
Air France 447: The ‘Coffin Corner’ and a ‘Mesoscale’ Maw - old-gregg
http://trueslant.com/milesobrien/2009/06/08/the-coffin-corner-and-a-mesoscale-maw/
======
DanielBMarkham
Miles is a pilot and aviation enthusiast, and I've admired his work in the
past.

I hope this bit of writing is more public-serving than self-serving. After
all, we still know very, very little about what happened, aside from the data
transmissions. Even speculating on structural disintegration is problematic
because the obvious next question was: why wasn't the plane configured for
heavy turbulence?

So you're left with this article that goes over some cool new facts (for those
of you outside the aviation community) but really doesn't shed much light on
the incident at all. It's not a news piece, it's not an opinion piece. It's
kind of a science piece hanging off a news story -- one that puts the author
in the role of expert without facts and one in which hundreds of people get
killed.

Not my cup of tea.

------
grandalf
The article suggests that a stall is a horrible outcome.

Old style biplanes used to do "stall landings" all the time. If you know the
characteristics of the wing, then a stall can be anticipated and is not
necessarily cause for alarm.

How is it that the autopilot system (or other systems on the plane) would not
be programmed to handle a stall gracefully?

In a stall the wing loses lift, but as the plane falls the air thickens and
the angle of attack decreases and the wing ought to regain lift sufficient for
the pilot to be able to control the plane.

I'm not suggesting that handling a huge jet in a stall would be easy, but I
would guess that knowing how to do it is part of the requirements for flying
one.

~~~
marvin
Glider pilot here. I have decent knowledge of aerodynamics, but have never
studied large jets in detail. This is my personal theory - essentially what
lies behind the words of a few articles I have read over the last few days,
but the authors haven't been able to formulate it clearly.

Assuming that the autopilot and fly-by-wire systems were somehow compromized,
a full stall in the "Coffin Corner" (Q-corner) would be a very, very serious
condition. A stall causes the nose to drop and speed to accumulate. Since the
difference between the stalling speed and the never-exceed speed is so small
at the altitude in question, this accumulation of speed could easily cause the
plane to exceed its critical Mach number, causing supersonic shockwaves around
certain parts of the airfoil. In planes not designed for supersonic flight,
these shockwaves will eventually cripple the effect of the control surfaces.
If the plane is in a nose-down position when it looses effect on its elevator
rudder, the plane will overspeed and eventually suffer structural failure
(essentially meaning the loss of some critical part) due to flutter (resonance
in parts of the airframe) or aerodynamic stresses.

A stall during normal flight conditions doesn't have to be a serious problem,
but these weren't normal flight conditions. And the information that we have
suggests that certain Airbus models have had problems with their pitot (speed
measurement) systems in icing conditions, leading to erroneous speed readouts.
The fly-by-wire system, which prevents the pilot from flying the aircraft into
stall or overspeed, cannot function correctly without a correct speed
measurement. And as I have detailed, a proper stall might be enough to doom
the airplane.

------
telma
The weather was never considered "horrible" and still isn't. [edit:] At least
12 planes took the same route that night without any incident.

[http://ibnlive.in.com/news/12-planes-shared-sky-with-
af-447-...](http://ibnlive.in.com/news/12-planes-shared-sky-with-
af-447-reported-no-trouble/94293-2.html)

~~~
joshwa
From the very last paragraph of the same article (which originates from CNN,
incidentally):

> Although none of the other flights are known to have reported weather
> problems en route, aviation experts said weather can change suddenly and
> vary over short distances, so one plane might experience conditions far
> worse than another.

------
shizcakes
Insightful but it seems that there's a lot of speculation about this. Theres
an article from timesonline that tied some pieces together and answered some
questions for me (like: "How do they know this much detail of the flight
without the black box?" A: ACARS).

I hope this is helpful to someone else:
[http://www.timesonline.co.uk/tol/news/world/us_and_americas/...](http://www.timesonline.co.uk/tol/news/world/us_and_americas/article6446268.ece)

~~~
samlittlewood
Thanks. I assume that the forum mentioned in the article is
<http://www.pprune.org>.

The current thread about this accident is <http://www.pprune.org/rumours-
news/376433-af447.html>

Apart from the current tragedy, it's a great window into another professional
sphere.

------
tomiles
Why when internet is becoming available in planes is something as simple and
and essential as updated weather reports not possible during a flight?

Why are these practices seemingly stuck in a stone age of paper weather
reports, printed before the flight leaves, that could have been outdated even
before the planes takes off.

Maybe this accident will speed up a much needed needed technological update in
this aspect of air-travel. We should stop wasting dollars on security theater
measures and invest it in real safety measures that can save lives.

~~~
JimmyL
They get weather updates en-route sent to them by their home airline (via the
radio system) - not to mention that jets of that size carry along with them a
better weather radar system than most local news channels have.

~~~
tomiles
I'm talking about satellite imagery like it is shown in the article, which is
the only kind that would provide reliable and usable info for storm evasion.
You need a view from above to see a storm size and not just a surface look at
it from the sides (with a radar). Weather radar only provides limited
information, like the article says.

"interpreting its display is a bit of a black art." - "It is akin to a blind
man with a cane;" - "For instance, the radar mostly detects rain and hail –
and if that first layer of storm cells was particularly heavy, it might have
acted like a curtain – hiding the reinforcements from radar beams."

You can't know what's inside a walled garden or know how big it is just by
looking at one side of the outside walls, you need something that allows a top
view.

~~~
dpifke
More raw data to the cockpit is unlikely to help. Pilots have a lot of things
going on and varying levels of weather knowledge and experience (even
professional pilots - weather is but one thing you train on).

A professional meteorologist on the ground who can interpret and summarize the
relevant information is of way more use.

~~~
tomiles
I agree that it's also useful but this is not black and white. It's not one
ore the other, it should be both. Because when your flying into a storm front
in the middle of the atlantic you are on your own and it's not that
interpreting a satellite picture is a black art like radar. Besides that's why
there are 2 of them in the cockpit. If a pilot can't handle that he shouldn't
be flying a plane. It's like saying we shouldn't invest in new CT machines or
other better medical imagery, doctors have more than enough data to handle.

~~~
vinutheraj
Er .. why should the pilot interpret it, can't we have a specialist inside the
cockpit to interpret the meteorological data ?!

~~~
tomiles
because you can't fit in the extra guy in all cockpits :-) Would be
unpractical and expensive to put a 3rd person there just for weather. Good
updated meteo from the specialists on the ground, and basic training in and
availability of satellite images in the plane.

Like it's said you might loose contact with any ground station when flying in
the middle of nowhere or you might lose imaging data of the storm. So both
should be there to provide a better standard than the current limited info of
printed weather maps in preflight briefings, especially for long flights.

------
biohacker42
_So while you are napping, eating or watching a movie on that flight to LAX,
you should know the plane you are flying is cruising along at the ratty edge
of its capabilities. Why? Money. The higher an airliner flies, the better gas
mileage it gets._

As libertarian I prefer an airline which will charge me premium for flying
more expensive but safer routes.

However, as a realist I realize that the barrier to entry for airlines is very
high and competition is sub-optimal.

So I'd settle for a government mandate of how high commercial airlines can
fly.

~~~
frisco
That's a bit of a jump. How'd you go from "As a libertarian..." to "So I'd
settle for a government mandate" in 3 lines?

~~~
biohacker42
Well simple.

I really do want the market to work, but I know in reality it very often does
not work at all. Most often with big industries where the startup costs are
high.

Do you prefer to continue to fly in a needle's eye rather then have the
government step in?

Ideally at least one airline would offer the safer option as a way to gain
customers, but what if no one does?

Is your libertarianism that pure? If so, that's admirable, I guess my ideals
are just not quite as strong.

~~~
anigbrowl
Seems like a rather suicidal market strategy. So you invite people to pay 2x
to fly with FlySafe (perhaps an existing airline with n outstanding safety
record that rebrands itself), milk the resulting controversy to sell tickets
for a while, only to later have every untoward incident, no matter how
trivial, spun into a damning indictment of your business philosophy? No
thanks.

Furthermore, the first time such a company did have a fatal or obviously
dangerous incident, they'd go insolvent immediately. I see the point you're
trying to make but it's simply impractical in a mass market like commodity air
travel. Uber-expensive executive flying, perhaps.

~~~
stcredzero
_it's simply impractical in a mass market like commodity air travel. Uber-
expensive executive flying, perhaps._

If it wasn't for the coverage of this incident, I would never have known of
the "coffin corner." How would market forces operate on factors of which the
public is not even aware?

~~~
anigbrowl
And until that pilot landed in the Hudson, I'm betting you never thought too
much about birds getting sucked into jet engines (I certainly didn't). Perhaps
the conclusion from this is that there isn't really much utility in your being
aware of it, since you're not a pilot. That is to say, the knowledge is of
little benefit to you as a consumer because the weight of this particular
factor in the overall safety of air travel is not that big.

Like say you design software for something critical like medical devices, and
one of these fails and somebody famous dies or a bunch of people die in
different places. Suddenly everyone is talking about unit testing and software
verification as it pertains to your field, someone with a talent marketing
starts up safercoding.com and so on. I'm not sure the stock of human knowledge
has really gone up.

~~~
biohacker42
I have to disagree. For one, I think birds flying into plane engines was
common knowledge. It's certainly something I've know for as long as I can
remember.

And when I got my CS degree we specifically studied accidents where bad
software in medical devices killed people. I recall an X-ray machine where the
hardware was upgraded and a bunch of software assumptions about when the fuses
would blow became wrong. That ended up killing people.

And as someone who has written software for medical instruments I can tell you
unit test coverage is part of the contracts we sign.

The coffin corner only played a small part in the accident but that's how
accidents always happen. It's always several small things that go wrong
together.

A safe airline would not flaunt its safety record, but it's safety practice.
Not flying the coffin corner would remove that one part that can go wrong from
any future accident scenario.

The safe airline having an accident would not automatically bankrupt it, every
other airline has had accident and this one would continue with its safer then
average practices.

However, I agree with you this will never happen because as you say the
airlines are a crap commodity business. Even Warren Buffet has mentioned how
bad a business airlines are for investors.

That's why even though I consider myself a libertarian I want a government
mandate to stay out of the coffin corner.

We already have much more complex and difficult to enforce regulations on
airlines, this one is simple and would be easy to enforce as we already track
all planes on rader closely all of the time.

------
chipmunkninja
While there is a lot of good information in this article, the tone is a bit
too tabloid-sensationalist for my tastes.

"So while you are napping, eating or watching a movie on that flight to LAX,
you should know the plane you are flying is cruising along at the ratty edge
of its capabilities. Why? Money. The higher an airliner flies, the better gas
mileage it gets."

Boo those big corporations for trying to pick optimal flight paths, save
customers flight time, or otherwise make a buck (and who cares about all the
environmentalists breathing down their necks about burning so much kerosene).
How DARE they? Think of the children!!

The one thing common after all these crashes is the amount of looney
speculation that goes on right after, and then we magically forget about it.
Does anybody even remember the British Airways 777 from Beijing that landed
short at Heathrow a couple of years back? The reason: entirely mundane -
faulty fuel pump.

------
run4yourlives
Reports seem to indicate that they almost made it through the stormcell.

Very unfortunate. Whatever it was probably happened extremely fast. Perhaps a
(ridiculously unlikely) wing snapped off? Or they stalled and spinned
violently?

~~~
stcredzero
Boeing tests its wings to breaking by bending them behind the back of the
plane until they are pointed up at ridiculous angles. The kind of force that
would break the wings of a modern jetliner would also break the necks of a
large number of the passengers.

<http://www.youtube.com/watch?v=pe9PVaFGl3o>

EDIT: I stand corrected. As pointed out below, that huge deflection doesn't
represent neck-breaking forces. But imagining the force of an updraft that can
accelerate an airliner upwards at 2G's -- that's still a heck of a lot of
power.

~~~
DocSavage
Cool video. I wonder how much of an engineering/structural difference there is
between the heavier 777 and the Airbus A330-200 that crashed.

~~~
yhnbgty
Both are tested to 150% of their maximum rated load.

------
TrevorJ
A very insightful examination. A lot of things I didn't know.

~~~
anigbrowl
True. Too bad about the tabloid-style typography and literary style, which
does serve a purpose of highlighting the takeaways but also gives it an air of
sensationalism.

------
noonespecial
I know its all very serious and its sad commentary on the mental baggage I now
carry from watching too much TV when I was 15, but I couldn't help but do a
double take when a guy named "Miles O'Brien", quoted Scottie describing
engines.

------
TweedHeads
I will always say it was a bomb, and the more they try to make it look like it
wasn't, the more I believe they are just trying to hide it from the public not
to scare them to fly like in 2001.

It was a bomb.

~~~
hunterjrj
Why has no one stepped forward to take credit for downing the plane with a
bomb? Isn't that the MO for terrorist organizations?

Accidents happen, unfortunately. Sometimes planes crash. Our technology isn't
perfect, and all we can hope for now are useful lessons to be learned from the
crash itself.

~~~
TweedHeads
If I was a terrorist org, I wouldn't take credit. The new modus operandi is
stealth mode, the days of TV shows about terror are over.

Terror to create havoc on the world economy and air traveling will be the
first hit.

Expect more "accidents" in the future.

~~~
abstractbill
Terrorist organizations use terror _to promote a cause_. If you're just making
people generally a little nervous, you're not doing a good job of advancing an
agenda.

