GB739598A - Improvements relating to aircraft undercarriage steering mechanism - Google Patents

Abstract

739,598. Aircraft undercarriages. DOWTY EQUIPMENT, Ltd., and THARRATT, A. March 25, 1954 [March 25, 1953], No. 8284/53. Class 4. In an aircraft retractable nose-wheel or tailwheel mounting having a wheel-carrying column mounted rotatably in a retractable leg and including piston-and-cylinder mechanism operative between the leg and the column for steering the mounting when the aircraft is ground-borne, and for centering the mounting when the aircraft is air-borne, the retractable leg comprises a central tubular support 4 and side arms 5, 6 united by a cross beam 7, the support 4 carrying a rotatable wheel-carrying column 11. The beam 7 carries an arm 16 which, with the arm 6, forms a fixed connection for a piston and piston rod assembly 14, 15, 18, the rod 14 being of smaller diameter than the rod 15. A cylinder 17 is slidably mounted on the assembly to form with the piston 18 two chambers 19, 20 and it has an arm 21 connected by a link 22 to a further arm 12 secured to the column 11. An auxiliary cylinder 27 is secured to the underside of the cylinder 17 and parallel therewith, the interior of the cylinder 27 being in direct communication with the chamber 20 and the piston rod 31 being arranged to abut, when extended, on a stop face 33 on the crossbeam 7. Pressure fluid is passed to the chambers 19, 20 through conduits 23, 24 and apertures 25, 26 in the respective piston rods 14, 15 and from the chamber 20 to the single-acting jack 27, 31. Because of the different diameters of the piston rods 14 and 15 the chamber 20 is smaller than chamber 19 and the effective cross sectional area of cylinder 27 is such that the combined cross sectional areas of chamber 20 and cylinder 27 is greater than the area of chamber 19. The fully extended length of the jack 27, 31 is such that, if after take-off, of the aircraft, the cylinder 17 is displaced either to the right or left of its central position on the piston rod assembly as viewed in Fig. 2, the admission of pressure fluid to the chambers 19 and 20 and the jack 27 will cause the rod 31 to become fully extended and abut on the face 33 and either force the cylinder 17 to the left to its central position or to limit the movement of the cylinder to the right when the central position is reached, thereby ensuring that the undercarriage is always centred before retraction.