Taiwanese investigators say a Far Eastern Air Transport Boeing 757's unnecessarily fierce response to a traffic collision-avoidance system descent instruction injured 20 people on board, four seriously.

Three passengers suffered broken bones and a fourth was left unconscious by the sudden dive, which exceeded 12,000ft/min (60.9m/s) for a brief time and subjected the jet to forces ranging from negative 1.06g to positive 2.48g.

The 757 crew was responding to a conflict at 34,000ft (10,370m) with a Thai Airways Boeing 777-300 while descending toward Jeju, South Korea, on 16 November 2006.

Taiwan's Aviation Safety Council says the evasive action was "excessive" and a correctly executed standard TCAS descent, maintaining 1,500ft/min, would have sufficed. Although the 757's crew had illuminated the seat-belt sign shortly before the encounter, several passengers were still moving around the cabin.

Source: Flight International