The Federal Aviation Administration (FAA) is investigating after a Boeing 737 MAX 8 jet experienced a “Dutch roll” event on May 25, causing “substantial” damage to the plane.
During a Dutch roll, the plane’s tail moves left to right in an oscillating motion—a “yaw” rotation—while the wings “roll” upward and downward along the plane’s vertical axis, causing the nose to make a figure-eight. The motion can cause serious safety risks.
However, a post-flight inspection revealed “substantial” damage to the plane’s “standby power-control unit,” a backup system that’s used if the main rudder power unit becomes inoperable during flight.
The U.S. National Transportation Safety Board (NTSB) and FAA are both investigating the accident.
The FAA told The Epoch Times that the agency is “working closely with the NTSB and Boeing to investigate this event” and will take “appropriate action based on the findings.”
Southwest Airlines “performed maintenance on the airplane and discovered damage to structural components” before notifying the NTSB about the incident and the plane’s damage on June 7, the safety board told The Epoch Times.
The NTSB said it received the airplane’s digital flight recorder data to “aid investigators in determining the length and severity of the event.”
However, the cockpit voice recorder, which is limited to two hours of recorded audio, “was overwritten and unavailable to investigators,” the NTSB added.
Boeing and Southwest Airlines didn’t respond by press time to a request by The Epoch Times for comment.
Juan Browne, a Boeing 777 first officer pilot for a major U.S. airline company, told The Epoch Times that during a Dutch roll, the airplane wobbles left and right and hitches up and down slightly.
“It’s not a violent maneuver, but a bit of wobbling around, and then it sounds like they got it under control and landed uneventfully,” he said.
Mr. Browne said that turbulence can set off a Dutch roll but that normally, airplanes have a component—known as a yaw damper system—that prevents this kind of oscillating motion.
He said the damage was “unusual” as the backup power control unit was affected instead of the main one, which usually handles rudder control first and would be harmed before the backup.
“And we’re just beginning to learn the extent of this damage,” Mr. Browne said, adding that the plane is grounded while the NTSB investigates.
Until the NTSB determines the probable cause of the accident, it’ll be hard to say what it was, the pilot said.
Another possibility is pilot error. While the jet’s yaw damper is supposed to autocorrect any turbulence-influenced rolls, a pilot can accidentally hit the rudder pedals while stretching his or her legs in the cockpit.
Mr. Browne said that accidentally striking a rudder pedal could induce a Dutch roll.
“We don’t know if it was a mechanical problem or a failure of the damper system that initiated this or was environmentally induced.”
