Patent GB-895022-A (GB)
Title: Improvements in or relating to aircraft undercarriages
Inventor: ORLOFF GEORGE
IPC: B64C25/66
Filed: 1958-02-12
Abstract: 895,022. Aircraft undercarriages. DOWTY ROTOL Ltd. Feb. 12, 1959 [Feb. 12, 1958], No. 4653/58. Class 4. An aircraft undercarriage comprises a landing leg having a skid, ski, or the like, mounted thereon, and arranged to carry one or more wheels, the skid being mounted on the leg by a retraction linkage the joints of which define a polygon and the members of which are relatively rotatable by means of a jack so that the skid can be extended and retracted relatively to the wheel, the jack being disposed within the polygon. In Fig. 1, a bogie 13 is pivoted at 12 to a retractable or non-retractable oleo-leg 11. The longer arms of two L-shaped links 27, 26 are pivoted to the bogie at 14a, 15a, concentrically with wheels 14, 15. There are wheels 14, 15, either side of the bogie and certain of the links shown are actually spaced pairs of links. A link 28 extends between pivots 29, 30, on the shorter arms of links 27, 26. The skid is in two parts 43, 47, pivoted at 46, the former part being suspended from links 27, 26, by links 37, 38, pivoted to links 27, 26 at 39, 40, and to the skid at 41, 42. A triangular plate 22 is mounted on pivot 15a, and an oleo-pneumatic damper 18 extends between pivot 21 on the plate and pivot 19 on the leg 11. Link 48 extends between pivot 50 on the plate and pivot 49 on skid part 47, and link 51 extends between pivot 50 and pivot 42. A skid retraction jack 33 extends between pivot 36 on the bogie and pivot 34 on link 28. The skid is shown extended in Fig. 1 for manoeuvres on soft ground, extension being ensured by contraction and locking of jack 33. Vertical shock-absorbing movement of the skid is damped by connection to the air spring 18 through link 51 and through rotation of plate 22 about pivot 15a, the skid moving on the parallel links 37, 38. On extension (and locking) of jack 33, the skid is raised to the inoperative position of Fig. 3, link 48 folding the rear skid part 47 as shown. In this position, the air spring 18 is free to expand, until pivot 21 abuts a seating on an extension 24 of the bogie. On take-off, from wheels or skids, the air spring expands freely, tilting the bogie about pivot 12, to facilitate stowage of the undercarriage, and to ensure that on touchdown, the rear wheels make contact first, and part of the initial shock is absorbed by compression of the air spring 18 as the bogie levels out. In Fig. 4, the undercarriage leg is in two telescopic parts 111, 112 incorporating a shock absorber and contracted on retraction in known manner. A scissors linkage 115 prevents relative rotation of the parts. A plate 117 is fixed to the leg by mounting on a twin wheel axle 113 and on one pivot 116 of the scissors linkage. A link 127 is suspended from the leg by pivotal connection at 126 to a link 125 on axle 113, and at 120 to a link 119 pivoted at 118 to plate 117. A rigid skid 130 is suspended from link 127 by parallel links 128, 131. An air spring 134 extends between a pivot 132 on the skid and a pivot 136 on the leg. A skid retraction jack 122 extends between a pivot 124 on link 125, and pivot 120. In the skid extended position shown, jack 122 is contracted and locked. Shock absorbing movement of the skid takes place on the parallel links 128, 131, and is damped by the air spring 134. To retract the skid to its inoperative position, jack 122 is extended and locked. The skid is thereby raised and rotated anti-clockwise through about 105 degrees, by distortion of the quadrilateral of links 117, 125, 127, 119, see Fig. 5 (not shown). In this position, an abutment 137 on link 119 lies opposite the lower link of the scissors linkage 115, and acts as a stop.