A monoplane has no lower planes, while the top planes sprout from the side of the body like the wings of a bird, but are rigid.
In either type of aeroplane it is the action of the air on the wing surfaces, both upper and lower, when the machine is travelling forward at a minimum speed of about forty miles per hour that keeps it in the air. If the speed is allowed to drop below this minimum (known as the flying speed) the machine “stalls,” i.e. becomes uncontrollable, drops its nose and dives to regain flying speed. If this happens near the ground—within a hundred feet—a serious, and often fatal, crash is the result.
Among the types of aeroplanes used in France during 1916–18, and mentioned in these pages but not described in detail, are:
B.E.2C., R.E.8, and Other Types of Two-seater Machines
All two-seater machines carrying one pilot and one observer which were chiefly used for artillery observation, i.e. correcting, by observation from the air, the fire of batteries on the ground.
These were tractor biplanes, i.e. the engine and propeller were in front, while the observer and pilot sat tandem in two cockpits, or nacelles, in the fish-shaped body.
F.E.2B.
A two-seater fighting biplane of the “pusher” type with the engine behind the pilot, who with the observer sat in a cockpit which protruded beyond the leading, or forward, edges of the planes. This aeroplane was used for day and night bombing, for fighting in 1916 and the first half of 1917, and also for reconnaissance and photographic work.
De Havilland 4
A high-speed tractor two-seater biplane used for bombing, reconnaissance work, and photography.