area? At similar weights, maybe, but with the typical higher weight of the P-40 it seems that advantage would be typically mooted.

It's a separate issue for managing logistics of engines slated to go into USAAF service ... that'd be fairly strictly limited to P-51 vs P-40 engine allocation.

US oil was not as "good" as Romanian oil, and the US had to invest in expensive boosting systems. This turned out to have benefits as the US started developing higher Octane fuel through boosting agents earlier than Germany. American gasoline was typically 130 to 150 Octane and could deliver more power by boosting the supercharger pressure.

Catalytic cracking was the major breakthrough US refining managed. German fuel production was heavily reliant on synthetic production derived from coal, so the technologies weren't directly comparable there. (boosting agents like TEL for leaded gasoline, aromatics, etc, were universal, though ... but different blends of different additives will have some differing properties)

On that note ... there's the separate 'problem' with British vs American fuel where Allison engines (turbo or otherwise on all planes) were having troubles with spark plug leading with British fuel. I think that's been pretty well covered elsewhere befor and not the problems being poked at above.

A very good idea that simply needed the laws of physics repealed. The P-40 prototype was developed to a point ( needed several tries) that it had 22% less drag than a P-36. Getting enough power into the P-36 or reducing it's drag at that point in time was simply not going to happen. Especially if you add weight and drag from extra guns and extra weight from more fuel. (P-36 and early P-40s carried the same amount of fuel).

Other numbers from test flights.
P-36 at 15,000ft needed 845hp ( full throttle) to go 290.5mph.
XP-40 at 15,000ft needed 800hp ( part throttle) to go 314.5mph.
XP-40 at 15,000ft needed 900hp ( part throttle) to go 319mph.
P-40B at 15,000ft at wide open throttle was 352 mph at 1090 bhp at 3000 rpm.
P-40B at 15,000ft at cruise was 286 mph at 600 bhp at 2200 rpm.

I have no idea how much help the P-40 was getting from exhaust thrust, the P-36 was getting darn little. Of course the P-40 at a cruise setting of 600hp wasn't getting a whole lot either.

You need around 1450hp with no increase in drag for the radial R-1830 powered P-36 to go as fast as the P-40B.

P W did get a radial powered P-40 up to 386mph in the fall of 1942 (over 3 years late) but they did it at 22-23,000ft where the air is thinner (less drag) and using a two stage supercharger and using exhaust thrust (and no guns).

The drag comparison here is for the R-1830 and not R-1820 powered P-36, I assume. And aside from the possibility of using a 2-stage R-1830 (with or without adapting a tighter cowling and fan), the Allison seems to be preferable on the whole. (you might manage to save some weight -and gain climb- with a single stage R-1830 ... maybe even the 2-stage, not positive there)

Still, compared to the P-40B/C/D/E (especially before WER clearance), a 2-stage twin wasp powered P-36 (or P-42) seems like it'd have some advantages above 10,000 ft.

 

[Neil Stirling]

The position as of August 1943.

How do we know that it was British fuel, that caused problems with the V-1710? since nearly 80% of UK fuel was of imported.

Neil.

 

[Shortround6]

I would note that 4.8cc per IMP gal is about the same as 4CC per us gallon and 5.5cc per IMP gallon is about the same as 4.6cc per US gallon.

We also have at least two different things going on.

One is the increase in lead which could and did cause trouble with spark plugs.
The other is the change in allowable aromatics. I don't know if the total amount was changed (total 20% or more) or if was a higher percentage of specific aromatics were allow within the total limit. I believe from the wording of what I have read it is the latter but I don't know. Accounts are not specific enough. Not all aromatics have the same specific gravity or the same vaporization temperatures and not all have equal performance number boosting ability or even the same BTUs per unit of weight or volume. Blending fuel to get ALL the desired characteristics was not an easy job.

 

[tomo pauk]

...
Water injection was empoyed on the 2-stage allisons in leu of ANY intercooling, much like the early 2-stage units used on Pratt and Whitney radials. It was a simpler quick fix than actually developing an intercooler arrangement.

Using the WI instead of inter-coolers does indeed offer some benefits, but also some shortcomings. WI is mostly used for WER; the inter-cooler is useful not just for WER, but also for making military power (= of longer duration). It is much easier to retrofit water injection on an inter-cooled engine (for even more power) than it is to retrofit inter-coolers on the engine that are not designed for it from get-go. The V-1710 flew as inter-cooled engine in 1939 in the XP-38, granted those were air-to-air inter-coolers;it took until 1943 for the 2-stage V-1710 to have WI installed.

The 2-stage R-1830 have had inter-coolers from 1941 on, it never received WI in an operational aircraft, to the best of my knowledge. 2-stage R-2800 received WI in winter of 1943/44, the inter-coolers were there from the time XF4U 1st flew in May 1940.

 

[gjs238]

The facts that S.D. Heron helped design engines in WW I (research in air cooled cylinders) and RAF 8, a 14 cylinder radial, developed what is known as the Heron cylinder head. The RAF 8 was later turned into the Armstrong Siddeley Jaguar (Heron had left by that time due to disagreements with management), worked for Curtiss for a short time. He helped develop the sodium cooled exhaust valve and then worked for the Ethyl Corporation until well into the 1950s.

Interesting, I had not known of the Ethyl Corporation.
https://en.wikipedia.org/wiki/Ethyl_Corporation

I had always assumed that ethyl alcohol was the reason "premium" or "hi-test" gas was referred to as "ethyl."

 

[Neil Stirling]

Flight article on the "Gains from Isooctane plus Tetraethyl Lead".

1943 | 2162 | Flight Archive

Neil.

 

[drgondog]

Hi Shortround,

Actually, it isn't a case of giving in or being stubborn. The guys who were there and were tasked with showing the air crews how the problems had been overcome stated such in speeches at the museum. I think Tony Levier would KNOW, don't you. I also believe Pete Law, who knows more about aircraft piston engines than anybody in here. He has over 20 Reno wins as the engine guy, still consults for the Lockheed Skunk Works, and is as much of a walking authority as there is about aviation piston engines. His credentials are impeccable. So are Tony's.

As for my own feelings about British fuel, I have none. I wasn't there.

Joe Yancey has Allison factory documents describing the problem (after it was found), Tony Levier said the same, and many different P-38 pilots over the years have described a "love-hate" relationship with the P-38. They describe the early engine issues and how it was so much better after the fixes had been accomplished. They guys who left the P-38 before the fixes were in place never DID like the aircraft and still don't today.

I KNOW the intake manifolds had turbulators installed in them to correct the rich-lean issue with the four 3-cylinder manifolds on the Allison since I worked at an Allison shop for two years, and that type of manifoild is all we used for aero engines. They are very easy to tell apart when seen beside each other. I KNOW they added an electric cabin heater. I KNOW they got some twin-engine training for the Lightning pilots on proper engine operations. And I very strongly suspect the fuel issue was there since several very notable people who were there and dealt with it have said so.

You might recall that Tony Levier didn't work for Allison, he worked for Lockheed. I doubt he'd have gone out of his way to help Allison but also don't really know. I also doubt he'd lie about it. I don't suspect him of lying about anyuthing else related to the war or flying and I don't supect this either.

Apparently you do or at least discount him, and that's fine. I am not aiming any posts at you, Shortround. Take it or leave it.

Greg - you have a tendency to equate disagreement with you as disagreement with Hinton or Mahurin or Levier, when that isn't the case. People are disagreeing with You based on facts at hand and, when confronted with a series of facts, you wave your arms around and re-state what you heard from an unseen and unheard expert, or whom you perceive to be an expert on the subject, or think you heard. But for all intents and purposes it seems like your first position is to confront the person you are debating 'with an opinion from an acknowledged source' - but you rarely if ever anchor the statement of fact from one of the respected advisors by re-stating precisely what they 'said' on the subject and how that relates to your point.

About any subject, if someone's mind is made up and they aren't interested in hearing anything else, that's just fine. I'm sure it can be investigated, but there would have to be some documentation still existing to prove it. I have no idea if there still is any. Lack of it doesn't mean it didn't happen, it means we have no first-hand evidence. After 70 years, I think there are a LOT of things about WWII that lack any currently-existing evidence. Despite our best efforts, documents get lost. There are Motorla technical documents that we developed in the mid-1980's, that I have copies of in my files (and authored some) ... and you cannot find them today. That was 40 years after WWII.

This is another 'Fall Back' position - "If you don't believe me - well there has to be some docs out there that support my position, but they have been lost in the mists of time". If Your (the person you are debating with) position is so fixed on facts (that GregP can't refutes with relevant documented facts), then "fine - believe what you want to believe - that's OK".. but what you really imply in most cases is that anybody that disagrees with you, and the phantom experts that you quote in a vacuum, is somehow free to disagree - but obviously foolish to do so.

Just as stubborn as you feel me to be, it seems exactly the opposite from my point of view, when I have first-hand statements of something from people who were there versus things I see about the same subject in this forum.

The main problem with that Greg, is that what was stated may have only peripheral relationship to the specific subject, there is no context with their statement in specific response to the question, and no way of follow up questions to ensure communication?

I can say the same about other subjects we have disagreed about in here. On any given day we have anywhere from five to 15 P-51's at Chino, and the pilots talk rather freely and friendly if you ask them. The Museum operate three P-51's, two P-51S and one P-5A. Some of the stuff I read in here just generates laughs from the real-life pilots. Most of them had fathers who flew them in WWII.

Well, nobody I know disrespect guys like Fahey, Maloney, Hinton, Law or the visitors like Anderson and Mahurin, etc - and one can only speculate on what you 'present' to them for amusement - you probably leave out some of your juicier leaps of faith. Perhaps you could share with the group some of the 'relayed Pearls of Wisdom' that showed the fellas how smart you are and how dumb some of us are that derived the fun and chuckles?

A forum is fun only for me and I've tried to shared some collected data on aerial victores in a format that is actually useful to someone who is interested in the subject. I have tried to share some drawings. So far, I mostly get flak. This is starting to not be fun.

I don't think you get flak for drawings and shared data Greg. You need to reflect what you get push back on and ponder 'why'.

So if you don't want to believe something, don't. If you don't want to entertain discussion, don't. Either way it's fine. But if all you want to do is post personal jibes, then why not just refrain? I honestly do not believe I have posted any jibes at you in a LONG time.

The problem is that you frequently a.) perceive disagreement and presentation of facts that don't coincide with your views and, b.) often take requests for sources as a personal affront and respond accordingly. This is a Generalization which I know is not 100% true - but think on your growing tension as you debate this subject with SR?

Actual recollections of guys who were there need to appear somewhere or else we're stuck with interpretations by people who never even TALKED with people who were there. Then all we will have is revisionist history written by people who interpret the events of WWII from the pespective of a modern person ... and WWII was NOT fought by modern people. It was fought by people who embraced the attitudes of the time and had motivations WAY different from someone today.

I think I'm outta' here for awhile.

Cheers to everyone.

Greg - you may have missed the Memo - if there are less than 100,000 books and papers published by guys that WERE there - mostly with fresh memories - then I would be surprised. Like any tide of time, parsing fact from opinions based on fact from bullshit will be with us as long as we exist.

 

[bobbysocks]

neil...your second scan about spark plugs....i remember my father talking about the subject years ago. the plugs the fighter groups ( merlin mustangs ) were supplied withtended to foul up with lead after aggressive flying. they switched to a plug from another country to remedy the problem. i thought he said the originals spares were a uk plug and they switched to an american plug (AC delco ) but i may not have heard him correctly. but i do know the the different plug did not foul out nearly as bad as the original. i tried talking to a couple crew chiefs a while back but could not get confirmation one way or the other. do you happen to know what brand they were using as replacement plugs? i am assuming the originals the engines had when shipped from the us had american plugs...after that ???