It strikes me that U.S. Naval aircraft in WWII (e.g., F4F, F6F, SBD) were powered by air-cooled radial engines , while most USAAF fighters (e.g., Kittyhawk/Tomahawk, Mustang, Lightning) were powered by liquid-cooled V-12s. Of course the Thunderbolt and the bombers had radials, but it seems that the preponderance of fighters had V-12s.
Was this a conscious decision by the forces to have common parts? Just the way Grumman and Douglas designed their aircraft, as opposed to North American and Lockheed? Better temperature stability with liquid-cooled engines in fighters in the European Theatre, while this wasn’t much of a factor in the Pacific? Something else?
I read somewhere (no cite, sorry) that radial engines were considered easier to maintain and therefore more reliable in carrier environment. When ground maintenance was available, V-12s was used because of their superior characteristics.
ETA - I read it probably in some military aviation magazine. I’ll check later, if I can dig up this article.
In the book Fighters 1914-1945, author Bill Gunston argues that the preponderance of liquid-cooled V (LCV) aviation engines in WWII fighters was due to the influence of the Schneider Trophy races, which evolved into contests of pure speed. Most, if not all, contenders in these races had LCV engines. These engines were favored by the racers because they made possible a more streamlined look than the “blunt-nosed” radial engine. Consequently, in the 1930’s the fastest planes in the world all had LCV’s, and this fact influenced the design of fighters. If a fighter was designed with a radial engine, it was usually because the company was unable to obtain the desired LCV’s due to all of them being used by a “more important” project: for example, the Fw-190 used a radial because the Me-109 production was using all the available LCV’s.
No cite, but my understanding was that the powers-that-be in US aircraft purchasing much preferred air-cooled (hence radial) engines for the reliability and simplicity reasons already mentioned. However, they would rather have a good aircraft with a water-cooled engine than a bad radial-powered aircraft, or no aircraft at all.
For the navy the constraint was the amount of available carrier decks and the number of planes that could be fitted on each one, rather than the production of planes or pilots, or the need for very high performance - so they could afford to be a bit pickier about their powerplants in order to maximise misision availability of planes on a carrier in the middle of the pacific. Parts interchangeability between TB, SB and F planes was probably a consideration too.
The AAF needed gazillions of planes, some with very specific characteristics, like long range plus the ability to outfly the bf109, and generally had a much easier time of it with the logistical tail - an airfield in e.g. england could have a bigger stack of spare planes, motors, parts and more mechanics etc. than could fit on a carrier. Given that the P-51 + Rolls-Royce was a great combination, and one of the few modern designs available to the US at the time, it would have been nuts to let a minor detail like its engine confguration stand in the way of adoption.
Again, this is only what I have understood from general reading, and is quite possibly totally wrong.
Note: an air-cooled radial engine can get half of its cylinders shot out, & remain functional, at a reduced level of efficiency. This means that long-ranged bombers can take damage & still get home. That ground attack aircraft, like the Thunderbolt or the Sturmavik can take small arms fire & be largely unaffected. That Naval fighters can limp back to the carrier & live another day.
Liquid-cooled engines outperformed air cooled radials, generally, but shoot out the coolant tubes, & they are going down, period.
The A1, later the AD1 Skyhawk was reportedly the most powerful piston engine (radial) fighter/bomber ever built by the U.S. There’s an old video of one getting airborne w/ it’s wings folded (for a brief flight before splashing in). These were sold to the VN gov’t as close air support aircraft. I actually watched one crash, from a distance. I’m pretty sure the pilot made a successful bailout.
Another factor: A lot of equipment decisions then were made (by the War Production Board, mainly) based on availability of parts - for instance, if production of one engine type was fully committed when the new airplane type was to enter production, then another available type would be designed into it instead.
The Navy didn’t need the same high-altitude performance that the AAF did with its inline engines, since the enemy fighters were also radials but with less power (lower-strength steels and lower-octane fuel available); and besides most of their flying was at lower altitudes anyway. Simplicity, damage tolerance, and commonality of spares were overriding considerations.
Psst: Skyraider. My dad was combat aircrew in an AD-4N Skyraider flying off Philippine Sea (CV-47) in Korea. He used to say that a Skyraider ‘had the instantaneous firepower of a light cruiser’.
The F6F Hellcat had a service ceiling of about 37,000 feet and a top speed of about 380 mph. A Bf-109-G could go 39,000 feet and 398 mph. (And the Hellcat had a greater combat radius and was, I think, more sturdily built.) An F4U Corsair could fly to about 37,000 feet and had a top speed of 425 mph. On paper it sounds like they were pretty well matched. I’ve often wondered how a fight would turn out.
Interesting. Are you aware of other books that talk about engine development?
No, but the book that I referenced does have a pretty good summary of the liquid-cooled vs. air-cooled debate. Unfortunately my copy seems to have disappeared.
I have read similar things, but again, no cite. My impression was that air-cooled radial engines were the standard for over-water operation, and that there was a stated Navy requirement that its aircraft engines be air-cooled.
(Perhaps not only radial, though. I know of an air-cooled boxer powered twin that was evaluated by the Navy in 40 or 41.)
Just looking at Wikipedia, it seems to me that both the Hellcat and the Corsair weigh almost twice as much as the BF-109, with much more powerful (but not twice as powerful) engines. I know nothing about planes, but certainly that must have some impact on the maneuverability of the beasts? I would guess that the BF-109 was a lot more nimble than the other two.
The A6M Zero was very nimble, but Hellcats shot a lot of them down. IIRC the Hellcat had like a 15 or 20 to one kill ratio (against all Japanese aircraft; not just fighters).
So? Is it your position that nimbleness counts for nothing? I could say the exact opposite was true up until 1942, precisely because the Zero was so nimble. What I’m saying is that the engine comparison you draw may be inadequate, because you are not comparing their use in similar sized aircraft.
Not at all. However nimbleness can be countered. The P-40 Tomahawk was no match for a zero in a turning fight. But the AVG scored very well by using the P-40’s strengths and avoiding its weaknesses.
AFAIK there was never a Hellcat vs. 109 fight during the war. (I could be wrong, but I don’t know of one.) Perhaps the closest match might have been the Ki-61 Tony, which somewhat resembled the 109 and had similar performance.
My copy of Flight Journal’s F6F special edition say the British Fleet Air Arm scored 52 victories in the Hellcat. It’s posible at least a couple were 109s.
My dad was combat aircrew in an AD-4N Skyraider flying off Philippine Sea (CV-47) in Korea. He used to say that a Skyraider ‘had the instantaneous firepower of a light cruiser’.