GB539390A - Improvements in retraction and extension arrangements for aircraft components and accessories - Google Patents

Abstract

539,390. Retractable aircraft undercarriages. DOWTY EQUIPMENT, Ltd., (formerly AIRCRAFT COMPONENTS, Ltd.), and BURKE, P. W. Feb. 1, 1940. Nos. 2007 and 2460. [Class 4] A retractable aircraft component such as an undercarriage leg is retractable against resilient resistance, the energy so accumulated being available for extending the component upon the release of locking means, and for ensuring the engagement of means for locking the component in its extended position. A tail wheel mounting is shown comprising a pillar 3 pivoted to the machine at 4 and provided with a sliding cap 9 pressed upwards by a spring 15 to cause engagement of a projection 13 with a recess in the aircraft frame to act as a downlock. A hydraulic jack 5 is connected between a lug 8 on the cap 9 and a fixed pivot 4a. When the jack is contracted the projection 13 is first withdrawn and simultaneously a pin 10 on the cap moves down the straight part of a cam slot 11 formed in a fixed plate 12. Further contraction of the jack causes the leg to swing about the pivot 4 and the pin 10 to move along the slot 11 which is involute to the pivot 4 so that the spring 15 is compressed by inward movement of the cap, the energy so stored being sufficient to extend the pillar when the jack is opened to exhaust. A trailing wheel is carried by a pivoted arm 18 controlled by a shock absorber 22 connected to a sleeve 21 rotatable in the pillar 3, the sleeve 21 having a cam 25 co-operating with a cam 26 which can slide without rotation against the thrust of a spring 27 so as to control deviations of the wheel from the central plane. According to the first Provisional Specification the spring 15 may be compressed by a link connected to a crank offset from the retraction pivot, the link passing through the dead centre position during the course of retraction so that during its later stages, retraction is assisted by the spring.