Did Similar Switches Confuse Pilots? -- Controls' Proximity Another Aspect Of Crash Probe
One pair of switches is labeled "cut out," the other "cut off."
Both are designed to be used only under unusual circumstances in flight. And they can be found in close proximity to each other in the cockpit of Boeing 767 jetliners.
The significance of the switches and their proximity is not clear as investigators press their inquiry into the Oct. 31 crash of EgyptAir Flight 990. For the moment, they are focusing on a theory that the backup pilot, alone in the cockpit, forced the jet into a suicide dive.
But investigators have not ruled out mechanical failure. And, among other things, they are looking into an alternative theory being discussed by some 767 pilots: that the EgyptAir crew inadvertently might have moved the fuel-system "cut off" switches, shutting down the plane's two engines, while intending to flip the nearby stabilizer-trim "cut out" switches in an effort to pull the jet out of its sudden dive.
EgyptAir 990's flight-data recorder revealed someone indeed moved the pair of levers designated to cut off fuel to both engines of the Boeing 767-300ER jetliner about 35 seconds into the dive.
Shutting down the engines at such a time goes against all pilot training and intuition.
The leading theory of the moment at the National Transportation Safety Board (NTSB), sources close to the investigation say, is that the backup pilot, Gameel el-Batouty, intentionally put the plane in its lethal dive, then struggled at the controls against Capt. Ahmed Mahmoud el-Habashy's efforts to right the aircraft.
Experienced aircraft crash investigators caution, however, that accurately correlating information from the cockpit and flight-data tapes is a tedious endeavor that often takes weeks or longer.
Conclusively determining who is saying what on a cockpit recorder involves painstakingly separating and identifying a cacophony of voices and background sounds, said Chuck Miller, a Sedona, Ariz.-based safety consultant and former NTSB crash investigator.
Deciphering what English-speaking pilots are saying often proves daunting, Miller said. The EgyptAir pilots were speaking excitedly in a Middle Eastern dialect full of cultural nuances, he said.
"I think the speculation being fueled by leaks of the cockpit transcript are absurd," Miller said. "I've seen arguments over interpretations (of voice transcripts) last years. It just doesn't make any sense for anyone to pick up bits and pieces and say this is the story."
In fact, it will take investigators many months to sort through less-sensational scenarios involving possible mechanical malfunctions that may have put the jet in a dive.
"We are not ruling anything out at this point," NTSB spokesman Keith Holloway said. "Everything is still being considered."
People familiar with the investigation said that, while continuing to pursue the pilot-suicide theory, authorities also are examining possibilities involving a mechanical emergency compounded by poor crew response.
One scenario is a "runaway stabilizer" - the horizontal stabilizer moving on its own during flight, tilting the aircraft's nose down. The stabilizer is made up of movable panels on the jet's tail section, which help it maintain level flight.
The emergency procedure for a runaway stabilizer calls for pilots to shut down hydraulic pressure to the stabilizer by removing a guard covering a pair of two-position toggles and flipping theses "stabilizer trim" switches from from "normal" to "cut out."
The stabilizer trim switches are located on the console between the two pilots' seats, directly alongside another pair of switches that control fuel being pumped into the engines. These fuel-control knobs must be lifted slightly to move among three settings: "run," "rich" and "cut off."
Some 767 pilots puzzling over the crash have started discussing whether the EgyptAir crew inadvertently might have moved the fuel-system "cut off" knobs instead of flipping the stabilizer-trim "cut out" toggles during the confusion of trying to recover from a sudden dive.
"I say let's exhaust the possibilities of a mechanical error or a dumb mistake the crew might have made before we create momentum for the malicious-pilot theory," TWA 767 pilot Bud Bensel said.
The crew of EgyptAir Flight 990 was not the first to shut down both engines of a Boeing 767 in midflight. At least twice before, veteran pilots have cut off fuel to both engines while reaching for a nearby switch.
On June 30, 1987, shortly after a Delta 767 took off from Los Angeles with 205 passengers on board, Capt. John Gilfoil mistakenly moved the fuel-control knobs to the "cut off" position while intending to move other switches on a nearby engine-control panel.
With both engines shut down, the 767 dropped from 2,000 feet to 500 feet above the Pacific Ocean, before Gilfoil restarted the engines and flew on to Cincinnati.
The Federal Aviation Administration stripped Gilfoil of his captain's license, but allowed him to continue flying as a first officer.
Noting that a similar incident had occurred on a United 767 flying over San Francisco on March 31, 1986, the FAA in 1988 ordered airlines to move the engine-control panel to an overhead console within one year.
That required move had been implemented on the EgyptAir jet that crashed into the Atlantic Ocean in the early morning of Oct. 31.
A definitive explanation for the EgyptAir crash awaits recovery of more evidence from the ocean floor and a thorough review of any history of malfunctions of the 767's autopilot, stabilizer and other parts and systems that may have come into play, said James McIntyre, a retired TWA 747 pilot from Waterville Valley, N.H.
"I feel those guys are falling into a trap," he said. "Everybody is speculating. Nobody is working off hard evidence yet. The hard evidence is there. They've just got to keep looking and getting things to match up."
Byron Acohido's phone-message number is 206-464-2352. His e-mail address is bacohido@seattletimes.com