Reports fail to identify causes in separate Qantas incidents

Investigators in Australia remained baffled by two major incidents involving Qantas.

On Friday, the Australian Transport Safety Bureau issued interim factual reports into both the violent upset of QF Flight 72, an A330 operating last fall from Singapore to Perth on which some 70 passengers were injured (ATWOnline, Nov. 17, 2008), and the August explosion of an oxygen bottle that crippled QF Flight 30, a 747-400 flying between Hong Kong and Melbourne (ATWOnline, Sept. 1, 2008).

ATSB said exhaustive tests of the A330's malfunctioning air data inertial reference units proved inconclusive. However, an ATSB spokesperson said further electromagnetic interference testing simulating transmissions from passenger laptops and other electronic devices is about to start. While testing has been completed using the same frequency (19.8 kHz) as the Harold E. Holt Naval Communication Station near Learmonth with no faults, interference from the base has not been ruled out (ATWOnline, Jan. 8).

ATSB found that the A330's primary ADIRU sent erroneous data (spikes) on many parameters to systems in the aircraft, including the primary flight computers, that resulted in the autopilot disconnecting and two violent pitch-down events. Disassembly of the units will not be done until EMI testing is complete in order to prevent disturbance to the hardware. After disassembly, individual modules will be tested separately.

Regarding QF30, investigators said that because the oxygen bottle, which blew a 2-m. hole in the fuselage, has not been found, the exact reason for the explosion probably never will be determined. Examination of cylinders from the same production batch did not identify any verifiable deficiencies.

"These two incidents involved extremely rare, if not unique, circumstances that were beyond Qantas's control," QF CEO Alan Joyce said. He defended the airline's safety record and said, "Importantly, both reports confirm that Qantas has responded appropriately to all safety actions required by the ATSB."