Showing papers on "Landing gear published in 1975"

Aircraft automatic braking system

Abstract: An aircraft automatic braking system which takes into account aircraft landing characteristics including touchdown rebound performance and nose high touchdown attitude. Signals representative of a nose gear loading (e.g. a nose gear squat switch) condition are utilized to control a dual interval time delay circuit controlling disarming of the automatic braking system. Signals representative of nose wheel speed are utilized to control rate of increase of braking pressure viz. between the first and second stages of on-ramping of pressure to a preselected rate of deceleration of main landing gear wheel(s).

Airframe noise - The next aircraft noise barrier

Abstract: Progress in quieting the commercial aviation fleet has been achieved by reducing the noise generated by jet engines. Recent tests have indicated that noise produced by airflow over aircraft surfaces (lifting surfaces, landing gear, flaps, and cavities) is only 8 to 10 EPNdB below certification requirements for current aircraft and will likely be a design consideration for aircraft of the future as engines become still quieter. This paper reviews the state of the art for understanding, predicting, and control of airframe noise. Levels and spectral content of the noise, correlation with important variables, and noise generation mechansims are discussed. The noise floors for future aircraft, the direction of research projects, and likely impact of this new technology on aircraft design are indicated.

Automatic controls for airplane take-off and landing modes

Abstract: A take-off and landing control device for automatic retraction of flaps upon stowing landing gear and upon attaining a predetermined airspeed and of indicating distance from brake release during take-off, and for an automatic decelerating approach with flaps extending as a function of distance from touchdown with automatic throttle cutback and automatic stabilizer trim in response to flap location maintaining an essentially constant angle of attack.

Articulated main landing gear

Abstract: An articulated, retractible landing gear for helicopters and the like includes a three member drag brace assembly having a retraction brace pivotally connected to the helicopter fuselage at its inboard end and to an upper drag brace at its outboard end, with the latter pivotal connection being along the articulation axis of the landing gear, the upper brace being pivotally connected at its other end to a lower brace which in turn is connected to the oleo strut of the landing gear by a universal joint, the pivotal connection between the upper and lower braces in the extended position of the landing gear being on an axis normal to both the drag brace center line and the articulation axis.

Aircraft engine fatigue cycle recorder

Abstract: In an aircraft, a system for recording aircraft fatigue cycles senses engine starting, engine shutdown, landing gear status, engine reversal and throttle setting and derives therefrom unit and fractional cycles. The system includes a first memory responsive to the aforementioned sensors for producing an indication of when the aircraft is in flight and a second memory for producing an indication of when the landing gear are dropped in flight. These memory indications are fed to gates which index the units counter when a takeoff, landing and engine shutdown cycle is completed and which index the fractions counter when a retakeoff without engine shutdown is accomplished. Other gates cause the units counter to be indexed when the engine is restarted in flight. In a multi-engine aircraft, sensors and counters are provided individually for each engine.

Air-cushion landing gear for aircraft

Abstract: The invention relates to aircraft and more particularly an air-cushion landing gear comprising a system of landing gear units suspended from an aircraft, with at least two of the units being spaced transversely with respect to the longitudinal axis of the aircraft, and one of them being arranged on the axis ahead of the aircraft center of gravity; each landing gear unit comprises a platform with an annular inflatable cell attached to its underside and used, when inflated, as a flexible curtain circumscribing an air cushion space under the platform, the inflation of each cell and the formation of the air cushion is accomplished by an independent injecting device built in the platform; the spaced-apart cells are provided with an operating device for decelerating and controlling the movement of the aircraft on the runway surface; such a design of the air-cushion landing gear makes it possible to easily and rapidly adapt modern planes and helicopters to such a landing gear with the take-off, landing and taxiing techniques being similar to those used with conventional wheeled landing gears; in addition, the proposed landing gear is more economical and simpler in manufacture and in service as compared to those of the prior art.

Diagnostic calculations of airframe-radiated noise

Abstract: Methods of calculating airframe noise due to the following components are presented: wings and stabilizers, flaps, landing gear 'self-noise', landing gear bay (wheel well) oscillations, separated flow interaction with edges of cavities, and doors associated with gear deployment. The predominant source mechanisms were dipole-like in nature, being related to the local fluctuating aerodynamic forces on struts, airfoil edges, cavity edges, etc. Available data are converted into semiempirical prediction methods to enable a tentative rank ordering of noise sources. A sample application of these prediction procedures is carried out for a typical CTOL passenger jet using actual aircraft parameters, where available.

Measurement of Steady State and Transient Aircraft Tire Forces

Abstract: Studies of aircraft directional control during takeoff and landing are best carried out with programmed simulators in which the pilot interacts directly with the aircraft systems. A vital input to such simulations is accurate tire force data, which at the present time are difficult to obtain because of lack of experimental facilities. This paper describes new test equipment for measuring aircraft tire forces which is now available at the Air Force Flight Dynamics Laboratory, Wright‐Patterson Air Force Base. Sample data are presented and discussed which pertain to conventional and experimental radial ply aircraft tires.

Landing Gear/Soil Interaction Development of Criteria for Aircraft Operation on Soil During Turning and Multipass Operations

Abstract: : The continuing design and operational requirements for military aircraft to operate on unimproved runways has led to the need to investigate those landing gear/soil runway parameters which most significantly influence performance. This report summarized those activities accomplished during the second year of a two-year research effort concerned with the development of criteria for turning, operation at high speed, and multipass operation. The work reported was conducted in several areas. The turned tire test data was completely analyzed and predictive equations incorporated into the turning program. A limited parametric study was conducted for three classes of vehicles to calculate wheel force ratios as functions of runway width required. A multipass test program was conducted at the Army Engineers Waterways Experiment Station to measure the response of rolling and braked tires in alternating paths. The data was reduced and predictive equations evolved from rut depths as a function of first pass response and subsequent path and braking. Limited start-up force data were examined to determine a preliminary estimate of start- up drag ratios. A soft tire/soil computer program was developed to study roughness effects.

Landing gear construction

Abstract: In a trailer landing gear assembly having a housing secured to a trailer and a foot adapted to engage the ground, attachment means for attaching an extension-retraction assembly to both the housing and the landing gear foot by respectively deforming the landing gear housing and the landing gear foot so that the deformations created support the axial load between the extension-retraction assembly and the landing gear. An axle secured to the downwardly depending end of the extension-retraction assembly is rotatably received in a pair of registering apertures formed in the landing gear foot. Each aperture in the landing gear foot is deformed to form a cylindrical portion coaxial with the aperture and integral with the foot so that the cylindrical portion supports the vertical load between the landing gear foot and the extension-retraction assembly. Similarly a gear base plate forms the attachment means between the upper end of the extension-retraction assembly and the landing gear housing. The gear base plate is received within the housing and includes a flange portion adjacent the interior of the housing. The housing is indented around the flange portion of the gear base plate so that the inward projections formed by the indentations overlap and secure the base plate flange portion to the housing. The projections then function to support the vertical load between the extension-retraction assembly and the landing gear housing.

Landing impact studies of a 0.3-scale model air cushion landing system for a Navy fighter airplane

Abstract: An experimental study was conducted in order to determine the landing-impact behavior of a 0.3-scale, dynamically (but not physically) similar model of a high-density Navy fighter equipped with an air cushion landing system. The model was tested over a range of landing contact attitudes at high forward speeds and sink rates on a specialized test fixture at the Langley aircraft landing loads and traction facility. The investigation indicated that vertical acceleration at landing impact was highly dependent on the pitch angle at ground contact, the higher acceleration of approximately 5g occurring near zero body-pitch attitude. A limited number of low-speed taxi tests were made in order to determine model stability characteristics. The model was found to have good pitch-damping characteristics but stability in roll was marginal.

An investigation of the increase in vortex induced rolling moment associated with landing gear wake

Abstract: Flight tests were conducted to verify the results found in ground base facilities of the effect of span lift load variation as well as the vortex attentuation of the high energy jet engine exhaust through proper thrust programming. During these flight tests a large increase in vortex strength was experienced as a result of extending the landing gear. Tests in the Langley Vortex Research Facility indicate that the wake produced by the landing gear may possibly form an aerodynamic endplate or reflection plane at the inboard edge of each inboard flap which increases the effective aspect ratio of the flap and thereby increases the strength of the flap outer edge vortex.

Turnout landing gear array carrier for high-wing aircraft

Abstract: The landing gear units for a high-wing aircraft are retractable into a single elongated carrier, which in turn revolves at a midpoint about a vertical axis in the fuselage. When deployed the carrier extends transversely outwardly from opposite sides of the fuselage to position the landing wheels in a transverse array. When stowed, with the wheels retracted into the carrier, the carrier is rotated into a longitudinal notch in the bottom of the fuselage.

State‐of‐the‐art in non‐aviation ship helicopter operations

Abstract: Results of tests to develop maximum day/night launch and recovery envelopes of the USS Bowen in January 1974, for the SH-2F helicopter show that helicopter hauldown equipment will probably not be needed to land in Sea States 5 and 6. Results of the USS Bowen tests (which included an instrumented ship and helicopter, and measurement of wave height and statistical analysis of ship motion) will be presented. The results will be related to future ship design requirements for Hauldown, Securing, and Traversing (HST); Stabilization; Lighting and Landing Aids; and Landing Gear and Dock Strength Requirements.

A Monte Carlo analysis of the Viking lander dynamics at touchdown

Abstract: The performance of the Viking lander has been evaluated by using a Monte Carlo simulation, and all results are presented in statistical form. The primary objectives of this analysis were as follows: (1) to determine the three sigma design values of maximum rigid body accelerations and the minimum clearance of the lander body during landing; (2) to determine the probability of an unstable landing; and (3) to determine the probability of the lander body striking a rock. Two configurations were analyzed with the only difference being in the ability of the primary landing gear struts to carry tension loads.

An experimental simulation study of four crosswind landing gear concepts

Abstract: An experimental investigation was conducted in order to evaluate several crosswind landing-gear concepts which have a potential application to tricycle-gear-configured, short take-off and landing (STOL) aircraft landing at crab or heading angles up to 30 deg. In this investigation, the landing gears were installed on a dynamic model which had a scaled mass distribution and gear spacing but no aerodynamic similarities when compared with a typical STOL aircraft. The model was operated as a free body with radio-control steering and was launched onto a runway sloped laterally in order to provide a simulated crosswind side force. During the landing rollout, the gear forces and the model trajectory were measured and the various concepts were compared with each other. Within the test limitations, the landing gear system, in which the gears were alined by the pilot and locked in the direction of motion prior to touchdown, gave the smoothest runout behavior with the vehicle maintaining its crab angle throughout the landing runout.

A Study of the Effects of Braking on Drag Force and Sinkage

Abstract: : In modern warfare it may be necessary to airlift men and supplies into areas of operations where airfields do not exist, are too few, or are too far away for proper support operations. It is suggested that cargo aircraft land on unsurfaced runways with only minimum preparation. This requires landing gear designed to withstand the drag force and wheel sinkage associated with soft soils. To determine the effect of braking on drag force and sinkage, and to ascertain the feasibility of scale modeling the equipment involved, braked wheel tests were conducted at low forward speed in a desert sand environment, using specified tires. The results are analyzed.