GB706351A - Improvements in or relating to braking systems for aircraft - Google Patents

Abstract

706,351. Aircraft brakes. DUNLOP RUBBER CO., Ltd. June 26, 1952 [July 25, 1951; April 1, 1952], Nos. 17582/51 and 8230/52. Class 103(1) [Also in Group XXXIII] In a fluid pressure brake control system for aircraft of the type described in Specifications 676,708 and 683,490 wherein the braking pressure on the wheels is regulated to prevent skidding by reference to the speed of an inertia flywheel, rotated by the aircraft wheels, and in which means are provided to prevent the brakes being applied until the wheels have been rotated by the first contact with the ground, the brakes are automatically applied when the undercarriage is raised and the fluid pressure control line closed, and the brakes are automatically released when the undercarriage is lowered. In the system shown in Fig. 4, pressure is supplied from a pump through a non-return valve 38 to an accumulator 39 and a reducing valve 40. From the reducing valve 40 one line leads to a differential control valve 41, operated by the pilot, and thence to a conduit 25 associated with the inlet valve of control valve mechanism as described in Specification 683,490. In addition a line is led to a sequence valve 42, connected also to a line leading to the exhaust valve 23 of the automatic control valve unit and having an exhaust outlet from a chamber 48. A plunger 44 at the base of the sequence valve is adapted to be moved by pressure applied to a double acting jack 57 which raises or lowers the undercarriage. As shown in Fig. 4, the latch member 7 is in the " uncocked " condition corresponding to the state in which the landing wheels have been rotated after touching down. The retraction side of the undercarriage jack 57 is connected to exhaust or liquid reservoir by cock 58 so that the piston 44 of sequence valve 42 is at its bottom position. In this condition an inlet valve 55 is shut and an exhaust valve 52 open so that the exhaust valve 23 of the skid control valve unit is also free to exhaust to atmosphere as necessary under the action of the automatic inertia control unit. On taking off the pilot operates the four-way cock 58 to retract the under carriage. Pressurizing the retraction side of jack 57 also pressurizes the piston 44 of valve 42 so that the exhaust valve 82 is closed and valve 55 opened. Under these conditions pressure from the reducing valve 40 passes through chambers 54 and 49 to operate the piston 11 for recocking the latch element 7 so that once again the brakes cannot be applied until the wheels have been run up to speed. Pressure is also passed through exhaust valve 23 and chamber 18 to apply the brakes to the wheels, now in the retracted state, to prevent them spinning for the duration of the flight. The arrangement including a reducing valve 40 and sequence or relay valve 42 is necessary since the pressure for operating the retraction gear are generally too high to be suitable for use directly on the wheel brakes. In another arrangement, the piston 44 of the valve unit 42, is operated by a direct mechanical linkage.