Faulty Air Conditioning System Cited As Contributing Factor

A Qantas 737 flew far below minimum altitude on a flight from Perth to Canberra last year in part because of co-pilot fatigue, according to the ATSB -- and the aircraft's air conditioning system was also a factor.

The situation could have been much worse, according to investigators.

It happened July 24th, when the flight crew, holding for the approach south of Canberra, was alerted to the altitude problem by an enhanced proximity warning device just installed on the aircraft. The ATSB said the flight was at 5,850 feet when the minimum safe altitude was 7,400.

Investigators stressed the flight was never in peril and that the crew was already reacting to the situation when the alarm sounded.

"The aircraft was fitted with an enhanced ground proximity warning system, which detected the aircraft's proximity to the terrain and provided the crew with a caution terrain message to which the crew responded by climbing the aircraft to 6,500 feet," the report said. It was quoted by the Australian AP.

The report found that the copilot, who suffered from fatigue at the time, had entered the wrong data into the aircraft's flight management system. The problem was compounded by the fact that short-staffed controllers weren't monitoring radars at Canberra.

The ATSB report cited all those factors as contributing to the incident -- stressing that it wasn't serious, but could have been.

"It was an incident because there were a number of issues involved, but it was not classified as a serious incident," said ATSB Deputy Director Alan Stay.

As a result of the incident, Stray said Qantas had modified its hold procedures south of Canberra, requiring aircraft to fly at higher altitudes. The chart manufacturer involved also pledged to more clearly publish holding limits to reduce the chance of misinterpretation.

FMI: www.atsb.gov.au