.................with apologies to Alistair Cook

Tuesday, 14 October 2008

So NOT a passenger at fault, eh Qantas?

From the R.I.S.Ks Digest:

Date: Tue, 14 Oct 2008 07:55:32 -0700
From: Paul Saffo
Subject: Investigator: Computer likely caused Qantas plunge
[Brings back memories of the early A320 accidents caused in part by a
stubborn fly-by-wire system... -p]
Investigator: Computer likely caused Qantas plunge
Rod McGuirk, Associated Press, 14 Oct 2008
A faulty computer unit likely caused a Qantas jetliner to experience two
terrifying midair plunges within minutes last week. More than 40 people
were injured when the Airbus A330-300 briefly nose-dived twice during a
flight from Singapore to the western Australian city of Perth last Tuesday.
Julian Walsh, chief air investigator at the Australian Transport Safety
Bureau, said an initial investigation indicated the cause was a computer
unit that detects through sensors the angle of the plane against the
airstream. He said one of the plane's three such units malfunctioned and
sent the wrong data to the main flight computers.
The flight data recorder indicated the plane, carrying 303 passengers and 10
crew, climbed about 200 feet from its cruising level of 37,000 feet and then
went into a nose-dive, dropping about 650 feet in 20 seconds, before
returning to cruising level, the safety bureau said last week. The sharp
drop was quickly followed by a second of about 400 feet in 16 seconds.
[The Air Data Inertial Reference Unit (ADIRU) was sending "erroneous,
spike" data to the Flight Control Primary Computers ("PRIM", comparable to
the A320's ELACs), which event disconnected the autopilot. A short while
later the ADIRU sent "very high, random, incorrect" values to the PRIM,
causing a pitch-down command. The same occurred again another short while
later. See the ASTB press release:
Incidentally, early suspicions centered on air turbulence, which were
incorrect. I have disregarded many of the earlier postings from RISKS
readers, but thank you for them. PGN]
The problem is the latest in a series of malfunctions and near-misses for
Australia's flagship carrier in recent weeks.
Australian authorities are still investigating an explosion aboard a Qantas
747-400 aircraft carrying 365 people over the South China Sea in July that
ripped a hole in the fuselage. That explosion caused rapid loss of pressure
in the passenger cabin but no one was injured.
Walsh said the French manufacturer Airbus had notified all operators of A330
and A340 aircraft, which are equipped with the same sensors, about how crews
should respond to such a malfunction. But aircraft are unlikely to be
grounded over a malfunction that had never happened before, he said. "It is
probably unlikely that there will be a recurrence, but obviously we won't
dismiss that," Walsh told reporters, saying they would investigate the
problem further.
The faulty unit will be sent to the U.S. component manufacturer for testing,
he said. A report on the accident is to be released next month. Qantas said
the preliminary findings showed that the fault lay with the manufacturer
rather than the airline. "This is clearly a manufacturer's issue and we
will comply with the manufacturer's advice," the airline said in a