Performance of the Fw 190A on the Deck?

[drgondog]

Originally Posted by Harri Pihl

However, you posted a formula:

V2/V1 = SQRT(W2/W1)

Which is valid only for the constant Cl/AoA and therefore wrong for this particular case. And this is exactly what Graham responded to you in the first page of this thread.

Actually if you look at the equations and substitute Weight for Lift and uses say a 5% increase in Fuel, your CL must increase by 5%. CL varies directly with Weight for Constant Velocity.

Also when the weight increases at the max Power setting for a given altitude, then the Velocity cannot increase, so the CL has to change, thereby increasing induced drag.

CD= CDi + CDp = Cl**2/(pi*AR*e) + CDp

CL=296*W/(S*density ratio*V**2)

For the case in which the velocity was maxed out at the lower weight and max power setting, the velocity must be reduced to achieve the required CL (increased by 5% in e.g.)



Note that the polar approach used by Graham and me works for any given flying condition while your approach works at one exact Cl/AoA.

I believe Crumpp is 100% correct

That is true and no one denies that. However, Graham was correct when he noted that at these particular conditions the effect of the fuel state is not that important, just few km/h.

Use the 51D versus the 51B-15 with the same 1650-7 engine. The weight increase was about 6%, the aerodynamics for Parasite Drag and Induced drag are the same for both airframes.

The 51B with same fuel load was about 600+ pounds lighter - mostly due to the extra pair of 50 cal plus 880 rounds extra ammo.

under these TO conditions the P-51B-15 was about SQRT (Wp51d/Wp51b) difference ~ 1.03 faster than the D... on the deck and at 25,000 feet and everywhere in between.

10+ mph is not insignificant - important enough for NAA to redesign the P-51B/D to the P-51H