Investigation Summary
The incident occurred while the aircraft was cruising at 41,000 feet. The Captain had left the flight deck to use the lavatory, leaving the First Officer as the sole occupant of the cockpit. When the Captain signaled to re-enter, the First Officer reached for the door-lock selector but inadvertently operated the rudder trim switch located nearby. Because the First Officer had recently transitioned from the Boeing 737-500 to the 737-700, he was susceptible to habit interference, as the layout and operation of these switches differed between the variants. The sustained rudder input caused the autopilot to disconnect and the aircraft to roll violently to the left. During the subsequent dive, the stick shaker activated, further confusing the First Officer who had not been trained for high-altitude stall recovery or solo-pilot emergency handling. The Captain was initially unable to stand due to the G-forces but eventually regained his seat to assist in the recovery.
Final Conclusions
The Japan Transport Safety Board (JTSB) concluded that the primary cause was the First Officer's erroneous operation of the rudder trim switch instead of the door-lock selector. Contributing factors included the First Officer's lack of familiarity with the 737-700 switch layout compared to the 737-500, and inadequate training regarding high-altitude upsets and stick shaker activation. The JTSB also noted that the similarity in the rotational operation of the two switches, despite their different functions, facilitated the error.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Pilot Flying (PF)
First Officer
Pilot Monitoring (PM); recently transitioned from B737-500.
Systems & Failure Modes
Rudder Trim Switch
A rotary switch on the aft electronic pedestal used to adjust the neutral position of the rudder. In this incident, it was rotated instead of the door-lock selector.
Flight Deck Door-Lock Selector
A switch used by the flight crew to grant or deny access to the cockpit. Its proximity to the rudder trim on the 737-700 led to the pilot's confusion.
Stick Shaker
A mechanical device that vibrates the control yoke to warn the pilot of an impending stall. Its activation during the dive surprised the First Officer.
Interesting Facts
- 01The aircraft reached a maximum bank angle of 131.7 degrees, nearly flying upside down.
- 02The dive resulted in a maximum vertical acceleration of 2.68 G's.
- 03The cockpit voice recorder (CVR) data was lost because it was overwritten by the 30-minute recording loop.
- 04The First Officer had only 197 hours of experience on the Boeing 737-700 at the time of the incident.
- 05All 112 passengers were wearing seatbelts, which prevented serious injuries during the upset.
- 06Six passengers later complained of feeling unwell following the incident.
Safety Actions & Advisories
Upset Recovery Training
JTSB recommended that airlines conduct inflight upset recovery training at various altitudes, including high-altitude scenarios where stall warnings may activate.
Cockpit Design Review
The JTSB issued a recommendation to the FAA to instruct Boeing to improve the design and placement of cockpit switches to prevent similar confusion between the rudder trim and door-lock controls.
Location
APPROXIMATE POSITION · AIRPORT LEVEL · Coordinates are the estimate published in the official investigation report. The ring shows the accuracy the record supports, not the point of impact.