GB878385A - Multi purpose aircraft landing gear with wheels in tandem - Google Patents

Abstract

878,385. Equalizing load on wheels; hydraulic shock absorbers. RECHERCHES ETUDES PRODUCTION S.A.R.L. July 15, 1959 [Sept. 3, 1958; Sept. 10, 1958], No. 24389/59. Classes 108(2) and 108(3). [Also in Group XXXIII] An aircraft tandem landing gear comprises two cranked parallel levers 1 and 8, Fig. 4, pivotally mounted on parallel axles A1, A2, an arm of each lever carrying a wheel, and the other arm of each lever being coupled to a movable member of a shock absorber, the body 9 of which, with the axles A1 and A2, is fixed to the aircraft, the two movable members and the body of the shock absorber forming one or more communicating cavities, the volume of which decreases when the wheels touch down together or separately, and which are filled with oil and communicate through a narrow orifice with one of two chambers into which a cylinder is divided by a free piston, the one chamber being filled with oil and the other with compressed air. In Fig. 4, the wheel carrying arm of lever 8 contains a normally vertical castoring axis X-X, two elastic members 43 (one shown) one each side of the axis X-X centring the wheel when not on the ground. Fig. 2 shows a section of the shock absorber. The body 9 contains a piston 11 with a hollow rod 12 coupled by a connecting rod 10 to lever 1. A cylinder 13 formed on piston 11 contains a piston 16 with a hollow piston rod 15 coupled by connecting rod 17 to lever 8. The interior of the hollow rod 15 is divided into two chambers 19 and Q by a piston 18. Chamber 14 formed between rod 12 and body 9 communicates with chamber C formed in piston 13, through a valve D. Chamber C communicates with the annular space H between rod 15 and cylinder 13 through an orifice J, and with chamber 19 through a valve G. These chambers are filled with oil, and chamber Q with compressed air. Shoulders 21 on cylinder 13 and 22 on rod 15 abut on to a slidable sleeve K when the wheels are fully extended. When the wheel on lever 1 comes under load, or increased load, piston 11 moves outwardly. Chamber 14 decreases and chamber C increases in volume, there being a nett decrease. Oil thus flows through valves D providing damping, into chamber 19, compressing the air in chamber Q to provide return spring action. When the wheel on lever 8 comes under load, or increased load, piston 16 moves inwardly, and oil flows from chamber C through valve G into chamber 19. The chambers are dimensioned so that the stiffness of the spring action is the same for each wheel. When the wheels do not move equally e.g. when the aircraft pitches on the ground, damping is provided by flow of fluid into and out of chamber H through orifice J. The shock absorber may also be used as a jack, to extend or retract the undercarriage or alter the height of the aircraft when on the ground, by connecting ports P and R, which are isolated during shock absorber action, to a source of fluid under pressure and a reservoir. Specification 872,265 is referred to.