Landing gear

About: Landing gear is a research topic. Over the lifetime, 3403 publications have been published within this topic receiving 25370 citations. The topic is also known as: landing gear & gear.

Analysis of separation of the space shuttle orbiter from a large transport airplane

Abstract: The feasibility of safely separating the space shuttle orbiter (140A/B) from the top of a large carrier vehicle (the C-5 airplane) at subsonic speeds was investigated. The longitudinal equations of motion for both vehicles were numerically integrated using a digital computer program which incorporates experimentally derived interference aerodynamic data to analyze the separation maneuver for various initial conditions. Separation of the space shuttle orbiter from a carrier vehicle was feasible for a range of dynamic-pressure and flight-path-angle conditions. By using an autopilot, the vehicle attitudes were held constant which ensured separation. Carrier-vehicle engine thrust, landing gear, and spoilers provide some flexibility in the separation maneuver.

Fuel-Efficient Descent and Landing Guidance Logic for a Safe Lunar Touchdown

Abstract: The landing of a crewed lunar lander on the surface of the Moon will be the climax of any Moon mission. At touchdown, the landing mechanism must absorb the load imparted on the lander due to the vertical component of the lander’s touchdown velocity. A large horizontal velocity must also be avoided because it could cause the lander to tip over, risking the life of the crew. To be conservative, the worst-case lander’s touchdown velocity is always assumed in designing the landing mechanism, making it very heavy. Fuel-optimal guidance algorithms for soft planetary landing have been studied extensively. In most of these studies, the lander is constrained to touchdown with zero velocity. With bounds imposed on the magnitude of the engine thrust, these optimal control solutions typically have a “bang-bang” thrust profile: the thrust magnitude “bangs” instantaneously between its maximum and minimum magnitudes. But the descent engine might not be able to throttle between its extremes instantaneously. There is also a concern about the acceptability of “bang-bang” control to the crew. In our study, the optimal control of a lander is formulated with a cost function that penalizes both the touchdown velocity and the fuel cost of the descent engine. In this formulation, there is not a requirement to achieve a zero touchdown velocity. Only a touchdown velocity that is consistent with the capability of the landing gear design is required. Also, since the nominal throttle level for the terminal descent sub-phase is well below the peak engine thrust, no bound on the engine thrust is used in our formulated problem. Instead of bang-bang type solution, the optimal thrust generated is a continuous function of time. With this formulation, we can easily derive analytical expressions for the optimal thrust vector, touchdown velocity components, and other system variables. These expressions provide insights into the “physics” of the optimal landing and terminal descent maneuver. These insights could help engineers to achieve a better “balance” between the conflicting needs of achieving a safe touchdown velocity, a low-weight landing mechanism, low engine fuel cost, and other design goals. In comparing the computed optimal control results with the preflight landing trajectory design of the Apollo-11 mission, we noted interesting similarities between their landing performance.

The application of a smart landing gear oleo incorporating Electrorheological fluid

Abstract: The objectives of this paper are to outline the use of Electrorheological (ER) fluid within an aerospace system. The advantages of ER fluid-based systems are given followed by design considerations which include those related to the non-linear behaviour of an ER fluid subjected to oscillatory shear. A control strategy is outlined for the use ofa smart landing gear (LG) oleo incorporating ER fluid. The paper also considers the issues associated with airworthiness requirements and ER fluid devices. For airw orthiness approval a smart oleo based LG system must primarily be shown to be safe and as such has to be fault tolerant. A major failure for this application would be if the control strategy failed and the oleo damping coefficient was consistently too low: a backup system is therefore incorporated into the design and other potential modes of failure considered. A semi-active control strategy applied to a variable damping coefficient LG oleo has specific requirements, partly due to the fact that for the take-off and landing phases of flight they are different. A semi-active control strategy is outlined based on the requirements for the alteration of damping coefficient according to the phase of an aircraft's flight. The strategy is the focus of current work to estimate the effectiveness of semi-active vibration control as applied to an undercarriage.

Aircraft nose landing gear

Abstract: An aircraft nose landing gear installation that utilizes a single piece pin inserted through the gear fittings and into the two piece, fail safe support structure without requiring mechanical retention on the outside of the wheel well.

Method and system for reducing aircraft stopping distance

Abstract: A method and system for reducing stopping distance for an aircraft on a wet runway, which includes blowing away water on a wet landing surface in front of the aircraft tires so that the tires contact a relatively dry surface and simultaneously blowing air on the tires to remove water that may have collected on them. The system includes ducting from the aircraft engine to the landing gear to receive high pressure air bled from the aircraft engine and nozzles connected to the ducting for exhausting high pressure air to the runway in front of the wheels and to the rear portion of the tires. A system of valves in the ducting can be actuated by switches in the cockpit to bleed high pressure air from the engine to the ducting and nozzles during landing of the aircraft.