In the October 7 incident, on Qantas flight QF72 from Singapore to Perth, passengers were hurled around the cabin after the Airbus A330 aircraft dropped with two plunges of 20 and 16 seconds 200 and 650 metres in a matter of seconds while flying over the Indian Ocean. The pilot was forced to make an emergency landing at Learmonth, 1200 kilometres north of Perth on the Western Australian coast, and 44 passengers required hospital treatment.
The Australian Transport Safety Bureau said it believed a faulty component, called the air data inertial reference unit (ADIRU), caused the problem by feeding “erroneous and spike values” about the angle at which the plane was flying to a flight control computer.
“This led to several consequences, including false stall and over speed warnings,” and later generated very high and incorrect values for the aircraft’s angle of attack. This led to the flight control computers commanding the aircraft to pitch down.
On this flight the plane acted of its own accord even after the pilot had taken manual control of the aircraft but minutes later, the plane made two downward plunges.
This was a situation which nobody have seen it before.
During the incident the flight crew should get a message from ECAM (Electronic Centralized Aircraft Monitor) signaling the pilots which system is faulty and what to do to fix it.
The thing to remember about Airbus is the flight control computer is always flying the plane wheather Auto pilot is on or not, even in manual mode all the controlling done through the flight control computer.
After the initial problem that led to the autopilot disconnecting, they were hand-flying the plane and then the aircraft pitched down by itself.
While they try to correct the situation it happened again … it pitched down a second time.
After the inciden they found one of the three Air Data Inertial Reference Unit (ADIRU) was defective and it sent to the US base of its manufacturer, Northrop Grumman for to find out what led to the (fault) and reduce the chance of that happening in the future.
As far as it is known , this appears to be a unique event and Airbus has admited that it is not aware of any similar event over the many years of operation of these tipe airplanes.
Qantas’s initial review of the aircraft’s maintenance history found no problems..
A Qantas spokeswoman said 21 of the company’s 217 aircraft were equipped with the component in question.
“This is now clearly a manufacturer’s issue and we will comply with the manufacturer’s advice,” she said.
Airbus issued a bulletin to all operators of its planes containing the component, with advice on how to reduce the risk of a crash in the event of such a malfunction.
The aim of the bulletin is to:
update operators on the factors identified to date that led to the accident involving QF72,provide operational recommendations to mitigate risk in the event of a reoccurrence of the situation which occurred on QF72. In order to “minimize risk in the unlikely event of a similar occurrence” … an Operational Engineering Bulletin is on its way … Is it simply to emphasize the already published procedure or is it something new the QF72 crew could not have known before ?
Importance of reading the ECAM messages and manipulating the appropriate switches is shown once again in this incident.
The A330 and A340 have identical systems, in the world there are 182 A-340 and 210 A-330 airplanes are flying.
The ATSB is expected to provide a preliminary factual report within three weeks.There had been suggestions the incident may lead to the grounding of Airbus A330-300 models.