Showing papers on "Landing gear published in 1982"

Takeoff weight computer apparatus for aircraft

Abstract: The takeoff weight of an aircraft is computed from measures of the thrust of the engines provided by sensors (11, 12, 13) and the forward acceleration provided by an accelerometer (10) of the aircraft detected over a time period when such acceleration is at a maximum following brake release on the runway. A major variable that must be considered is the coefficient of rolling friction of the landing gear of the particular aircraft involved and other factors inducing ground roll drag. The present invention calculates this variable as a function of engine thrust and manifest weight (36) for each takeoff of the aircraft and updates weighted filter values thereof (28) for use during subsequent takeoffs. For each takeoff, therefore, an average value of rolling friction is used to calculate takeoff weight, which average value becomes more nearly the actual value for the existing condition of the landing gear.

Short take off jump mode for airplane landing gear struts

Abstract: A telescoping energy-dissipating oleo landing gear shock strut set which can provide both the main landing gear and forward landing gear function, and which is affixed to an airplane, is restrained in an unenergized, shortened condition. A high pressure gas charge is then provided between the extendible element of the strut and the element affixed to the airplane. Early in the takeoff run, the charge gas in the forward strut is released so as to jump the nose and rotate the airplane to a high angle of attack appropriate for takeoff. Subsequent to this rotation, but before the conventional takeoff speed is reached, the charge gas in each of the main struts is released to impart a vertical velocity to the entire airplane, thus jumping it into the air. Both the forward strut and main struts incorporate a hydraulic flow bypass function, so that the landing shock dissipation function does not compromise the aforesaid energy release. The struts also incorporate valves to discharge enough residual gas immediately at the end of the jump stroke so that the landing energy dissipation mode is not compromised.

Experimental investigation of active loads control for aircraft landing gear

Abstract: Aircraft dynamic loads and vibrations resulting from landing impact and from runway and taxiway unevenness are recognized as significant in causing fatigue damage, dynamic stress on the airframe, crew and passenger discomfort, and reduction of the pilot's ability to control the aircraft during ground operations. One potential method for improving operational characteistics of aircraft on the ground is the application of active control technology to the landing gears to reduce ground loads applied to the airframe. An experimental investigation was conducted which simulated the landing dynamics of a light airplane to determine the feasibility and potential of a series hydraulic active control main landing gear. The experiments involved a passive gear and an active control gear. Results of this investigation show that a series hydraulically controlled gear is feasible and that such a gear is very effective in reducing the loads transmitted by the gear to the airframe during ground operations.

Convertible amphibious aircraft wheel position warning system

Abstract: An apparatus is provided for an amphibious aircraft which also has retractable landing gear. The apparatus senses changes in aircraft speed indicative of an imminent landing or a takeoff and prompts the pilot to verify that the landing gear is in a position compatible with the type of surface, land or water, chosen for landing.

Tandem type landing gear

Abstract: The present invention relates to landing gears. The landing gear includes essentially two legs (1, 2) comprising respecitvely two arms (10, 28) and two rocker beams (3, 24), a bar (21) forming with the two arms (10, 28) a deformable parallelogram, a strut (37) consisting of two levers (23, 38) placed on a diagonal of the parallelogram, two locking links (50, 51) cooperating with the strut (37), these two rotatably mounted links being rotated by an actuator (70) and a spring (60). The landing gear finds its application in commuter aircraft fitted with tandem type landing gears.

An electronic control for an electrohydraulic active control landing gear for the F-4 aircraft

Abstract: A controller for an electrohydraulic active control landing gear was developed for the F-4 aircraft. A controller was modified for this application. Simulation results indicate that during landing and rollout over repaired bomb craters the active gear effects a force reduction, relative to the passive gear, or approximately 70%.

Fuselage landing gear with tandem wheels

Abstract: The landing gear for aircraft comprises at least two rocker beams respectively carrying wheels, the rocker beams being connected rigidly and respectively to two points of the rigid structure of the aircraft, each rocker beam being connected to two other rigid points of the aircraft structure by an assembly composed of a lever and a shock absorber mounted rotatably on each other, and a connecting rod of constant length connecting two levers and an actuating cylinder to rotate at least one of the two said levers. The landing gear finds a particularly advantageous application as a fuselage landing gear with tandem mounted wheels.

Tripod type landing gear

Abstract: This invention relates to landing gears. The described landing gear is characterized essentially by the fact that it comprises a leg (3) at one end of which is fixed a wheel (14 ) for rolling around a pivoting pin (11), a shock absorber (15) of which one end (22) is connected to leg (3), a strut (24) whose end is connected to leg (3) and links (39, 37, 41) connecting the end of strut (24) to the pivoting pin (11) so as to cause the wheel to pivot when the landing gear is retracted. This landing gear finds an advantageous application as a fuselage landing gear of the tripod type.

A Study of Analytic Modeling Techniques for Landing Gear Dynamics.

Abstract: : The ability to accurately predict the dynamic response of an aircraft while it is operating in the taxi mode depends, in part on the correct modeling of the dynamic characteristics of the landing gear system. Traditionally, landing gear have been designed to absorb landing impact ('shock absorber') and their characteristics during periodic, oscillatory response ('spring') have been considered as secondary. With the increased emphasis on the rough or damaged field taxi operation, there is a requirement to determine the best methods for modeling the gear system. This report documents a brief review of the state of the art of gear modeling. A study was then conducted to evaluate important model parameters, using a simple cantilevered gear computer simulation. Also included is the development of a technique for the experimental determination of important gear system parameters. (Author)

Aircraft Dynamic Response to Damaged and Repaired Runways.

Abstract: : The conclusions of the Meeting were: damaged and repaired runways are likely to be very uneven and possibly dangerous to aircraft operations; there is very little realistic data on the expected amount and extent of the unevenness. With respect to existing NATO aircraft; each aircraft/runway combination must be checked analytically and experimentally; the existing mathematical models for dynamic response of aircraft structures and landing gear are reasonably accurate; some simple modifications to aircraft equipment and pilot technique show substantial improvements in dynamic response. For future aircraft or modifications to the current fleet, there is a need for a NATO-wide 'groundworthiness' requirement to allow true interoperability of NATO's air forces. (Author)

Take-off ramps for aircraft

Abstract: An aircraft take-off ramp, for causing an aircraft with a compressible, shock absorbing and damping landing gear to be so urged from a horizontal path that it follows an initially ballistic trajectory on leaving the ramp, has its profile derived from a notional generally circular arc. The notional arc has its radius selected so that the center of gravity of the aircraft, if its landing gear was incompressible, would follow a desired locus. The derived profile is so modified from the notional arc that during traverse of the ramp the compressible landing gear is compressed so that the center of gravity of the aircraft follows the desired locus.

Planar equations of rollout motion for an aircraft with free or steerable landing gears

Abstract: SUMMARY Longitudinal, lateral, and heading equations of rollout motion were derived for an aircraft in a three-point attitude equipped with freely castoring or steerable landing gears and subjected to applied forces. Equilibrium constraints normal to the runway surface and about the aircraft roll and pitch axes were imposed. Transient tire forces from steady-sta-te data were introduced by inserting a time lag between the computed tire yaw angle and the resulting tire force. The planar equations derived were used to describe the position and heading of an aircraft relative to a runway coordinate-axis system. Computed trajectories were compared with those found experimentally for a small-scale landing-gear model traversing a laterally sloping runway with and without nose-gear steering. Correlation with experiment was good. Numerical studies indicated that trajectories were sensitive to the initial transla- tory velocities of the test, tire drag, and angular landing-gear misalinement. The effect of the time lag on the computation of the tire forces, however, was found to be negligible for the trajectories of this paper. INTRODUCTION The landing of an aircraEt in a strong crosswind is a difficult and possibly hazardous operation. Crosswind effects have not been as significant in the past because they have been lessened by airport design considerations such as alining runways in the direction of prevailing winds or providing several runways with dif- ferent headings. However, such consideratiahs are not practical €or all airports; and, in particular, airports envisioned for short take-off and landing (STOL) air- craft operations are expected to offer few choices of runway headings. Such runway alinement restrictions potentially expose the aircraft to higher. crosswinds than those currently encountered. Furthermore, the slow landing speeds of STOL-type aircraft make them especially sensitive to crosswinds. Methods are needed to reduce this sensitivity and increase landing flexibility. Landing-gear systems have been conceived to increase control of the aircraft on the ground in the presence of a crosswind, and tests of some crosswind gear concepts using a small model were reported in reference

Aircraft landing gear

Abstract: The present invention relates to atterrisage trains Landing gear for aircraft comprises a leg (1) rotatably mounted about a first fixed axis (14) against a plug (30) formed by two levers (30,31) rotatably mounted one above the other by one of their ends about a fourth axis (33) the other two ends (35,34) against the plug being mounted for rotation about a second axis respectively fixed (37) linked to the aircraft and a third fixed shaft (36) connected to the leg (1), means (40,41) for controlling the rotation of the two levers (30,31) with respect to thee other, the first, second, third and fourth axes being parallel to each other Application to the main aircraft landing gear

The undercarriage layout

Abstract: The basic requirements for the design of an undercarriage are that it must be capable of absorbing a certain amount of energy, both vertically and horizontally, and that during taxying, liftoff and touchdown no other part of the aircraft will touch the ground. No instabilities must occur, particularly during maximum braking effort, crosswind landings and high-speed taxying. In addition, the undercarriage characteristics must be adapted to the load-carrying capacity of the airfields from which the aircraft is intended to operate. This chapter indicates how these requirements can be translated into an acceptable initial choice of the undercarriage layout, without going into the details of its structural design.

Vertical accelerations of a large aircraft during landing and taxiing

Abstract: Vertical accelerations diiring landing and taxiing have been extracted from the AIDS-data base. This data base contains fatigue related data derived from the AIDS-system, used by KSSU-Boeing 747 operators. Results are presented axid compared with similar data from other sources.

Steerable and retractable aircraft landing gear.

Abstract: The landing gear according to the invention comprises a leg (1) supporting at least one wheel (10), a shock absorber (12) arranged in a housing (14) of the leg (1), a part (15) interacting with the shock absorber (12), this part (15) emerging from the leg (1), and means for controlling the rotation of the leg (1) about a longitudinal axis, and is characterised in that the means for controlling the rotation of the leg (1) are situated in a cartridge (18) covering the leg and surrounding the emerging part (15). Application to the steering control of a landing gear.