| Ace |
| A military aviator or airman credited with shooting down five or more enemy aircraft. |
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| Aerodrome |
| The place "where...aeroplanes are landed and kept and cared for and where the pilots live and start... their trips over the lines... a smooth field covered with sod and occupying a situation near a town and good highway. It is on comparatively level ground and is square in shape and each of the four sides is about half a mile in length." |
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| Altimeter |
| An instrument for indicating the height of the aeroplane from the ground |
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| Angle of Incidence |
| The angle that the chord of a wing makes with the direction of motion relative to the air. A particularly muddling term, as it is often measured as the distance in inches that the front spar is above the rear spar when the aeroplane is in the flying-level position |
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| Archie |
| Anti-aircraft fire |
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| Aspect Ratio |
| The proportion of span to chord of a plane |
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| Back |
| A change of wind in a counter-clockwise direction (i.e. from E to N) |
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| Backwash |
| The disturbed air in the wake of an aeroplane in flight |
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| Balloon, To |
| The upward glide of an aeroplane near the ground caused by the pilot descending too fast and pulling the control lever back too much or too quickly |
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| Bank, To |
| To raise one wing for the purpose of turning |
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