Warbird Information Exchange

I hope this is not too far off topic. I read once that some claim the P-40 was better at ground attack than the Mustang because the forward location of the coolant radiators meant it saw less damage than the center lower fuselage mount of the Mustang. The theory is that ground gunners aimed at the engine of an attacking aircraft and invariably did not use enough lead so that thier shots missed aft of the aiming point thus having a higher probability of hitting a Mustang radiator than a P-40. Of course this assumes that in either case they missed the cockpit entirely! I wonder if there was any serious study of this claim?

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"I can't understand it, I cut it twice and it's still too short!" Robert F. Dupre' 1923-2010 Go With God.

I wonder if the P-40 was limited by structure and aerodynamics from being as high in performance as a 109 or Spitfire, even given the same power. The P-40 was tough but overbuilt, the radiator created drag and turbulence, and the landing gear were dirty when retracted. It may have come with too much of a built-in headwind to get out of the Hurricane class.

August

If you can differentiate between the lines on this graph, it would go a long way to verifying (or discounting) your premise. I'm not sure I can differentiate the lines well enough to form a conclusion...


http://www.wwiiaircraftperformance.org/ ... -chart.jpg

been searching for BSFC #s for the Allison V1710-39 (P-40E?) and -81 (P-40N) as well as the Packard V1650-7 without much luck other than this paper
http://www.enginehistory.org/Convention/2009/Presentations/SuperchargingAllison.pdf
which gives a 48 gallon per hour fuel burn (.60 bsfc) at cruise (using 520bhp) in the P-51D using the Packard/Merlin -7.

the link given earlier (very informative by the way) contains this flight test data on fuel consumption for several P-40 models
http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/P40s%20compared.pdf
if I'm reading correctly using 520bhp in the P-40E resulted in 226 knots and 38 gallons per hour. In short it would appear the Merlin 61 (Packard-7) would have increased fuel consumption considerably probably without much of an increase in speed due to the drag limitions of the airframe brought up earlier and range of the P-40 would have suffered in my opinion.





the increase in range with the Merlin engine swap has more to do with 269 gallons of fuel carried internally in the P-51B/C/D rather than the 184 gallons carried internally in the Allison engined P-51A

That's why I love this place! You learn new things all the time.

Thanks for that, I didn't realise they had upped the internal capacity.

A lot depends upon which P-51 version was plotted out.

I'm glad some likes the link to the RAAF data. There is a speed and consumption chart in the P-40E handbook. It shows 2000rpm and 30" manifold pressure giving 210mph and 48gph. The P-40N I've flown in (and flown from the back) tends to be operated at this setting. I'm told the fuel burn is right at 50gph.
The increase in internal fuel capacity on most WWII fighters came at the cost of increased instability. You burned the fuselage tank fuel first so it would be safe to do combat maneuvers when to reached the enemy. If I remember correctly, the fuselage tank on the P-51 has to be removed or disconnected for the "limited" category. In the MKXVI Spitfire, the handling with a full fuselage tank is so bad it was restricted to ferrying the A/C only, and the tank was wired shut when on operations. The description is the A/C hunts constantly and tries to continue in any pitch direction once it starts. Sounds like a very unpleasant handful!

As for Spitfire handling with the fuel in the rear fuselage tank, Mike, you are right, but the nest section of the Notes tells the pilot how to operate using the rear tank, so sort of confusing.. Now, I am not certain, never having flown one that way, but the manual, that is the official Pilot Notes is the same book for the IX (like mine) and the XVI, also the XI. It says when the rear fuselage tank is full, there "is a marked reduction in longitudinal stabilty, the aircraft tightens in turns------, is restricted to straight flying and gentle manuevers, and instrument flying is to be avoided." It's worse at high altitude and the hard to trim to be steady,and worse for the low back like the XVI. The IX like mine is better. So this does NOT prohibit use of the rear tank, just warns and restricts it's use. This may not be the whole story, there could have been some RAF order issued or local order. But I have a book about lot's of combat, including strafing, in XVIs and they certainly used the fuselage tank.
I think it holds about 60 U S gal, thus 360 lbs of fuel. The problem is that this weight is aft of the CG, thus making the plane tail heavy and not as stable, It is worth having by a long shot, as that 60 is another 1 hour 10 min of vital flight time, and is worth a little extra care at the start of the flight. After takeoff on the main tank, which is a forward fuselage tank so has the opposite effect, you would burn the rear tank on the way to the target. Once the rear tank is empty you have normal handling, and still have your main fuel. Most Spits do not have wing tanks like a 51, fuel is in the 2 main tanks between the engine and cockpit.
SL 721, the Mk XVI now in Canada, that Dave has flown, I believe, had a rear fuselage tank, I know, I saw it more than once, don't know if they used it. Then it was made into a baggage area. You need baggage room in a Spit, but I would have kept the tankage. It makes a 2hour fighter into a 3 hour one, and sure takes a lot of the edge of seat concern out of going cross country in a Spit. 3 hours fuel is enough. You can take off, climb, and then cruise 2 hours, (almost 500 nm) and land with a 45 min reserve. That's long enough to sit on a parachute, without a break. MIne has a normal cruise of 1 1/2 hours, not quite enough, unless I add an hour with my drop tank, but it slows you down about 10 mph and is not quite as easy to use as the internal tank would be.
I want to check some figures before I comment on the speed and fuel burn Mike gives of the P-40. I know that sounds quite a bit slower, at the same power my Spit would be 245 to 250 mph.
Do you think those guys up north use that baggage room to carry Molson?

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Bill Greenwood
Spitfire N308WK

The XP51 and probably the P51A, given the time and context. So what we have is a comparison of 3 Allison powered airframes - P39, P40, and P51. But I'm still not certain I can identify with certainty which lines represent which airplanes.

51A would have been my guess as well since the curves were so close. And ah yes when I blow up the image I see it's the XP-51

It's easy to pick out the 51A and P-40F (GW 8450#)prelim flight test data lines (solid and long dash respectively).

The plots seem to suggest that the 8450 pound P-40F gets to 25,000 feet faster than the 8824 pound XP-51 by
something like 4-5 minutes.....that up to 15,000 feet they match up pretty well. That's quite a large difference.

The rate of climb of the two match up to 15,000 feet but then the P-40F has a big "Z" in the curve around 13k and then the P-40F maintains the same rate of climb only 10k feet higher. That "Z" might represent a kick in of some supercharging.

As for max speed (True) at military power looks like the XP-51 maintains a few miles an hour advantage up to about 17,000 feet plus. After that the P-40F holds an ever diminishing advantage until the curves converge at about 27,500 feet at which point they are the same.

IIRC, North American had a hard time getting an Allison delivered for the XP-51 and some misty memory tells me it was not the model of Allison that they wanted. But I could be wrong about that.

I'm curious as to how much the additional 400 pounds GW of the 51 mattered.

The Merlin used in the P-40L and F was not the 60 series, with the 2-stage 2-speed supercharger. It was the earlier one, V-1650-1, still 2 speed, but only single stage. Thus its supercharging was slightly better than the Allison, but not much.

The reason for the change was not really a wish for upgrade. At that time, the USAAC had finally woken up to the fact that they needed a high-altitude escort fighter. (Previously, "the bomber will always get through" "flying fortress" mentality had prevailed.) The only one they had flying at the time was the P-38, which used Allisons equipped with turbochargers (various models). Thus all Allisons were diverted into P-38 production. (Whitney: Vs for Victory, page 318) And there were hopes for the P-63.

At the same time, Packard was converting from producing the early Merlin, to the 60-series which would eventually show up in the P-51 and the Spit XVI. A whole warehouse of the early Merlins (V-1650-1)were complete, with no place to go. So, since the P-40 was still in max-rate production, these surplus Merlins were put in the P-40. (The RAF was cryong out for any and all fighters.) They weren't a huge success. One of the main factors was the updraft carb in a Merlin. In the desert, Merlins needed an elaborate filter to deal with the dust. Since this was never applied to the P-40, the Merlins there didn't last long. Also, the early Merlins were no longer supported by the factory, and spare parts became more difficult to find.

Later, some of these were converted back to P-40Rs, with Allisons, although not overseas.

As for fuel, I've done quite a few cross-countries lately, and I get about 32 US Gal/hr. That's 1900 rpm, 24", and Auto Lean. That delivers about 190 mph IAS. I have double-checked this scrupulously because the VWoC P-40 has no fuselage tank, being modified for a second cockpit. I only have 90 US Gal total, in the wing tanks. And Canada is a big place! And the airfields are few and far between! Thus, I had to make certain of that data. This is less burn than a Merlin.

The bigger chin cowl of the D and later versions was in reaction to an engine model change. The early Allisons used a planetary reduction gear. The later ones used a simple spur gear. This meant a change in cowling because the engine got shorter. At the same time they'd had feedback from the desert, and from China/Burma, where the airplane was operating at high ambient temps, and decided to give it more cooling.

By that time the designer, Donovan Berlin, had been promoted out of the design office. His replacements made the chin cowl much larger -- too large in Berlin's opinion. He always believed that the large cowl "spilled" air out the front, causing a turbulent flow back over the fuselage, degrading the performance of the rudder, and making the airplane squirrelly on the ground (D and E models). The fix was to lengthen the fuselage 19", but Berlin always thought that was crude, and that the chin cowl should have been reduced slight in size.

I have certainly found the coolant rads to be easily able to handle the 85F temps found in the summer airshow circuit here in N.A..

I have spoken with Stocky Edwards extensively about his fights in the desert against 109F and Gs. (In the context of picking his brain about how to fly the airplane, pilot-to-pilot.) These 109s were always up high, 25,000 ft or so. The P-40s (in which Stocky shot down 13 axis a/c in that campaign, including a 109 on his first sortie) were always down around 15,000. (They weren't even issued oxygen.) Thus, the fights nearly always started with a bounce from above. Stocky flew with his eyeballs outside the cockpit, always searching, and was thus never bounced unawares. He'd pick the moment, then turn into the attacker. If the 109 refused combat, and yo-yoed back up, the P-40s would go back on course. If the 109s stayed to tangle, guys like Stocky would nail them using the rapid roll rate, and small turn radius, of the P-40.

The kill ratio, which greatly favours the 109 in that campaign, comes from that initial bounce. Not everyone saw them coming. Stocky had superb eyes, and never stopped looking.

Stocky's main complaint about the P-40 was the guns. They tended to jam when fired under high-G. Most pilots tended to fire from line-astern. (Not all pilots are great shots.) Stocky was able to connect with high-deflection shoooting, and since this usually involves high-G, he got ticked right off when the guns would jam, and he'd be reduced to 1 or 2 .50s.

Anyhow, if anyone wants to try ours, sponsorship flights in it are available. Crank it around yourself.

Dave

Dave, you got my attention with the line about sponsorship flights, I think I will give you a call soon as I can get over my vow to not spend any money frivolously. I don't smoke, don't drink much, so don't have too many bad habits to give up to save money, other than airplanes, maybe donuts.

And I can't believe you guys have less fuel in the P-40 than I have in the Spit, without the drop tank. Is that really only 90 U S? It sure makes one a good flight planner and very careful to top off every last drop before a flight. If I just had about 25 more internal, I'd have 2 hour cruise, and that would be ok for most flights, and my bladder. We have thought some about a leading edge tank, but it would take some creative engineering.

As for the P-40 in combat ,I'll give you one maybe, and two nays.
The first maybe, I was lucky enough to meet Tex Hill and get to be a friend. He had a huge respect for Zeros, they shot him up and shot down his wingman in their first encounter with them .Yet, with the right tactics, mainly one high speed diving pass, an expert like Tex could fight against a them in a P-40. He mainly tried to hit the Japanese bombers and not stick around to mix it with Zeros. He didn't encounter 109s.
The first nay comes from a book I have about the great aces of all nations .In talking about the one on one, P-40 vs Me109 in the desert it says the German pilots definitely considered their 109 superior to the American planes, and the Huri and of course Spit better than the P-40. The 109s took a bigger toll on the P-40s, but I think there were more P-40s than Hurris and lot's more than Spits. Of course, if any German pilot was shot down, he probably claimed it was by a Spit and not a P-40.
The final nay was told to me by a Canadian pilot and it must be true, cause those guys would never tell a lie, least not while sober. Jerry Billing, in discussing wheel vs 3 point landings, said that in pilot training that if one could not land a Spit 3 point( actully the best and easiest way, I think) then the RAF sent you to fly P-40s,and thus your life expectancy went down quite a bit ,if you met a 109. I don't think Jerry ever fought in a P-40, but he sure met 109s in a Spitfire.

Dave, if you have flown both the Huri as well as SL 721, how about givin us your pilot report comparing the 3 fighters? It would be worth a seperate topic, and I'd be intrerested in what a pillot today would think and feel, not just what they did or might have done in combat. I'd love to fly the Hurri, but am not raising my hand if they are looking for 109 vlounteers. I'd love to taxi it, carefully of course. I think I could fly a Spit in my sleep, and as a matter of fact , I often do. Hope to get back to flying one for real one day.

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Bill Greenwood
Spitfire N308WK

Mike, I checked my figure for my plane's speed and fuel consuption.
At 0 boost,(30in) and 2000 rpm the Pilot Notes give fuel burn as 45 Imperial GPH, thus 54 U S gph, actaully, I'd either use 30 and 1800 which is 47 gph or 34 and 2000 which is 52gph. The Allison figure of 50 is not too far off. My speed at 30/2000 would be 246 mph true, or 214k.
This is a lot faster than the 210 mph you give of the P-40. I would usually be cruising at 10,500 or 11,500. I live at 8000 feet and even from sea level these planes are just much faster and effeicent if you get up a bit . And Iam talking true airspeed, not indicated. If a P-40 indicated 210 down low, he might really be doing about 230 mph at say 10,000. The rule is you add 2% per 1000 ft to the indicated speed to get true. This does not even consider instrument error, which in the Spit is really nil at cruise speeds. A single seat Spit would be a little lighter and perhaps 5 mph faster. I have flown a little cross country in formation with a P-40 and notice I do throttle back a little, especially compared to a 51.

Dave, I have never run my plane for any length of time below 0 boost,then engine prefers a little power . I do know the Notes give fuel figures down around minus 4 boost of like 30 imp ghp or some such, don't have it in front of me.

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Bill Greenwood
Spitfire N308WK

P-40N NL1195N "Parrothead"

30" 2000rpm @ 9500ft and about 70 degrees indicates 220mph and burns 50gph in auto lean.

Internal fuel is 100 gallons and I usually use the 75 gallon belly tank for cross country.

JC

I found the flight operation chart I was thinking of. P-40E 9000ft density alt, 2000rpm, 28" manifold pressure (my bad memory) . Says 208 IAS mph and 48gph. The N model is a bit lighter in full military trim than an E, and civilian planes tend to be a bit lighter still. Field altitude here is 2500 ft MSL, I flew a Cub this last July when the density altitude was 4800 ft at takeoff. I've been in the back of the P-40M Tiger had, and in the back of "Parrothead" though that time we didn't fly straight and level enough to get good cruise numbers (I NOT complaining!)