Tuesday, January 18, 2005

But Will the Tail Fall Off?

Airbus unveiled their new giant deathtrap today, the A380, a "super jumbo" that in its initial iteration - there will likely be larger models - can carry up to 550 unfortunates in all the comfort of a sardine tin.

I have a rather low opinion of Airbus. A friend of mine, an aeronautical engineer who works at NASA Dryden does too. Referring to the American Airlines Airbus crash in New York in 2001, he said, flatly, "The tail should not have fallen off no matter what the copilot did." Others agree. Here's Peter Garrison, a columnist for Flying Magazine:

Ever heard of Sten Molin? He was the pilot whose overaggressive use of the rudder pedals of an American Airlines Airbus brought the airplane down on Long Island late in 2001 with the loss of 265 lives. His name was in all the papers. The National Transportation Safety Board said it was his fault.

Close reading of the NTSB report, released in late December 2004, reveals, however, that Molin was merely a convenient fall guy. The real cause of the accident was a conspiracy of ignorance persistently tolerated by the Federal Aviation Administration, the airlines and the airplane manufacturers. The pilot was the last link in a chain of causes that made him as much the innocent victim as anyone else who died in that airplane.

Molin, whom colleagues described as a smooth, accurate and above-average pilot, was just doing what he had been trained to do, and under circumstances in which he and all other pilots believed that nothing they did could possibly hurt the airplane. That a few not-very-hard kicks on the Airbus' unusually sensitive rudder pedals could actually break the vertical fin off the plane, dooming it to certain loss of control, was a fact that only some aeronautical engineers, and a few oddly reticent bureaucrats at the FAA, understood.

The Federal Aviation Regulations prescribe the strength of every part of an airplane. Some requirements are based on turbulence, others on maneuvers that the pilot can perform. Because the strains that maneuvers impose on an airplane increase as the plane's speed increases, engineers select a certain speed, called the maneuvering speed, as an upper boundary. Before the Airbus accident, nearly all pilots believed that as long as an airplane was flying at or below the maneuvering speed, nothing they could do would break it.

That belief was universal in part because it was so logical. After all, what would be the point of publishing a "maneuvering speed" if it were not a safe speed for maneuvering? Besides, the FAA explicitly supported it. The government's own Pilot's Handbook of Aeronautical Knowledge says "any combination of flight control usage (below the maneuvering speed), including full deflection of the controls ... should not create an excessive air load."

Airlines and manufacturers had developed training curricula designed to encourage pilots, who normally fly with a velvet touch to keep passengers comfortable, to use all the controls uninhibitedly in certain emergencies. Sometime before the Airbus crash, when an instructor pilot asked Molin why he had used the rudder so vigorously during a simulated wake turbulence encounter, Molin had cited an American Airlines pilot-education program that specifically encouraged doing so.

Molin's Airbus was below the maneuvering speed when it broke apart. Its fin came off because he stepped on the rudder pedals alternately, in quick succession, in an attempt to steady the aircraft after it had been jolted by the wake of another airliner.

Strangely, federal regulations require the vertical fin to be strong enough to withstand full deflection of the rudder -- the movable rear portion of the surface -- only when the airplane is flying straight ahead, but not when it's "yawed" -- that is, pointed a few degrees to one side or the other. The effect of alternating rudder inputs is just that -- to yaw the airplane. Yet no pilot's handbook, no simulator curriculum and no FAA publication mentioned the possible dire consequences before the Airbus crash.

Indeed, and the NTSB report, which I have read, crucifies Sten Molin (safely dead and unable to complain) at the expense of Airbus Industrie, which constructed an airplane that would fall apart at low speeds with less than full rudder deflection. What crap. Fly them if you like. I don't.


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