Airbus 330 design flaws under scrutiny in the AF447-court case.
On March 9, the lawyers of the Association of Victims of Air France 447 and the Air France Flight Attendants Union (SNGA), remit their conclusions to a French criminal judge who is investigating the responsibility of Air France and Airbus in the air disaster of 2009. We had an exclusive interview the ex-pilot Gérard Arnoux, one of the authors of the expertise.
Q: There were important technical flaws on the Airbus 330 that crashed in 2009. The malfunctioning pitot tube heating system, the Flight Director that went back to default mode and gave orders to climb, the erroneous values of altitude and vertical speed, faulty alarms… Have these flaws have been adressed since and fixed on the current A 330’s that are still flying around?
Arnoux: There was a series of malfunctions of breakdowns and flaws on the accident of June 1, 2009. First of all, the pilots did not get a message on the ECAM screen that the speed readings were incorrect, the « NAV ADR disagree; SPEED…X check». This was a malfunction, not a design flaw of the Airbus 330 models. Then there were erroneous values of altitude and vertical speed. This flaw only affected the A330–200 model of the Airbus fleet and most A330’s since then have been retrofitted.
Also the Flight Director which shut off and reappeared, displaying wrong information, has been fixed. There have been 4 Airworthiness directives by EASA (European Aviation Safety Agency) for from 2010 to 2012 which addressed this problem and now the Flight Director does not work anymore after a situation of unreliable speed. Then there are some features on the Airbus which haven’t changed after the accident, despite of all the criticism: the dangerous logic of the autotrimmable THS (Trimable horizontal Stabilizer) even when the plane is in Alternate Law. It induced the pilots to leave the protective flight envelope. The pilots did not feel that they were too pitched up, because they had no feedback on the joystick.
The design of the Airbus sidesticks has been much criticized. Even by an Airbus-man as Captain Chesley “Sully” Sullenberger (link video). Why don’t they install a different system?
Arnoux: It’s strange, it is part of the Airbus design philosophy and they won’t change that, even after AF447. Recent aircrafts like Bombardier or Embraer, also have sidesticks but active ones, meaning that action on one sidestick will move the other too, like connected yokes. On Airbus there is no feedback and no linkage between the joystick. Airbus doesn’t do that. It’s something dogmatic.
What about the fact that the stall warning on the Airbus is inoperative under 60 knots?
Arnoux: I found it strange that the legal experts did not mention it in their reports, because that is actually illegal. As far as I know, the stall alarms on Airbus still don’t work under 60 knots, this hasn’t changed. It’s clear that Airbus completely underestimated this problem. Before June 1, 2009, the pilot-chief of training and flight at Airbus, Pierre Baud, stated in the in-house magazine FAST, that “anti-stall training on Airbus planes wasn’t necessary”.
Then there were the infamous Thales pitot tubes, of which the heating system did not work?
Arnoux: There has been a recent (December 2017) airworthiness directive by EASA which ordered all of the Thales probes to be replaced by Goodrich ones. The flawed pitot probes is still the strongest argument in our criminal courtcase against Airbus and Air France, since they knew there were not working well and they did not replace them on time.
Apparently not only Airbus, but also EASA, DGAC (French civil aviation authority) and BEA (French bureau for airline accidents) failed to recognize this problem and act upon it.
Arnoux: From the summer of 2018 on there were numerous failures with the Thales AA pitot probes on the A330. Earlier pitot blockage incidents on two Air Caraïbes flights had lead to a exhaustive report by that airline, but this was ignored by the DGAC and BEA. Very likely these failures were due to the replacement by Airbus of the Probe Heat Computers (PHC) without having conducted any safety evaluation beforehand.
You mentioned that in the nineties, the French authorities already dealt with faulty probes on Airbus.
Arnoux: Airbus had a problem in 1994 with a pitot tube, but then it was made in the USA, by Rosemount. So in 2001 the DGAC forbid the use of that Rosemount probe. Now the situation, with Thales being a French company, was quite different. The DGAC remained passive and did not forbid the use of the AA probes. Until the accident Rio-Paris.
Gérard Arnoux is a retired pilot who has flown smaller aircraft like Dassault Falcon and Mercure for Air Inter before switching to A320 (for Air France) in 1998 until 2014. He is currently a judicial expert for the families and relatives of the victims of Air France 447 in the case before the French criminal court.
Tom Dieusaert recently published “Computer Crashes”, highlighting the risk of automation in aviation. Click here for print version or e-Pub version
