A Southwest Airlines jet that experienced “Dutch roll” while flying at 34,000 feet had undergone routine maintenance before being parked outside during a strong storm, after which pilots noticed unusual movements of the plane‘s rudder pedals.
Following the incident in May, Southwest Boeing mechanics found “substantial” damage to the plane’s tail, where the rudder is located.
However, the National Transportation Safety Board said it had not determined when the damage occurred.
According to data from Flightradar24.com, the Boeing 737 Max was grounded for more than a month before resuming flights last week.
“Dutch roll” is a swaying, rhythmic combination of yaw, the tail sliding sideways, and the wingtips moving up and down.
The Southwest jet suffered dangerous movement while flying at 34,000 feet and then again when descending to 32,000 feet while flying from Phoenix to Oakland, California.
While the condition can be dangerous, modern planes now have a “yaw damper” to stop the oscillation, which causes the Dutch roll.
After the planes landed, airline mechanics discovered fractures in the metal bracket and ribs, which hold a backup power control unit to the rudder system.
Investigators last week examined the damaged parts in Ogden, Utah.
The plane was parked overnight at the New Orleans airport on May 16 during thunderstorms and heavy rain.
The plane underwent scheduled maintenance on May 23 before pilots noticed the rudder pedals moving when the yaw damper was engaged.
The NTSB said that on May 25, pilots felt the pedals moving during the Dutch roll and after landing.
NTSB issues the preliminary report for its ongoing investigation of the May 25 "Dutch roll" incident involving a Southwest B-737-8. Download the report PDF: https://t.co/9aYAKJhXEL
— NTSB Newsroom (@NTSB_Newsroom) July 9, 2024
All of the 31 Max jets were inspected by Southwest, but no other cases of damage were found around the rudder power units, NTSB said.
The most recent Boeing incident was reported last month, when a Korean Air Boeing 737 Max 8 experienced a sudden emergency plummeting 26,900 feet before making multiple erratic loops before stabilizing.
Fifteen passengers suffered injuries ranging from severe hyperventilation and eardrum pain, according to the Ministry of Land, Infrastructure and Transport.
READ: Southwest Boeing Plane Takes Sudden Dive, Comes Just 500ft of Residential Area
