As has been plastered all over the main stream media sights, an ANA Boeing 737-700 travelling from Okinawa to Tokyo had an inflight 'upset' that resulted in two flight attendants being injured and a few passengers complaints. The incident itself took place on September 6th but wasn't brought to the airlines attention until the next day and was just recently reported to the public this weekend.
What happened was that the pilot of the airplane left the cockpit to utilize the lavatory. The co-pilot was in command 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. This caused the plane to eventually enter a descending roll. According to reports the plane descended 6,200 feet in less than 30 seconds and rolled 130 degrees, or 50 degrees short of being fully inverted. The Japan Transport Safety Board 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 first officer and captain were able to regain control of the airplane and continue the rest of the flight uneventfully (though I'm sure there was some interesting conversation on the flight deck after that as well as in the cabin.) The pilot was reported to be near or at 60 years of age with over 16,000 hours of flight time and the first officer was 38 years old with 2,400 hours of flight time.
Now, how could this happen? If you look 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; however, if not really paying attention and reaching over blindly, you can see how they MAY be mistaken. I have added the following picture of a KLM 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. I've included the link to the photo at Airliners.net so you can see the large version and the respective switches more easily.
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.
Some closer pics of the same knobs, but on older models of the Boeing 737 when the knobs were actually a little farther apart. You can see they are still they same design in regards to shape and size.
Now, watching the video animation of the actual movement of the airplane, I'm still having a bit a trouble visualizing this ONLY being a rudder trim issue, and I've spoken with two Boeing 737 pilots for other airlines and it seems there had to be more at play. Both knobs are twist and hold, with a spring-return mechanism. So once you release, the knob should return to the neutral position. If this is accurate, than the first officer had to twist and hold the rudder control knob long enough to cause a significant enough trim move that the autopilot disconnected. If you watch the animation video, it seems like the plane started some motion to the right, compensated back to straight and level, and then snapped into the left roll and dive.
Now, this is ONLY my assumption and speculation, it would appear that the pilot probably reached over blindly to open the flight deck door. He accidentally twisted and held the rudder trim, and continued to hold it as the captain tried to open the door. The autopilot tried to compensate, resulting in the initial correction to back left as shown in the animation. Once the deflection in the trim caused enough motion, the autopilot disengaged, allowing the plane to snap into the roll/dive. It's amazing the pilot (not sure if the captain was back on the flight deck by that point) recovered in less than 30 seconds. Remember, this occurred at 1030 PM local time, and apparently over water, which could easily lead to further spatial disorientation. (The darkness and lack of ground reference could be why the initial yaw was not noted by visual cues outside the windows.)
The cause could be a combination of any factor, but fatigue (given the late hour of the flight) as well as even complacency that resulted in the pilot simply reaching over blindly to activate the door lock knob.
As for what happened behind the flight deck, the articles in other media have quoted the safety board as saying 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. At first I was a little hesitant to believe it, but this is actually plausible as only two flight attendants suffered minor injuries and a couple of passengers complained of 'feeling strange' (you think?!).
I hope that the safety board releases a detailed report, with CVR and FDR transcripts to see exactly WHAT occurred aboard the flight that night. It's should be utilized as a great learning experience not only for the pilot's involved or ANA pilots, but all pilot's in any airplane.
Remember, the Air France Flight 447 was allegedly a result of pilot error resulting from spatial disorientation after the autopilot shut off following erroneous instrument readings. (Not saying this is related at ALL, but shows the need for pilots to always be aware of all circumstances surrounding the flight at each moment.)
If you are a B737, please provide your comments, opinions and thoughts below. I would love to have more first hand accounts on this issue.