Hi grippen, turn the page of your copy of AHT to the P-51, you will note that the D model has fallen to 1,200 hp at about 25,000 ft and that at 30,000ft it has fallen to 900hp. I do not remember the hp figures for the -3 engine, but I do remember it has a definite edge above 20,000ft
I do not doubt that at high speeds that the P-51 has a better CL max. however of what importance is this when the mustang does not have the hp to support this.
10,200 lbs and 900 hp vs 17,600 and 3,200 hp does not look like a good power to weight compairison. the 1,720 hp the -7 made falls off to below 1,600 hp at any altitude above 6,250 ft. those hp figures mean that at altitude the mustang has about 11 lbs per hp vs the 38 which is around 5.5 or half the loading. that is also in americas hundred thousand, near the back in the plane compairisons.
while in the book look at the speed for a P-51B that has taken off at full weight and is not a stripped down version. the TAS is 425-430 mph. the 450 mph in the test states all the improvements and special care taken to make the P-51B much faster than a common front line fighter. special sanding of wings and care to improve the fit of cowlings, special high octain fuel, rear tank removed, etc.
the 443 is a plane of similar care and no rear fuselage tank and the 440 is one with the tank in place, but empty on take off. that is also in americas hundred thousand.
it has been stated earlier that the P-38L's max speed begins to fall off above its critical altitude. this is just more misinformation. look at the AH cart for the P-38L and then look at the AHT chart for the P-38J. they are exactly the same. this is because the data floating around in every book is from one test and that is of a P-38J at a take off weight of 17,600 lbs so it is one with the leading edge tanks. and critical altitude is 26,400ft because it is a pre J-25-LO and does not have the engine/turbo improvements and that matches the curve of both AH and AHT. it is not due to propellers, but that the actual critical altitude is 26,400 ft. I believe that is also in AHT.
The high performance 3,500 fpm climb and 440 mph tas of the mustang is always taken from specialy prepaired mustangs which do not represent front line fighters taking off for a long mission full of fuel with scuffed and or dull paint. while the 38s in the tests always appear to be in poor condition.
since the P-51B is mentioned a lot in this thread please take note that the critical mach number is .75. the B model and early D models all had fabric covered elevators. this caused the plane to buffet uncontrollably. so the plane with fabric covered surfaces cannot be safe above mach .75 and the pilots manual says to quickly reduce power and ride it out until it reaches denser air closer to sea level. it states that the a/c will begin to buffet and porpoise and this condition is very dangerous.
the 4,000 + fpm climbs for the P-51 have to be from some very special mustangs. considering this is better than spitfire perfromance. any altitude above 6,250 ft the spit IX and 51 have about the same hp and somebody stated that a 10,200lb P-51 is suppose to climb with a spitfire that weighs 3,000lbs less. how can it do this? high speed climbs are very shallow and do not approach 3,000fpm. the pilots manual states best climb speeds for the mustang is around 160 mph IAS.
I purposely state the lowest data available because it looks like it is taken from a common mustang which does not have special improvements done. I do this because the 414 mph and 3,800 fpm is from a common P-38J model with 410 gal fuel capacity internal and is also the lowest data available for this plane type.
[ 12-15-2001: Message edited by: bolillo_loco ]
