Landplanes are fitted with either a nose wheel or tailwheel. The landing gear not only has to support the aircraft on the ground but must be capable of withstanding the considerable stresses and shock loadings experienced during landing. The gear is always sprung. This can be by the use of spring metal, rubber or by oleo. An oleo is in effect a spring and shock absorber combined.

oleo construction

Most modern aircraft have are fitted with a nosewheel (tricycle). Earlier designs are most likely to have a tailwheel (taildragger).

tricycle gear

tricycle gear

spring metal landing gear of a fixed undercarriage

Nosewheel airplanes have the "third" wheel in front of the main landing gear (i.e., under the nose) as pictured below. Nose-wheel airplanes have much better handling (due to less airplane behind the pivot point) and visibility characteristics while taxiing. Almost all new airplanes are nose-wheel design. It is most important that the pilot does not land the aircraft on the nose wheel. This is called a ' wheelbarrow ' and often results in serious damage. The nose wheel is usually dampened with a shock absorber or friction ring to prevent shimmy. click here for shimmy animation.

A torque link is also fitted to maintain correct nose-wheel alignment. Braking is usually controlled from the tops of the rudder pedals, and a separate parking brake is often fitted.

Most light aircraft have steering nose wheels. When on the ground a linkage is actuated between the rudder pedals and the nose wheel. This  disconnects automatically once that aircraft leaves the ground. A small number of aircraft are fitted with castoring nose wheels. Steering is effected below rudder authority by the use of the differential brakes on the main wheels. An example of an aircraft with a castoring nose wheel is the Grumman Tiger series. Many homebuilt aircraft are also similarly equipped.

castoring nose gear of pilotfriend editor's retractable Glasair

Main Gear

typical light aircraft oleo main gear

Brakes are usually of the disc type and when used differentially may be used to reduce turning circles.

Creep marks are painted on the tyre and wheel rim so that the pilot can check that the tyre is not moving on the rim. A maximum of 1/4" is permitted.
 

Tailwheel

These airplanes have the "third" wheel under the tail. Taildragger aircraft can land on much rougher terrain and, consequently, are used by bush pilots. In a tailwheel airplane, this gear supports the weight of the rear portion of the airplane. They are harder to control, (imagine driving a rear steering dumper truck at high speed) and extra training is required to handle them.

tailwheel retractable. The beautiful Globe Swift

monowheels with outriggers

A small number of aircraft use a single central landing wheel and are laterally supported by outriggers. Example are the U2 spy plane and the homebuilt Europa. Ground handling is not all that it could be with this configuration.

the now defunct Europa

Retractable landing gear

Retracting the gear reduces drag and increases airspeed without additional power. The landing gear normally retracts into the wing or fuselage through an opening which may be covered by doors after the gear is retracted. The smooth door will provide for the unrestricted flow of air across the opening that houses the gear. The retraction or extension of the landing gear is accomplished either electrically or hydraulically by landing gear controls from within the cockpit. Warning indicators are usually provided in the cockpit to indicate whether the wheels are extended and locked, or retracted. In nearly all airplanes equipped with retractable landing gear, a system is provided for emergency gear extension in the event landing gear mechanisms fail to lower the gear. The pilot operating manual will specify the maximum speed at which the gear can be lowered.

retractable ('complex') aircraft in flight