Showing papers on "Landing gear published in 1981"

Landing gear door mud guard

Abstract: A combination landing gear door and splash guard for an aircraft landing gear which includes a linkage to control the clearance between the door/splash guard and a runway surface with respect to the extension of a shock absorbing strut of the landing gear.

System for braking an aircraft taxiing on the ground

Abstract: The present invention relates to a system for braking an aircraft taxiing on the ground. According to the invention, if an abnormality such as hydroplaning or bursting of a non-braked wheel is detected, the speed most representative of the real speed of the aircraft with respect to the ground is memorized. This memorized speed is regularly reduced to allow braking for the whole duration of the disturbance, avoiding locking or elimination of braking of the wheels of the main landing gear. The invention is more particularly applicable to the braking of wide-body aircraft.

Landing gear for aircraft

Abstract: The invention concerns a landing gear. The landing gear is characterized essentially by the fact that it comprises at least one shock absorber (15), this shock absorber being mounted in the leg (1) and casing (2) assembly by means of two convex surfaces (22, 31) made on the cylinder (16) of the shock absorber (15) and cooperating with two concave surfaces (25, 32) integral respectively with the leg (1) and the casing (2). This landing gear finds an application as a nose gear of the rocker-beam type.

Process and device for detecting the under-inflation of a tire of the landing gear of an aircraft

Abstract: Process for detecting the under-inflation of a tire of the landing gear of an aircraft in the course of taxiing, said landing gear being formed by at least one bogie comprising a beam provided with a pair of twin wheels at each of its ends provision is made of two bridge assemblies of four strain gauges disposed on each of the parts of the beam located between the median spindle for articulation of said beam to the leg and the corresponding pair of wheels, each bridge being supplied by its diagonal transverse to said beam, while the torsion signal is taken from the diagonal longitudinal with respect to the beam.

Helicopter Landing Gear Design and Test Criteria Investigation

Abstract: : This program was an investigation of the criteria relating to helicopter landing gears. A computerized literature search was conducted and a bibliography is included in this report. Existing criteria were reviewed and conflicts were identified. An analysis of survivable Army helicopter accidents was performed. The results were used to formulate a tentative criterion. A design study was conducted to evaluate the practicality of the tentative criteria. This investigation compared wheel and skid-type landing gears designed to the tentative criteria and to MIL-S-8698. A crashworthiness analysis of the tentative criteria tailwheel tricycle gear was performed. Weights and landing loads were calculated. A cost comparison was made between tailwheel tricylce gears designed to the two criteria. The gear designed to the new criteria was cost-effective. The results of the investigation were used to modify the tentative criteria and recommendations were made for a new helicopter landing gear military specification and for changes to the existing criteria.

Aircraft landing gear test rig - uses dummy of same weight and moment of inertia as aircraft, launched onto runway from railway track

Abstract: The installation is used for investigating the landing-action of aircraft and for testing the undercarriage under operating conditions. It is based on a length of rail-track with a girder- carriage running on it. The aircraft is represented by a dummy of appropriate weight and moment of innertia about all axes, and fitted with the undercarriage units to be tested. It may test wheels, skid or slip landing gear or carries aircraft arrestor hooks. The dummy is arranged on the carriage at the correct angles of incidence, sideslip and bank for a simulated landing, and at such a height that when launched its flight-path angle at the touchdown point equals the natural landing angle of the original. Undercarriage behaviour under a wide variety of landing conditions may be investigated.

Minimum fuel paths for a subsonic aircraft

Abstract: to the afterbody by three supporting beams, one at each wing root and one below the fin. The slot between the afterbody and the leading edge of the ejector, divided into three parts by the beams, is the combined inlet for ambient air and nozzle for reverse exhaust gas. Instead of blow-in-doors, the slot has a translating sleeve which in the open position is retracted into the afterbody structure by hydraulic power. In the ejector shroud there are three blocker doors flush with the surface in the retracted position. When the reverser control is engaged, the doors are turned to their closed position by hydraulic actuators and the exhaust gas is deflected forward through the slot, forming one ground jet and two jets above the wing on either side of the fuselage. (See Fig. 1.) Thrust reversal can be preselected by the pilot in the air, and is then automatically initiated at touchdown of the main landing gear. The development work on the reverser system included a number of activities. Besides model testing in wind tunnels and rigs and full-scale testing on the engine test bed, a large number of test runs (including landings) were carried out in prototype aircraft for evaluation of the complete reverser system and for demonstration of roll distance and aircraft stability at thrust reversal. During thousands of reverser operations in the flight test program, invaluable but also hard-earned experience was gained. The problems encountered were mainly due to influences on aircraft pitch and yaw stability. Owing to the aerodynamic ground interference from the lower jet of the deflected flow, a strong variation in pitching moment with forward speed and degree of reverse thrust occurred. The yaw stability problem was also caused by aerodynamic interference. With the upper jets close to the fin, small asymmetric disturbances in the jet boundaries could result in side forces and yawing moments too great to be controlled by the

Investigation of Landing Gear Alternatives for High Performance Aircraft

Abstract: In an effort to improve rough field performance for a specific high performance aircraft, the modeling of runway profiles, the aircraft structure, landing gears, and aerodynamics was accomplished. Various load alleviation schemes are modeled and then combined with the aforementioned runway and aircraft models into a dynamic simulation which allows the evaluation of the control schemes through numeric and graphical means. These combined evaluation tools (numeric and graphic) add efficiency to the design process along with increasing physical insight into the problem. Results are presented which indicated that a number of control configurations (both passive and active) ranging in various degrees of complexity increase the rough field performance (in some cases significantly) for the selected high performance aircraft (F-16). I. Introduction C ONVENTIONAL landing gear designs which minimize rolling moments on takeoff/landing and/or hold ground clearance approximately constant over a wide range of load configurations tend to also stress low weight and volume with the result of sacrificing rough field performance. A logical question is then, are there any types of landing gear configuration that can be retrofitted to existing high performance aircraft or designed into new aircraft which ameliorate the rough runway performance? The goal of this effort4 was to investigate various landing gear configurations to see which of these improved the performance of an aircraft (F-16) during ground operation on rough runways. Approach To determine the performance capability of the landing gear alternatives, the runway profile, aircraft airframe, aerodynamics, and landing gear are modeled as discussed in Sees. II and III. Section IV delineates alternative landing gear which are designed to attenuate vertical loads during takeoff and landing roll. The characteristics of the alternative landing gear are changed by adding forces (in the active case) or by changing the nonlinear characteristics of the strut. The models are shown to accurately represent the current F-16 structural support system in terms of dynamic response to runway inputs. The performance of the current landing gear and four alternative designs is tested by simulating the dynamic response of a fully loaded (33,500 Ib) F-16 taking off from, and landing on, rough, temporarily repaired runways. Validation of the simulation was accomplished with aircraft data. The runway used simulates one with two large craters which are repaired using established rapid runway repair techniques.1 By simulating the aircraft accelerating or decelerating over the runway with many different initial velocities, a spectrum of system responses is developed. In all cases, the accelerations and loads transmitted to the aircraft structure are calculated and compared with the aircraft's design limit loads, pylon acceleration limits, and ground

Influence of landing gear flexibility on aircraft performance during ground roll

Abstract: An analysis is made of the influence of landing gear deflection characteristics on aircraft performance on the ground up to rotation. A quasi-steady dynamic equilibrium state is assumed, including other simplifying assumptions such as calm air conditions and normal aircraft lift and drag. Ground incidence is defined as the angle made by the mean aerodynamic chord of the wing with respect to the ground plane, and equations are given for force and balance which determine the quasi-equilibrium conditions for the aircraft during ground roll. Results indicate that the landing gear deflections lead to a substantial increase in the angle of attack, and the variation in the ground incidence due to landing gear flexibility could be as much as + or - 50%, and the reduction in tail load requirements almost 25%.

Influence of friction forces on the motion of VTOL aircraft during landing operations on ships at sea

Abstract: Equations describing the friction forces generated during landing operations on ships at sea were formulated. These forces depend on the platform reaction and the coefficient of friction. The platform reaction depends on the relative sink rate and the shock absorbing capability of the landing gear. The friction coefficient varies with the surface condition of the landing platform and the angle of yaw of the aircraft relative to the landing platform. Landings by VTOL aircraft, equipped with conventional oleopneumatic landing gears are discussed. Simplifications are introduced to reduce the complexity of the mathematical description of the tire and shock strut characteristics. Approximating the actual complicated force deflection characteristic of the tire by linear relationship is adequate. The internal friction forces in the shock strut are included in the landing gear model. A set of relatively simple equations was obtained by including only those tire and shock strut characteristics that contribute significantly to the generation of landing gear forces.