Pitbull,
Quote:
Never mind the L/D ratio, CD, CL, which way the forces are pointing.... if you know the cruise thrust, speed and mass of the aircraft the rate of descent is a one line calculation.
How about sharing it with us.
Its not a state secret.
Rate of Climb = Excess Power / Weight
Hopefully that'll ring a bell.
This is just a case of a negative value for Excess Power that will result in a negative value for Rate of Climb. i.e.
Rate of Descent = Power Deficit / Weight.
In this case the power deficit is Drag x Speed, and since in the cruise thrust = drag, if we knew the cruise thrust we also know the drag at the start of the descent.
i.e.
Rate of Decent = Thrust Reduction (from that required to maintain level flight at the TAS in question) x TAS / Weight
Stick it all in the same units and you're in business.