Conventional landing gear
From Wikipedia, the free encyclopedia
Conventional landing gear describes an aircraft landing gear configuration with an undercarriage arrangement consisting of two main wheels and a tail wheel. In early aircraft, a tail skid made of metal or wood was used. In modern aircraft, a small, articulated wheel assembly is attached to the most posterior part of the airframe. The terms taildragger and tailwheel are aviation jargon for conventional gear.
[edit] History and current use
Tail-wheel aircraft are no longer commercially produced in large numbers, yet they are still made in high numbers by individuals who build aircraft from plans or kits. Examples of these tailwheel aircraft are the Vans RV-4, kitfox, and the Murphy Moose. Commercially made tailwheel aircraft are still preferred for use in speciality applications such as aerobatics, agriculture, and back-country flying.
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 the Cessna 150, Cessna 172 and Piper PA-22 Tripacer.
An ideal "taildragger" landing is referred to as a "3-point" landing, referring to all three wheels hitting the runway at the same time.
[edit] Characteristics
This section applies to General Aviation aircraft only.
Taildraggers will behave just like tricycle gear aircraft when flying. Taildraggers, though, have ground handling characteristics that can be challenging. In a taildragger, the center of mass is located behind the front landing gear, which is an inherently less stable configuration than a tricycle landing gear. If the pilot is not able to keep the longitudinal axis of the aircraft aligned with the runway, then the center of mass of the aircraft will tend to rotate around the landing gear (the highest point of drag, or friction while on the ground) until the center of mass is in front of the highest point of drag. This results in an abrupt turn known as a ground loop, typically causing damage. There is no doubt that more skill is needed to take off and land a tailwheel aircraft, and some translate this to mean that tailwheel aircraft are harder to operate. However, the added skill is a benefit to any pilot, and some nosewheel pilots develop similar levels of skill without ever flying a tailwheel aircraft.
The tailwheel landing gear configuration has benefits when landing in high winds and rough, unimproved runways in that in such applications the sometimes fragile front landing gear could be easily damaged as it is often relied upon to counter any transverse loading, or side loads. A tailwheel aircraft offsets side loads and maintains direction by using control surfaces, which along with the leverage from the structure of the aircraft, are made to handle such loads. In high crosswinds, as a tailwheel aircraft slows and the forces exerted by the control surfaces decrease it may be necessary to simply let the tailwheel aircraft rotate around and point nose-first into the wind. This tends to alarm untrained nosewheel pilots. The use of a locking tailwheel may reduce this weather vane tendency, but it once again adds transverse loads to parts of the aircraft structure that are not typically designed for such loads. Many nosewheel landing gear struts are structurally little more than props to hold up the front of the aircraft, and do not deal well with sideloads. It should be noted that skilled pilots of tricycle landing gear use techniques very similar to tailwheel pilots in order to avoid damaging the front landing gear in challenging situations. Also, single engine tricycle gear aircraft typically have very little clearance between the front propeller and the ground, making operations on rough or unimproved airfields problematic. This can be countered on tricycle gear aircraft by modifying the landing gear to accommodate larger tires and wheels.
While on the ground, visibility over the nose may be reduced due to the pitch attitude of the aircraft, depending on the model and geometry of specific aircraft. But, not all taildraggers have poor forward visibility on the ground. For example, the Cessna 170 taildragger has better visibility over the nose than later model tricycle gear Cessna 172's due to the increased size of the instrument panel in the later model 172's.
Taildragger versions of the same aircraft often have higher useful loads and cruise speeds due to the elimination of the nose gear and its associated drag and weight.
There are experienced tailwheel pilots who insist that the added challenges of a tailwheel aircraft arise largely from a lack of skill that results from poor training when transitioning from a tricycle landing gear aircraft. Most pilots now learn to fly in tricycle gear aircraft (e.g., Cessna 152 and Cessna 172) and only later transition to taildraggers. Since the number of factory-built general aviation aircraft with a tailwheel is fairly low, the numbers of instructors experienced in this type of aircraft are also limited.
