Aircraft Undercarriage Research Articles

Efficient multidisciplinary modeling of aircraft undercarriage landing gear using data-driven Naïve Bayes and finite element analysis

Efficient multidisciplinary modeling of aircraft undercarriage landing gear using data-driven Naïve Bayes and finite element analysis

Uncertainty and Sensitivity Analysis of Bifurcation Loci Characterizing Nonlinear Landing-Gear Dynamics

A methodology is developed to efficiently, yet accurately, determine the uncertainty bounds of the bifurcation loci of nonlinear dynamic systems subjected to parametric variations. The chosen approach makes use of numerical continuation, higher-order singular-value decomposition, and surrogate modeling. The technique is demonstrated on a representative model of an aircraft undercarriage, where the effect of uncertainty in the structural parameters is propagated onto the prediction of the conditions for the onset of shimmy. Comparison with numerical integration results demonstrates the accuracy of the methodology.

Thermo-Mechanically Controlled Processed Ultrahigh Strength Steels

A low-carbon, titanium and niobium (Ti-Nb) bearing and a low-carbon titanium, niobium and copper (Ti-Nb-Cu) bearing ultra high strength steel have been thermo-mechanically processed on a laboratory scale unit. Evolution of microstructure and mechanical properties of the above air cooled steels have been studied at different finish rolling temperatures (FRTs). Microstructural characterization reveals largely a mixture of granular bainite and bainitic ferrite along with the precipitation of microalloying carbide/carbonitride particles and/or Cu-rich precipitates. (Ti-Nb) bearing steel yields higher yield strength (1114-1143 MPa) along with higher tensile strength (1591-1688 MPa) and moderate ductility (12-13%) as compared to (Ti-Nb-Cu) bearing steel having yield strength (934-996 MPa) combined with tensile strength (1434-1464 MPa) and similar ductility (13%) for the selected range of 850-750°C FRT. Due to higher strength-ductility combinations, these present investigated steels can be regarded as the replacement material for ballistic applications as well as other sectors like defense, pipeline, cars, pressure vessels, ships, offshore platforms, aircraft undercarriages and rocket motor casings etc. Key words: Thermo-mechanical controlled processing, ultra high strength steel, microstructure, mechanical properties.

Research on modeling and fuzzy control of magneto-rheological intelligent buffer system for impact load

So far the magneto-rheological (MR) effect mechanism of MR damper has not been known completely, especially in the impact load, and the problem becomes more complicated and difficult for analyzing. A set of characteristic tests and parameters’ identification are made to the MR damper by the experimental platform. The dynamical model of the damper is constructed based on the Bingham plastic model, and the buffer control strategy of aircraft undercarriage based on MR technology is established. Finally, the fuzzy control algorithm is applied to the process of automatic control for landing buffer of aircraft undercarriage. The simulation results show that the proposed MR damper pulley buffer can effectively recognize the impact energy. The research has a better application in the engineering.

Research of the Key Technologies for Undercarriage Landing Buffer System

Abstract The research of undercarriage buffer system is one of the key Technologies for the design of aircraft. Especially in the phase of landing and taxiing, the role of aircraft undercarriage buffer system is to ensure the safety of aircraft landing and taxiing and to improve the comfortableness of driver's sitting. The writer lists several structure forms of aircraft undercarriage's bumper, recounts the key technologies and existing major problems of the design for the modeling, parameter optimization, control, simulation and experimental validation, and finally makes some discussions to the developing trend of the design for undercarriage buffer system.

Design and Evaluation of a Wireless Sensor Network Based Aircraft Strength Testing System

The verification of aerospace structures, including full-scale fatigue and static test programs, is essential for structure strength design and evaluation. However, the current overall ground strength testing systems employ a large number of wires for communication among sensors and data acquisition facilities. The centralized data processing makes test programs lack efficiency and intelligence. Wireless sensor network (WSN) technology might be expected to address the limitations of cable-based aeronautical ground testing systems. This paper presents a wireless sensor network based aircraft strength testing (AST) system design and its evaluation on a real aircraft specimen. In this paper, a miniature, high-precision, and shock-proof wireless sensor node is designed for multi-channel strain gauge signal conditioning and monitoring. A cluster-star network topology protocol and application layer interface are designed in detail. To verify the functionality of the designed wireless sensor network for strength testing capability, a multi-point WSN based AST system is developed for static testing of a real aircraft undercarriage. Based on the designed wireless sensor nodes, the wireless sensor network is deployed to gather, process, and transmit strain gauge signals and monitor results under different static test loads. This paper shows the efficiency of the wireless sensor network based AST system, compared to a conventional AST system.

Equipment

Aircraft undercarriages take a lot of punishment, and the wheel bearings have to be changed regularly to ensure that they continue to do their job properly.

The Complete Landing Gear

Aircraft undercarriage design involves the application and dissipation of energy within all the various mechanisms making up the complete gear. The functions of landing, taxying, retraction, lowering, steering and braking must be optimised such that each participating component plays its part in the processes. The gear must also be able to deal with emergencies such as rejected take‐off and the very high loads involved.

Machining Undercarriage Bogie Beams

To expand the capacity for manufacture of wide‐body aircraft undercarriages, Dowty Rotol has established a new £7.5 million machine shop at its Staverton, Gloucester works. Centre‐piece of this facility is a five spindle Droop & Rein gantry type copy mill supplied by Elgar Machine Tool Co. Ltd. of London.

Spray from aircraft undercarriages at high speed—a model investigation

The ability to operate when runways are flooded or slush-covered to some degree, must be demonstrated during the certification programme of any new civil transport aircraft. Failure to meet the requirements laid down will result in operating restrictions which may jeopardise the sales prospects of the aircraft. Most other types of aircraft will also have to operate occasionally in these adverse conditions.The main problems result from the spray generated at the wheels, and are engine malfunction due to spray ingestion and damage due to its impingement on the airframe. An associated problem is the packing of slush into ducts, flap cavities, undercarriage bays, etc, with the attendant risks of damage to internal systems and jamming of mechanical parts. There is also a large additional drag load on the aircraft, due to the displacement of fluid by wheels and to spray impact on the airframe: this increases roughly in proportion to the depth and effectively limits the slush depth that can be tolerated on the runway. For many aircraft this limit is little more than one centimetre.

The Salvage of Aircraft Undercarriages

THE routine maintenance of aircraft undercarriages is an important function whether the aircraft is operated by large or small airlines, and it is a fact that these costly items start wearing from the very first day they are installed. The amount of wear that takes place on an aircraft undercarriage depends very much on the type of work on which it is employed. It will be obvious that aircraft on short runs take‐off and land very frequently and consequently show signs of wear sooner than those on long distance flights. Regular maintenance to the undercarriage parts will no doubt be carried out from the time the aircraft is delivered, as specified under the maker's maintenance manuals, but there will come a time when the permitted amount of wear has taken place and the undercarriage must be overhauled.

Lockheed Undercarriage and Hydraulic System for the HFB.320 Hansa

A RESOUNDING British success in the export market, despite interne foreign competition, was achieved recently by Lockheed Precision Products Ltd. when they secured an order worth well over £200,000 for undercarriages and general hydraulic control equipment for the Hamburger Flugzeugbau HFB.320 Hansa business jet. The principal features of this air‐craft—including the reasons for the adoption of the novel sweptforward wing—were discussed in detail in the August 1964 issue of AIRCRAFT ENGINEERING (Ref. 1). Design and production of the undercarriage and hydraulics for the HFB.320 have been carried out at Lockheed's Liverpool factory with a drop test and development programme being conducted simultaneously at their Leamington research establishment. This co‐ordination of the Group's resources has made possible the delivery of the first sets of equipment in only nine months from the time of order. The following article deals solely with the aircraft's undercarriage and hydraulic system and their mode of operation.

Structural Design

THE structural design of the BAC One‐Eleven generally follows closely that of the Vickcrs Vanguard and the VC10†—involving the use of a considerable number of integrally‐machined components. As a short‐haul aircraft the average time per flight of the BAC One‐Eleven is expected to be of the order of 45 min. during which period full cabin pressure differential will be attained, speeds of the order of its design cruising speeds will be achieved and the undercarriage and flaps will be operated for take‐off and landing. Based on current estimations this involves a design aim of a minimum crack‐free life of 40,000 flights, landings and take‐offs —a much more severe requirement than that for the long‐range subsonic jets. Critical areas of the aircraft (undercarriage, flaps, tailplane and cabin pressure skins) are thus designed on fatigue considerations related principally to the number of flights made. The accent has therefore been placed on building a rugged structure which is easy to maintain and has a long service life. Small amounts of additional weight, properly disposed, can effect large improvements in the service life, particularly necessary on a short‐haul aircraft, and although weight saving is always of prime importance it must be balanced by other factors—especially in the primary structure.

British Patent Abridgements

An aircraft undercarriage comprises a retractable nose wheel unit N, which supports approximately 10 per cent of total aircraft weight and a main unit comprising a retractable leg C positioned in the mid‐part of the fuselage on its fore‐and‐aft centre line and two lateral legs O1,O2 each arranged for retraction into an engine nacelle at the tip of each wing. The legs of the main unit may be in transverse alignment or leg C may be forward of the transverse plane containing legs 01 and 02. Leg C is arranged to carry approximately 40 to 70 per cent of total aircraft weight whilst the remaining 20 to 50 per cent is divided between undercarriages 01 and 02.

U.S. Patent Specifications

An aircraft undercarriage of the tandem type comprising in combination: an undercarriage leg, a common axle journalled in the said leg, one arm fixedly connected to one end of the said axle and a second arm rotatably mounted on the other end of the said axle, stub axles mounted on the free ends of the said arms parallel to the said common axle of the latter and pointing in opposite directions, and wheels journalled on the said stub axles and having their centre planes alignment with one another.

Ground Loads on Aircraft Undercarriages at Touch‐down

THE most severe ground loads to which an aircraft undercarriage is subjected when landing usually occur during the fraction of a second following the instant of touch‐down. Generally, less critical ground loads occur during the landing run, e.g. due to the application of wheel brakes, turning or swinging of the aircraft, the wheels striking obstacles, unevenness of runway, etc.

Month in the Patent Office

An aircraft undercarriage comprises a four‐wheeled bogie, of which two of the wheels, 16, 17, are independently rotatable and are mounted on a common transverse axle 15 at the lower end of the undercarriage leg 13, the other two wheels 21, 24 being mounted in tandem in a fore‐and‐aft plane extending between and parallel to the wheels 16, 17, and being castorable and/or steerable. The wheels 21,24 are carried by brackets 18, 19 mounted on the axle 15 and provided with supplementary shock absorbers 26, 27 connected to a cross‐head 28 on the leg 13. Antishimmy devices may be provided for the castoring wheels, together with means for aligning them when the aircraft is airborne.

Roadability and Landing Ability in Aircraft Undercarriages

Roadability and Landing Ability in Aircraft Undercarriages

Theory of Shock‐Absorber Design

THE aim of this paper is to provide a survey of some of the principal theoretical considerations affecting the design of aircraft undercarriages.

Theory of Aircraft Undercarriages in Relation to Absorption of Initial Landing Impact

Many complex machines and mechanical systems have an ideal and abstract form which has been evolved from fundamental theory without reference to those engineering principles that are so essential in practice. Thus the heat engine has its Carnot cycle and the propeller its actuator disc. With these, and numerous other examples, the object is to provide a standard of reference, to give an ideal which can be approached but never reached and, most important, to indicate the fundamental limitations imposed by theory and prevent profitless investigations.