Curtiss P-40Q
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Curtiss P-40Q

Ray Cox, e-mail, 08.04.2021 08:56

"Hap" Arnold, nor anyone else, "impeded" the P-40Q. The P-40Q had a top speed of 422 mph, but at the same time a production P-47D had a top speed of 433 mph, and a production P-51D could go 437 mph. Also, the P-40Q's service ceiling was 31,000 ft, but the service ceiling for the P-47D was 40,000 ft, and the P51D was 41,500 ft. The performance of the P-40Q was simply inferior to the P-47s and P-51s already in service. That was the reason why the P-40Q was not put into production.

arrowBFlight, e-mail, 02.04.2017 21:27

It makes one wonder. 'Hap' Arnold probably did more to
impede this a/c, that had so much potential. There was
ample time to sort out a half dozen or less items on
this a/c. Get weapons clearance done ( 4-20mm cannons,
75 gal lrt, tote a pair of 500 pounders ) put her in the
field, and let her run a muck. This was a much improved
P-40. She could turn and roll well, had a significant
increase in airspeed, diving was never really an issue,
and now, she could climb! Case in point; The Tempest V
was delayed for months over a pay dispute by assembly
workers at Langley. Tempests arrived in Feb/Mar of '45
and in a short period of time did a bang up job! LWP'S
feared and respected Tempests. It scared the living
day lights out of them. The XP-40, should have been given
the green light. What could have been ? Boggles the mind.

arrow, e-mail, 15.05.2016 19:36

Touche,Boris. Thanks for the reminder. I forgot about that
formula, torque x rpm divided by 5252 = H.P. All of the
engine constructors during that period used dynomometers,
and the h.p. rating was at 3000 rpm at sea level for take
off. These v-12's produced some serious 'grunt'. I've
recently come by some images of a dyno cell at Allison.
Some h.d. plumbing,air ducting, and the water brake was
huge by large ! It looks like a generator from G.E. and
is a good 4'ft in diameter. I guess Allison and others
chose not to advertise these figures.Impressive all the
same. I've also found some great info on p-40's, lots of
test data et al, to much to go over here, however there
is a good piece on how hard the v-1710-39 and 73 series
engines could be pushed, ie:'over boosting' by the ausies. Try 66"hg m.p.= 18lbs boost on the 39 and 70"m.p.
for 20lbs boost on the 73 for extended periods @ 3200rpm
Allison reps. estimated the engines were making north of
1700 h.p. That would make for one screamin' hawk !
it's all good.

Boris, e-mail, 01.05.2016 04:04

I picked 1700HP @ 3,000 RPM.
It is pretty simple.
about 2976 ft lbs at that speed.

arrow, e-mail, 07.04.2016 01:08

good answer. it makes sense. as for torque/thrust values
they may very well not exist. if by chance they do, i think the numbers would be interesting. allison used
supercharger ratios from a low 0f 6.00:1 with a mix of
ratios, topping out at 9.:80.1 . during the depression
era, i believe g.m did little if any r & d on the allison. rolls royce did. rolls had one other advantage
going for them. they were involved in the schnieder cup
air races. much was learned from this, no doubt. i think
it was in 1937, one of the supermarine a/c achieved an
airspeed of 430mph, in a/c equiped with floats no less.
they were on the right track, to be sure. history is,
as history was. if not for if's, but's, and maybe, things
would certainly be different. take care.

Boris, e-mail, 31.03.2016 17:38

In aircraft engines Horse Power is converted to the desired
"torque" and thrust by gear reduction and controllable propeller pitch. So the rated torque is un important.

A good example would be turbo prop engines. Th eturbines are turning at 13,000RPM + but the prop is turning about 1,100 RPM.

Similar for WWII era piston engines, most had a gear reduction of between 1.33:1 and 3:1

As far as I know Allison V-1710s were equipped with 1.5:1 (prop turning slower than the engine) gear reduction and 7.3:1 or 8:1 blower drive ratio. ALL airworthy Allison V-1710 engines were supercharged. Some, like the one in the P-40Q had a two stage unit and the P-38 had a turbo supercharger as a first stage along with the gear driven blower.

arrow, e-mail, 20.03.2016 00:23

there was a u.s. gen. who once said" the p-40 was damned by
words, but was flown into glory".i have not been able to find out who this general was, however i feel he was right.
the p-40 was a much better a/c than many have given her credit for. she was the only fighter that could turn with the a6m zero. a move known as low yo - yo. she could roll
with best of them, dive like brick, and dish out a beating as well as take a pounding that would finish off others, yet more often that not, return to base. as for the p-40q. as stated else were, to little to late. however, had events taken place sooner she may have seen the light of day. i guess we 'll never know. the "q" ship
looked to be quite the performer. angels 20 could be attained in 4.8 min. that's a r.o.c of 4,167ft/min. that's nothing to sneeze at. with 4 20mm cannons, 1425 hp
422mph at full chat, yeah ! add h2o/meth injection and you have a 20% boost in h.p. that's 1 h.p./per cu inch.
back in the day, that was magical ! the p-40, her pilots, and the g/c's did a great job. to all of those great guys
thank you. in closing, we all know the h.p rating of those beautiful v-12's, works of art. does anyone know
what the torque rating was in lb/ft of an allison v-12
1710-121 or other allison's ? h.p. is all good but, torque is what gets you moving ! have fun, and take care

Boris, e-mail, 03.01.2016 20:06

Also the Oscar and more so the zero could not turn right worth beans at full power at any speed. This was easily compensated for at low speeds but at over 250 mph they were at full or nearly full power.

As far as I know no version of the P-40 had flight control boost. Flight control boost was a rare thing in piston engine fighters.

Ed Foster, e-mail, 20.12.2015 20:59

The P-40 was the only Allied fighter that could out turn the Zero or Oscar at speeds above about 280 m.p.h. The lack of hydraulic boost on Japanese aircraft controls meant their maneuverability suffered at speeds near or above 300 m.p.h. Saburo Sakai would order his pilots to break off rather than engage Australian or New Zealand P-40's in high speed turning matches.

TORBJÍRN KAMPE, e-mail, 08.03.2015 00:01

P-40 war the United States ever airplanes that are worthy of the name fighters. It was as long in the air like me-109 and FW-190, spitfirer and hurrkan.
P-40Q is not fun that it had to be with WW2, but was RENO aircraft. Boring.
Everyone talks about the P-51 Mustang, the beginning of WW2, was the only one attack aircraft named A-36 Aptche. US only real jack plane, the P-40.

Boris, e-mail, 14.11.2013 02:18

oh yes, I had forgotten, Kermitt Weeks is restoring a Fury V powered by a 2,400 hp Sabre. The aircraft will be fully airworthy and have a (maybe at this point) running Sabre. Kermitt admitts it will never fly though we may get to see and hear a running Sabre for the first time in half a century. Reason for not chancing a flight? The legendary "reliability" of Napier's masterpiece!


Boris, e-mail, 13.11.2013 00:56

P-51 and that "lousy Allison"?
The P-51A and A-36 were powered by an up-rated V-1710-81
that gave better performance and speed rose to 408mph@15,000'.
Some say 390 mph, but I tend to believe the USAAC/USAAF
numbers at 408.
To put that in perspective the A model was the best performing
version of the P-51 under 10,000' till the H model came around.
Above 10,000' the two stage Merlin ruled.


Sven, 04.11.2013 01:19

I think Boris just about
Nailed it.A different
engine doesn't make a
different aeroplane.
Before anyone says P51.
Exeptions are there for all to see but as rare
as rocking horse manure

Boris, e-mail, 03.11.2013 20:22

Napier's 3,500HP Sabre was a running but still born project.
Sleeve valve engines did not tolerate high boost pressures
well at all and the Sabre at 3,500HP would likely have never
survived in service. In any event the advent of 100+ PN (octane)
fuels made poppet valve engines a more viable option. As much
as I admire the British Sleeve valve en gines they were extremely
costly to build and operate. Roughly twice the operating and
purchase price of equivalent poppet valve engines. If you want
to talk one off fantasy piston engines there were dozens
of candidates from the P&W 4200 hp R-4360 VDT to the previously
mentioned Allison Turbo compounded engines.
Curtiss Wright built the awesome R-3350 TCW series of radials
that made between 3,250 and 3,800 HP! In service to boot.
Mass produced and used in everyday service....
Sabres are cool, but utterly unreliable at any power setting.
When WWII ended so did the Sabre, as far as i know there are
NO running Sabres static or otherwise, and for good reason.

The highest power output for a Sabre in regular service was the Sabre V at around 2,500-2,600 HP.

Weight was decidedly piggish at over 2,350 lbs for the
power unit only.

Allison weight was about 1,400 lbs depending on model.
As a result Sabre installation in a P-40 would have been
an impossability.

Steve Round, e-mail, 03.11.2013 04:43

Ever heard of the Napier Sabre IV 24 cylinder sleeve valve 3500 horsepower no more frontal area than a Merlin and barely 8 ft long the Napier would have made this kite go some

juan, e-mail, 30.03.2012 19:30

Fue una hermosa maquina de limpia arquitectura americana
Literalmente una joya de la mecanica

Klaatu83, e-mail, 22.12.2011 19:08

The P-40Q was the best of the P-40 series, but it was a case of too little, too late. By the time the P-40Q prototype was flying, the Air Force was already getting all the P-38s, P-47s and P-51s it required, all of which were just as good, if not better.

Boris, e-mail, 03.10.2011 03:35

After pouring over everything I have I have found no reference
to a two stage Merlin ever being installed in any P-40.

I would love to read about that, got a reference?

The XP-60 started life as a P-40N and got a British built Merlin 28.
That's a two stage Merlin similar to the Packard V-1650-7 used in the P-51D.
The P-60 was a non performer despite having a laminar flow wing.
Other engines were tried and also failed to impress before the project was cancled.

The Allison V-1710-127 was a turbo compounded engine that was static
tested to 2,800hp and may have been capable of more.
Exhaust temps were high and corrected and a quick fix was
to ingect water into the exhaust stream to drop the temps
to the level the turbo could survive.

No P-40 ever flew with a 2 stage Merlin. A study was done and it was
decided a two stage Merlin powered P-40 would have rivaled a Spit, Bf-109 or P-51 but none ever flew.

The P-60 proved the concept to be a fantasy.



a.machiaverna, e-mail, 25.09.2011 07:37

Curtiss cheif designer, Don Berlin, tested a p-40N with a 1,695 h.p. Merlin V1650 as used in the P51D, and results showed a better airplane than both the ME-109 and Spitfire. The Merlin powered production P-40s used a 1,395 h.p. Merlin V1650. The ultimate Allison V1710 was the E27 variant capable of 3,000 h.p. and was slated to be installed in the P-63 Kingcobra. Extremely high exhaust temperatures prevented further development as it came late in the war.

Boris, e-mail, 30.08.2011 04:21

P-40F and P-40L, which both featured Packard V-1650 Merlin engine in place of the normal Allison. Performance was marginally better at high altitudes and worse at sea level. The Allison V-1710 in it's most developed versions was far better than most know today.

Robert Hill, e-mail, 27.08.2011 22:05

Imagine if this had been available to the AVG.
Part P-40, part P-51 and Part Spitfire!
Now imagine if it had a Merlin!

mwnuk, e-mail, 09.08.2011 02:24

the mustang, lightning, corsair and hellcat were all great aircraft, but you have to keep in mind the us turned the tide in the pacific using the p-400 (bell airacobra), the grumman wildcat and the p-40. for political reasons the airacobra gets little credit (the soviets used it more effectively than we did and since it was an american product the soviets played down its role as well as that of the p-40.) there was good reason that the p-40 stayed in production throughout the war, it was a great fighter aircraft in all its versions!

GLF, e-mail, 07.06.2011 00:12

It's not the aircraft, it's what it's used for.
The Soviets had great low level service from the P39 and P40. The US tried to cover too many bases and ended up covering none. A lesson for today perhaps?

Boris, e-mail, 13.04.2011 04:34

actually the P-40Q had the most advanced version of the Allison,
It had a two stage constant boost supercharger on a variable speed drive.
Performance at all altitudes was excellent.
Problem is as you noted, it was too late.
The P-51 and P-47 did the job better and had far greater range.
Also they were already in the fight.


a.machiaverna, e-mail, 09.04.2011 04:15

The Allison was a fine engine, proved itself in the P-38. Not turbosupercharged in the P-39 and P-40, this US Army decision doomed both machines to mediocrity. If the P-40Q had the right engine ( a turbosupercharged Allison V1710 ), it could have been one of the greatest fighters of World War 2. Too bad Curtiss didn't start the P-40 "clean-up" program sooner. A rugged machine , capable of very high dive rates and more manueverable than the P-51, the P-40 if fully developed sooner would have been a very feared airplane in the skies over the Pacific and in Europe. On hand when needed early on in the war, the P-40 in the hands of a good pilot proved to be a formidable weapon despite its lack of level flight high speed especially at high altitude.

Jim Farry, e-mail, 27.12.2010 05:31

The P40 and C46 were built in Cheektowaga, a suburb of Buffalo, New York. My father was Chief Maintenace Man for all three plants. We did not see much of him during that time. I remember touring the plant on a Sunday in 1943 and being allowed to enter a C46 and peer into the cockpit of a P40. I was 9 years old.

Boris, e-mail, 09.09.2010 02:31

At the time of the US entry into WWII
the P-40 was better than any Japanese
fighter if used properly.
Few if any monoplane fighters could turn
with an Oscar or zero.
I know of none that could combine the turn,
speed and climb of a Zero or Oscar under 5,000'
But the P-40 was faster at all altitudes than
either Japanese plane.
It also posessed a far higher terminal speed
in a dive. The P-40B's climb was not far behind either
Japanese fighter.
Add self sealing tanks and pilots armour and shatter
proof glass then the P-40 don't look all that bad!
The obvious was not that obvious in 1941.
The obvious being hit and run tactics.
Dive, hit em at 400+ MPH and zoom up out of range.
Re-group and hit em again.

A P-40B or C could easily survive a 500mph dive.
It's doubtful a Zero or Oscar could survive more than 400.

Add to the above the P-40 turned rather well and gave
excellent stall warning.

The issues of the P-40, and for that matter the P-39
were mostly speed and range.

We Americans hate to take casualties when a simple matter
of money spent and brain power can give a better weapon.
Speed is life in any fighter.
Range became mission critical!
That is why the P-38, P-51 and P-47 got more kills and
better press.

Oh yes, the P-40 lacking a two stage supercharger still
gave better high altitude performance than any Japanese
fighter of 1941!


Rick Ramsey, e-mail, 18.08.2010 04:42

My father, Glyn Ramsey, is an old "China hand", and he flew this great warbird in a lot of combat. He also flew the P-51 in the same theater. He swears by the P-40 as the toughest thing there was, and he made the Japs respect it even more. It is one of WWII's greatfighters...because it was there, and it did the job!

Sturm, 04.06.2010 05:09

Hrm....If a later-model Spitfire and a P-40 made love, would this be the result?

Boris, e-mail, 08.09.2009 13:50

"The first altitude-rated C engine with integral supercharger, the V-1710-C13, was installed in the Curtiss XP-40 in 1938 and this engine was put into production as the V-1710-C15 in 1939."

There is nothing incorrect about this statement.
It is easily miss understood as the first Allison
with a integral supercharger.

In reality it was the first Allison with an altitude rated integral supercharger
to be installed in a XP-37....

All airworthy Allison V-1710 engines were equipped with a integral engine driven supercharger.

Jane's 1945-46, of which I own an original, is not incorrect.
It is a mere miss understanding ;-)


Leo Rudnicki, e-mail, 01.09.2009 21:14

Sorry. Myself and Jane's 1945/46 are wrong."The first practical flight installation of the C model was made in 1937 in the Curtiss XP-37. This engine was the V-1710-C10 with exhaust-driven turbo-supercharger. The first altitude-rated C engine with integral supercharger, the V-1710-C13, was installed in the Curtiss XP-40 in 1938 and this engine was put into production as the V-1710-C15 in 1939. Sir William Stephenson,"Intrepid", once said "A document is the best lie". Dr. Theodore von Karman once asked "how can there be progress without controversy?" For myself, I do not have an original thought without the germ of fact to support it.

Elvis, e-mail, 01.09.2009 11:41

On the versions of the V-1710 that included a turbocharger, the Turbo was the second, or, "auxillary" stage.
Leo, A Turbocharger is still a supercharger, it just isn't an "engine-driven" supercharer.

Boris, e-mail, 21.05.2009 03:19

V-1710-11 (C7) Engine driven blower ratio was 7:1.
Turbocharging was also used but the results were poor.
All Allison V-1710s were equipped with a engine
driven superchager with a gear ratio of 7:1 or 8:1.
The original contract was for a airship and that version had no blower.
It was also reversable.
All aircraft versions had a supercharger driven by the engine )I am repeating myself!).


Leo Rudnicki, e-mail, 20.05.2009 17:06

1937 allison V-1710-C10, fitted to the Curtiss XP-37?

Boris, e-mail, 20.05.2009 14:41

All Allison V-1710s had a engine driven supercharger.
Turbocharged versions had the engine driven unit and a turbosupercharger as a first stage.



Leo Rudnicki, e-mail, 20.05.2009 04:16

Never heard the myth but semantically speaking, turbo-charged Allisons weren't supercharged. No Allison engines were equipped with viable high-altitude-rated superchargers worthy of being in service. And without picking Stanley Hooker's brain, there never would have been a two-stage supercharger with anti-backfire screen. But, that's just semantics.

Boris, e-mail, 20.05.2009 02:53

Correction, for those who still believe the myth, NO Allison V-1710
was ever built with no supercharger (except the airship version).
The Allison powering the P-40Q was a two stage supercharged engine
with intercooler.

I repeat, NO Allison V-1710 that ever got into an airplane was un supercharged.


a.machiaverna, e-mail, 12.05.2009 14:15

yes Leo, the Merlin was a great engine, its h.p. rating equal or better than its total cubic inches. The Merlin was 1,650

a.machiaverna, e-mail, 12.05.2009 14:00

Do you know what company built critical components for Allison? If you dont know , the answer will probably surprise you.

leo rudnicki, e-mail, 12.05.2009 01:24

I don't believe I ever suggested that the P-40N was the ultimate P-40 but it was the ultimate production P-40, the "Q" being a one-off. The P-40Q was much improved in performance but very short-ranged. Both the P-40Q and Fisher P-75A suffered in comparison to the Merlin Mustangs already in full production. Max Mil. hp rating for V-3420-19 was 2600hp for 15 minutes

a.machiaverna, e-mail, 12.05.2009 01:13

My research shows that the Q did have six .50 calibers, and ample range, using a 1,475 h.p. Allison V1710, but still w/o supercharging. To say the P-51 was a success, would be a complete understatement, its one of aviations elite, along w/ the Vought F4U. Still, the P-40 was on hand when needed, and in the hands of a seasoned pilot, not even the Mitsubishi Zero was a match. Ask the Japanese pilots who went up against the Flying Tigers in China.

a.machiaverna, e-mail, 11.05.2009 14:16

Correction on Allison V-3420, h.p. output was 2,885. Slightly under anticipated output, this was not the primary factor of the failure of the p-75 design. Mixing parts from various aircraft could and did produce some surprising results. Aileron control was extremely heavy, and engineers actually calculated the center of gravity incorrectly!

a.machiaverna, e-mail, 10.05.2009 23:16

If your info. is accurate, the addition of guns and fuel tanks , weight being a factor, would have brought the Q into the 400 mph range.

a.machiaverna, e-mail, 10.05.2009 23:13

So you are saying the ultimate p-40 design was the N model? Still, the Q was a design w/ many aerodynamic refinements, wasnt aware of absense of guns and fuel tank. The Allison V3420 did produce 2,800 hp, came too late.

leo rudnicki, e-mail, 10.05.2009 07:09

Berlin left Curtiss because he was unhappy with corporate decisions which affected his designs. That the Eagle was unsuccessful could be predicated on the use of a double Allison engine being no better than a single engine. It didn't work in the Boeing B-29 version or the Lockheed P-58. How were they supposed to clean up the P-40? On the P-40Q, they removed fuel tanks and guns for performance. The P-51 had guns, fuel, and performance. Have you seen the movie,"1941' with John Belushi and the P-40? A classic. " Lemme hear your guns!" A great scene.

a.machiaverna, e-mail, 10.05.2009 04:25

Why did Don Berlin go over to Fisher? His P-75 wasnt the work of a gifted aviation designer. Mixing parts of dif. existing aircraft proved unsucessful, perhaps practical in theory but unimaginative.

a.machiaverna, e-mail, 10.05.2009 04:20

were dif. airframes.

a.machiaverna, e-mail, 10.05.2009 03:17

P-46's etc. where different airframes.

a.machiaverna, e-mail, 10.05.2009 03:17

P-46's etc. where different airframes.

a.machiaverna, e-mail, 09.05.2009 01:10

my point was to clean up the p40 early on....

leo rudnicki, e-mail, 09.05.2009 00:12

Don Berlin went to Fisher, Curtiss went to the toilet, and yes, Allison finally developed their engine in time to fight a Jet war. Curtiss built a turbo fighter, the P-37. Didn't work out. Took forever to lengthen the tail. The P-46 and P-60 was their attempt to clean up the P-40. The Mustang and it's pilots won the air war over Germany.

a.machiaverna, e-mail, 08.05.2009 13:07

Don Berlin went over to North American? The Allison V-1710 was a rugged and powerful engine, in final form used in the twin mustang in the Korean war. Removal of the turbosupercharger doomed aircraft using this engine to medicocrity, unless of course one considers the p-38, with turbosuperchargers used to give maximum h.p. output at higher altitudes. Back to the p-40, much more rugged and manueverable than the p-51, it only lacked the turbosupercharger, and an early "clean-up" program. Curtiss became involved in too many projects, instead of focusing on this magnificent airplane.

leo rudnicki, e-mail, 07.05.2009 19:00

The P40Q shouldn't be counted as a separate aircraft type but rather blocked with all Kittyhawk/ Hawk 87 models, as apart from Tomahawk/ Hawk 81 models. The P-40, like the Hurricane, was an effective and tractable warplane, available in quantities, thanks to an efficient production line, at a time it was sorely needed. Like the Hurricane, it was produced too long. Curtiss was a corporate entity lacking the spark of brilliance, when Don Berlin left, to create a Mustang or any other great airplane. The P40Q was , like all other Curtiss projects, almost as good, when first built, as aircraft already in service. The Allison V-1710 was nearly ready to fulfil its destiny as a Hydroplane racing engine.

a.machiaverna, e-mail, 07.05.2009 04:36

Your Curtiss aircraft timeline puts the p-40q2 at 1941. Everything I have read in the past 25 years suggests this p-40 model did not appear until 1944.

a.machiaverna, e-mail, 07.05.2009 04:29

Instead of wasting effort on the p-46, p-53, p-55, p-60 and p-62, Curtiss had a thorouhbred from the start with its p-40. Had it began immediately in cleaning up the high drag design, this airplane would not be a bit of an enigma, but one of aviations elite. Much more manueverable than the p-51, this would have been the star aircraft of WW2. However, often outclassed in speed during most of its service life, this rugged design certainly helped win the war.

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