CLIMBS BADLY.—Such a condition is, apart from engine or propeller trouble, probably due to (1) distorted surfaces, or (2) too small an angle of incidence.
FLIGHT SPEED POOR.—Such a condition is, apart from engine or propeller trouble, probably due to (1) distorted surfaces, (2) too great an angle of incidence, or (3) dirt or mud, and consequently excessive skin-friction.
INEFFICIENT CONTROL is probably due to (1) wrong setting of control surfaces, (2) distortion of control surfaces, or (3) control cables being badly tensioned.
WILL NOT TAXI STRAIGHT.—If the aeroplane is uncontrollable on the ground, it is probably due to (1) alignment of undercarriage being wrong, or (2) unequal tension of shock absorbers.
CHAPTER IV. THE PROPELLER, OR “AIR-SCREW”
The sole object of the propeller is to translate the power of the engine into thrust.
The propeller screws through the air, and its blades, being set at an angle inclined to the direction of motion, secure a reaction, as in the case of the aeroplane's lifting surface.
This reaction may be conveniently divided into two component parts or values, namely, Thrust and Drift.
The Thrust is opposed to the Drift of the aeroplane, and must be equal and opposite to it at flying speed. If it falls off in power, then the flying speed must decrease to a velocity, at which the aeroplane drift equals the decreased thrust.