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Computer Error Caused Qantas Jet Mishap
highways sends word that preliminary investigations into a Qantas Airbus A330 mishap where 51 passengers were injured has concluded that it was due to the Air Data Inertial Reference System feeding incorrect information into the flight control system — not interference from passenger electronics, as Qantas had initially claimed. Quoting from the ABC report: "Authorities have blamed a faulty onboard computer system for last week's mid-flight incident on a Qantas flight to Perth. The Australian Transport Safety Bureau said incorrect information from the faulty computer triggered a series of alarms and then prompted the Airbus A330's flight control computers to put the jet into a 197-meter nosedive ... The plane was cruising at 37,000 feet when a fault in the air data inertial reference system caused the autopilot to disconnect. But even with the autopilot off, the plane's flight control computers still command key controls in order to protect the jet from dangerous conditions, such as stalling, the ATSB said."
I'm sure this comes as no surprise to the /. community. Nice to see the truth actually did surface though.
Umm... the attitude sensor was a Northrop Grumman part, used in some Airbus models (2 A330 models, and A340) and "some other non-Airbus" aircraft. So it doesn't sound like an Airbus problem - it may even also be a Boeing problem! And it sounds like a software problem, not a Queerarse maintenance issue, for once! But what happened to quadruplex-redundant FBW - are only the flight control computers truly quadruplex redundant? It sounds like a single point of failure in a design which should have considerable redundancy. Jim
Correct - the Habsheim crash was caused by pilot stupidity in that he was both below the visible height of surrounding obstacles, and had brought the throttles back to idle. Engines take some time to come back from idle to 'take off - go around' thrust (TOGA), and he applied that thrust far too late.
If you need an autopilot to keep the airplane from stalling, then yes, you probably have a stall within seconds after disconnecting the autopilot. And in a stall situation you have no lift from the wings, therefore the plane will immediately and rapidly lose altitude. Modern Airbus and Boeing are engineered to dive forward in these cases, so the stall is self-limiting in the sense that the aircraft will fall until the air is denser or airspeed is higher to let the wings generate lift again thus recovering from the stall.
The resulting forces are well within design limits of current airframes but may seriously injure passengers that had not used their seatbelts or were walking around at this moment.
No. I am a pilot, and you are confusing 37000 feet with 56000 feet. At the altitude where the U-2 flys, over 3 miles higher than 37000 feet, the stall and maximum allowable speeds are nearly on top of each other.
At 37000 feet you have a wide margin of speed available between stall and cruise. What gets closer together is the airplane's top cruise speed and the Mach limit.
The dive after autopilot disconnect is crap; the airplane should be trimmed for level flight by the autopilot to save fuel and system wear.
The dirty secret about airbus airplanes is that the autopilot is never really disconnected; the flight computers will always play 'nanny'. In this case, the computer got 'vertigo' and said 'ZOMG we're too steep', slammed the plane around to keep up speed. Wrong move by the wrong system. If the autopilot disconnects, the airplane should hand control to the pilots, not try to tear the plane apart.
Looking at the article, people suffered spine damage as a result of the (improper) maneuver. Considering that one Airbus aircraft has had a tail fall off in flight due to stress cracking, I'd wonder if this airplane hadn't exceeded it's structural G-force limits during the computer's unscheduled aerobatics.