Conventional landing gear, or tailwheel-type landing gear, is an aircraft undercarriage consisting of two main wheels forward of the centre of gravity and a small wheel or skid to support the tail.[1][2] The term conventional persists, having begun in the time when the majority or "convention" of airplanes were thus configured, even though nowadays most aircraft are configured with tricycle landing gear.
The term taildragger is aviation jargon for an aircraft with a conventional undercarriage, although some writers have argued that the term should refer only to an aircraft with a tailskid and not a tailwheel.[2][3]
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In early aircraft, a tailskid made of metal or wood was used to support the tail on the ground. In most modern aircraft, a small, articulated wheel assembly is attached to the rearmost part of the airframe in place of the skid. This wheel is steered by the pilot through a connection to the rudder pedals, allowing the rudder and tailwheel to move together.[2][3]
The tailwheel configuration offers several advantages over the tricycle landing gear arrangement.[2]
Due to its smaller size the tailwheel has less parasite drag than a nosewheel, allowing the conventional geared aircraft to cruise at a higher speed on the same power. Tailwheels are less expensive to buy and maintain than a nosewheel. If a tailwheel fails on landing, the damage to the aircraft will be minimal. This is not the case in the event of a nosewheel failure, which usually results in propeller damage. Tailwheel aircraft are easier to man-handle on the ground and, due to their lower tail, they will fit into some hangars more easily.[2][4]
Due to the increased propeller clearance on tailwheel aircraft less stone chip damage will result from operating a conventional geared aircraft on rough or gravel airstrips. Because of the way airframe loads are distributed while operating on rough ground, tailwheel aircraft are better able to sustain this type of use over a long period of time, without cumulative airframe damage occurring.[2]
Tailwheel aircraft are also more suitable for operation on skis.[2]
The conventional landing gear arrangement does have some disadvantages, compared to the nose wheel equipped aircraft.[2]
Tailwheel aircraft are much more subject to "nose-over" accidents, due to main wheels becoming stuck in holes or injudicious application of brakes by the pilot.[2]
Conventional geared aircraft are much more susceptible to ground looping. A ground loop occurs when directional control is lost on the ground and the tail of the aircraft passes the nose, in some cases completing a full circle. This event can result in damage to the aircraft's undercarriage, tires, wingtips and propeller. Ground-looping occurs because, whereas a nosewheel aircraft has its CG (i.e. center of gravity of an aircraft) ahead of its main wheels, a taildragger has its CG behind the main gear, so that on the ground a taildragger is inherently unstable, whereas a nosewheel aircraft will self-rectify if it swerves on landing. Avoiding ground loops requires increased pilot training and skill.[1][2]
Tailwheel aircraft generally suffer from poorer forward visibility on the ground, compared to nose wheel aircraft. In some cases this necessitates "S" turning on the ground to allow the pilot to see while taxiing.[2]
Tailwheel aircraft are more difficult to taxi during high wind conditions, due to the higher angle of attack on the wings. They also suffer from lower crosswind capability and in some wind conditions may be unable to use crosswind runways or single-runway airports.[2]
Taildragger aircraft require more training time for student pilots to master. This was a large factor in the 1950s switch by most manufacturers to nosewheel-equipped trainers, and for many years nosewheel aircraft have been more popular than taildraggers. As a result, most PPL pilots now learn to fly in tricycle gear aircraft (e.g. Cessna 172 or Piper Cherokee) and only later transition to taildraggers.[2].
Landing a conventional geared aircraft can be accomplished in two ways.[5]
Normal landings are done by touching all three wheels down at the same time in a three-point landing. This method does allow the shortest landing distance but can be difficult to carry out in crosswinds.[5]
The alternative is the wheel landing. This requires the pilot to land the aircraft on the main wheels while maintaining the tailwheel in the air with elevator to keep the angle of attack low. Once the aircraft has slowed to a speed that can ensure control will not be lost, but above the speed at which rudder effectiveness is lost, then the tailwheel is lowered to the ground.[5]
Examples of tailwheel aircraft include:
Several after-market modification companies offer kits to convert many popular nose-wheel equipped aircraft to conventional landing gear. Aircraft for which kits are available include:
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