1 (return) [ Propeller Slip: As the propeller screws through the air, the latter to a certain extent gives back to the thrust of the propellor blades, just as the shingle on the beach slips back as you ascend it. Such “give-back” is known as “slip,” and anyone behind the propellor will feel the slip as a strong draught of air.]
2 (return) [ Helicopter. An air-screw revolving upon a vertical axis. If driven with sufficient power, it will lift vertically, but having regard to the mechanical difficulties of such construction, it is a most inefficient way of securing lift compared with the arrangement of an inclined surface driven by a propeller revolving about a horizontal axis.]
3 (return) [ Pancakes: Pilot's slang for stalling an aeroplane and dropping like a pancake.]
4 (return) [ Morane parasol: A type of Morane monoplane in which the lifting surfaces are raised above the pilot in order to afford him a good view of the earth.]
5 (return) [ Skin friction is that part of the drift due to the friction of the air with roughnesses upon the surface of the aeroplane.]
6 (return) [ Banking: When an aeroplane is turned to the left or the right the centrifugal force of its momentum causes it to skid sideways and outwards away from the centre of the turn. To minimize such action the pilot banks, i.e., tilts, the aeroplane sideways in order to oppose the underside of the planes to the air. The aeroplane will not then skid outwards beyond the slight skid necessary to secure a sufficient pressure of air to balance the centrifugal force.]
7 (return) [ An explanation of the way in which the wash-out is combined with a wash-in to offset propellor torque will be found on p. 82.]
9 (return) [ Butt means to thicken at the end. Screw means to machine a thread on the butt-end of the wire, and in this way the wire can make connection with the desired place by being screwed into a metal fitting, thus eliminating the disadvantage of the unsatisfactory loop.]
10 (return) [ Deviation curve: A curved line indicating any errors in the compass.]
11 (return) [ A propeller screws through the air, and the distance it advances during one revolution, supposing the air to be solid, is known as the pitch. The pitch, which depends upon the angle of the propeller blades, must be equal to the speed of the aeroplane, plus the slip, and if, on account of the rarity of the air the speed of the aeroplane increases, then the angle and pitch should be correspondingly increased. Propellers with a pitch capable of being varied by the pilot are the dream of propeller designers. For explanation of “slip” see Chapter IV. on propellers.]
12 (return) [ Getting out of my depth? Invading the realms of fancy? Well, perhaps so, but at any rate it is possible that extraordinary speed through space may be secured if means are found to maintain the impulse of the engine and the thrust-drift efficiency of the propeller at great altitude.]
13 (return) [ Box-kite. The first crude form of biplane.]
14 (return) [ See Newton's laws in the Glossary at the end of the book.]
16 (return) [ “In effect” because, although there may be actually the greatest proportion of keel-surface In front of the vertical axis, such surface may be much nearer to the axis than is the keel-surface towards the tail. The latter may then be actually less than the surface in front, but, being farther from the axis, it has a greater leverage, and consequently is greater in effect than the surface in front.]
