What happened
On the night of September 12, 1993, an Air France Boeing 747-428 B, registration F-GITA, was operating a scheduled flight from Los Angeles to Tahiti. During the final approach to runway 2 and 22 at Tahiti Faa’a International Airport, the aircraft was performing a VOR-DME approach.
As the aircraft descended through 500 feet, the captain noted changes in the Flight Mode Annunciator (FMA) instructions. The aircraft's speed increased to 180 knots at 150 feet, and the copilot noted that the controls were tending to move forward, requiring him to hold them in the idle position. The copilot also reported being unable to disconnect the autothrottle.
Touchdown occurred at 21:05 local time with a speed of 168 knots. Approximately two seconds after the wheels touched the runway, the number 1 engine (outside left) experienced a sudden increase in power, stabilizing at 107% N1 in full forward thrust. This surge prevented the deployment of spoilers and disarmed the automatic braking system. The crew attempted to use reverse thrust on engines 2, 3, and 4, but the asymmetric thrust caused the aircraft to veer laterally off the runway. The aircraft eventually came to a halt in the adjacent lagoon, with the forward section submerged in water.
The investigation
The investigation focused on the behavior of the automatic flight systems during the approach and the specific mechanical failure of the engine thrust regulation. Investigators examined the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) to reconstruct the sequence of events. Key areas of study included the VNAV approach mode, the interaction between the autothrottle and the pilot's manual inputs, and the failure of the number 1 engine's thrust reverser to actuate correctly following the surge. The investigation also reviewed the crew's management of the non-stabilized approach and their subsequent attempts to control the aircraft during the excursion.