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"Why was the BF109K faster than the P51D? MW 50!"
- Thread starter steve podleski
- Start date
Everybody loves the lines of a p-51 but those big radials weren’t as draggy as they seem, the NACA figured out a good cowling shape and lip for radials that made them competitive at speed, and being air cooled made for a more reliable airframe and power plant combination. Water cooled engines made for sleek noses but you still have to pass air through a radiator to ditch the heat and cooling drag is a bitch. Again the Corsair was a great aircraft but it was difficult to land on a carrier due to its long (comparable to a Grumman) nose.it’s also said that the f4u was a better fighter than an f6f 2/7 days a week, the rest of the time it’s in pieces in the hanger deck. The Grumman f6f while round and huge, had the highest kill to loss ratio of any allied fighter in the whole war. “Grummans get you home” big and heavily armed as well as heavily armored, they could take a lot of lead and keep going. A lot of the navy’s success in the pacific can be attributed to starting the war with the f4f wildcat being 30 mph slower and a lot less maneuverable than the zero, they had to develop good tactics like the thach weave, and world class gunnery, then when aviators got good performing aircraft, they were true world beaters.
I believe the radiator cowling on the mustang actually provided thrust nullifying drag....
I believe he's missing a comma!
@7.62willdo - Correct. They actually experimented in the wind tunnel with the shape of the radiator air intake lip, and critically - the distance between the top of the inlet and bottom of fuselage (notice it has a gap). When they settled on the best configuration, the numbers were better than they should have been. It was found that expansion of the hot air as it rushed out the cooling duct outlet was providing a net thrust that more than offset the drag of the radiator by a measurable amount.
@7.62willdo - Correct. They actually experimented in the wind tunnel with the shape of the radiator air intake lip, and critically - the distance between the top of the inlet and bottom of fuselage (notice it has a gap). When they settled on the best configuration, the numbers were better than they should have been. It was found that expansion of the hot air as it rushed out the cooling duct outlet was providing a net thrust that more than offset the drag of the radiator by a measurable amount.
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The p-51 used the Meredith effect in its radiator inlet and duct system probably better than any other piston engine fighter, the thrust produced can nullify the drag caused by the cooling system but it only works at high air speed and requires careful control of the cooling system temperature and careful engine management to keep the temperatures and air speed in the right window, giving an advantage to a long skinny v-12 properly trimmed out and on the step for economy cruise, hence the mustangs excellent range and cruise speed. A well designed NACA cowl like both the hellcat and Corsair had, combined with ejector exhaust on an air cooled radial do a slightly less efficient job but without all the complexity, weight, and added maintenance/combat survivability issues of the water cooling system, if it ain’t there it can’t leak. The navy and air force made different compromises based on the roles they were operating in and our production and engineering prowess at the time meant that each service got what it needed to do it’s specific jobs,
All that said, the P-51 is a sexy beast and a great aircraft with an awesome combat record and a lot of brave airmen owe their lives to it, and kids will still have mustang posters in their walls in 100 years. I got to spend about 4 hours drooling over one my uncles buddy owned when I was 12 and then got to watch him fly it at a private strip.
If you’re a real nerd ( I am) and you want a really interesting read/watch on high speeds with minimal power, look up “Mike Arnold, Ar-5” in the 90’s he achieved a record at 213 mph with a stock 65 hp Rotax two-stroke. He’s not the most interesting presenter but he built a plane with a lower drag coefficient than the P-51 without an engineering degree and baffled professional aerodynamicists, who said nobody could ever achieve such a low frontal area in a manned vehicle.
If we’re talking sexy WWII fighters...
Obviously performance wasn’t all there compared to the aircraft that are being discussed, but it looked good doing it.
Obviously performance wasn’t all there compared to the aircraft that are being discussed, but it looked good doing it.
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The p-40, f4f wildcat, and hawker Hurricane and their pilots deserve admiration for holding the line against superior aircraft with tactics, cunning, and massive balls until engineering and manufacturing could turn the tide. Without them midway, Guadalcanal, North Africa, and the Battle of Britain might have been recorded differently.
Good read. One question. If you and I are standing on the ground in 1944 discussing the cooling on a P-51 and you said all that, I would look at you and ask, “What the hell is the Air Force?”
Ha too true, for 1944 it should read US Army Air Forces, in 41 it would have been air corps, the name changes get pretty hard to keep track of. And just think, now we have the US Space Force “gaurdians”. Maybe Biden will give us a special cyberforce too, the “neck beards”.
LOL, we both know that but that is the excuse that they give on their website. PC correctness and all.
Um...no. The Pfeil was a very fast aircraft with great acceleration. But not fastest by a significant margin
Definitely, but an engine will have an oil system anyway, so you add in a hot line, a heat exchanger and a cold line and you have maybe 5 additional points for a leak or failure, maybe you get goofy like vought and have two oil coolers stuck out in your bent wing roots, still pretty manageable. But if you have a water cooled engine, you have an oil pump, lines, and cooler plus you have to add a water pump and seals and a drive belt or shaft and probably some gearing or a pulley to get it to the speed you want, then all the lines to balance the cooling load and keep the cylinders similar in temp, the water jackets themselves, then your hot line, a radiator, a cold line, and it has to have a catch tank, and it has to be pressurized, functional and leak free at both sea level and 30,000 ft. It adds a bunch of weight plus another fluid that is corrosive to iron and can’t mix with oil, you cant lose much of the coolant before it’s a problem and it could be a real hassle to get clean water and glycol for coolant in the middle of a combat zone. It’s all compromises and each service tailored what it needed out of its aircraft, I’m just glad we live in a country where we had the ability to design, test, and build specific aircraft for specific jobs. North American was very smart with the P-51/A-36 and built the rest of the aircraft around the engine and it’s cooling system, the brits didn’t always do such a good job with that and always had cooling inlets that looked like an afterthought the production floor came up with even though they used essentially the same engine for similar purposes.
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