The Aeroplane Speaks. Fifth Edition

HOW TO DIAGNOSE FAULTS IN FLIGHT, STABILITY, AND CONTROL. DIRECTIONAL STABILITY will be badly affected if there is more drift (i.e., resistance) on one side of the aeroplane than there is on the other side. The aeroplane will tend to turn towards the side having the most drift. This may be caused as follows: 1. The angle of incidence of the main surface or the tail surface may be wrong. The greater the angle of incidence, the greater the drift. The less the angle, the less the drift. 2. If the alignment of the fuselage, fin in front of the rudder, the struts or stream-line wires, or, in the case of the Maurice Farman, the front outriggers, are not absolutely correct--that is to say, if they are turned a little to the left or to the right instead of being in line with the direction of flight--then they will act as a rudder and cause the aeroplane to turn off its course. 3. If any part of the surface is distorted, it will cause the aeroplane to turn off its course. The surface is cambered, i.e., curved, to pass through the air with the least possible drift. If, owing perhaps to the leading edge, spars, or trailing edge becoming bent, the curvature is spoiled, that will result in changing the amount of drift on one side of the aeroplane, which will then have a tendency to turn off its course. LATERAL INSTABILITY (FLYING ONE WING DOWN).--The only possible reason for such a condition is a difference in the lifts of right and left wings. That may be caused as follows: