AIRCRAFT LANDING GEAR SYSTEM Almost all airplanes with tricycle landing gear utilize some type of nose-wheel steering on the ground by controlling the nose wheel. NOSE STEERING WHEEL SYSTEMS CLICK ME 1ST! I AM SMOL CLICK ME! I AM BIG HEHE SMALL AIRCRAFT SMALL AIRCRAFT Usually controlled by a direct connection between the rudder pedals and the nose gear. WHAT MAKES A SMALL AIRCRAFT? CLICK HERE TO GO MEET BIG - Has a castering nose wheel. - Differential braking does the steering. - Other small airplanes link the nose wheel to the rudder pedals directly. LARGE AIRCRAFT LARGE AIRCRAFT Usually activated by a hydraulic actuator that is controlled by the rudder pedals or by a separate steering mechanism. HOW DO NOSE WHEELS ON LARGE AIRCRAFTS WORK? Click me to know!! 1. They are steered on the ground by directing hydraulic pressure into the cylinders of dual shimmy dampers. 2. Steered on the ground by directing hydraulic pressure into the cylinders of dual shimmy dampers. The actual control of the fluid can be transmitted from the pilot’s control to the hydraulic control unit mechanically, electrically, or hydraulically. SHIMMY DAMPERS SHIMMY DAMPERS SHIMMY DAMPERS SHIMMY DAMPERS SHIMMY DAMPERS A small hydraulic shock absorber that is installed between the nose-wheel fork and the nose-wheel cylinder. SHIMMY DAMPERS They prevent the nose wheel from shimmying, or oscillating back and forth at certain speeds. STEERING DAMPERS STEERING DAMPERS STEERING DAMPERS STEERING DAMPERS Cylinders that prevent the nose wheel from vibrating or shimmying. STEERING DAMPERS Because of being constantly charged with hydraulic fluid under pressure, steering actuators serve as steering dampers. STEERING DAMPERS They are widely used on larger aircrafts. LANDING GEAR ALIGNMENT, SUPPORT, AND CONTROL In order for the wheels to perform effectively, optimal structural support from landing gear must be maintained. It must meet all the requirements needed in order for the landing gear system to work efficiently. WHEEL ALIGNMENT Proper alignment of the main gear wheels is critical during landing and take-off, in that a little misalignment could adversely affect the aircraft’s ground performance. Torque links, shimmy dampers, and some other more supporting parts are used to keep the wheels straightly aligned. Click to meet Mario Some smaller aircraft use a simple mechanical retraction system, incorporating a roller chain and sprockets operated by a hand crank.. To raise the landing gear, the gear selector handle is placed in the GEAR UP position. This starts the hydraulic pump, forcing fluid into the gear-up side of the actuating cylinders to raise the gear... To lower the landing gear, the selector switch is placed in the GEAR DOWN position, which releases the pressure on the up-side of the cylinders... Normally, large aircraft have wheel-well doors that are closed at all times the landing gear is not actually moving up or down. Sequence valves are used in the system to ensure the doors are opened before the landing gear is actuated. Most large aircraft use mechanical locks to hold the landing gear in its UP or DOWN position… Most of the large aircraft landing-gear systems use an orifice check valve in the fluid lines to the actuators... EMERGENCY EXTENSION SYSTEMS If the primary method of lowering the landing gear fails, there must be a secondary means in case of emergency. Generally, emergency extension systems use a variety of methods to lower the gear. Some of them include: mechanical, alternate hydraulic, compressed air, or free-fall techniques. In order to prevent undesirable events from happening, safety devices are employed to prevent raising the gear on the ground, gear locks, and indicators to tell the pilot what position the gear is in. A landing gear squat switch, or safety switch, is found on most aircraft with retractable gear systems. This is a switch positioned to open and close depending on the extension or compression of the main landing gear strut. used to secure the landing gear in the down position. These locks generally consist of a pin inserted into the retraction mechanism in such a manner to block the retraction of the landing gear. Generally located close to the landing gear lever, is a set of three green lights to indicate all three wheels are down and locked and three red lights to show that they are up and locked. Is located in the nose wheel shock strut. Using centering cams, the nose wheel is centered when the strut is extended after take-off. The nose gear will remain centered until it compresses upon landing due to the weight of the aircraft.
