P-40 with Griffon engine

Shortround6 said:

Why do people automatically assume the radiator on the P-40 was so bad?
Or assume that all ventral radiators were good?

The P-40 was fitted with several different radiator set-ups, While test results may be lacking we can note that they never changed the production versions.

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Agree, and would be interested to hear from people who think the chin radiator was high drag.

The radiator was "hidden" aerodynamically and increased frontal area only slightly, and that could have been reduced further IMO.

The chin installation was supposedly tougher in combat because the coolant and oil radiators were just below the engine.

And the P-40 was about the only plane tested in wwiiaircraftperformance.org that didn't overheat.

All in all a very good radiator installation IMO.

The chin radiator made the airflow turbulent across the bottom of the airframe and induced yaw instability as well as a few other bad handling characteristics that the earlier P-40s did not have. Don Berlin quit Curtiss around the time this change took place, if I recall correctly.

The European fighters didn't have such a big advantage over the P-40 after they were "tropicalized" to survive in North Africa.

Venturi said:

The chin radiator made the airflow turbulent across the bottom of the airframe and induced yaw instability as well as a few other bad handling characteristics that the earlier P-40s did not have. Don Berlin quit Curtiss around the time this change took place, if I recall correctly.

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What model(s) of the P-40?

spicmart said:

Would a P-40 with Griffon engine have been a competitive late war fighter?

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Actually, we went down this road 13 years ago.
It was a good thread. Probably in the archived section now.
...however, I can reiterate some of those points here. So, to answer the OP's question....
I don't think the Griffon engine would do much for the P-40.
Its a physically larger engine, so the cowling would have to be modified and probably stretched out, throwing off the balance of the plane.
What might work better is a redesign of the engine that's already in the airplane.
Bore out the cylinders (.445") to bring displacement up to 2000 cu.in would invoke a 16.7% increase in available power. Add to that a redesign of the supercharger housing and impeller to take advantage of that increase in displacement and it all could yield an engine powerful enough to add notable performance to the aircraft.
What the plane lacks is room for a two-speed/two-stage supercharger, which is what it really needed.
A cross-sectional look at the plane shows there's just not enough room behind the engine to house such a device, without major structural changes being made to the plane, and at that point, you might as well just design a whole new airplane.
However, the increased displacement of the engine and larger (two-speed/single stage) supercharger would definitely improve performance.....but by how much?

Elvis

Venturi said:

The chin radiator made the airflow turbulent across the bottom of the airframe and induced yaw instability as well as a few other bad handling characteristics that the earlier P-40s did not have. Don Berlin quit Curtiss around the time this change took place, if I recall correctly.

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Don Berlin quit in Dec of 1941, The P-40F had been test flown and was about to go into production.
The P-40F had a bigger lower air scoop than the P-40E and later Allison powered P-40s. Due, in part, to the change incooling requirements of the RR engine and also due to the carb intake being in the ventral scoop instead of in the seperate scoop on top.

Some of the lateral (or Yaw) instability came from the more powerful engines, and in fact the P-40 may have had a few yaw problems (or was border line) anyway.

First Hawk 75 with Curtiss with a 900 hp Wright XR-1670-5 14 cylinder radial (soon to disappear and never be heard from again).
Just about all Hawk 75s, 81s and 87s (at least until the summer of 1942) used pretty much the same fuselage and tail.
By the time you get to the Fs and the Ks you had engines that were rated at about 1300hp without WEP. This change in power, like on many other aircraft, may have required either a larger vertical stabilizer or an extend fuselage or......?
The Later Merlin powered Fs and most of the Ks (and later) first got a small dorsal fin and later the fuselage was extended by 20in moving the entire vertical stabilizer and rudder back.

Blaming all the handling problems on the chin radiator might be correct but it seems a bit too convinent.
Please note the plane in the picture grossed 4843lbs.

another picture.

GregP said:

The P-40Q was a very good airplane, but it DID come to the table somewhat late. It flew Jun 43, but didn't really make a splash until Nov 43. The thought to install a Griffon engine could have been as early as the first XP-40Q since the Griffon was around at the time. But isolationist views at the time likely would have prevented Curtiss and the Army from buying other than an American. The Merlin in the P-51B first flew 30 Nov 42. The only reason they tried the Merlin was that it was not a fighter anticipated to be used by the USAAC/F. Once they flew it, it was another story.

So, the move to out a Griffon in the P-40 might easily have cropped up if they had any Griffons ... that is doubtful since the Griffon was being used in the UK and the U.S.A. wasn't making them. I doubt the British had the Griffon capacity to export them to the U.S.A. Still, the beast would have been interesting!

A P-40Q bubble-canopy variant COULD have been flying in late 1943 - early 1944, but never materialized. Another "might have been" that could have made a difference in the war.

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The Brits only managed to make 8100 griffon engines so doubt any would be available to the USA !!!

The P-40 (not the XP-40) first flew in April of 1940 looking much like this.

SO there are at least 3 different "chin" radiators on P-40s and the 1st was was in production 1 2/3 years before Don Berlin left the company and the 2nd was being designed in the 2nd part of 1940 and went into production 5-6 months before he left the company (tooling up was even earlier).

So which 'chin' radiator caused the problem/s????

Hi Soaringtractor,

They only went into Fireflies, Spitfires, Shackeltons (post-war, like some Griffon production), Seafires, Spitefuls and perhaps a few others. During WWII, especially early-on, there were never enough first-line combat fighters. Perhaps you could tell me which of these scarce resources and maybe how many the Brits might give up so we could field Griffon-powered P-40s with somewhat better performance, probably few of which might see British service.

First-line fighters were so short in supply that they accepted American fighters for front-line use, which would never have happened had there been enough domestic units available for service.

Now, had we opened a U.S.-based Griffon production line, then maybe. But I doubt it would have produced anything in 1942. It MIGHT have flown about coincident with the first P-51B or so ... what would be the odds of it having any significant advantage over the Merlin P-51?

GregP said:

Now, had we opened a U.S.-based Griffon production line, then maybe. But I doubt it would have produced anything in 1942. It MIGHT have flown about coincident with the first P-51B or so ... what would be the odds of it having any significant advantage over the Merlin P-51?

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You certainly wouldn't be getting a 2 stage Griffon produced in the US in 1942.

If US production of the 2 stage Griffon did go ahead, I suspect that the P-51 would have been the ultimate US recipient. It was, apparently, a lot of extra work to convert to the Griffon compared to the Merlin, but it it was feasible for the P-40 then it would be for the P-51.

Rolls-Royce were advocating a P-51/Griffon 65 in 1942.

GregP said:

The P-40Q was a very good airplane, but it DID come to the table somewhat late. It flew Jun 43, but didn't really make a splash until Nov 43. The thought to install a Griffon engine could have been as early as the first XP-40Q since the Griffon was around at the time. But isolationist views at the time likely would have prevented Curtiss and the Army from buying other than an American. The Merlin in the P-51B first flew 30 Nov 42. The only reason they tried the Merlin was that it was not a fighter anticipated to be used by the USAAC/F. Once they flew it, it was another story.

So, the move to out a Griffon in the P-40 might easily have cropped up if they had any Griffons ... that is doubtful since the Griffon was being used in the UK and the U.S.A. wasn't making them. I doubt the British had the Griffon capacity to export them to the U.S.A. Still, the beast would have been interesting!

A P-40Q bubble-canopy variant COULD have been flying in late 1943 - early 1944, but never materialized. Another "might have been" that could have made a difference in the war.

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The P-40Q could have flown in early '43 since the -93 engine was in production from April. Not quite as high critical altitude, but that would have been corrected by simply putting the carb on the engine stage (as in the actual P-40Q) instead of the auxiliary stage. Should have been done on the -93. Both the P-40 and the P-39 would have been greatly improved in '43.

Shortround6 said:

Why do people automatically assume the radiator on the P-40 was so bad?
Or assume that all ventral radiators were good?

The P-40 was fitted with several different radiator set-ups, While test results may be lacking we can note that they never changed the production versions.

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Resp:
From just looking at it, 'drag' is what I initially see as compared to later production fighters.

wuzak said:

Indeed.

The XP-40 had a ventral radiator, but it was changed because it was so bad and didn't work.

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It worked just fine but the gov. told Curtis Wright to move it.
If you want to know why Curtis Wright really did what is did, read Curtiss -Wright-- Greatness and Decline.
Their being U.S Armies leading supplier was a great part of what destroyed them as the people running the company put money first and usually if the Army said crap, they dropped their pants and squated.

I do not have the book here but the one on their fighters says exactly why it was moved and it was not Curtiss Wright's idea.
Sadly Don Berlin was never interviewed for the dung that happened at CW neither nor was he given and say on P-40 changes.
Lack of an altitude engine was its main short coming; the P-60D, which was in reality just a P-40 with a modified airframe had the Merlin used in the Mustang installed and even with the huge air drag chin radiator was capale of 400 mph.
Same engine in the P-40Q would have made it heads-up equal to the Mustang in most respects and from handling reports in the book I have on Curtiss fighters , better in some respects.
I sadly do not have the book here for an exact quote.

RpR said:

It worked just fine but the gov. told Curtis Wright to move it.

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It worked so fine the plane with could not break 300mph.

The Gov told Curtiss to change things, not a whim, but on the recommendations of the NACA at Langley field after wind tunnel testing.
Wind tunnel tests showed less drag for the chin radiator setup. After incorporating the NACA suggestions the plane was good for 342 mph.

With a few other tweaks and the different engine the regular P-40s manged to go 14mph faster.

IIRC the very first Mustangs converted by RR,

Were fitted with chin radiators. Though thankfully NAA redesigned the radiator setup which was a lot more easy on the eye.
The RR book ''The Merlin Mustangs'' mentions there was no difference in speed or performance with the production P-51B's but it would never have won any beauty contest.

Edit :
'' The Rolls-Royce conversions were experimental improvisations. The conversions featured a deep chin scoop underneath the prop spinner that was faintly reminiscent of late-model P-40s, and gave them a unique appearance among the Mustang family. The first Mustang X was originally fitted with a standard Rotol (Rolls-Bristol) four-bladed propeller, as used by the Spitfire IX. This was later upgraded to a custom-built propeller, though it proved to have little influence on performance.

The performance was nonetheless very satisfactory. The Merlin 65 could provide more horsepower at altitude than the Allison V-1710 did at takeoff, and the initial Mustang X conversion achieved 700 KPH (433 MPH) at an altitude of 6.7 kilometers (22,000 feet). The aircraft could reach an altitude of 6.1 kilometers (20,000 feet) in 6.3 minutes, about two-thirds the time required by an Allison Mustang. Greater power and torque resulted in a degree of lateral instability in the Mustang X. Various fixes for this problem were considered during the evaluation, including a bigger tail fin, but the problem would get worse before it got better.

The second Mustang X flew on 13 November 1942, and the third flew a month later. Rolls-Royce kept NAA informed of the results of the tests while NAA refined their own conversion, which had been re designated "XP-51B" in the meantime. The first XP-51B flew on 30 November 1942. As with the Mustang X, performance of the XP-51B demonstrated that faith in the Merlin conversion was justified. NAA test pilot Bob Chilton achieved a level speed of 710 KPH (441 MPH) at an altitude of 9 kilometers (29,800 feet), and the XP-51B could climb almost twice as fast as an Allison Mustang.

This first XP-51B was roughly an "80% conversion", but the second, which flew soon afterward, was close to a production design. The Merlin 65 had a similar physical "envelope" to the Allison V-1710, but weighed about 136 kilograms (300 pounds) more, and required fitting the intercooler someplace in the fuselage.

The Merlin Xs had the inter-cooler under the nose, but that arrangement was cluttered, and after a six-week bout of headaches NAA engineers managed to accommodate it in the radiator system under the cockpit. They also managed to obtain a small amount of thrust out of the radiator exhaust. In any case, the modification resulted in the belly air scoop hanging a bit lower than in the Allison Mustang. This was a slight visible change, as was the slightly fatter nose; more noticeable was the switch of the carburetor intake from above to below the prop spinner, giving the new Mustang version sleeker looks than its predecessor. The new design also featured a four-bladed Hamilton Standard propeller with a span of 3.4 meters (11 feet 2 inches), replacing the 3-bladed propeller used on the Allison Mustangs....''
source: [2.0] The Merlin Mustangs. Identical to what is written in the book ''Rolls Royce And The Mustangs''.

P-39 Expert said:

The P-40Q could have flown in early '43 since the -93 engine was in production from April. Not quite as high critical altitude, but that would have been corrected by simply putting the carb on the engine stage (as in the actual P-40Q) instead of the auxiliary stage. Should have been done on the -93. Both the P-40 and the P-39 would have been greatly improved in '43.

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Was the two stage V1710 in production for the P63 Kingcobra by then?

Koopernic said:

Was the two stage V1710 in production for the P63 Kingcobra by then?

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The V-1710-93 was the engine for the Kingcobra and in production from April '43. Problem was the Kingcobra airframe would not be ready until October. The AAF should have just put the -93 in the P-39 until the King was ready

Sid327 said:

IIRC the very first Mustangs converted by RR,

Were fitted with chin radiators. Though thankfully NAA redesigned the radiator setup which was a lot more easy on the eye.
The RR book ''The Merlin Mustangs'' mentions there was no difference in speed or performance with the production P-51B's but it would never have won any beauty contest.

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The Rolls-Royce conversion had a chin mounted intercooler radiator. The main engine radiator remained in the standard P-51A scoop.

The P-51B had a larger belly scoop which contained the engine and intercooler radiators.

P-39 Expert said:

The V-1710-93 was the engine for the Kingcobra and in production from April '43. Problem was the Kingcobra airframe would not be ready until October. The AAF should have just put the -93 in the P-39 until the King was ready

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Was this feasible for the P-39?
Is there room for it? What about COG? Could it have been sorted out prior to the P-63 entering production? Who would use it? Who needed it?

P-39 Expert said:

The V-1710-93 was the engine for the Kingcobra and in production from April '43. Problem was the Kingcobra airframe would not be ready until October. The AAF should have just put the -93 in the P-39 until the King was ready

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If USA is awash with 2-stage supercharged V-1710s in second half of 1943, shove it in P-40s, if installing them on P-51s is too much of hassle.