Table of Contents
Seminar on Landing Gear Arrangement Analysis Report Download
Landing Gear basics
The landing gear is that portion of the aircraft that supports the weight of the aircraft while it is on the ground. The landing gear contains components that are necessary for taking off and landing the aircraft safely. Some of these components are landing gear struts that absorb landing and taxiing shocks; brakes that are used to stop and, in some cases, steer the aircraft; nose wheel steering for steering the aircraft; and in some cases, nose catapult Components that provide the aircraft with carrier deck takeoff capabilities. The landing gear is the principle support of the airplane when parked, taxiing, taking off, or when landing. The most common type of landing gear consists of wheels, but airplane is can also be equipped with floats for water operations, or skis for landing on snow.
The landing gear consists of three wheels—two main wheels and a third wheel positioned either at the front or rear of the airplane. Landing gear employing a rear mounted wheel is called conventional landing gear.
Airplanes with conventional landing gear are sometimes referred to as tail wheel airplanes.
When the third wheel is located on the nose, it is called a nose wheel, and the design is
referred to as a tricycle gear. A steerable nose wheel or tail wheel permits the airplane to be controlled throughout all operations while on the ground.
The landing gear is the structure that supports an aircraft on the ground and allows it to taxi, take-off, and land.
The primary functions of a landing gear are as follows:
1. To keep the aircraft stable on the ground and during loading, unloading, and taxi.
2. To allow the aircraft to freely move and maneuver during taxing.
3. To provide a safe distance between other aircraft components such as wing and fuselage while the aircraft is on the ground position to prevent any damage by the ground contact.
4. To absorb the landing shocks during landing operation
5. To facilitate take-off by allowing aircraft acceleration and rotation with the lowest friction.
Landing Gear design
In order to allow for a landing gear to function effectively, the following design requirements are established:
1. Ground clearance requirement
2. Steering requirement
3. Take-off rotation requirement
4. Tip back prevention requirement
5. Overturn prevention requirement
6. Touch-down requirement
7. Landing requirement
8. Static and dynamic load requirement
9. Aircraft structural integrity
10. Ground lateral stability
11. Low cost
12. Low weight
The first job of an aircraft designer in the landing gear design process is to select the landing gear configuration. Landing gear functions may be performed through the application of various landing gear types and configurations. Landing gear design requirements are parts of the aircraft general design requirements including cost, aircraft performance, aircraft stability, aircraft control, maintainability, producibility and operational considerations.
In general, there are ten configurations for a landing gear as follows:
1. Single main
4. Tricycle or nose-gear
7. Releasable rail
9. Seaplane landing device
10. Human leg
The features and the technical descriptions of each landing gear configuration will be presented in this section. The common alternatives for landing gear configurations are illustrated in figure 1. The landing gear configuration selection process includes setting up a table of features that can be compared in a numerical fashion. It needs to be clarified that for simplicity the term “gear” or “wheel” is sometimes employed for a single strut and whatever that is connected to it which comprises such items as tire, wheel, shock absorber, actuators, and brake assembly. Hence, when the term “nose-gear” is used, it refers to a landing gear configuration; while when the term “nose gear” is employed, it refers to a gear that is attached under the fuselage nose. In general, most general aviation, transport and fighter aircraft employ tricycle landing gear, while some heavy weight transport (cargo) aircraft use quadricycle or multi-bogy landing gear. Nowadays, the tail-gear is seldom used by some GA aircraft, but it was employed in the first 50 years of aviation history by majority of aircraft.
Landing Gear Geometry
At this point, the landing gear configuration is selected and retraction configuration is decided. Now, the designer needs to perform mathematical calculations to determine few parameters such as height, wheel base, wheel track, and the distance between main gear and aircraft center of gravity. These parameters are interrelated through geometrical relations and several mathematical principles. These relationships are described in this Section. The guidelines for determining these parameters are presented in the following subsequent sections.
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