Curtiss P-36 Engines
- Thread starter Akuma
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That was one of my 1st what-ifs on this forum
Benefits - a lot of power vs. V-1710, talk, in late 1941, 1450 HP at 12000 ft instead of 1150 HP at the same altitude; 1700 HP at 3000 ft; all per manufacturer's data - ie. no field mechanic or pilot over-bosting the engine and hope for the best.
Shortcomings - Installed weight goes up by 500 lbs even because the liquid cooling system is gone now; drag also goes up; the exhaust thrust benefits will not be good as with the V-1710 of the day unless the better exhausts go from test and experiments to actual usage*; fuel consumption** will go up by a good deal (necessitating usage of at least 150 gal drop tank instead of the more common 52 or 75 gal ones or two drop tanks, plus early increase of internal fuel to 160 gals).
*exhaust thrust accounted for another 10-15 mph on the ~350 mph aircraft of the era if the exhausts were well executed
** the 1750 HP R-2600s were using 50-100% more fuel on same settings vs. V-1710 as used on P-40D-K, granted they were making more power
P-39 Expert
Non-Expert
Wonder what the performance of a P-36 would be if it just had the R1830-76 two stage engine that was in the F4F?
Probably 330-340 mph, unless the individual exhausts are employed, like the ones NACA tested on the XP-41 (powered R-1830-19 2-stage supercharged engine), that added up to 18 mph at 18000 ft there on just 900 HP (-19 was good for 1050 HP there).
- Thread starter
- #5
Meant as an addition to the above. I have read that field maintenance on radials was generally easier than on WC engines. Also, even with airframe and fuel capacity modifications, CG/CL calculations might have been more straightforward at the engineering end. I mention this because initially the flight reports spoke of the P-36 having harsher stall characteristics than the P-40. It was found later through wind tunnel tests that the wing filleting was the cause for the handling improvement. I've also read accounts that the P-40 would, in certain stall regions, tumble as the engines distance from CG/CL would make it act like a pendulum.
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Shortround6
Major General
When?
1938/39?
1940?
1941/42?
There were two different R-2600s in those years, the 1600hp take-off 'A' and the 1700hp take-off 'B'.
The 5th production A series engine was delivered March of 1938. The 5th production B series engine was delivered June of 1941, about the time P-40Ds and Es show up in production.
Wright did do some preliminary design work on the concept, I will try to look it up later.
- Thread starter
- #7
When did Curtiss start design work on the P-40? It would have been logical for someone to have suggested that they might look into putting in a more powerful radial at that time. I'm curious as to what they were thinking. Did they think the Allison could give more power per weight? Maybe they thought the radials could not get anymore powerful? Was it overall manufacturing costs? Did a potential buyer suggest they use a watercooled engine?
Shortround6
Major General
I haven't found anything on the R-2600 in a P-36/P-40 yet.
There was a proposal to use a P & W R-2180 twin Hornet. Never made it off paper.
Curtiss proposed putting an Allison in the P-40 (XP-40) in March of 1938 for the 1938 fighter competition, which was delayed until Jan 1939. Army accepted and the 10th P-36 airframe was taken for conversion. First flight Oct 14th 1938. Neither the P & W R-1830 or Wright R-1820 were as powerful at altitude at this time. Two fighters did make the Jan 1939 competition with two stage P & W R-1830s but P & W was nowhere near the level of development they would be at in early/mid 1940.
The P-40 was the highest performing low risk engine/airframe combination the USAAC could find at the time. Anything much riskier or needed more engineering work might have meant hundreds fewer fighters available in 1940 and 41.
There was a proposal to use a P & W R-2180 twin Hornet. Never made it off paper.
Curtiss proposed putting an Allison in the P-40 (XP-40) in March of 1938 for the 1938 fighter competition, which was delayed until Jan 1939. Army accepted and the 10th P-36 airframe was taken for conversion. First flight Oct 14th 1938. Neither the P & W R-1830 or Wright R-1820 were as powerful at altitude at this time. Two fighters did make the Jan 1939 competition with two stage P & W R-1830s but P & W was nowhere near the level of development they would be at in early/mid 1940.
The P-40 was the highest performing low risk engine/airframe combination the USAAC could find at the time. Anything much riskier or needed more engineering work might have meant hundreds fewer fighters available in 1940 and 41.
As interested as Curtiss was in selling more aircraft, the Army ordered the XP-40 only to evaluate the relative advantages of inline and radial engines on a common airframe. (This from a contemporary Wright Field report on the subject.) The advantages of the inline were enough to convince the AAF to order a production run of P-40s as the European war showed how far behind US capabilities had fallen.
Cheers,
Dana
Shortround6
Major General
The AAF ordered 524 aircraft as complete aircraft and 36 as spare parts on April 27th 1939, about 4 months before the Initial Attack on Poland. Also included was one "skeleton" aircraft and all sorts of drawings, stress analysis, parts catalogs, manuals, etc.
The US didn't need the shooting war to start to realize that the P-36 with a single speed single stage supercharger was not up to world standards.
- Thread starter
- #11
It sounds like the AAF, decided to go with an engine/airframe similar to what the Europeans were fielding. Spitfire and Hurricane were water-cooled, Messerschmitt same, apparently they were not so worried about engine performance as to start asking manufacturers to put water-cooled engines in AAF bombers.
Not quite the same thing but there was this XP-37 proposal with an R2600: Curtiss YP-37 with the R-2600 Radial Engine
- Thread starter
- #13
Greg Boeser
2nd Lieutenant
I remember a website that had several P-36 proposals using different engines. Can't find it anymore.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Thanks for posting that link. It was very informative and a good read.
Admiral Beez
Major
This old site has some great additional info on what ifs for the P-36, including stats on a potential R-2600 variant.
"For the Navy fighter trials in May 1938 Curtiss proposed four versions of the Hawk 75, two powered by the twin-row Wright R-2600…Curtiss never received authorization to proceed to mockup stage on any of the four proposals. All four of the Curtiss proposals ranked last among the 10 presented. The Vought F4U Corsair won the competition, while a Brewster entry also using the R-2600 was ranked third."
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Greg Boeser
2nd Lieutenant
Yup, that's the one.
Shortround6
Major General
Unfortunately a good number of these Uber P-36 discussions tend to overlook reality.
Why does anybody suppose the Curtiss Hawk 75 proposals ranked last of the 10 proposals submitted to the Navy?
Navy didn't like Curtiss or were there some fundamental flaws?
The P-36 introduction to service with the USAAC was not without troubles. Like buckling of the fuselage and skin wrinkling on the wings near the landing gear. Both signs of insufficient strength. But Heh, lets rip out the 1050hp engine and stuff in the 1600-1700 hp engine and all will be well?
The French were going through wings with their Hawks at a higher than anticipated rate. They tried to by 30 wings from Curtiss as an emergency solution and have the USAAC agree to defer delivery of 30 of their fighters (P-40s) while Curtiss built the wings for the French. The USAAC did not agree.
There are reasons the Hawk wing went from about 850lbs on the export Hawks and P-36s to about 1000lbs on the long nosed P-40s and to 1100lbs on the P-40D&E and up.
You don't use the same strength wing on a 6000lb airplane as you do on an 8000lb airplane.
You want to stick an engine that is over 500lbs heavier than the one that is in the plane and stick on the size prop needed to use the extra power you need to beef up the whole airframe or risk structural failures in flight.
There are reasons that the P-40 was built and it is not because the inline engine was the flavor of the month in engine selection. It offered a major reduction in drag and it offered easy use of exhaust thrust.
Perhaps a R-2600 installation could have been made to work but it requires knowledge that was not available in 1939-40 even if it was available in 1942-43.
Things changed quickly during those times.
Why does anybody suppose the Curtiss Hawk 75 proposals ranked last of the 10 proposals submitted to the Navy?
Navy didn't like Curtiss or were there some fundamental flaws?
The P-36 introduction to service with the USAAC was not without troubles. Like buckling of the fuselage and skin wrinkling on the wings near the landing gear. Both signs of insufficient strength. But Heh, lets rip out the 1050hp engine and stuff in the 1600-1700 hp engine and all will be well?
The French were going through wings with their Hawks at a higher than anticipated rate. They tried to by 30 wings from Curtiss as an emergency solution and have the USAAC agree to defer delivery of 30 of their fighters (P-40s) while Curtiss built the wings for the French. The USAAC did not agree.
There are reasons the Hawk wing went from about 850lbs on the export Hawks and P-36s to about 1000lbs on the long nosed P-40s and to 1100lbs on the P-40D&E and up.
You don't use the same strength wing on a 6000lb airplane as you do on an 8000lb airplane.
You want to stick an engine that is over 500lbs heavier than the one that is in the plane and stick on the size prop needed to use the extra power you need to beef up the whole airframe or risk structural failures in flight.
There are reasons that the P-40 was built and it is not because the inline engine was the flavor of the month in engine selection. It offered a major reduction in drag and it offered easy use of exhaust thrust.
Perhaps a R-2600 installation could have been made to work but it requires knowledge that was not available in 1939-40 even if it was available in 1942-43.
Things changed quickly during those times.
