I think you are getting lost. The whole thing revolves around energy management. There is the thrust from the engine and the potential energy in the airframe.
An engineless Glider on a still day with no up or down air currents relies totally on the potential energy in the airframe. Ie the aircraft trades height for forward speed.
The danger to a student in a low powered aircraft is that relying on the energy from the engine could lead to a situation where at slow speeds and high angles of attack the energy from the engine may not be enough to counteract the drag.
That for an inexperienced student pilot is a dangerous situation.
hence the safer way for a student in a low powered single is to make sure that he doesnt get into a high drag/stall situation by being taught to pitch for speed.
To put it in simple terms imagine the aircraft has two engines. The first the thrust the second engine being the potential energy available to the pilot through the elevator.
Again think of two throttles the one for the conventional engine and then think of a second throttle being the elevator.
A cyclist riding along a flat road will expend energy to maintain a given forward speed.
He comes to a slope maintaining the same energy to maintain that speed. He now has that energy plus the kinetic energy from him and the bike rolling down the slope.
He will accelerate and can only maintain his flat ground speed by either reducing the angle of the slope back to level or reducing the energy from his legs.
The engine is the primary energy source with the airframe as the second energy source so following on from that the engine is the primary speed source.
There was the old joke about the student sitting on the runway pumping the elevator up and down. The instructor asked him what he was doing? The student said " well you told me to pitch for speed".
Pace
Last edited by Pace; 19th December 2008 at 00:51.