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alexat
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As a first year aerospace engineer student I had a problem today.
The question was :
Does the altitude effect the endurance of an aircraft (provided that the aircraft engines can generate enough trust at this higher altitude).
Maximum endurance is minimum fuel flow [N/s] F = Ct T
in a steady, horizontal, symmetric flight F = Ct D
D = Cd (1/2) rho V² S
D: Drag
T: Thrust
Cd: Drag coefficient
Cl: lift coefficient
Rho: air denisty
V: velocity
S: wing area
So higher altitude = lower density = lower drag = lower fuel flow = higher endurance.
But also true is that F = Ct (Cd/Cl) W and none of these parameters are effected by the altitude.
Which one is correct and why? And why is the other one wrong?
Kind regards,
Alex
Edit:
D = Cd (1/2) rho V² S
but V is sqrt (W*2*1/(S*rho*Cl))
so the rhos cancel each other out.
Is there a delete button somewhere?
The question was :
Does the altitude effect the endurance of an aircraft (provided that the aircraft engines can generate enough trust at this higher altitude).
Maximum endurance is minimum fuel flow [N/s] F = Ct T
in a steady, horizontal, symmetric flight F = Ct D
D = Cd (1/2) rho V² S
D: Drag
T: Thrust
Cd: Drag coefficient
Cl: lift coefficient
Rho: air denisty
V: velocity
S: wing area
So higher altitude = lower density = lower drag = lower fuel flow = higher endurance.
But also true is that F = Ct (Cd/Cl) W and none of these parameters are effected by the altitude.
Which one is correct and why? And why is the other one wrong?
Kind regards,
Alex
Edit:
D = Cd (1/2) rho V² S
but V is sqrt (W*2*1/(S*rho*Cl))
so the rhos cancel each other out.
Is there a delete button somewhere?
Last edited: