GB873632A - Improvements in and relating to arresting gear for aircraft - Google Patents

Abstract

873,632. Aircraft arrester gear. BAAS, E. Jan. 3, 1958 [Jan. 28, 1957], No. 275/58. Class 4. Aircraft arresting gear comprises a net or cable stretched across the runway, two series of hydraulic piston and cylinder assemblies located one on each side of the runway, adjacent assemblies being connected piston to cylinder, the effective diameters of the pistons of the assemblies of each series being graduated, and one end of each series being anchored, and block and tackle connected between the other end of each series and the net or cable, so that during an arrest, the assemblies of each series come into operation successively by reason of their graduated diameters, to exert an increasing arresting force. As shown, each end of a net 10, Fig. 1, is connected by lines 11 to a cable 5 wound on and secured to a two-sheaved block and tackle device 4, one sheave of which is fixed to a base plate 9, and the other sheave of which is attached to the piston rod of a hydraulic damping cylinder 1, itself attached to the piston rod of a hydraulic damping cylinder 2. The latter is attached to the piston rod of a hydraulic damping cylinder 3 secured to the base plate 9. The movable sheave and the cylinders 1, 2 and 3 are guided for movement parallel to the length of the base plate by rails 8. The base plate is pivoted on a vertical pivot 16 to a foundation 15 below ground level, Fig. 3, and provided with arcuate rails (not shown) co-operating with rollers 17 on the base plate to allow movement about pivot 16 to accommodate lateral movement of the cable 5. When an aircraft runs into the net, the cable 5 contracts the block and tackle and extends the hydraulic cylinders, which are of increasing effective diameter in the order 1, 2, 3. The cylinders of each series are connected to discharge through a common pressure relief valve into a reservoir, so that the pressures in all of them are the same. The assembly of smallest effective diameter will thus extend first, when the cable tension reaches a certain value. The cable tension must then reach a higher value before the assembly of next highest effective diameter begins to extend, and so on. Fluid is pumped from the reservoir back to the cylinders for recovery. Should the aircraft not engage the net centrally, the base plates 9 will be turned about their pivots 16, and the braking forces required from the two series will no longer be equal. Turning of the base plates about their pivots is therefor arranged to operate relays to effect the appropriate adjustments to the pressure relief valves.