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Report: Overreliance on autoflight system causes Japanese Saab 340 crew to descend to 90 feet during go-around
27 November 2014

 

Saab 340B JA03HC (Photo: Kentaro Iemoto / CC:by-sa)

Saab 340B JA03HC (Photo: Kentaro Iemoto / CC:by-sa)

The Japan Transport Safety Board (JTSB) released their investigation report into a serious incident in which a Saab 340B had descended to 90 feet during a go around procedure. The flight crew probably excessively relied on the autoflight system, according to the JTSB.

The Saab 340B, registered JA03HC, operated by Hokkaido Air System, took off from Hakodate Airport, Japan as a scheduled Flight 2891. During the approach to runway 31 of Okushiri Airport, the aircraft executed a go-around and started climbing, reaching an altitude of 750 feet. The airplane then began to descend. When flight crew became aware of the situation they executed an emergency climb from a radio altitude of 90 feet.
The aircraft flew back to Hakodate Airport, following some holdings over Okushiri Airport.
No one was injured and there was no damage to the aircraft.

Probable Causes:
In this serious incident, during the approach to Runway 31 of Okushiri Airport, the Aircraft executed a go-around and once started climbing but it soon reverted to descend and came close to the ground. Consequently, flight crewmembers came to realize the situation and executed an emergency operation to avoid crash to the ground.
It is highly probable that the Aircraft’s descent and approach to the ground was caused by the following factors:
(1) The PIC followed the Flight Director command bar instructions, which indicated the descent because the altitude setting was not changed to the initial go around altitude, and subsequently the PIC made the Aircraft descend even lower than the FD command bar instructions.
(2) The PIC and the FO could not notice descending of the Aircraft and their recovery maneuvers got delayed.
It is highly probable that these findings resulted from the fact that the PIC could not perform a fundamental instrument flight, the PIC and the FO used the Autopilot/Flight Director System in an inappropriate manner without confirming the flight instruments and the flight modes, and the FO could not transiently carry out closer monitor of the flight instruments because of the other operations to be done.
Moreover, it is probable that the FO’s operation of engaging an autopilot and changing the vertical mode to make the Aircraft climb by using the Autopilot/Flight Director System eventually became a factor to delay avoiding maneuvers against ground proximity.
It is probable that the Company didn’t create a standard procedure, reflecting the contents of Aircraft Operating Manual, for its crewmembers to confirm and call out the changes mode, without noticing its importance and didn’t carry out adequate training. Furthermore, it is probable that the PIC and the FO excessively relied on the autoflight system.

 

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