No fallacy, better climb rate on warm day than cold, at V fs
Further to my original post, an acquaintance has shown me Falcon 50 climb performance that shows at both
V2 and V final segment, the climb gradient DOES NOT vary with temperature, within the flat rating temperatures.
Boeings/airbusses different?
SOOOOO, since V final is practically the calibrated airspeed for minimum drag speed, one can
conclude that the warmer it is, the better the climb rate at that speed. (for flat rated operations).
Runaway
thanks. While I agree with most of your points, I’m not sure they explain the situation I
described, that is an aircraft at min drag speed, within a temperature range that the engines are flat rated.
Reference to your formula, while rho does change with temperature, so does TAS, since the V in your
formula is true airspeed. Warmer day is less rho, but since calibrated airspeed for min drag stays the
same, the tas goes up. This explains why lift then is the same, since we’re talking about same climb angle
and weight.
I’m not sure about "more air flowing over the wings" as you put it. And engine thrust stays the same for
flat rating operation.
alatriste,
However, in this example, the aircraft is climbing at min drag, or put another way at a calibrated airspeed
that allows the most excess thrust. The excess thrust is the same regardless of the temperature, for flat rated operation.
Since the climb gradient is the same, warm or cold, the warmer temperature gives a higher TAS.
Accordingly, the aircraft will climb at a higher rate of climb on a warmer day. Hence the paradox that I think I can explain
Crossunder
Power is not the issue here. We’re talking about the aircraft flying at a speed for maximum excess thrust,
since the aircraft is flying at minimum drag, and hence getting the best GRADIENT.
Drag does not increase if you fly at minimum drag speed, except at high machs.
If excess power was the consideration, then we would be looking speeds for RATE OF CLIMB.
I can only conclude then that jets should climb at a higher rate on a warm
day at V fs, than on a cold day, when flat rated. Further dissentions?
Hawk37