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Aviation History
1985
1985 - 2361.PDF
Far left A BAe test pilot demonstrates feasibil ity by hovering a Harrier underneath a mockup of the SkyHook head. Left An artist's impres sion of a vessel operating SkyHook. Below left A Harrier in the docking cradle. Below The pilot's hover sight. In the first diagram the aircraft is too low, correct in azimuth, but too close. In the second the aircraft is slightly aft of optimum position, still within capture window, at the correct height, and the correct distance out. In the third diagram the aircraft is at opti mum position the ability of the crane to stabilise only 0-05 per cent of the time. But the clear ance between the crane and the aircraft, say the designers, is sufficient to render the chance of a collision negligible—less than the chance of engine failure while in the hover over the deck, and that has never happened. Automatic arrest Capturing the aircraft is done through a series of manoeuvres. First, the pilot posi tions the aircraft within the lOft-cube capture window. A simple parallax sight attached to the crane head guides the pilot in. As soon as the aircraft is within the capture window the robotic IR system senses its presence and the lock-on jack is guided to engage and lock on to the aircraft's pickup probe. The whole system works automatically—there is no crane operator. The system being proposed by British Robotics Systems uses an IR image sensor mounted on the head. The sensor views a pattern of IR-absorbing patches on the aircraft's upper surface and, from a knowledge of their size and relationships, calculates the aircraft's position relative to the crane head. This data is converted to instructions to the lock-on jack to engage the pick-up probe. The pilot then reduces power, but main tains the aircraft's attitude using the reaction control system. The lock-on jack senses the unsupported weight and pulls the aircraft up into the docking cradle, thus rigidly capturing the aircraft. An internal lock is then engaged and the aircraft can be idled, if it is just being refuelled, or shut down if it is to be swung inboard and lowered either on its under- FLIGHT International, 3 August 1985 ---j! Hover sight rHI Aircraft low Correct in azimuth TOO CLOSE 5 Aircraft slightly aft of optimum position, still within contact window Correct height Correct distance out Note: pilot formates A/C on hover sight aiming to align arrows on marker 25
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