Computer-Related Incidents with Commercial Aircraft

The Sydney A320/DC10 Incident

21 August 1991

Synopsis Sydney Airport was conducting Simultaneous Runway Operations on intersecting Rwys 34 and 25. A Thai Airways International DC-10 was landing on Rwy 34, and at the same time an Ansett Australian A320 on Rwy 25. Landing instructions to the DC-10 included that it stop short of the intersection. The A320 captain, who was not Pilot-Flying, judged that the DC-10 might not be able to comply, and initiated a successful go-around. The enquiry discovered "anomalies [....] with regard to the attitude control inputs on the A320, and in the braking system of the DC-10." In particular, the A320 DFDR recorded neutral and nose-down control inputs from the co-pilot, after he thought he had relinquished control to the captain (on the latter's go-around request); and there was an autobrake malfunction on the DC-10 that wheel braking on the DC-10, which should have occurred 4 seconds after deployment of ground spoilers, didn't commence until 23 seconds after spoiler deployment. I include some excerpts from the report B/916/3032 of the australian Bureau of Air Safety, forwarded to me by Robert Wilson of The Australian newspaper. My thanks to Robert for bringing this incident to my attention.