Federal authorities and Boeing are investigating an incident involving a 737 Max 8 aircraft that experienced a rare and potentially unsafe oscillating motion known as a Dutch roll during flight. The Federal Aviation Administration described the incident as the nose of the aircraft making a figure-eight. The incident occurred on Southwest Airlines flight 746 on May 25, with no injuries reported, but the plane suffered “substantial” damage. The incident involved damage to the standby power control unit (PCU), which controls the rudder, but it is unclear if this damage led to or resulted from the roll. The aircraft has not flown since the incident and has been moved to a Boeing facility in Washington state for further inspection.
Southwest Airlines has referred the incident to the FAA and National Transportation Safety Board and is actively participating in the investigation. The NTSB has confirmed that they have opened an investigation into the incident and have downloaded data from the flight data recorder to aid in their investigation. Voice recordings from the voice data recorder were overwritten, limiting the information available. Authorities are still determining if the previous FAA requirement for inspections of the rudder assembly on some 737 Max 8 aircraft is related to this incident.
The Dutch roll is a rare and uncomfortable movement that few passengers have felt and even fewer airline pilots have experienced in actual flight. It involves excessive rolling and yawing of the aircraft, making it an uncomfortable and unsettling experience for those onboard. Modern airliners are designed to be stable in the air, but a Dutch roll can be challenging to control and may require specific maneuvers from pilots to correct. In a worst-case scenario, a Dutch roll can lead to significant damage or loss of control of the aircraft, as seen in a previous incident involving a Boeing 707 in 1959.
Aviation experts explain that airplanes move along three axes: pitch, roll, and yaw. While these movements are typically coordinated by the aircraft’s computers, the Dutch roll involves excessive rolling and yawing that is not easily corrected. Pilots may undergo training scenarios where yaw dampers fail, simulating the conditions of a Dutch roll to prepare for such situations. In the event of a Dutch roll, pilots may need to slow the aircraft and descend to thicker air to regain control and stabilize the plane. Despite being a rare occurrence, the Dutch roll can pose a serious safety risk if not addressed promptly and effectively.
