The Curtiss XP-37: My, what a big nose you have!

"ttyymmnn" (ttyymmnn)
09/13/2018 at 12:35 • Filed to: wingspan, planes you've (probably) never heard of, Planelopnik

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From the Planes You’ve (Probably) Never Heard Of Department of Wingspan , we bring you the Curtiss XP/YP-37.

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(San Diego Air and Space Museum)

Before the outbreak of WWII, the US military had developed a penchant for radial engines. Not only were they powerful, they were also air-cooled, which meant there was no need for the complicated radiators required for liquid cooling and, as a result, radial engine technology in the US became highly advanced. But on the other side of the Atlantic Ocean, European designers had a preference for sleek inline engines. While the inline engine can be a bit more complex, it has the benefit of being more aerodynamic, though the radiator remained an Achilles heel in combat.

Curtiss P-36A Hawk, which formed the basis of the XP-37. (NASA)

In the early 1930s, Curtiss was working on the latest in their !!!error: Indecipherable SUB-paragraph formatting!!! of Hawk fighters, the !!!error: Indecipherable SUB-paragraph formatting!!! and, like many other fighters of its day, the P-36 was powered by a !!!error: Indecipherable SUB-paragraph formatting!!! radial engine. By all accounts, it was a fine little fighter and displayed good maneuverability. But fighters in Europe were emerging with slender inline engines that outpaced the Hawk. and the Army thought that an inline engine might make it more competitive. So the Army invested in the development of their own inline engine, and gave the !!!error: Indecipherable SUB-paragraph formatting!!! , a division of General Motors, $500,000 (more than $9 million today) to develop the 12-cylinder !!!error: Indecipherable SUB-paragraph formatting!!! , so-named for its 1,710 cubic inch displacement. A single !!!error: Indecipherable SUB-paragraph formatting!!! testbed, known as the XA-11A, received the first of the new engines

More race plane than fighter, the XP-37 posed a serious challenge to any pilot who wanted to see the runway on takeoff or landing. (Author unknown)

But the P-30 was designed from the start to hold an inline engine, and fitting the V-1710 into the P-36 posed a significant challenge for Curtiss. The Hawk had been designed around the comparatively compact Twin Wasp radial, so the aircraft had to be modified to fit the V-1710 and all its plumbing. In 1936, Curtiss took a single P-36, kept the wings and tail, but stretched the fuselage by four-and-a-half feet to make room for the engine, radiator and turbo-supercharger. With all the engine and associated bits up front, the cockpit had to be moved far to the rear to help balance the center of gravity. This new aircraft, dubbed the XP-37, looked more like a race plane than a fighter.

Despite the unreliable turbo-supercharger, the Army was generally pleased with the performance of the XP-37. They had wanted a fighter that could fly in excess of 300 mph, and the XP-37 managed a respectable 340 mph at 20,000 feet—when the turbo-supercharger was working properly. Pilots, however, were none too happy about the nonexistent visibility over almost comically long nose, which made it impossible to see the ground during takeoff and landing. Nevertheless, the Army placed an order for 13 pre-production aircraft which now became the YP-37.

A hastily-camouflaged pre-production YP-37. (San Diego Air and Space Museum)

With the YP-37, Curtiss tried to address some of the shortcomings of the XP-37. The airplane grew another 22 inches in length while also moving the cockpit forward, though only slightly. They also installed an updated V-1710 engine with an improved turbo-supercharger. But the YP-37 ended up 450 pounds heavier and actually lost nine mph of top speed. And the “improved” turbo-supercharger turned out to be just as frustratingly unreliable as the first.

YP-37 in flight. Had it entered production, the YP-37 would have been armed with one .30 caliber and one .50 caliber machine gun in the nose. (San Diego Air and Space Museum)

Ultimately, the YP-37 did not turn into the V-12 speedster the Army was looking for, and the project went no further. Most of fighters ended up at the Army’s school for mechanics, and Curtiss turned its attention to the !!!error: Indecipherable SUB-paragraph formatting!!! of !!!error: Indecipherable SUB-paragraph formatting!!! fame, an Allison V-1710-powered fighter that had a significantly more successful career. And once a reliable turbo-surperchager was developed, the V-1710 found a home in the remarkable !!!error: Indecipherable SUB-paragraph formatting!!! , the !!!error: Indecipherable SUB-paragraph formatting!!! , and the !!!error: Indecipherable SUB-paragraph formatting!!! .

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Connecting Flights

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For more stories about aviation, aviation history, and aviators, visit !!!error: Indecipherable SUB-paragraph formatting!!! . For more aircraft oddities, visit !!!error: Indecipherable SUB-paragraph formatting!!! .

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DISCUSSION (12)

OPPOsaurus WRX > ttyymmnn
09/13/2018 at 12:45

i was hoping for an inline 12

Kinja'd!!!

Cé hé sin > OPPOsaurus WRX
09/13/2018 at 12:52

Inline 14 any good to you?

Kinja'd!!!

OPPOsaurus WRX > Cé hé sin
09/13/2018 at 12:54

14? thats just craz iness

Cé hé sin > OPPOsaurus WRX
09/13/2018 at 12:57

1,810 litres.

No, not in total.

Each cylinder....

ttyymmnn > Cé hé sin
09/13/2018 at 13:13

Think I can swap that into my Odyssey?

RamblinRover Luxury-Yacht > ttyymmnn
09/13/2018 at 13:18

And the “improved” turbo-supercharger turned out to be just as frustratingly unreliable as the first.

A lot of people don’t realize what a liability the operating environment of a turbo is. What’s a few hundred CFM of 1200F corrosive gas between friends? They worked it out in fighters eventually, but the tech still wasn’t ready for prime-time in its first mass-produced automotive applications twenty years later (Corvair turbo and Olds 215 turbo) . And that was with methanol and oil injection into the intake to keep temps down and manage compression while keeping it lubricated.

ttyymmnn > RamblinRover Luxury-Yacht
09/13/2018 at 14:36

I will readily admit that I know very little about the history or even the technology behind turbo/supercharging. I was trying to get my head around the concept, and even asked Oppo about it . And, the more I learn, the more I understand why Sanford Moss got a Collier Trophy for his work in the field. Most sources about airplanes focus, not surprisingly, on the airplane itself, and simply say, “The turbocharger sucked.” But not in so many words.

When I teach, I try to get my students to understand the difference between being critical and criticizing. The first one gives you information you can use to get better. The second one slaps a value judgement on something and gives you no information to work with. So, instead of saying “frustratingly unreliable,” it might be better to say that “ difficulties with reliability of the complex systems remained to be worked out.”

Thanks for you comment.

user314 > ttyymmnn
09/13/2018 at 15:05

So the Europeans were building advanced but somewhat unreliable engines while the US was working on simpler, brute force engines. Yup, plus ça change...

ttyymmnn > user314
09/13/2018 at 15:52

It’s a bit if an oversimplification, to be sure. Each side had fantastic aircraft of both engine types. But there is no question that the US was just about all-in with the radial in the 30s, and the Mustang didn’t take its maiden flight until 1940, and with a British engine. Still, some of the greatest planes, like the Thunderbolt and the Fw 190, had radials. And all of the US Navy fighters had radials for their reliability over open ocean.

Cé hé sin > ttyymmnn
09/13/2018 at 17:41

If not, they did 9, 10, 11, 12 and 13 cylinder variants.

InFierority Complex > ttyymmnn
09/13/2018 at 18:29

The US reliance on the radial led to the consequence of most of the early tanks being radial powered as well. This is pretty much the reason for the tall silhouette in the M3 and M4

Kinja'd!!!

M1 Combat car for fun. The Cavalry was prohibited from having “tanks ” which were Infantry only so they changed the turret and called them “Combat Cars.”

ttyymmnn > InFierority Complex
09/13/2018 at 18:37

It’s not really my area, but the story of engines in that era is also fascinating. You could write volumes about the Liberty L-12 . I was also surprised to learn some years ago that the Sikorsky S-55 had a radial engine in it. Of course, that explains the bulbous nose.

Kinja'd!!!