[Graham Boak]

Crumpp: There is no point in doing calculations using this equation of simple ratios. It contains no effect of altitude, which is relevant to the effect of weight on speed. It would be true if all the drag was lift-induced, but it is not. It would be more appropriate for addressing the stall speed, if in the inverse sense. There it is induced drag which is the dominant term, and zero-lift drag that can be neglected. I assume that you are working to some derived system of equations, which do not hold true for this case. It is always better to go back to the basic principles of lift, drag and thrust (power).

Your comments on power drop is puzzling, as there would be no power drop. Maximum speed is when thrust = drag: over such small differences (yours or mine), inputs such a propellor efficiency and engine power will not change so thrust is constant. The only change is drag: I repeat that the only component of the drag that changes with weight is the lift-induced drag. The size of the change in the induced drag is of the order of that I quoted.

Drag is dependent upon the square of the speed. I think I see what you mean about "power of drag" being to the cube of speed, but it is not a concept I'm familiar with, nor necessary in this case. I think you are trying to say that to regain 8.5 mph (on a Typhoon sl top speed around 300 mph) would take an extra 34% of power - even on a cube law this is overstated as only some 9% would be required (1.03 cubed).

Harri: your calculation shows an even smaller change than mine, but given the respective assumptions we are clearly in the same ballpark. My estimate of 15% induced drag may be out by some percent, but equally I don't think that any Typhoon actually achieved 2200hp at its top speed, which I think you may be overstating. Perhaps some of the later Tempests did. Actual performance of the Sabre is not defined very well in the references I have.

Nick: the main effect of the loaded case is the additional drag of the bombs and carriers.