Friday, November 09, 2018

Crash of Lion Air 737 MAX Raises Questions About Autopilot And Pilot Skills

The FAA issued an emergency airworthiness directive Wednesday to airlines operating the new Boeing 737 MAX, calling on them to better instruct pilots on how to deal with a potential faulty reading from a key gauge, an angle of attack sensor, that's supposed to help keep planes from falling out of the sky. The directive follows the discovery that the sensor was malfunctioning on a Lion Air 737 MAX that plunged into the sea off Indonesia on Oct. 29, killing all 189 aboard.

The accident and the FAA warning, which comes after Boeing issued a similar bulletin, may be less an indication that there’s anything wrong with the new version of Boeing’s top-selling plane than a sign of how increasingly automated flight systems are eroding pilot skills, says Keith Mackey, a Florida-based safety consultant who’s a former airline pilot and accident investigator.

To put it simply, says Mackey, the FAA’s directive tells pilots to turn off the plane's autopilot system, and if necessary the pitch trim system too, and fly the plane yourself.

“It’s unfortunate that they even have to write something like this,” says Mackey. “It should be understood.”

The angle of attack sensor is a vane on the wing that gauges air flow to determine if the wing is generating enough lift. That air flow can be disrupted if the plane slows down or goes into too steep a climb, putting the plane in danger of stalling. In that situation the 737 MAX has a pitch trim system that automatically pushes the nose down to prevent a stall. The FAA's and Boeing's bulletins explain to pilots how to disengage the system in the event that a faulty reading from the angle of attack sensor leads it to push the nose down.

Shortly after takeoff from Jakarta, the Lion Air plane’s pilots requested to return to the airport, but they never turned back, plunging into the water at high speed.

Based on the evidence available, says Mackey, the pilots may not have disengaged the autopilot or the trim system, which given the faulty angle of attack reading, may have lowered the nose and dived the plane into the water.

“The pilot should have recognized that I’m getting an erroneous indication on my airspeed,” he says. “It’s a nice day, you can look out the window and see that the airplane isn’t flying nose high.”

He sees the accident as indicative of two problems: the increasing use of autopilot is giving pilots less flight time to maintain basic skills, and a lower level of experience and training among pilots in the developing world.

“You get a lot of takeoffs and landings but no one gets much flying practice,” says Mackey. “They’re getting to be good computer programmers, they know which buttons to push and when to push them. When something begins to fail it becomes a puzzlement.”
08/11/18 Jeremy Bogaisky/Forbes