Autoland og contaminated runways - Eurocontrol video

Use of Autoland on Contaminated Runways

Autoland was originally devised to achieve approach and landing in poor visibility conditions, so it was focussed on the necessary approach and touchdown/de-rotation and not on the low friction surface case and certainly not on the variable asymmetries that, in reality, usually apply with this circumstance. In terms of the firmness of touchdown, autoland should do a reasonable job and this touchdown will also be in the touchdown zone. The typical range of autoland vertical speeds at main gear touchdown is normally considered to be in the range 2 - 5 feet per second/120-300 fpm - firm enough for the contaminated case. Although autoland de-rotation is optimised for comfort, it can be expected to take only 4 - 5 seconds for a larger aircraft, which should not be excessive. Thereafter, the case for keeping autoland engaged after it has been used for the touchdown may become more problematic. Whilst system certification testing does consider the cases of asymmetry of braking and reverse thrust, it is impossible to consider the range of surface friction asymmetry which is likely to be encountered during the landing roll on a contaminated runway. And it is certainly the case that autoland is not designed for the situation where directional control issues may become more evident as speed reduces, rather than less so as with a normal landing runway surface. Many aircraft type procedures will therefore advise considering an autoland with manual reversion after nose landing gear contact.

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