Originally Posted by
Just This Once...
My big skool stuff is in there somewhere but still need your teaching on why a constant rate of descent requires the same thrust as for level flight of how a g-meter can be used in establishing a rate of descent before you expand your teachings further. Heck, until you offered to help I thought I could set and maintain a constant RoD and speed with no thrust at all.
"why a constant rate of descent requires the same thrust as for level flight" can't be explained because it's false.
In a climb or descent you're adding a component of weight (weight times the sine of the climb/descent angle) to drag (for a climb) or to thrust (for a descent). If you want to maintain the same speed, thrust will have to be adjusted to compensate. The steeper the descent, the more forward weight component added to thrust, the less thrust you will need, all the way until this forward weight component equals drag. Then you cannot do a constant-speed descent any steeper, unless you add more drag to absorb even more forward weight component.
In all of these cases, once the angle is established and we've seen the speed not to move, (or, everything is settled down) all the forces are balanced and there is no acceleration.
"how a g-meter can be used in establishing a rate of descent" It can't. At all steady rates of descent (even a million feet per minute) the zenith-nadir value of G is 1, and the aircraft Z-axis value of G is the cosine of the descent angle. (That would make it zero in your previous example of a 90 degree descent)