by the way, don't use the rudder or you might snap the tail section of the plane off... Time to get John Edwards on the case. What? Liability laws are different for European companies than for American companies? Well, just sue Boeing instead!

The controls on an Airbus are all electronic; one would imagine they could have been programmed not to allow such a maneuver. To be fair, one couldn't be sure that restriction would never be triggered erroneously...

Do you think the government would ever admit that it was brought down by a Muslim terrorist with a hand-held missile?

"Most pilots assumed that they could make full use of the rudder and other aircraft controls within normal operating speeds."
Sounds like a very reasonable assumption to me.

Why anyone who doesn't live on a 6,000 acre ranch would drive an SUV (Such a Usless Vehicle) is beyond me. eh, Orrin?

Mike:

The controls on the A-300 are not, so far as I know, all electronic. The honor of the first commercial totally fly-by-wire aircraft is the A-320.

Bart:

I hope you aren't serious. If for no other reason than MANPADS have a very low Pk (probability of kill) against airliners.

JD:

Well, it isn't. It depends upon what means by full. In commercial aircraft, the amount of available rudder deflection is limited by airspeed. At the speed the A-300 was flying at breakup, full deflection was available. To be FAA certified, the vertical stabilizer has to be able to withstand %150 of design load, where %100 is that imposed under the condition of max rudder deflection at the max airspeed for max deflection.

So far, so good.

However, the problem comes with a rapid rudder reversal. Because that can happen much more quickly than the aircraft's yaw angle can respond, rapid rudder reversals can can impose extreme spike loading far exceeeding the %150 certification limit.

Here is where the problem begins. Aircraft flight manuals are written with the intended operation of the aircraft in mind. For instance, a fighter-type aircraft flight manual will talk in depth about roll-coupling. But for a commercial aircraft, such a discussion is completely irrelevant.

In the case of the rudder, a fighter type aircraft will, depending upon the generation, not impose any rudder limits at all, and make specific warnings about rapid rudder reversal.

Whereas, a commercial aircraft, for which the primary use of the rudder is to coordinate flight under asymmetric thrust (engine out) conditions.(Secondarily, it--depending upon the aircraft generation--improves roll response when initiating and rolling out of turns)

Airbus actively decided to keep the rapid rudder reversal warning out of the flight manual, since it doesn't pertain the properly operating the aircraft.

Unfortunately, they didn't consider the response a pilot might make to crossing wake turbulence with a shallow closing angle, where the pilot would be faced with rapid, sequential, wake induced rolls in both directions.

Hence the vertical stabilizer failure.

And it has not the first thing to do with SUV rollovers. That is far more akin to what race car drivers call a "tank slapper," and in the aviation world is called a pilot induced oscillation.

Thanks, Jeff.

However, doesn't the story say that the information was published, and along with 'a range of issues'?

:What other issues did that co-pilot not bone up on?

Don't pilots RTM? Or RTFM?

Robert:

No moose near you, eh?

Harry:

As I understand it, there had been some discussion between the FAA, NTSB and Airbus as to whether the information should be in the Flight Manual. However, at the time of the mishap, the information simply was not available to line pilots.

It is now.

And yes, we do read the heck out of flight manuals. I'm sure the training at American is the same as at my airline: very high quality, and very demanding. On top of that, the peer pressure is pretty intense. Getting caught on the flight deck not knowing something is unpleasant.

Wonder if the consortium's engieers and executives will catch anywhere near the grief McDonald-Douglas did for their engine mount problem with the DC-10 back in the 1970s?

John:

The DC-10 engine mount problem was a result of American maintenance practices--they used a device to position the engine for installation on the pylon that couldn't move in sufficiently precise increments, resulting in banging into the pylon, causing compressive loads on a structure designed for tensile loads.

MD did catch grief, though, for designing a hydraulic system vulnerability into the airplane--all three systems ran through the tail assembly, meaning an uncontained engine failure in the tail could result in total hydraulic failure.

Does that ring a bell?

The current report suggests the rudder movement snapped off the tail - but didn't the initial reports state that the rudder movement caused one of the engines to snap off? There were pictures after the crash of an engine sitting in the parking lot of a gas station.

Isn't this a major change in the scenario?

Jim:

No.

When the vertical stabilizer departed, the airplane was no longer dynamicaly stable in the yaw axis, and it started an uncontrollable yaw divergence.

The more the divergence, the faster it got worse. And, as is particularly the case with swept wing airplanes, the yaw divergence coupled into the roll axis, so the airplane also went into a rapid roll.

There are a bunch of good reasons to hang engines on wings, but resilience in the face of aerobatic flight just isn't one of them--the combination of roll and yaw forces simply slung the engine off the wing (remember, the engine, spinning at some 10,000 rpm, is one heck of a gyroscope, and wanted to resist mightily these movements).

The sudden full throw of the rudder in the opposite direction after the airplane reached, or nearly so, its yaw limit caused something like a 30,000 pound force on the vertical stabilizer; the 150% design factor was roughly 20,000 pounds. It was the third rudder swap that finally did it in.

Jeff:

Thank you for the details.