Qantas warns pilots of potential dangers of overspeed manoeuvre

Qantas has warned its pilots of the potential dangers of a common manoeuvre that left two cabin crew seriously injured.

Qantas Boeing 737 aircraft line up in Melbourne.

Qantas has warned pilots of the potential dangers in a manoeuvre that was used on a flight where two members of the cabin crew were injured, with one fracturing her leg.

The nation’s transport safety operator today said that Qantas had issued a safety information notice after the accident.

The Australian Transport Safety Bureau also said that aircraft manufacturer Boeing was considering a revision to guidance on “overspeed” in the flight crew manual for the Boeing 737.

In March last year, the Qantas Airways B737 carrying 177 passengers from Perth was descending towards Canberra when, at 22,000 feet, there was an abrupt change in the direction of the wind that ultimately led to higher airspeed.

To avoid an overspeed, the pilot did what was a common practice for Qantas B737 flight crews by applying control column force to over-ride the autopilot.

While it was expected that the autopilot would revert to a different mode and raise the aircraft’s nose, in fact the autopilot unexpectedly disengaged.

The cabin crew member who was standing in the rear galley “felt the cabin floor drop and then quickly come up,” the ATSB report released today said.

“The force due to the aircraft’s movement resulted in the cabin crew member fracturing her leg,” the report said.

Another cabin crew member fell and banged her head on a trolley.

On its website, the ATSB said the pilot’s manoeuvre was “understandable, and consistent with previous responses of other flight crew in similar situation”.

“Modification of the autopilot, however, had inadvertently left the aircraft vulnerable to this type of scenario,” the statement said.

The flight deck and centre consol controls of the 737-800. Picture: Charles Brewer

Qantas did an internal investigation and found that in the last six years, there had been 47 overspeed events involving its B737-800 aircraft. Of these, the manoeuvre had been used 20 times.

The move was part of initial B737 training.

“The common practice of flight crews to prevent an overspeed was not a documented Qantas or Boeing procedure,” the ATSB report found.

“As a result, the potential consequence of this practice was not considered when the autopilot was modified.”

Qantas has since told flight crew in a safety information notice that during an overspeed or it is impending, it’s preferable to keep the autopilot engaged.

Boeing is considering revising its overspeed guidance in the training manual for the 737 to indicate a preference for the use of speedbrakes to prevent overspeed.

“The intervention by the pilot flying to prevent the impending overspeed was understandable, and consistent with previous responses of other flight crew in similar situations,” the report found.

“However, as detailed in the Qantas safety information notice, when faced with an impending overspeed, abrupt pitch changes may have more adverse consequences than an overspeed event. The manufacturer’s preferred use of speedbrakes to manage increasing airspeed, removes the hazard associated with abrupt pitch changes.”