| 摘要 |
<p>A warning device, for a helicopter with a tail rotor and a mechanical protection device therefor, for giving during emergency power-loss landings a flare signal to the pilot to initiate flare followed by a tail/ground contact warning signal when the helicopter tail approaches too closely the ground. The warning device comprises in one embodiment a height-finder with two switchable transmitting/receiving antennas mounted at the helicopter tail to produce respectively, when switched into use, a height-finding beam backwards and obliquely downwards or forwards and obliquely downwards. Height signals obtained initially using antenna 40 are processed by computing means and initiate at a predetermined initial flare altitude a flare warning signal whereafter height signals from antenna 26 are used to determine the sink rate of the tail and in dependence upon this sink rate and the instantaneous height, a warning signal is initiated if this corresponds to a predetermined relative relationship. The higher the sink rate, the greater is the height at which the tail/ground contact warning signal is initiated and vice versa.</p><p>In a second embodiment, the height-finder uses a single beam the main axis of which extends backwards and obliquely downwards but of which the lobe pattern is broad enough such that vertical height measurement can be made with the helicopter in both the flare and pre-flare situation.</p> |
