7 ms·

Qantas flight plunge blamed on computer

36 points by pwg 15y ago

yread 15y ago
http://www.atsb.gov.au/media/3532398/ao2008070.pdf http://www.atsb.gov.au/media/3532398/ao2008070.pdf is the final report. Quite a scary read. 30 warnings on the displays with master caution and master warning going on and off. All of it because of a bug where the binary representation of the altitude was interpreted as angle of attack and a design problem in the flight computer which does filtering on the signals but couldn't cope with spikes exactly 1.2 seconds apart. Result - the vertical acceleration went to -1.5G in 3s and then to 1.7G in the next 2s. That can look something like this http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/turbulence/media/cabin_turbulence.asx http://www.faa.gov/other_visit/aviation_industry/airline_o... I don't understand why the flight computers don't perform more aggresive smoothing on the signals from the sensors - AoA just can't go from 4 deg to 50 deg in 1/25s.
- wazoox 15y ago
  Your link doesn't seem to work: here's a retry: http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/turbulence/media/cabin_turbulence.wmv http://www.faa.gov/other_visit/aviation_industry/airline_ope...
- deleted 15y ago
  [deleted]
- teyc 15y ago
  Here's another link http://www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-070.aspx http://www.atsb.gov.au/publications/investigation_reports/20...
- gnaffle 15y ago
  I think the biggest problem is simply that it was a software bug that occured infrequently enough. To change a working piece of software that has thousands if not millions of problem free flying hours behind it is not something you do "just because". It requires lots of analysis and testing to make sure that they don't introduce new problems.
- thisrod 15y ago
  > I don't understand why the flight computers don't perform more aggresive smoothing on the signals from the sensors In this case, you can solve the hard AI problem, and you're just getting started. Witness Air France.
extension 15y ago
TL;DR: This incident was, as usual, the result of multiple failures happening together. 1. An airspeed sensor starts outputting intermittent data spikes. This is a software failure, but they still don't know what caused it. There is some theory about high energy particles hitting the CPU. It seems very strange to me that a critical system like this can output garbage data and nobody knows why. 2. The flight control computer usually detects these spikes and filters them out by using the last good data for the next 1.2 seconds. However, at the end of the 1.2s, it assumes that the input from the sensor is good. If another spike is occurring at the moment it switches back, it isn't detected. That seems like a rookie mistake to me. I've definitely run into the same sort of issue in other contexts -- handling a second event while reacting to the first one.
- ypcx 15y ago
  Happened in November 2010 in the timespan of 4 days. (I think there were even more but this is what I remembered I can quickly grab from http://goo.gl/FgcAv http://goo.gl/FgcAv) 11/4: Quantas Airlines Grounds All Airbus A380s After Engine Fire Over Indonesia http://www.huffingtonpost.com/2010/11/04/qantas-airbus-problem-ai_n_778719.html http://www.huffingtonpost.com/2010/11/04/qantas-airbus-probl... 11/5: Engine Problems Hit Second Quantas Aircraft -- This Time a Boeing 747-400 http://www.reuters.com/article/idUSTRE6A435P20101105 http://www.reuters.com/article/idUSTRE6A435P20101105 11/8: Quantas Uncovers More Engine Problems http://www.abc.net.au/news/stories/2010/11/08/3059568.htm http://www.abc.net.au/news/stories/2010/11/08/3059568.htm
vorg 15y ago
> The air-speed sensor malfunction was one of only three such malfunctions known worldwide in 128 million operating hours ... In a strange coincidence, all three sensor malfunction events occurred on Qantas flights off the coast of Western Australia. This line in the article seems designed to elicit comments about "the Christmas Island triangle" and "Canberra conspiracies".
- count 15y ago
  Or somebody who didn't turn their cellphone off while in flight?
- tjmc 15y ago
  There's a very powerful transmitter from a US spy base in Exmouth that was suspected at one point: http://www.takesontravel.com/web/index.php?option=com_k2&view=item&id=1353:us-spy-station-possible-culprit&Itemid=14 http://www.takesontravel.com/web/index.php?option=com_k2&#38...
  - goatforce5 15y ago
    I don't know anything about antennas, but that thing looks freakin' massive: http://maps.google.ca/maps?q=exmouth+western+australia+harold+e+holt&hl=en&ll=-21.817042,114.164858&spn=0.052431,0.090895&sll=-21.943046,114.125977&sspn=1.676276,2.90863&vpsrc=6&gl=ca&hq=harold+e+holt&hnear=Exmouth+Western+Australia,+Australia&t=h&z=14 http://maps.google.ca/maps?q=exmouth+western+australia+harol...
- jedc 15y ago
  And here I was just thinking Quantas had found the island from Lost...
vectorpush 15y ago
Does anyone know why an investigation like this takes three years? I would have guessed that since the plane landed safely it would be a pretty quick diagnosis.
- lutorm 15y ago
  Debugging a bug that has showed up 3 times ever doesn't seem exactly like it would be easy...
Havoc 15y ago
I've got great faith in planes as a whole, but these sudden vertical accelerations (wind pockets etc) is one area where they don't seem to have much of a plan aside from hoping you're wearing a seat-belt at that particular point in time. Maybe they should add something crumple-zone like in the panel above the passengers heads. Or put something air-bag like there.
- pavel_lishin 15y ago
  I don't think they can add much crumple zone up there - that area has to be strong enough to hold people's luggage. (On another note, I'm a very nervous flyer, and I put my seatbelt on as soon as I sit down, and don't take it off unless I'm using the restroom, or until we're at the gate. Hurray, paranoia!)
  - zandor 15y ago
    Make sure to take it off if they are refueling though. You'd want to get out of there if things light up.
    - weaksauce 15y ago
      How often does that happen?
      - pavel_lishin 15y ago
        It's probably fairly comparable to a trifecta of software bugs causing a plane to suddenly plummet twice, causing injuries.
      - Nick_C 15y ago
        Effectively never. The fuel is kerosene which has a high flash point, and the plane is grounded to the refuelling apparatus to prevent any static sparks.
_THE_PLAGUE 15y ago
Airbus could easily be the most unsafe major airline in history. No surprise when I read this article that it said this happened on Airbus. Those things have a nasty habit of randomly crashing for no reason whatsoever. Unfortunately planes cannot be booted back up after a crash. I would not be caught dead on an Airbus because that is probably what I would end up being, dead.
- yread 15y ago
  http://www.atsb.gov.au/publications/investigation_reports/2005/aair/aair200503722.aspx http://www.atsb.gov.au/publications/investigation_reports/20... Here a similar thing happened to B777

36 points by pwg 15y ago

yread 15y ago

http://www.atsb.gov.au/media/3532398/ao2008070.pdf http://www.atsb.gov.au/media/3532398/ao2008070.pdf is the final report. Quite a scary read. 30 warnings on the displays with master caution and master warning going on and off. All of it because of a bug where the binary representation of the altitude was interpreted as angle of attack and a design problem in the flight computer which does filtering on the signals but couldn't cope with spikes exactly 1.2 seconds apart. Result - the vertical acceleration went to -1.5G in 3s and then to 1.7G in the next 2s. That can look something like this http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/turbulence/media/cabin_turbulence.asx http://www.faa.gov/other_visit/aviation_industry/airline_o... I don't understand why the flight computers don't perform more aggresive smoothing on the signals from the sensors - AoA just can't go from 4 deg to 50 deg in 1/25s.

wazoox 15y ago
Your link doesn't seem to work: here's a retry: http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/turbulence/media/cabin_turbulence.wmv http://www.faa.gov/other_visit/aviation_industry/airline_ope...
deleted 15y ago
[deleted]
teyc 15y ago
Here's another link http://www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-070.aspx http://www.atsb.gov.au/publications/investigation_reports/20...
gnaffle 15y ago
I think the biggest problem is simply that it was a software bug that occured infrequently enough. To change a working piece of software that has thousands if not millions of problem free flying hours behind it is not something you do "just because". It requires lots of analysis and testing to make sure that they don't introduce new problems.
thisrod 15y ago
> I don't understand why the flight computers don't perform more aggresive smoothing on the signals from the sensors In this case, you can solve the hard AI problem, and you're just getting started. Witness Air France.

extension 15y ago

TL;DR: This incident was, as usual, the result of multiple failures happening together. 1. An airspeed sensor starts outputting intermittent data spikes. This is a software failure, but they still don't know what caused it. There is some theory about high energy particles hitting the CPU. It seems very strange to me that a critical system like this can output garbage data and nobody knows why. 2. The flight control computer usually detects these spikes and filters them out by using the last good data for the next 1.2 seconds. However, at the end of the 1.2s, it assumes that the input from the sensor is good. If another spike is occurring at the moment it switches back, it isn't detected. That seems like a rookie mistake to me. I've definitely run into the same sort of issue in other contexts -- handling a second event while reacting to the first one.

ypcx 15y ago
Happened in November 2010 in the timespan of 4 days. (I think there were even more but this is what I remembered I can quickly grab from http://goo.gl/FgcAv http://goo.gl/FgcAv) 11/4: Quantas Airlines Grounds All Airbus A380s After Engine Fire Over Indonesia http://www.huffingtonpost.com/2010/11/04/qantas-airbus-problem-ai_n_778719.html http://www.huffingtonpost.com/2010/11/04/qantas-airbus-probl... 11/5: Engine Problems Hit Second Quantas Aircraft -- This Time a Boeing 747-400 http://www.reuters.com/article/idUSTRE6A435P20101105 http://www.reuters.com/article/idUSTRE6A435P20101105 11/8: Quantas Uncovers More Engine Problems http://www.abc.net.au/news/stories/2010/11/08/3059568.htm http://www.abc.net.au/news/stories/2010/11/08/3059568.htm

vorg 15y ago

> The air-speed sensor malfunction was one of only three such malfunctions known worldwide in 128 million operating hours ... In a strange coincidence, all three sensor malfunction events occurred on Qantas flights off the coast of Western Australia. This line in the article seems designed to elicit comments about "the Christmas Island triangle" and "Canberra conspiracies".

count 15y ago
Or somebody who didn't turn their cellphone off while in flight?
tjmc 15y ago
There's a very powerful transmitter from a US spy base in Exmouth that was suspected at one point: http://www.takesontravel.com/web/index.php?option=com_k2&view=item&id=1353:us-spy-station-possible-culprit&Itemid=14 http://www.takesontravel.com/web/index.php?option=com_k2&#38...
- goatforce5 15y ago
  I don't know anything about antennas, but that thing looks freakin' massive: http://maps.google.ca/maps?q=exmouth+western+australia+harold+e+holt&hl=en&ll=-21.817042,114.164858&spn=0.052431,0.090895&sll=-21.943046,114.125977&sspn=1.676276,2.90863&vpsrc=6&gl=ca&hq=harold+e+holt&hnear=Exmouth+Western+Australia,+Australia&t=h&z=14 http://maps.google.ca/maps?q=exmouth+western+australia+harol...
jedc 15y ago
And here I was just thinking Quantas had found the island from Lost...

vectorpush 15y ago

Does anyone know why an investigation like this takes three years? I would have guessed that since the plane landed safely it would be a pretty quick diagnosis.

lutorm 15y ago
Debugging a bug that has showed up 3 times ever doesn't seem exactly like it would be easy...

Havoc 15y ago

I've got great faith in planes as a whole, but these sudden vertical accelerations (wind pockets etc) is one area where they don't seem to have much of a plan aside from hoping you're wearing a seat-belt at that particular point in time. Maybe they should add something crumple-zone like in the panel above the passengers heads. Or put something air-bag like there.

pavel_lishin 15y ago
I don't think they can add much crumple zone up there - that area has to be strong enough to hold people's luggage. (On another note, I'm a very nervous flyer, and I put my seatbelt on as soon as I sit down, and don't take it off unless I'm using the restroom, or until we're at the gate. Hurray, paranoia!)
- zandor 15y ago
  Make sure to take it off if they are refueling though. You'd want to get out of there if things light up.
  - weaksauce 15y ago
    How often does that happen?
    - pavel_lishin 15y ago
      It's probably fairly comparable to a trifecta of software bugs causing a plane to suddenly plummet twice, causing injuries.
    - Nick_C 15y ago
      Effectively never. The fuel is kerosene which has a high flash point, and the plane is grounded to the refuelling apparatus to prevent any static sparks.

_THE_PLAGUE 15y ago

Airbus could easily be the most unsafe major airline in history. No surprise when I read this article that it said this happened on Airbus. Those things have a nasty habit of randomly crashing for no reason whatsoever. Unfortunately planes cannot be booted back up after a crash. I would not be caught dead on an Airbus because that is probably what I would end up being, dead.

yread 15y ago
http://www.atsb.gov.au/publications/investigation_reports/2005/aair/aair200503722.aspx http://www.atsb.gov.au/publications/investigation_reports/20... Here a similar thing happened to B777