Recent Progress in All-Weather Landing Techniques

Extract

It was quite a few years ago that BLEU showed the feasibility of automatic landing. In the intervening period, considerable development has taken place. Before we look at the recent developments, it is worthwhile reiterating the early findings of BLEU. They showed that an aircraft could be landed automatically using an extension of a standard autopilot plus radio altimeter and an autothrottle system. In the pitch plane the aircraft is controlled on the glide slope as usual, but continues to a low height (100ft-150 ft) (30-36 m); a short period of constant attitude flight follows to about 50 ft (15 m) when the autopilot switches to flare and the throttles are closed at a steady rate. The control for the flare comes from the radio altimeters and an exponential flight path is aimed for. The rate of descent is kept to one-fifth of the height. In the lateral plane the control is purely an extension of the usual localiser control. Originally it was intended to use leader cable, but this had added complications of installation, and as techniques developed the localiser was found to give adequate performance.