
Intact tail fin offers clue to Air France crash - DanielBMarkham
http://www.latimes.com/news/opinion/la-oe-garrison14-2009jun14,0,5581001.story
======
jgrahamc
Pure speculation, and this and the previous LA Times article have the
underlying "it's safer in a Boeing" bias.

Oddly, the other LA Times article was complaining (inaccurately) that the
computerized controls in the Airbus would limit the pilot's ability to use the
controls. This article complains that the controls don't limit the pilot's
ability to mess things up.

What's needed is the truth, not this speculation. Perhaps the vertical
stabilizer did rip off. If it did we need to know why.

~~~
gort
"the underlying "it's safer in a Boeing" bias."

Indeed. I saw a documentary on Flight 587 a while ago, and seem to distinctly
remember that both Airbus and Boeing planes suffer from this "rudder reversal"
issue.

~~~
foldr
Rudder reversal is a different issue. It's where hydraulic problems cause
sudden rudder movements, or cause control inputs to the rudder to have the
opposite of the expected effect. The problem here is with the structural
strength of the vertical stabilizer under full (pilot-commanded) rudder
deflection. The stabilizer is not strong enough to handle full ruder
deflection in the whole flight envelope, so /if/ the fly-by-wire system is not
functioning for some reason, the pilot's rudder inputs could cause a
structural failure.

~~~
gort
"Rudder reversal is a different issue."

I don't believe so.

> The bulletin also stated that a rudder reversal was also known as a "rudder
> doublet" and was defined as "a large rudder deflection input in one
> direction followed immediately by a rudder deflection input in the opposite
> direction." In addition, the bulletin stated that "large 'rudder reversals'
> or 'rudder doublets' must be avoided on Transport Category Aircraft" because
> "these inputs can result in loss of control or structural failure of the
> aircraft."

\-- Report on Flight 587: <http://www.ntsb.gov/publictn/2004/AAR0404.pdf>
(page 114)

[Edited to add: i.e. the pilot goes from having the rudder full left to full
right, or vice versa. This is what happened to Flight 587.]

~~~
foldr
The problems on the Boeing planes resulted from /uncommanded/ rudder reversal
due to a problem in the hydraulic systems. There's no suggestion that an
uncommanded rudder reversal occurred in this crash. The suggestion is that
pilot-commanded rudder inputs put the rudder beyond its structural limits.
Thus, the issue is one of the structural strength of the vertical stabilizer.
This was not the primary issue in the Boeing incidents (the stabilizer
remained in tact in most cases but the planes were in serious trouble anyway
since they were pretty much uncontrollable).

In short, while Boeing and Airbus both have rudder-related problems, they are
different problems. Boeing have an issue with uncommanded rudder movements,
whereas Airbus' older models (if the author is correct) have the problem that
it is too easy for pilot-commanded rudder inputs to put the plane beyond its
structural limits. This problem can surface on the newer models if the fly-by-
wire systems go down.

~~~
gort
"The suggestion is that pilot-commanded rudder inputs put the rudder beyond
its structural limits."

I know - my point was that, as far as I can remember from the documentary I
saw, this danger wasn't/isn't peculiar to Airbus planes. And as I think the
above quote from the Flight 587 report shows, this issue can correctly be
called "rudder reversal".

~~~
foldr
"Rudder reversal" is just a particular kind of rudder movement. There are many
different problems with an aircraft which could lead to rudder reversal
occuring.

As mentioned in the article, pilot-commanded rudder reversal is relatively
easy to obtain on older airbus models because they have very sensitive rudder
pedals. This is not an issue on Boeing aircraft. As I said, I think you are
recalling the problem that certain Boeing aircraft have with uncommanded
rudder reversal, but although this is an equally serious problem, it is not
the /same/ problem. In particular, there is no evidence that boeing aircraft
have insufficiently strong vertical stabilizers. (In the rudder reversal
incidents, the stabilizer remained in tact IIRC, it was the loss of control
that was problematic.)

~~~
gort
"This is not an issue on Boeing aircraft."

Well. OK. I'm willing to concede that either the programme, or my memory of
it, could be wrong.

[Edited to add: Wikipedia backs you up on the very sensitive rudder controls
on an Airbus. I think what I was remembering was that, if a pilot of any large
plane did this deliberately, the same problem could occur. But yes, it seems
it might be easier to do accidentally on an Airbus.]

"As I said, I think you are recalling the problem that certain Boeing aircraft
have with uncommanded rudder reversal"

I assure you I'm not.

------
vinutheraj
_The rules that govern the structural integrity of airliners should not
include asterisks._

~~~
marvin
This is actually a huge point of misunderstanding among pilots.

The angle of attack (alpha) is the angle between the wing and the airflow. If
you increase alpha above a certain angle, the wing stalls, and ceases
generating lift. Stalls are commonly encountered when flying really slow, but
can occur at any speed. Pull the stick hard enough, and the elevator rudder
will increase alpha above the threshold, momentarily causing the wings to
cease generating lift and no longer stress the airframe.

The lifting force generated by the wings is proportional to the angle of
attack. However, when the airplane reaches a certain airspeed, flying the
wings at an alpha just below stalling will cause the wings to generate more
lift (measured in accelleration, or G units) than the airframe is designed to
handle. This is the "maneuvering speed", the maximum speed at which full
rudder deflection in smooth air will not cause the plane to exceed its design
loads.

The misunderstanding lies in that this speed is considered an absolute safe
speed to do whatever you want with the controls. This is not the case.
Turbulence, the airframe's current position in relation to the airflow, the
plane's attitude and current position of the flight control surfaces can all
add to the forces that work on the airframe. So when you pull 4G at the
maximum maneuvering speed and encounter a 2G gust of turbulence, the air works
6Gs on the airframe, which will cause you to exceed the design specifications.

Every professional pilot should know this, but it wouldn't surprise me if
there are some who don't. It is really, really common among hobbyist pilots.

------
DLWormwood

        The manufacturer who adds extra "beef" to its structure ends up with a heavier
        airplane that carries fewer passengers or uses more fuel, and loses sales to the
        lighter and more efficient, though "weaker," competitor. The same is true of
        cars. We willingly sacrifice greater safety to get cheaper, more
        fuel-efficient vehicles.
    

If this wasn't published by a U.S. based paper, I'd think this writer was
European or something. The historical trend (prior to the recent price hikes
with gas of the last couple of years) has been the direct opposite. Americans
were buying bigger and beefier cars (read: SUVs and minivans) to protect
themselves and any children. (The whole "soccer mom" phenomenon, remember?)
This was a contributing factor to the implosion of the U.S. car industry,
since they faced selective pressures at home that caused them to develop
vehicles that didn't sell as well to the world at large. And now that fuel
prices are starting to invert the equation, foreign auto makers are eating our
lunch,

~~~
stcredzero
Two examples of failure of the market. If _everyone_ was driving light fuel-
efficient cars, then engineering quality, not greater mass, would be the
dominant safety factor for the buyer. Also, the market seems to drive the
lightness of the tail on an airliner right down to the limits set by the
regulations. If the market was doing what it should, then engineers would stop
short.

~~~
anamax
> If everyone was driving light fuel-efficient cars, then engineering quality,
> not greater mass, would be the dominant safety factor for the buyer.

Light fuel-efficient cars don't meet everyone's needs. (Yup, mom-mobiles/mini-
vans are needed.) And few people can afford to have both a commute car and an
"everything else" car per daily-driver. (Besides, a commute-only vehicle means
that you can't do as much in transit.)

Besides, the "if everyone drove small, everyone would be safe" assumption is
wrong because many car accidents don't involve another car.

I'm unaware of significant efforts to make "not cars" (not just trucks, but
immobile structures) more crash friendly. (Yes, I know about break-away
traffic signs. Even if all signs were break-away, that wouldn't be enough.)

~~~
stcredzero
_Besides, the "if everyone drove small, everyone would be safe" assumption is
wrong because many car accidents don't involve another car._

Lose points for misreading and putting words in my mouth. I said that,
"engineering quality, not greater mass, would be the dominant safety factor
for the buyer." It is the _prevalence_ of large passenger vehicles that makes
greater mass an issue in North America. I wouldn't see so many small single
women driving around alone in Suburbans, Expeditions, and other SUVs if there
wasn't an on-road arms race here in terms of vehicle mass.

I've spoken with two other people who have been in major collisions in a
little teeny Honda CRX. The engine dropped out the bottom of the car, the
front end crumpled, and everything happened exactly like it was supposed to,
and everyone came out mostly unscathed. Consumers here as a whole would be
much better served by paying attention to the safety engineering of vehicles,
instead of just feeling secure because they are perched high in a huge metal
behemoth.

No scheme or factor is going to make everyone safe. Don't put that straw man
on me. More consumer attention to safety engineering is going to ground the
market on more economical principles, however.

~~~
anamax
> Lose points for misreading and putting words in my mouth. I said that,
> "engineering quality, not greater mass, would be the dominant safety factor
> for the buyer." It is the prevalence of large passenger vehicles that makes
> greater mass an issue in North America.

Lose points for continuming to assert something after being told of counter
examples.

Trucks exist. So do overpass supports. All other things being equal, mass and
distance helps. Bigger vehicles provide more of both.

But, let's not stop there.

> I wouldn't see so many small single women driving around alone in Suburbans,
> Expeditions, and other SUVs if there wasn't an on-road arms race here in
> terms of vehicle mass.

You're assuming something about them that's false. The fact that someone is
driving alone doesn't mean that said someone always drives alone.

Do you really think that they should drive the kids to {wherever}, leave the
car and take the bus home and then take the bus back to pick them up?

Besides, I've shown the arithmetic - it rarely makes sense to buy an extra car
to save gas - the other costs dwarf the savings.

~~~
stcredzero
_Lose points for continuming to assert something after being told of counter
examples._

No, you still don't get it. I'm talking about motivation, not about safety
directly. If the motivations of consumers are misplaced, it's harder for the
market to work from the right ones.

 _Trucks exist. So do overpass supports. All other things being equal, mass
and distance helps. Bigger vehicles provide more of both._

Yes, mass matters in a collision. I never said it doesn't. I paid attention to
momentum in high school physics. Again, it's the _prevalence_ of large
vehicles that's the issue. It's the distortion of the North American market
that causes many more large vehicles than are actually needed to be on the
road.

 _You're assuming something about them that's false. The fact that someone is
driving alone doesn't mean that said someone always drives alone._

Uh, you're assuming the opposite? I'm not assuming anything about a particular
individual. I estimate that the _prevalence_ of the phenomenon is out of
whack. Please stop putting inaccurate renditions of my ideas into my mouth!

Step 1 - misread other's post. Step 2 - respond to the distorted/simplistic
idea you just misread. Step 3 - repeat until you feel smart.

Look, if your brain can't handle the one level of indirection involved with
_prevalence_ or _motivations_ in a market, then get out and go back to the
mental kiddie pool. At least criticize me for using mental impressions of
prevalence instead of hard numbers. Then you'd be actually criticizing my
_actual idea_ and not your misreading.

Tiresome.

~~~
anamax
> I'm talking about motivation, not about safety directly.

As am I. I'm pointing out that people don't just see cars when they think of
safety so it's absurd to think that their safety motivation would be just
cars.

I've actually talked with people about this. The ones who express safety
concerns tend to be concerned by trucks and most don't consider cars at all.
Maybe they're wrong, but that's their motivation....

You have actually talked to your target audience about this, right?

>>> I wouldn't see so many small single women driving around alone in
Suburbans, Expeditions, and other SUVs if there wasn't an on-road arms race
here in terms of vehicle mass.

>>You're assuming something about them that's false. The fact that someone is
driving alone doesn't mean that said someone always drives alone.

> Uh, you're assuming the opposite? I'm not assuming anything about a
> particular individual.

You were asserting something about a broad population that isn't true. The
stated basis for your assertion is your observation. I'm pointing out why your
observations are inadequate.

I know a lot of people who have these vehicles, so I'm not assuming anything
about them. I know that the vast majority use close to their vehicle's
capacity an interesting amount of time even though they also do a lot of
single-passenger driving.

How do you know which of your fellow travelers also do kiddie runs or other
activities where they need more than a single passenger vehicle? (Kiddie runs
tend to be disjoint from commute-corridors in time if not space.)

Let's get specific. My vehicle carries 2-3 divers and their cold water gear
fairly often. How do you identify such use when I'm driving alone, which is
the majority of my driving?

You can argue that they don't "need" a large vehicle to do their kiddie runs.
(I certainly don't know why taking a couple of kids requires more equipment
than invading France.) You could also argue that they should rent for fairly
rare "very heavy" tasks and buy a little smaller. (However, be sure to run
actual numbers.)

Either way, you're going to have to deal with the fact that they have these
needs and acknowledge that their vehicle choice is driven by the totality of
their use and your observations aren't seeing that.

~~~
stcredzero
_I've actually talked with people about this. The ones who express safety
concerns tend to be concerned by trucks and most don't consider cars at all._

And, yes, I'm concerned with the _prevalence of truck-sized vehicles_. Thanks
for finally getting on the same page, only requiring me to repeat the phrase 3
times. (Though you seem to do this by claiming the concept as your own.)

 _I know a lot of people who have these vehicles, so I'm not assuming anything
about them. I know that the vast majority use close to their vehicle's
capacity an interesting amount of time even though they also do a lot of
single-passenger driving._

Your sample size is, what, 12? 24? Look, I'm not pretending to have a
significant sample size, or rigorous methods, but in terms of people I've
observed in Houston Rush Hour, it's more like 100's. Also note that I'm not
assuming anything about any individual. I'm just thinking: "My god, there are
a _lot_ of those goddamned things!"

Just because you know a handful of people who use their big vehicles a lot,
doesn't mean you have anything resembling a _refutation_ of my position. At
most you have some relevant anecdotes. Please remember "anecdotes are not
data." Recalling a few anecdotes then declaring the someone _wrong_ on their
basis is an all too common display of mental fluffiness.

 _I certainly don't know why taking a couple of kids requires more equipment
than invading France._

Been over in Europe lately? We Americans just like driving much bigger
vehicles than we really need to. The marketing strategies of US auto
manufacturers were designed to exploit this specifically. Why is it some
random guy in Tuscany can run a plumbing business with a little mini-pickup as
small as an econobox hatchback, while my friend has to have his Ford Ranger to
run his? He'd love to spend 1/3rd as much on gas, but his customers would
_look at him funny_.

By and large, the populace is brainwashed into doing things against their best
economic interests. I suspect that choice of vehicle is one of these cases.

~~~
anamax
>> I've actually talked with people about this. The ones who express safety
concerns tend to be concerned by trucks and most don't consider cars at all.

> And, yes, I'm concerned with the prevalence of truck-sized vehicles.

That's nice but irrelevant because we're not talking about you. We're talking
about the motivations of people who buy big vehicles. You remember them - you
want them to do something different.

Those folks are concerned about actual trucks. Cars don't much register. We
can argue about what they should be concerned about, but what they're actually
concerned about is pretty clear.

> Look, I'm not pretending to have a significant sample size, or rigorous
> methods, but in terms of people I've observed in Houston Rush Hour, it's
> more like 100's.

And that's exactly my point. Your observation just tells us that a lot of
people commute alone. It doesn't tell us what they do with those vehicles the
rest of the time.

That's why I asked you how you know about their other usage.

Or, do you want to argue that their other usage is irrelevant? It's fairly
easy to show that the economics of multiple vehicles are tough....

> Been over in Europe lately?

Not in the last three years, but yes, multiple times, one time being three
months in Demark. I've recently been spending time in the Caribbean, Mexico,
the Philippines, and the ABC islands. I've started to pay for trips to the
Galapagos, Fiji, and the Baltics.

I'm not sure why this is relevant, but since you do, let's see your passport
log.

