An Air New Zealand plane plunged into the Mediterranean after its pilots mistakenly began a test of sensors they did not know had been damaged three days earlier when the Airbus A320 had been washed down with a fire hose, France's state crash investigator has ruled.
Because the sensors had iced up the pilots managed the rare event of stalling the plane and because they were too low, they were unable to recover before hitting the sea, the Paris based Bureau d'Enquetes et d'Analyses (BEA) said in its final report into the crash off France's Mediterranean coast on November 27, 2008, which killed five New Zealanders and two Germans.
BEA Director Jean-Paul Troadec said the pilots were not qualified to carry out the test that in the end killed them.
"They were not prepared for that, they were very surprised to stall, which is not normally the case with such an aircraft, with an aircraft like this you cannot stall normally," he said.
Mr Troadec said with three pilots in the cockpit, coordination was "not working well".
While all three were well trained airline pilots, they were not test pilots and not qualified to carry out the tests that they undertook.
Air New Zealand chief executive Rob Fyfe said the airline supported the report's safety recommendations.
"While this report will not change the fact seven families lost dads, husbands, brothers and sons and we lost great colleagues, the findings will benefit the entire aviation industry."
New Zealand's Transport Accident Investigation Commission (TAIC), which assisted with the investigation, welcomed the report.
"The BEA's report has identified the key safety issues and lessons to be learnt from this complex accident, and made worthwhile recommendations to help prevent a similar accident in the future," TAIC chief investigator Tim Burfoot said.
At the time of the crash, the plane was being handed over from charter operator XL Airlines of Germany, back to Air New Zealand.
German pilots Norbert Kaeppel, 51, and co-pilot Theodor Ketzer, 58, were flying, monitored by Air New Zealand Captain Brian Horrell, 52, of Auckland.
Also killed were engineers Murray White, 37, also from Auckland, Michael Gyles, 49, and Noel Marsh, 35, both from Christchurch, and Jeremy Cook, 58, an airworthiness inspector from Wellington.
LAST WORDS REVEALED
For the first time, the BEA has revealed the last words said on the flight deck.
As the trio begin a low speed test, Kaeppel says "Okay here we go".
Several seconds later he says: "oh oh oh".
Ketzer then says "Ich nehm die Speed noch mal hoch ja?" ("I increase speed yeah?")
They retract the landing gear and change the flaps but just over a minute after the test began, Horrell, who is not named in the transcript but is identified in the report as supervising the test, is recorded by the cockpit flight recorder saying "What's wrong here?".
Stall warnings are heard and then Horrell calls "Speed brakes" less than a second before the plane crashes into the sea.
BEA said the pilots were not competent to fly at such a low level.
The Airbus had been at maintenance firm EAS Industries in Perpignan for repainting and preparation for hand-over.
On November 24 - three days before the crash - EAS used a fire hose without a nozzle to wash down the plane.
Sensors protruding from the plane's side were not protected during the operation.
BEA believes water got into a sensor that measured the angle of attack - the angle of the wing - and the water froze in flight.
The sensor was crucial to a system that prevented the Airbus from stalling.
'NO COORDINATION IN THE COCKPIT'
The pilots did not know three days later what had happened.
The plane left Perpignan and performed some tests before returning back over the sea toward the city.
They had been prevented by air traffic control earlier from performing the low speed test and so decided to do it.
The Airbus was flying at 167 knots and was 4084 feet (1238 metres) above the sea.
With three pilots on the flight deck, there was, the BEA said, an "absence of prearranged coordination and of precise task sharing" and during the test it became obvious.
There had been many tasks for perform at that level.
"It was in this extremely busy context that the low speed manoeuvre was started," the report said.
The crew had no concern at what was initially happening.
"The passive wait for the protections to trigger, influenced by the confidence in the operation of the aeroplane systems, as well as lack of awareness of the risk, tend to show that the Captain and the Air New Zealand pilot started the manoeuvre as a demonstration of the functioning of the angle of attack protections rather than as a check," the BEA said.
AFP said the report noted that the journey was not a formal "test flight", legally speaking, but an improvised run-out and that this might have led the pilots to improvise rather than follow pre-assigned procedures.
"There was no coordination between the three people in the cockpit," said BEA investigator Sebastien David at a press conference in Paris.
BEA said the accident "was caused by the loss of control of the aeroplane" caused when the pilots tried to demonstrate systems protections, unaware that some sensors may be have been blocked.
"They did not take into account the speeds mentioned in the programme of checks available to them and consequently did not stop the demonstration before the stall."
They said the decision to carry out the test at a low height was a contributing factor.
BEA said the following factors also probably contributed to the accident:
- Inadequate coordination between an atypical team composed of three airline pilots in the cockpit;
- The fatigue that may have reduced the crew's awareness of the various items of information relating to the state of the systems."
The report recommends that stricter rules be drawn up for special flights like the one that led to the tragedy, which do not fall under the rules for commercial flights with passengers or official test flights.
A separate criminal investigation is underway in France into the crash and the final report will become evidence.
"The BEA report will be entered as evidence in the procedure being carried out by two investigating judges in charge of the manslaughter inquiry. It will be studied," Perpignan prosecutor Jean-Pierre Dreno told Agence France Presse.
The investigating magistrates have come to broadly the same conclusions as the BEA as to the cause of the crash, and have said they currently have no plans to level charges against any company or individual.
- with AGENCE FRANCE PRESSE and NZPA
- © Fairfax NZ News