P-47C v. Spitfire IX.............
Climb – The rate of climb if the Spitfire is much higher at these heights than that of the P-47C. .............. The difference, however, is not nearly so marked in zoom climbs, and if the P-47 dives slightly and then pulls up in the climb, its performance is similar to that of the Spitfire over limited intervals.
Dive – The P-47 is able to out-dive the Spitfire quite easily.
Do you mean to infer these tests show weight helps the P-47C zoom and dive better? It would be a mistake to make that inference.
Thrust, drag, and velocity in accelerated flight (e.g. zoom climb, dive) varies dramatically as the aircraft accelerates/decelerates. Understanding why the P-47C & Spit IX behave as reported means accounting for weight AND
thrust, drag, and velocity simultaneously & as they change dynamically. The reported differences don't give us enough detail to appropriately assess all variables to demonstrate what's really going on.
And we have such a relationship that combines them all simultaneously to help us understood, specific excess power (P
s) - of which Stoney is referring too:
P
s = (thrust - drag) * velocity / weight
It's an innocent looking equation but be very careful, that thing is DYNAMIC meaning in accelerated flight the only variable that is constant in that equation is weight (assuming 0 mass change). It's well known aerodynamically that the airplane with the greatest time average P
s in a zoom climb will out zoom one with a lower P
s. If you look at that relationship you can see that all else being equal (thrust, drag, velocity) increasing weight ALWAYS reduces P
s.
Yes, it's more complicated than all that if you want to understand the effect of mass in it all (please see my provided links for details) but the bottom line is P
s is reduced by increased weight which reduces zoom over the duration of a zoom climb.