Patent GB-674237-A (GB)
Title: Improvements in or relating to retractable undercarriages for aircraft
IPC: B64C25/34
Filed: 1949-04-25
Abstract: 674,237. Aircraft undercarriages. ELECTROHYDRAULICS, Ltd., and PERDUE. J. April 4, 1950 [April 25, 1949; Aug. 10, 1949], Nos. 10958/49 and 20845/49. Class 4. A retractable undercarriage for aircraft comprises a resilient strut provided with bearing means adapted to be held in a fixed position to the aircraft when the undercarriage is lowered, a rigid bracing member of fixed length pivoted at one end to the aircraft and at the other to the resilient strut, guide means slidable in or pivoted to the aircraft and pivoted to the resilient strut and adapted to guide said strut during lowering and retraction of the undercarriage and means for raising and lowering the undercarriage, said bearing means and rigid bracing member transmitting substantially the whole landing loads of the undercarriage on to the aircraft. The undercarriage leg 1, which comprises a resilient strut 2 carrying landing wheels, carries a lug 3 to which is pivotally connected one end of a bracing member 4 pivotally secured at 6 to the aircraft structure. A retraction jack 8 is pivotally secured to the rod 4 and the aircraft structure and the upper end of the leg 1 is provided with trunnions 10 which slide in fixed slots 12. The trunnions 10 are formed on the ends of a cross shaft fast with the undercarriage leg and arms 13, fast with the cross shaft, are pivotally connected to further arms 15 pivoted at 17 to another cross shaft which carries at the midpoint of its length an arm 18 to which is connected a subsidiary jack 20. When the undercarriage is extended as shown in full lines the jacks 8 and 20 are substantially unloaded by landing or taxying loads since the leg is braced by the rod 4 and the in-line links 13, 15, though the jack 20 may be provided with internal locks to hold the links rigid. When the undercarriage is folded the various members occupy the position shown by the chain dotted lines. In a further embodiment, Fig. 4 (not shown), the slot 12 is dispensed with and the trunnions 10 seat in half bearings, the upper end of the leg 1 being connected to the aircraft structure by a pivoted link, the trunnions being held fast in the half bearings by a lock which is released by initial movement of the jack 44 through a lost motion connection. Further, the jack 8 is connected to the knee-joint of a pair of break links, the other extremities of which are respectively connected to the member 4 and the aircraft structure. A claw type uplock is provided to engage a pin on the wheel axle to hold the undercarriage in the retracted position. In a still further embodiment, Fig. 6 (not shown), the upper pivoted link used in the previously described embodiments to connect the upper end of the leg 1 to the aircraft is retained but the retraction jack 8 is pivotally connected at one end to the member 4 intermediate its ends and at its other end to the trunnions 10, the subsidiary jack and the external locks being omitted and the retraction jack being provided with internal locks. Electric actuators may replace the fluid pressure jacks described.