| Factor of Safety |
| Determined by dividing the stress at which a body will collapse by the maximum stress it will be called upon to bear |
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| Fin |
| A fixed vertical plane generally fitted in front of the rudder to increase the stability of the machine |
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| Flares, Ground |
| Waste soaked in petrol, or petrol in buckets and set on fire; used as a landing lights during hours of darkness |
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| Flares, Parachute |
| Magnesium lights, electrically fired and attached to a small parachute; released near the ground to aid in landing an aeroplane during the hours of darkness |
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| Flares, Wing Tip |
| Magnesium lights, electrically fired whilst attached to the wing tips; used to aid in landing an aeroplane during the hours of darkness |
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| Flattening Out |
| A phrase used to describe the gradual decreasing of the glide angle of an aeroplane until it merges into the horizontal a few inches above the ground |
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| Flieger Abteilung Artillerie |
| German aviation reconnaissance and photographic unit working in cooperation with Artillery; same as FA(A) |
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| Fliegertruppe |
| Flyer troops; Aviation troops |
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| Flight |
| A small group of aeroplanes |
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| Flying Speed |
| The speed an aeroplane must reach or exceed in order to stay aloft |
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