P-40? How good vs Me 109, Spitfire, Hurricane, etc.??????

[Bill Greenwood]

On the other topic Kurt is talking about how good the P-40 is or was, and what it could have been with a Merlin. Dave Hadfield has some good info about that and how much he likes flying the P-40.
So here is the question, if it had the Rolls Royce instead of the Allison which just did not perform above 15,000 feet, how good could the P-40 have been? Would it have been as good as a Hur or even a Spit and an even match for a 109?

One flaw in Dave's case for the P-40, was that one version actually did have a Merlin, not a Rolls, but a Packard, and I don't know that it made the plane good enough. Now I am not sure, but that version of the Merlin may have been the low altitude one,thus not as good as the full 60 or 70 series Merlin in Spits or Mossi.

I have some Spitfire experience, but only a taste of P-40 and of course, like Dave, I never flew either plane with a 109 shooting at me, thankfully.

[The Inspector]

Good call B.G.!
I was wondering how come everyone leaves out the P-40F which DID have a Merlin, easily discerned because it doesn't have the top of the cowl inlet due to the Merlins updraft carburetor.
I think that Don Berlin and the design teams @ CURTISS just flat ran out of ideas, witness all the 'next' P-40 models after the 'N' and adaptations that followed the original series were all flops and the P-40 was the last successful design that CURTISS came up with. Everything else after the P-40 series was third rate against it's competitors (witness XP-87 BLACKHAWK) or wasn't what the customer wanted. Berlin extended the aft fuselage on the N to overcome a stability problem and later discovered that he could have achieved the same effect by modifying the shape of, and sealing around the carb intake.
I'm also certain that the Government wanted the P-40 to keep chugging along 'as is' because it was fairly sucessful, it was in series production, and it could be handed out to Allies in 'off the front page' theatres (Russia, Egypt, Alaska, China, etc.) by the boatload until bigger fish were fried and newer equipment could eventually be fed into the now more important theatres.

[Nathan]

The P-40 "F" and "L" both powered by Packard Merlins. Still only a two stage supercharger. They were not any better then the Allison engines.

[mas]

Nathan,
The Merlins in the F and L Warhawks were two speed, not two stage, which only gave a slight altitude improvement over the Allison. It would have been really interesting to see what the two-speed, two stage Merlin 60s would have done in the P-40 but unfortunately it was not a simple, drop-in fit.

[Mike Halbrook]

My 1.5 cents worth as a long time warbird fan.

From my reading and talking to a couple of local current P-40 pilots, it has to do with how well you know your aircraft and how hard you are willing to push it.
Also, what altitude you are fighting at. Many of the engines used in other fighters were optimized for anywhere from 18,000 to 28,000 ft and did not always produce full power at low altitude. Some of the MKV Spitfires had special engines with cropped supercharger impellers to develop low altitude power.

This is a link to "Perils P-40 Archive Data"

http://www.raafwarbirds.org.au/targetvr ... 0_data.htm

There is an original test report on the P-40F (Packard Merlin). The A/C did perform better at high altitude, but was perhaps slightly slower at low altitude.
The kicker is a confidential letter from Allison saying "please don't run our engines at 70" manifold pressure" of course they then proceed to tell you how to do it.
I had heard about running them this hard in the book "The P-40 Kittyhawk in Service" by Geoffrey Pentland. I thought it was a misprint until I saw the factory letter! Allison estimated the engine would produce about 1785 hp @ 3250 rpm and 70" (if it didn't blow up).

[brucev]

I would assume the Merlin 60 has higher fuel consumption than the Allison, how significantly would range have been affected on the P-40?

[Bill Greenwood]

Renown Eagle Sqd pilot Steve Pisanos was hired to test fly P-63 with "improved" Allisons running at 70 in or even more. He did two tests flights, then engines failed both times, he bailed out, I think the 2nd time, and told the engineers to go fly it themselves the next time. He personally told me this story, and he is such a nice guy and with a sense of humor.

I don't really know about fuel consumption of an Allison, but the Merlin is pretty good and if they were running the same power output, I'd guess the Merlin is as good or better, more efficient than the Allison. I think a stock P-40 is ok on range.

If the Allison was reliable and more fuel efficient than others, it might have been used in postwar airliners. Instead it was radials and some Merlins.

Last edited by Bill Greenwood on Wed Sep 22, 2010 10:06 pm, edited 1 time in total.

[The Inspector]

Yeah, but you can still fly an ALLISON further than you can ship a MERLIN-

[Richard Woods]

Really? So why did the Mustang have to trade up to a Merlin then..

[The Inspector]

A) because the customer, the RAF wanted it more as an interceptor than a ground attacker and were already testing a modified MUSTANG in Britian while the U.S,was still working with the A-36 attack program, and B) the USAAF looked @ the data from Britian and figured they could get a better high altitude interceptor cheaply and quicker by doing the same. Remember the ALLISON grew out of continuing development from the LIBERTY of WW1 and was always meant to be a medium to low altitude engine unless turbocharged. Essentially the ALLISON is a flying truck engine, very rugged and reliable just not a dazzler. When I was crewing in boat racing in the late 60's we'd finish heats on 11 cylinders when we converted to ALLISON, giving us heat points and when we ran MERLINS we'd finish heats on the end of 50 ft. of nylon rope for no points. But, few things are more spectacular to see than a MERLIN coughing a blue/white flash out of the carb intake as it expired leaving rods all over the bottom of the boat.
The XP-37 carried a turbo that was very unreliable as did the prototype P-39. The P-39 was a classic case of 'lets see what else we can strap on this' and it's performance went downhill in direct proportion to the items the USAAF demanded be put on it.

[Richard Woods]

True.. the first Merlin was put in a Mustang by Rolls Royce at Hucknall about 15 miles from where I sit typing this. I seem to recall the poor unsupercharged performance of the Allison was one of the reasons the RAF cancelled the order for the P-38s, as they had been offered a version without them.

My post was more meant about the range of the Mustang after it's engine swap.

Interesting about the boat racing though. I would have thought boat racing would have been quite heavy on engines in terms of shock loadings. Does the Allisons have rods that are more substantial compared against the Merlin's?

Regards,

Ric

[The Inspector]

Racing put horrible loads on engines, 5500+ RPM's and turning the prop @ 16000 revs via a 3 to 1 gearbox, sort of like digging a trowel sized hole in a paved street 16000 times a minute. Rebuilders won't touch an ex racing motor because they are stressed to fragility. Every team had a forest of V 7 and V 5 MERLIN blocks out back of the race shop where blown rods would saw the block in half. That's one reason the boats went to the LYCOMING T-55 CHINOOK helicopter motors, they are as cheap and plentiful today as surplus ALLISONS and MERLINS were in the 50's/60's.

The MERLIN is built like a fine watch or a highly stressed racing vehicle, tough but pretty fragile, the main bearing webs in the block are very thin, whereas the ALLISON is built like a really big truck engine. H#ll for stout, easy to work on regarding the number of tools needed unlike the MERLIN that is festooned with many different types and 'standards' requiring a really good relationship with the SNAP ON man. The ALLISON was designed around an anemic two speed centrifugal gear supercharger and was limited in boost manifold pressure because that's what the customer (the USAAF) asked for.

In racing apps inevitably some new team would lock the blower in 'HIGH' which gave really cool looking manifold pressures until the ram log manifolds, held in place by rubber connecting hoses and band clamps would let go under the pressure and send the manifolds into the lake bringing that heats participation by that boat to an end.
ALLISONS could be reversed (from L/H to R/H rotation) by swapping the crank saddle and crankshaft end for end in the block and a few other side to side parts swaps (friggin' saddle was /is pretty heavy too!) that's how we made left hand engines work with the R/H rotation gearboxes so the boat would begin to turn left when the throttle was backed off @ the end of the straightaways.

[Bill Greenwood]

I don't know much about boat racing, except I wish Merlins had not been used and damaged that way.
But while reliability is a part of racing,the main point is to go fast. If just finishing was the point, I would have been a great ski racer, instead of a Texan out of his natural element.
Which engine, Merlin or Allison has the speed records or most wins in the boat racing?
I know that at Reno the Merlins turn around 3200 or more, but not 5500, and the props don't come out of the water like a boat might. They are some of them, use Allison rods which are stronger.
I can't remember any Allison powered airplane that is within 50 mph of Strega or Dago Red or even Vodoo, maybe closer to 100 mph difference.

A few years back they built the Pond racer. It had great P R, it's whole premise was how much smarter someone(Rutan?) was now than Rolls Royce was back then years ago. Sounds like a reasonable premise, and the Toyota or Nissan ? car engines were going to be not only faster than the Merlins, but more reliable and the plane was supposed to be safer. It was neither, it never turned a single race lap over 400 mph, it overheated and broke down, and finally killed a friend.
Sure had good P R, though. It could have run for President, just not the gold at Reno.

But we are getting away from Dave's premise, which I put at the start of this topic. It is not which engine was/is better, but how good would a P-40 be with a Merlin?

[Saville]

But we are getting away from Dave's premise, which I put at the start of this topic. It is not which engine was/is better, but how good would a P-40 be with a Merlin?

I don't believe the P-40 had as efficient a wing section as the P-51; I believe the radiator intake/exhaust design of the P-51 was superior resulting in less drag; I would think P-40 landing gear (when retracted) would be far more draggy than the P-51 (exposed wheel plus the "hump" on the LE of the wing); the P-40 fuselage was pretty wide as it was essentially a P-36 fuse (fitted to a radial) so without access to the actual measurements I would suspect the P-40 fuselage was wider and therefore more draggy due to the width.

So even if you somehow could drop the hi altitude Merlin into the P-40, I would think the P-40 would be slower. I suspect it would have been slower than the Spitfire. How it would stack up against a Hurricane is a good question (assuming to bolted on the typical B0B Hurricane engine to the P-40).

Those are the first order differences. I *think* the P-40 wing has no taper (or very little) on the leading edge whereas the P-51 LE has a slight sweep back. Don't know if that would make a difference at hi diving speeds.

Last edited by Saville on Thu Sep 23, 2010 12:56 pm, edited 1 time in total.

[brucev]

If i'm not mistaken there was a fair amount of north Africa fighting against the Me109 from which a decent comparison of the two aircraft could be made. Though i have no details of it.