There is also a pedestal landing gear that is not used much. Its front and front wheels are arranged in front of and behind the plane of symmetry of the aircraft (ie, in the lower part of the fuselage), and the center of gravity is almost equal to the front wheel and the main wheel. In order to prevent dumping during cornering, an auxiliary small wheel is also arranged under the wing. This type of arrangement is less used due to difficulty in raising the head during takeoff.
It solves the problem of retracting the main landing gear of some thin wing aircraft.
(1) The front landing gear is subjected to a large load, which increases the size and mass.
(2) It is not easy to leave the ground when the take-off is running, and the take-off distance is increased. In order for the aircraft to reach the take-off angle of attack, special measures such as lengthening the front landing gear strut or shortening the rear landing gear strut length during take-off run are required.
(3) The method of braking the main wheel cannot be used, but the steering mechanism must be used to achieve ground turning.
Due to the above disadvantages, bicycle landing gear is generally not used unless it is not allowed. At present, only a few aircraft adopt this type of landing gear layout, such as the British “Haicang” vertical take-off and landing fighter.
This type of landing gear is similar to the front three-point landing gear. The center of gravity of the aircraft precedes the main landing gear, but it has multiple main landing gear struts that are typically used on large aircraft. Such as the United States Boeing 747 passenger aircraft, C-5A (military transport aircraft (takeoff quality are more than 350 tons) and the Soviet Union's Il 86 passenger aircraft (takeoff quality 206 tons).
The use of multi-point type can reduce the local load, which is beneficial to the structure of the force structure; it can also reduce the volume of the wheel, thereby reducing the space for the landing gear.