919,677. Grounded aircraft trainers; vehicles supported by gaseous cushions. DEL MAR ENGINEERING LABORATORIES. Nov. 16, 1961 [Feb. 16, 1961], No. 41124/61. Class 4. Apparatus for training in piloting of an aircraft which can hover, comprises such an aircraft coupled to a mobile base by means comprising rigid members jointed together so as to permit the attitude of the aircraft relative to the base to alter, whilst constraining the mobile base to follow all horizontal movements of the aircraft, the base being able to resist being turned over by the aircraft. In Fig. 1, a helicopter comprising a seat 10, main rotor 24, engine 12, tail rotor 27, and conventional collective and cylic pitch levers, throttle control, and pedals 32, is mounted by a ball joint 66 near its centre of gravity, on a support 35 slidable and rottable in a pedestal 58 on a base 34. The base may move on castors or, as , shown, may form a square plenum chamber supplied with compressed air by fans 52 driven by engines on the base, so that the whole apparatus is supported off the ground, and can move horizontally on application of cyclic pitch by the trainee. The helicopter can pitch and roll relative to the base, and complete rotation in azimuth and limited vertical movement are permitted by relative movement of support 35 and pedestal 58. Limit switches 132 and 133 on the pedestal operate lights 130, 131 in front of the trainee to show when the upward or downward limit of movement has been reached. The helicopter may be unable to lift the base clear of the ground cushion, or stops may be placed to limit the collective pitch or throttle setting to prevent take-off. Rotation in azimuth or vertical movement may be preventable by the insertion of pins in the pedestal, see Figs. 5 and 6 (not shown). Loss of air from the plenum chamber may be reduced as in Fig. 3, where the four side walls 40 of the chamber are hollow, and each contain a bar 42 having downwardly extending bristles 44 or skirts of plastic or elastomeric material deflectable by obstacles. Slots 45 in the bars work over bolts 45 through the walls, the bars being retractable into the walls on touching obstacles or the ground. Springs may urge the bars downwardly. Gas for the plenum chamber may be fed through the interior of support 35 from a compressor driven by engine 12, or from the engine exhaust. Castors 78 may be lowered by hand wheels 79 for ground manoeuvring when the gas supply to the plenum chamber is off. The base may be octagonal in plan, and be divided by radial partitions into sight separate plenum chambers. Outriggers 55, Fig. 1, with castors 56, prevent overturning of the base. Automatic stabilization signals in pitch, roll, and yaw channels may be added to the trainee's command signals, and the composition of these signals may be varied to alter the apparent control and stability characteristics of the helicopter as they appear to the trainee, see Figs. 8-10 (not shown).
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