Tailskid

Conventional landing gear, or tailwheel-type landing gear, is an aircraft undercarriage consisting of two main wheels forward of the center of gravity and a small wheel or skid to support the tail. The term taildragger is also used, although some claim it should apply only to those aircraft with a tail skid rather than a wheel.

The term "conventional" persists for historical reasons, but all modern jet aircraft and most modern propeller aircraft use tricycle gear.

In early aircraft, a tailskid made of metal or wood was used to support the tail on the ground. In most modern aircraft with conventional landing gear, a small articulated wheel assembly is attached to the rearmost part of the airframe in place of the skid. This wheel may be steered by the pilot through a connection to the rudder pedals, allowing the rudder and tailwheel to move together.

Before aircraft commonly used tailwheels, many aircraft (like a number of First World War Sopwith aircraft, such as the Camel fighter) were equipped with steerable tailskids, which operate similar to a tailwheel. When the pilot pressed the right rudder pedal — or the right footrest of a "rudder bar" in World War I — the skid pivoted to the right, creating more drag on that side of the plane and causing it to turn to the right. While less effective than a steerable wheel, it gave the pilot some control of the direction the craft was moving while taxiing or beginning the takeoff run, before there was enough airflow over the rudder for it to become effective.

Another form of control, which is less common now than it once was, is to steer using "differential braking", in which the tailwheel is a simple, freely castering mechanism, and the aircraft is steered by applying brakes to one of the main wheels in order to turn in that direction. This is also used on some tricycle gear aircraft, with the nose wheel being the freely castering wheel instead. Like the steerable tailwheel/skid, it is usually integrated with the rudder pedals on the craft to allow an easy transition between wheeled and aerodynamic control.

The tailwheel configuration offers several advantages over the tricycle landing gear arrangement, which make tailwheel aircraft less expensive to manufacture and maintain.

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Wikipedia