The Aeroplane Speaks. Fifth Edition

SUMMARY. Essentials for Maximum Climb. 1. Low velocity. 2. Large surface. 3. Large angle relative to propeller thrust. 4. Large angle relative to direction of motion. 5. Large camber. Essentials for Maximum Velocity. 1. High velocity. 2. Small surface. 3. Small angle relative to propeller thrust. 4. Small angle relative to direction of motion. 5. Small camber. It is mechanically impossible to construct an aeroplane of reasonable weight of which it would be possible to vary the above opposing essentials. Therefore, all aeroplanes are designed as a compromise between Climb and Velocity. As a rule aeroplanes are designed to have at low altitude a slight margin of lift when the propeller thrust is horizontal. By this means, when the altitude is reached where the margin of lift disappears (on account of loss of engine power), and which is, consequently, the altitude where it is just possible to maintain horizontal flight, the aeroplane is flying with its thrust horizontal and with maximum efficiency (as distinct from engine and propeller efficiency). The margin of lift at low altitude, and when the thrust is horizontal, should then be such that the higher altitude at which the margin of lift is lost is that altitude at which most of the aeroplane's horizontal flight work is done. That ensures maximum velocity when most required. Unfortunately, where aeroplanes designed for fighting are concerned, the altitude where most of the work is done is that at which both maximum velocity and maximum margin of lift for power are required.