An ANA Boeing 737-700, traveling from Okinawa to Tokyo, had an inflight ‘upset’ that resulted in two flight attendants being injured but only a few passengers complaints. The incident took place on September 6th around 10:50 pm local time but wasn’t brought to the airlines attention until the next day and was just recently reported to the public this weekend.
The incident began when the 60 year old captain with 16,000 hours of flight time left the cockpit to utilize the lavatory. The first officer, who was 38 and had 2,400 hours of flight time, remained in control and secured the door per safety requirements. When the captain tried to re-enter the flight deck and the first officer reached for the door lock controls, it appears that he accidentally turned the wrong knob, the rudder trim control. The plane then experienced an extreme roll maneuver and dive that resulted in a loss of more than 6,200 feet in less than 30 seconds. During the incident, the aircraft also rolled 130 degrees, just 50 degrees shy of being fully inverted. The first officer and captain were able to regain control of the airplane and continue the rest of the flight uneventfully.
Looking at the cockpit layout of the 737-700, the ‘Flight Deck Lock’ knob and the ‘Rudder Trim’ knob are located in the same section, and one right above the other. They ARE different sizes. The first link below if of the center console of a KLM Airlines 737-700 cockpit for reference. The two knobs are located at the bottom of the center console, in the middle. You can see the words, ‘Flt Dk Door’ above the bottom one that controls the lock on the door.
Click Here to view the photo (click on large for full detail)
Another photo from a different airlines B737-700 shows the same knobs, but in a different location:
Click Here to view the photo.
The Japan Transport Safety Board also released a computer animation of the event and can be watched (.wmv file) here. (http://www.mlit.go.jp/jtsb/video/JA16AN-movie1.wmv)
The incident is only in the preliminary review stage; however, it appears that as the first office reached for the knob to unlock the door to let the captain in, he inadvertently turned and held the rudder trim knob. This caused the plane to begin the roll and, once past a certain point, caused the autopilot to disengage. This would then lead to a sharp and quick snap into the extreme roll and dive as seen in the animation.
Only a few passengers complained of feeling strange. The safety board did state that the forces resulting from the roll and concurrent dive would actually have resulted in the passengers not feeling the full effects of a 12,000 FPM drop or 130 degree inversion.
The airline has already stated it is focusing on ensuring proper training and identification of the knobs to avoid similar errors in the future and the safety board is reviewing the flight data recorders and cockpit voice recorders to fully understand the events that led up to the incident.