B-29 Escort: P-38, P-47N or P-51H ?

windswords said:

I may be wrong but wasn't it a fact that most (or all) F-47's in 1950 were assigned to Air National Guard units? I always thought that the Air force didn't want to use the Air Guard units who were familiar with the 47 in the conflict so they went with the more plentiful front line F-51.

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The USAF units which flew F-51's in Korea were not equipped with them at the beginning of the war but rather F-80's. So either F-51 or 47 would have been a conversion, but most of the fighter units in Far East AF *had* flown the F-51 a few years earlier, which is why the FEAF was better able to re-adopt that type, having also leftover spares, maintenance experience and even around 20 of the a/c still on hand in depots in Japan. Those particular a/c were used to equip the ROKAF, though they were also used by USAF pilots on combat missions (the 4 victories over NK a/c credited to F-51's June 29 1950 were those a/c flown by USAF pilots). Then a larger number of F-51's were shipped by carrier from the west coast in July, mainly stripped from ANG units in the western US. The 8th (2 of 3 sdns), 18th (all three) and 35th (39th and 40th FIS) Fighter Groups already operating over Korea used those to start converting back from the F-80 to the F-51. The 8th went back to all-F-80 in late 1950, 18th remained an F-51 group until it converted to F-86F's in 1953; 39th FIS became an F-86 unit in 51st FIG in 1952, 40th rotated out of Korea in 1951.

Re: P-51 WEP setting, 67" Hg manifold air pressure WEP was standard in 8th AF (though often exceeded in practice to at least around 70, according to combat reports), but many sources say the 7th AF used 80" on 115/145 fuel. The RAF used 81" on its Mustangs for low altitude V1 hunting. 67> 80 was found in RAF tests to add 30mph at s/l.
One source particularly for RAF v USAAF:
P-51 Mustang Performance

Joe

JoeB said:

The F-51D was used in Korea rather than any of the somewhat different lightweight Mustangs (H) or morever the apparently more suitable F-47D or N because not only did more F-51D's remain in total USAF inventory (though the difference between total F-47 and F-51 in June 1950 wasn't as great as is sometimes portrayed) but those in ZI were concentrated on the West Coast, and moreover the FEAF still had a small number of F-51D's in inventory in Japan (though not distributed to units).

My father commande the 35th FBW equipped with 51D's out of Johnson AFB from 1949 to early 1950.

Those were the a/c sent to Korea in late Jun for the ROKAF but which flew some missions w US pilots. Also it had spares stockpiles and remaining maintenance and pilot experience with the F-51D, not with the H nor the F-47. The H would have offered little advantage in Korean conditions anyway, D being adequate in the handful of combats pitting F-51's against NK prop a/c and any prop fighter was heavily outperformed by the MiG-15 later on. But FEAF later regretted the decision of 51 v 47 as F-51 losses soared especially in 1951 v more heavily AA armed Communist field armies by that time. But, the USAF wasn't willing to support operation of multiple prop fighter types in Korea and (commanding general) Stratemeyer was told to forget it when he broached the idea of adding the F-47 later on (see "Stratemeyer Diary").

Joe

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Simply the 51D's were in Nasty Guard, the 47's were ZI, there were 51's in Japan - someone had to make a decision based on data available at the time.

Erv Ethell was a Squadron CO under my father, and that's how I met and became long time friends w/Jeff Ethell.

jimh said:

I would love to see your sources for the Mustang. I am always looking to learn more. AFAIK all Mustangs, even today are rated to 61" of MAP, 67" for temporary war emergency power. The Merlin can operate with octanes as low as 87 and as high as 145. The power settings are the same, no manual I have read indicates otherwise. We operate under the instructions dictated by Jack Roush. His shop has produced some of the finest running Merlins in recent times. For longevity we limit the engine to 55" for takeoff...most of us use 45-50". Cruise and aerobatics are done with 35-40". The only time you will see higher MAP's are from the transport series Merlins and Reno racers. Anyway, I'd love to see the source. Thanks

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In April, 1944, the Army Air Forces Materiel Command approved 75" Hg for the V-1650-7 engines. I understand that some commands limited this operationally to 72". Combat reports showed this usage by pilots in ETO. I do not have indications that more boost, 80" Hg, was approved until the -9 engine became available in the P-51H, which, I think, used water injection.

http://www.wwiiaircraftperformance.org/mustang/75inch-clearance-v-1650-7.jpg

http://www.spitfireperformance.com/mustang/combat-reports/357-yeager-6nov44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/353-hinchey-14nov44.jpg

Very cool read! It was a big deal to break the copper wire on the throttle, to me, its like pulling the pin on a hand grenade. Merlins are sooo fragile.

jim

75in hg + ram = 1500 HP @ 25,000, or 1800 @ 10-12,000 ft?

Which engine are you referring to?

There is going to be a 220-300hp difference between low gear and high gear (takes a lot of power to get 75-80 in of pressure at high altitude) The V-1650-9 in the P-51H shows a 300hp difference.

V-1650-3, if that was possible for that one?