What happened
On June 11, 2017, a Boeing 738 was performing its final approach to the Lepa area. During the descent, the pilot attempted to extend the flaps from position 15 to position 30. However, the actual flap extension failed to reach the commanded setting, instead reaching only position 25 as indicated on the cockpit instruments.
Following this discrepancy, a "TOO LOW FLAPS" aural warning was triggered in the cockpit. Rather than executing a missed approach, the crew activated the flap inhibit switch to silence the alert and continued the approach. The aircraft landed without further incident or damage.
The investigation
The investigation, conducted by the operator, focused on the crew's response to the mechanical discrepancy and the subsequent handling of cockpit alerts. Post-flight inspections and system tests were performed on the aircraft's flap mechanism, which were completed successfully, indicating no permanent mechanical failure.
Findings
- The primary cause of the incident was the failure to follow established landing approach procedures following a system discrepancy.
- The crew chose to silence the cockpit warning via the flap inhibit switch instead of initiating a Go-Around (G/A) procedure.
- The crew failed to perform the required Non-Normal Checklist (NNC) for a "TRAILING EDGE FLAPS DISAGREEMENT."
Safety action
Following the event, the operator's training department conducted a disciplinary interview with the crew. During this session, the importance of executing a Go-Around and following the appropriate checklists during flap malfunctions was reinforced.