

Qantas flight plunge blamed on computer - pwg
http://www.stuff.co.nz/travel/australia/6163633/Qantas-terror-blamed-on-computer

======
extension
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
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>)

11/4: Quantas Airlines Grounds All Airbus A380s After Engine Fire Over
Indonesia [http://www.huffingtonpost.com/2010/11/04/qantas-airbus-
probl...](http://www.huffingtonpost.com/2010/11/04/qantas-airbus-problem-
ai_n_778719.html)

11/5: Engine Problems Hit Second Quantas Aircraft -- This Time a Boeing
747-400 <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>

------
yread
<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_o...](http://www.faa.gov/​other_visit/aviation_industry/​airline_operators/​airline_safety/turbulence/​media/cabin_turbulence.asx)

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
Your link doesn't seem to work: here's a retry:
[http://www.faa.gov/other_visit/aviation_industry/airline_ope...](http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/turbulence/media/cabin_turbulence.wmv)

------
vorg
> 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".

~~~
tjmc
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&...](http://www.takesontravel.com/web/index.php?option=com_k2&view=item&id=1353:us-
spy-station-possible-culprit&Itemid=14)

~~~
goatforce5
I don't know anything about antennas, but that thing looks freakin' massive:

[http://maps.google.ca/maps?q=exmouth+western+australia+harol...](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)

------
Havoc
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
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
Make sure to take it off if they are refueling though. You'd want to get out
of there if things light up.

~~~
weaksauce
How often does that happen?

~~~
Nick_C
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.

------
vectorpush
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
Debugging a bug that has showed up 3 times ever doesn't seem exactly like it
would be easy...

------
_THE_PLAGUE
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
[http://www.atsb.gov.au/publications/investigation_reports/20...](http://www.atsb.gov.au/publications/investigation_reports/2005/aair/aair200503722.aspx)

Here a similar thing happened to B777

