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- MSNBC - Golf champion Payne
Stewart,s tragic flight across the nation,s heartland was the result of
a strangling lack of oxygen that left a high-tech autopilot system in control,
aviation experts say. It was a rare but not unprecedented odyssey.
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- Even while the twin-engine Lear 35 jet was in the midst
of its flight, aviation experts speculated that the plane had suffered
a catastrophic loss of cabin pressure.
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- The plane took off Monday morning from Orlando, Fla.,
heading for Dallas. The crew,s last contact with controllers occurred over
Gainesville, Fla., when the pilot was given the go-ahead to climb to 39,000
feet. But instead of turning westward, the plane continued on a northwest
heading.
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- When Air Force jets scrambled to intercept the jet, pilots
saw no indication that anyone was at the controls. What,s more, the plane,s
windows seemed fogged or frosted over, said Air Force Capt. Chris Hamilton.
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- For four hours and 1,500 miles, the plane followed a
straight line, at altitudes as high as 46,000 feet, until it ran out of
fuel, finally crashing into a marshy farm field near Mina, S.D. Stewart
and at five others were dead. All this is consistent with a loss of pressure
so sudden that the pilot and co-pilot could not put on their oxygen masks.
As altitudes rise above 10,000 feet, the air gets so thin that the brain
gradually becomes starved of oxygen. That,s why airline cabins are pressurized,
and that,s why the masks are required to be at the ready at high altitudes.
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- If cabin pressure is suddenly lost at 40,000 feet, the
pilots would have about 15 seconds to put on their masks before they lose
consciousness.
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- To guard against a loss of pressure, the Learjet was
equipped with an array of redundant systems, warning lights and alarms.
The pilot and co-pilot " and even Stewart " were trained to recognize
the signs of oxygen deprivation and take action within just a few seconds.
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- "There may have been more than one failure, speculated
David Stempler, president of the Air Travelers Association.
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- Stempler cautioned that it was too early to eliminate
alternate scenarios for the accident " ranging from a more gradual,
undetected pressure drop to asphyxiating smoke in the cabin. But the outcome
was clear: The plane,s autopilot system, which is routinely used to keep
a plane on track even when the pilot is at the controls, kept the jet climbing
into the air after the crew was incapacitated.
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- The Learjet leveled off at what was most likely its operational
ceiling " the altitude at which the craft,s aerodynamics reach the
upper limits " and stuck to its straight-line course until the fuel
was gone.
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- PAST PRECEDENTS Such scenarios involving autopilots have
arisen before: Some military pilots have blacked out from lack of oxygen
at high altitudes, and Stempler said "we,ve had cases where pilots
have fallen asleep.
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- The best-known incident dates back to Jan. 10, 1980,
when Louisiana State University football coach Bo Rein and his pilot were
killed in a crash reminiscent of Monday,s tragedy.
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- Rein,s Cessna Conquest plane left Shreveport, La., for
what was to have been a short hop to Baton Rouge. But en route, controllers
lost contact with the pilot. The plane climbed to 41,000 feet, heading
on a straight-line course to the Virginia coast. Military jets intercepted
the Cessna, but pilots could see no signs of life within the cabin "
only the glow of the instrument panel,s indicator lights.
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- Three and a half hours after the flight began, the plane
fell out of the sky and crashed into the Atlantic. No debris or remains
were recovered. Although the National Transportation Safety Board could
not determine the cause of the crash, observers speculated that sudden
loss of cabin pressure played a key role. (The tale is told on the Parascope
Web site in an account titled <http://www.parascope.com/articles/0997/oblivion.htm"Flight
to Oblivion.)
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- LOOKING FOR ANSWERS
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- Monday,s incident is different in that the wreckage may
provide clues as to the tragedy,s cause " although the investigators,
task is complicated by the fact that small planes such as the Learjet don,t
carry the flight recorders used on commercial airliners.
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- Stempler said controllers were able to minimize the risk
to air traffic by diverting airplanes from the runaway jet,s path. In this
regard, the Learjet,s high altitude was a blessing: "Most airplanes
don,t operate at 40,000 feet, he noted.
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- But it was a sheer stroke of luck that the jet came down
in an open field rather than a populated area, he said.
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- "I think the military did a wise thing tracking
this airplane, Stempler said. "They probably should have shot it down.
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- The Associated Press quoted Pentagon officials as saying
the Air Force pilots tracking the Learjet could tell that the aircraft
was not headed toward a heavily populated area. Thus, the option of shooting
the jet down was never brought up, said Pentagon spokesman Kenneth Bacon.
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- Might downing the jet have become an option if it headed
toward a major city? "It never reached that point, Bacon said.
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