
Gimli Glider - lelf
https://en.wikipedia.org/wiki/Gimli_Glider
======
Karellen
Ah yes, The Fundemental Failure Mode Theorem[0] at work: Complex systems
usually operate in failure mode.

Or, "That's why I'm skeptical of people who look at some catastrophic failure
of a complex system and say, "Wow, the odds of this happening are
astronomical. Five different safety systems had to fail simultaneously!" What
they don't realize is that one or two of those systems are failing _all the
time_ , and it's up to the other three systems to prevent the failure from
turning into a disaster." [1]

[0]
[http://en.wikipedia.org/wiki/Systemantics#System_failure](http://en.wikipedia.org/wiki/Systemantics#System_failure)

[1]
[http://blogs.msdn.com/b/oldnewthing/archive/2008/04/16/83984...](http://blogs.msdn.com/b/oldnewthing/archive/2008/04/16/8398400.aspx)

~~~
LordHumungous
See also United 232
[http://en.wikipedia.org/wiki/United_Airlines_Flight_232](http://en.wikipedia.org/wiki/United_Airlines_Flight_232).
The DC10 has three separate hydraulics systems, therefore the probability of
all three failing is p^-3 right?? But wait, the lines are all grouped together
through the tail, meaning if one is severed there, the other two are likely to
be severed as well.

~~~
WalterBright
You might conclude from this that airliner designers are fools. An airliner is
a very complex machine, and can have unexpected interactions between its
components. Look at the other side:

1\. the airframe held together despite an explosion at the back. The rudder
and horizontal stabilizer stayed on.

2\. the aircrew figured out how to control the airplane with no hydraulics,
i.e. there was still some redundancy in the system.

3\. the landing gear was designed so it could be extended and locked with no
hydraulic power, and that worked

4\. if the airplane or aircrew was any less, nobody would have survived

5\. electric power stayed on

And, airframe companies learn from these disasters, which is why airplane
travel is incredibly safe. Boeing airliners, for example, do not locate
critical components inline with the turbines. Hydraulic lines do not extend
past the inboard engine. There are a number of other improvements as well.

Having worked on 757 flight controls for three years, I can assure you that
none of the engineers want any part of a defective design. None want to make
any decisions that lead to a smoking hole in the ground. An awful lot of
effort is spent pouring over the designs again and again looking for mistakes.

~~~
rogerbinns
I don't know if they existed at design time, but hydraulic fuses could have
prevented draining of all the fluid. That makes the design take longer,
increases weight, introduces new scenarios such as the fuse activating when it
shouldn't, increases cost, and increases maintenance & parts (cost of
ownership).

As with these matters there is no one true correct answer, but rather a very
complicated set of tradeoffs and probability estimates. In hindsight it is
easy to see designs as defective, but they could all be done in good faith.

------
yurisagalov
A similarly interesting incident happened with another Canadian airline -- Air
Transat Flight 236[1].

[1]
[http://en.wikipedia.org/wiki/Air_Transat_Flight_236](http://en.wikipedia.org/wiki/Air_Transat_Flight_236)

~~~
refurb
Transat 236 is an amazing story. How lucky were they to run out of fuel, out
in the middle of the Atlantic, but be able to glide to the Canary Islands?

If it had had a few hundred pounds less of fuel, it would have ditched in the
middle of the ocean and likely many of the passengers would have died.

~~~
brc
Azores. They are on the mid-atlantic ridge. The Canaries are off the coast of
Africa.

~~~
refurb
Thanks for correcting me! I thought the Canary Islands didn't sound quite
right.

------
oscilloscope
If you enjoyed this Wikipedia article and like video games, check out Kerbal
Space Program. You'll be running out of fuel in no time.

~~~
crystalmace
This is true.

------
shadeless
I heard about this recently on smodcast (podcast featuring Kevin Smith and his
producer Scott Mosier), their reenactment was hilarious and I heartily
recommend it - [http://smodcast.com/episodes/true-tales-of-canadian-
heroism/](http://smodcast.com/episodes/true-tales-of-canadian-heroism/)

------
mrbill
"the cockpit warning system sounded again with the "all engines out" sound, a
long "bong" that no one in the cockpit could recall having heard before and
that was not covered in flight simulator training."

I hope that's something that IS now covered. Why would you never train for
that secenario?

~~~
eskil
Did your drivers ed/school teach you how to drive with a hood that's flipped
up at highway speed? Mine didn't, then it happened to me.

(but yeah you're right)

~~~
adrianpike
Mine did, actually. My instructor used a clipboard to block my field of view,
and walked me through coming to a controlled stop with minimal visibility.

~~~
ceejayoz
We didn't even cover highway driving in mine, let alone something like that.

~~~
gambiting
In Germany part of the training in many schools involves getting to the
nearest autobahn and going at least 120mph to teach you driving at such
speeds. Yes,there are training courses which don't do that, but it's not
uncommon.

~~~
fossuser
From what I've heard the driving/licensing test in Germany is actually a test
- in the United States the written test questions show a picture of a stop
sign and ask what it means (there are then three multiple choice options).

The driving portion is not much more difficult.

~~~
gambiting
Yeah, it involves quite complicated questions about driving (a diagram with
yourself, a pedestrian, a cyclist, a tram, and 3 other cars - you have to
specify who goes in what order), and also technical questions, like "your
temperature gauge is going into the red zone - what do you do?" or "on a
winter day your windows get foggy from inside when driving - what is the
safest solution?", and also general question about laws "what is the bac
limit?", "how fast can you go on the autobahn when the conditions are
poor?"(answer:130km/h(~80mph)).

~~~
gamerdonkey
While I feel that US driver education and testing has many faults, I don't
want everyone to have the impression that the test is as simple as 'What does
a STOP sign mean?'. Hyperbole is good for humor but can be misguiding in a
discussion about actual solutions.

While it has been some time since my driver's test, I remember somewhat
complicated questions about right-of-way, dealing with vehicle problems,
handling adverse driving conditions, and responding to potential accident
situations. Of course, part of the problem I have with our driver education
system is how much it varies among the states. Most of what is shared deals
with the operations of highway driving, while I think there needs to be more
requirements for overall safe driving.

Also, I was a little incredulous at first that 80 mph is the answer for 'poor'
conditions. But, I suppose I have driven on 80 mph interstates here under
extremely heavy rain while everyone maintained the speed limit. I suppose it's
just one of those things where we have a different sense of scale.

~~~
fossuser
While it may have been in isolation the "What does a STOP sign mean?" question
is a question that I actually had on my written test.

I think it was phrased a bit differently, but that was the essential question.
The multiple choice answers were also extremely leading with one being even
more obviously correct than you would expect.

In California you're also able to take the test 3 times in a row if you fail
it every time, you can then take it another three times immediately if you pay
$20. Since there aren't many questions it's basically impossible to fail.

------
grimmfang
If any of you are really interested in these incidents they have recently been
added to netflix titled "Air Disasters" and additionally you can find many
more on Youtube from
[https://www.youtube.com/user/aircrashofficial](https://www.youtube.com/user/aircrashofficial)
and similar uploaders!

------
rcthompson
Nice of the airline to find the pilots at fault.

~~~
lutorm
It is the pilot's responsibility to ensure that there is enough fuel for the
flight, so that's no big surprise, _especially_ since the fuel gauges were
inoperative and they did not attempt to verify fuel level any other way. They
weren't the _only_ ones at fault, though.

~~~
sejje
Bullshit, the article clearly states they attempted to verify it with dipstick
measurements and (faulty) math/conversions.

In fact, they did that twice, before initial takeoff and after their first
landing in Ottawa.

~~~
mikeash
That they attempted to verify and still came up with the wrong answer just
reinforces their fault.

They did a great job of handling the subsequent emergency, but I see no way
around blaming them for it happening in the first place.

~~~
wdewind
The way around blaming them is that it has a horrible systemic effect to do
so. In the future pilots are less likely to admit fault, less likely to
provide details in investigations and so the organization has less data to
learn with.

Instead look at what happened and say "if things had been different this
couldn't have happened" and then make those things a reality. Maybe the answer
is putting a sticker with metric/imperial conversion on the tank or something,
so pilots aren't confused when checking with dipstick.

~~~
baddox
> The way around blaming them is that it has a horrible systemic effect to do
> so.

That's why it's a good idea in complex systems to pre-assign to each
requirement a responsible party. Otherwise, you could just use the "systemic
effect" argument to either blame every party or no party in the system,
neither of which is very useful.

~~~
p0ckets
The fuel requirement was pre-assigned (for every other model of plane in the
Air Canada fleet) to the flight engineer. Who that requirement was assigned to
for this one model of plane wasn't really clear in the article.

~~~
sswezey
It was never explicitly said. The plane used to have a 3-person crew and had
moved to a 2-person crew (missing the flight engineer). This left the check
unassigned. It is mentioned in the 2nd paragraph under the Investigation
header.

------
8ig8
As noted on "Some Famous Unit Conversion Errors"

[http://spacemath.gsfc.nasa.gov/weekly/6Page53.pdf](http://spacemath.gsfc.nasa.gov/weekly/6Page53.pdf)

------
crystalmace
I was at that airfield last summer for a cadet course (I'm an air cadet) and
I'll be going again this summer to get my glider pilot's licence; just like
the pilot of the Gimli Glider did so many years ago! I can't wait!

~~~
efm
The pilot (or co-pilot), I don't recall, was also an Air Cadet at that
airfield, which is how he knew that it was there, a good long strip, and well
maintained.

~~~
crystalmace
Yes, and he was a glider pilot in the air cadet program which aided to his
ability to properly land the plane without engines

~~~
seanmcdirmid
The pilot was a glider pilot, the first officer was an air cadet, and the
field was already turned into a race track.

------
bjg
I'm curious if the submitter has been listening to SModcast[0]? They had a few
episodes on the Gimli Glider recently.

[0]
[http://smodcast.com/channels/smodcast](http://smodcast.com/channels/smodcast)

------
sargun
A great talk on failure: [http://www.infoq.com/presentations/Debugging-
Production-Syst...](http://www.infoq.com/presentations/Debugging-Production-
Systems)

------
shruubi
I'm guessing OP is a fan of Smodcast.

[http://smodcast.com/episodes/true-tales-of-canadian-
heroism/](http://smodcast.com/episodes/true-tales-of-canadian-heroism/)

------
reddit_clone
There is an episode in the series 'Air Disasters' currently available in
Netflix about this.

Terrifying to say the least.

------
hyp0
WTF/m theshold exceeded

------
eddanger
I hope the Americans don't use this as an excuse to stick with their old
school system. I guess in one way they are closer to the Kingdom of England
than us Canadians are.

~~~
Patrick_Devine
In the aviation world it's really mixed. ICAO uses imperial and metric
measurements for different things. Feet are used for altitude and knots for
distance, but temperature is always measured in centigrade.

It's convenient to use feet because planes are stacked in 500' increments and
not 152.4m increments. VFR (visual flight rules) flights are usually on the
500's (eg. 3500', 4500', etc. depending on heading) whereas IFR (instrument
flight rules) flights are on the 000's (4000', 5000', etc.).

Knots are convenient because 1 knot is equal to 1 minute of 1 degree of arc on
a great circle. If you're flying anywhere far away this ends up being
important as a great circle is the shortest route between any two places.

Oddly enough, the metric system is useful with temperature because the
standard lapse rate is 2 degrees per 1000' of altitude. So if you had to climb
from 6000' to 8000' on an IFR flight plan, you would usually drop 4 degrees
centigrade, which might be significant if it was raining out and it dropped
below freezing. Having water on your wings and climbing up to an altitude
where it's freezing is going to make you have a really bad day.

~~~
stepstep
> a great circle is the shortest route between any two places

Wouldn't it be faster to adjust the heading to point directly to the
destination and then fly in a straight line?

~~~
Patrick_Devine
Remember that we live on a sphere (or something approximating one -- it's a
sphere that bulges). A great circle route actually is a straight line, it's
just that on a 2D map it looks like you're constantly turning.

------
chasing
Is there a "news" element to this link (since the name of this site is "Hacker
News")?

Otherwise, it's an interesting story and it makes a good lesson, but I've been
hearing it, now, for almost twenty years...

~~~
scott_s
From the guidelines
([http://ycombinator.com/newsguidelines.html](http://ycombinator.com/newsguidelines.html)):

 _On-Topic: Anything that good hackers would find interesting. That includes
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