GB537464A - Improvements in automatic locking devices for aircraft undercarriages - Google Patents

Abstract

537,464. Aircraft undercarriages. SOC. OLAER (SOC. ANNON. DE. MATERIEL OLEOPNEUMATIQUE), and MERCIER, J. Sept. 1, 1939, No. 25137. Convention date, Dec. 6, 1938. [Class 4] Relates to the control of the hydraulic jack or jacks for operating the undercarriage of an aircraft in such a manner that while the undercarriage may be lowered at all times, it can be retracted only after the weight of the aircraft is removed therefrom on taking-off. As shown, a wheel support 3 is mounted elastically in a leg or part 2 adapted to be operated by a double acting hydraulic jack 4 provided with fluid through pipes 5, 6. A non-return valve 7 is arranged in the pipe '5 and, when the aircraft is in the air and the part 3 is freely projected from the leg 2 of the undercarriage, a rod 12 connected to a valve 11 maintains a byepass connection 9, 10 across the valve 7 in the pipe 5. When the part 3 moves upwardly with respect to the part 2 where the aircraft is on the ground, the valve 11 closes the passage between the pipes 9, 11, and, while fluid can pass the valve 7 to operate the jack to lower the carriage, the jack cannot operate to retract it. In a modification, the valves 7, 11'are replaced by a normally-open non-return valve in the pipe 5 which is rendered operative by the deformation of the undercarriage when the aircraft rests upon it. The valve means for rendering the jack inoperative to retract the undercarriage when it is supporting the aircraft may be operated by a flexible or electromechanical distant control device actuated by the deformation of the undercarriage. A dash-pot or delay-action relay may be employed to maintain the undercarriage in the lowered position for a certain time after taking- off.