p51 vs p47

[drgondog]

Originally Posted by kool kitty89

The flaps worked quite well to increase CLmax (CL= lift coeficient) on the P-51's otherwise low-lift wing.

There was a definite airspeed limitation on deployment of flaps on a 51. The P-38 manuevering flaps on the other hand were designed (for late J and L) for combat speeds.

I don't know where the comes from (probably due to the spifire) but the only thing the eliptical shape does is increase lift to drag ratio, in a full eliptical wing (like the Spit) this also makes for violent stalls, but the straight leading edge of the P-47 mitigates this iirc. (fairly gentle stalls, moreso than the P-51 as well)

The 47 had a gentler stall in a high G turn as it is easy to spin a 51 at stall. Having said that both power on and power off stalls in level flight are very gentle in a 51.

Power doesn't mean much on is own. I's when you put weight into the equation that you can get a comparable figure. Hell the P-38L had over 3500 hp in WEP! Plus the P-47M/N had the R-2800-57C capable of 2,800 hp in WEP up to 32,000 ft. The R-2800-59/63 of the P-47D was cleared for 2,600 hp with 100/150 avgas at 70" HG. (but 70" was only good up to ~23,500 ft) with this a late model P-47D could manage 444 mph at critical altitude. Some may have been tuned up to 2,700+ hp as well.

Drag is an even bigger factor KK. That is why a 51 which didn't have as good a power to weight ratio as a P-38 was nevertheless faster and flew much farther on same fuel load.

But bact to power-loading (weight/power) or (what I prefer) power/weight: the late P-47D weighed 14,600 lbs (clean, full internal fuel), the P-51D in the same configuration was 10,100 lbs. The P-47D had 2,600 hp, the P-51 had ~1,700 hp. So: P-47D: .178 hp/lb P-51D: .168 hp/lb. P-47 is ~6% better. But this is just one simplified comparison.

Back to drag. The 47 compared speed wise above 30,000 feet because the R-2800 blower was more efficient than the Merlin above 25,000 feet (for the -7)

[kool kitty89]

THat post is 7 months old Bill. I've learned a few more things from you guys since then. (and my reading on the subject)
Thanks for adding it in though.


On the stall issue, I think a distinction should be made between a gentle stall and a well warned stall. In the case of the P-47 (or P-38 ) I believe the stall its self was quite gentle and easy to recover from. (with spins very unlikely, or nearly impossible in the P-38's case, unless the pilot intended to spin) With the P-51, there was a lot of warning but the stall was rather violent. (I believe the Spitfire was somewhat similar -both being pretty snappy-)


Also, in the case of power, at the full 70" WEP had a critical altitude (for the R-2800-63 or -59) was only ~24,000 ft. (though I'm not sure how the V-1650-7's power curves compare with 100/150 grade)


I also am not sure how the airfoil properties wouls compare, as I have no information for the P-47's wing other than it used the Seversky S-3 airfoil.


I agree that P-51 was a much cleaner plane. (even with size taken into account) The XP-47J's cowling arrangement would have substantially improved this for the P-47, but that's another issue.

[drgondog]

Originally Posted by kool kitty89

THat post is 7 months old Bill. I've learned a few more things from you guys since then. (and my reading on the subject)
Thanks for adding it in though.


On the stall issue, I think a distinction should be made between a gentle stall and a well warned stall. In the case of the P-47 (or P-38 ) I believe the stall its self was quite gentle and easy to recover from. (with spins very unlikely, or nearly impossible in the P-38's case, unless the pilot intended to spin) With the P-51, there was a lot of warning but the stall was rather violent. (I believe the Spitfire was somewhat similar -both being pretty snappy-)

All you say about 51 and Spit for High G turn is true. Good warning (time to release a little pressure on stick and rudder).. In level flight in steep climb, same good warning but the stall wasn't violent.. sometimes it would stall with wings level, sometimes fall off on one wing but pretty gentle.


Also, in the case of power, at the full 70" WEP had a critical altitude (for the R-2800-63 or -59) was only ~24,000 ft. (though I'm not sure how the V-1650-7's power curves compare with 100/150 grade)


I also am not sure how the airfoil properties wouls compare, as I have no information for the P-47's wing other than it used the Seversky S-3 airfoil.

Simply - more drag for both the 38 and 47 wing as well as fuselage parasite drag


I agree that P-51 was a much cleaner plane. (even with size taken into account) The XP-47J's cowling arrangement would have substantially improved this for the P-47, but that's another issue.

True.

[Timppa]

As, this poll is still alive, P-51. Considered the best by most German and Japanese opponents.
P-47 is close second, lower total loss rate AFAIK.