Wednesday, July 30, 2008

More information released about the Qantas B747 decompression incident

Qantas logoThe Australian Transport Safety Bureau (ATSB) has released new information regarding their investigation into the recent Qantas Boeing 747-400 depressurization accident. Readers will recall that the aircraft, operating as Qantas Flight QF30, experienced a rapid depressurization at 29,000 feet while en route from Hong Kong to Melbourne on July 25, 2008. The aircraft diverted to Manila where it made a safe emergency landing. No injuries were reported, however the aircraft was found to have a large hole in its fuselage.

First the good news. Today's ATSB news release stated that, "From the evidence gathered to date it appears that the flight crew have responded to and managed the emergency situation extremely well. It is apparent that they followed the procedures they have trained for in simulators, which ensured the best possible outcome for the aircraft, the passengers and crew."

Earlier this week the ATSB reported on the initial inspection of the damaged aircraft, noting (among other things) that one oxygen cylinder, which had been located near the site of the hull breach, was missing. Today the ATSB confirmed that pieces of the missing oxygen cylinder were found in the passenger cabin.
The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabin and impacted the number 2 right door frame handle, thereby moving the handle part way towards the open position. However, the door handle mechanism has been sheared as it is designed to do if an attempt is made to open the door in flight, so the position of the door handle is not representative of the position of the door lock mechanism or the security of the door.
Thus, there seems to be little doubt that the oxygen cylinder exploded inside the cargo bay. The question is, how and why did that happen? And did the exploding oxygen cylinder cause the hull breach and subsequent depressurization, or was it incidental to another causal event?

Here is a rundown of other important points made public today by the ATSB:
  • Descent rate - Initial analysis of data from the Flight Data Recorder showed that that immediately following the decompression event at 29,000 feet, the aircraft descended to an altitude of 10,000 feet. The emergency descent took about five and a half minutes, with an average descent rate of about 4,000 fpm.
  • ILS - The ATSB confirmed that the aircraft's three Instrument Landing Systems (ILS) and the anti-skid system were not available for the arrival and landing at Manila. However, evidence to date indicates that all of the aircraft's main systems, including engines and hydraulics were functioning normally
  • Cabin Oxygen Masks - The team found that most of the oxygen masks had deployed correctly from the passenger modules and had been pulled to activate the flow of oxygen to the mask. In all, 484 masks had deployed. Of those, 418 had been activated by pulling on the mask to activate the flow of oxygen. Only a small number of masks appeared to have had the elastic retaining strap adjusted by the passengers. It also appears that a small number of masks did not deploy from the passenger modules.
Also relevant to the oxygen issue, the ATSB says they are in the process of establishing whether or not "the flow of oxygen was adequate for the five and a half minute descent to 10,000 feet, where the masks were no longer required." Some news reports had mentioned some passenger complaints about malfunctioning masks or sub-optimal oxygen flow.

The ATSB expects to issue a preliminary factual report about this accident within the next 30 days.

RELATED: Click here to view all posts about Qantas Flt 30 on Aircrew Buzz.