What happened
On February 12, 2018, at 16:40 UTC, a Beechcraft 76 Duchess, registration CS-DCS, operated by Escola de Aviação Aerocondor S.A., was performing a flight at Ponte de Sor Airfield in Portugal. During the landing phase, the aircraft experienced an abnormal contact with the runway because the landing gear had not been extended.
The investigation
The GPIAAF investigation examined the aircraft's landing gear system, maintenance records, and the crew's operating procedures. The investigation focused on the effectiveness of the landing gear warning horn and the consistency between the Pilot’s Operating Handbook (POH), Standard Operating Procedures (SOPs), and checklists. The investigators also reviewed similar historical events involving gear-up landings in flight training environments.
Findings
- The primary cause of the incident was the landing gear being in the retracted position during touchdown.
- The investigation noted that modern noise-cancelling headsets used by crews can significantly reduce the audibility of the landing gear warning horn.
- There was a lack of uniformity between the POH, SOPs, and checklists, which can hinder quick and accurate information retrieval during critical flight phases.
- Pilot distraction or the interruption of established routine patterns was identified as a common factor in similar gear-up landing occurrences.
- The landing gear warning horn test was not specifically mandated during every annual inspection at the time of the event.
Safety action
Following the investigation, several safety actions were established or are under development:
- The training department will perform random written tests for instructor pilots regarding SOPs and manual knowledge.
- Maintenance procedures will now include a specific test of the landing gear warning horn during annual inspections.
- An operational placard will be placed on the instrument panel to remind pilots to verify the gear position.
- A visual warning (a "G" sign) is being developed for the flight display to trigger when the aircraft reaches the appropriate speed for gear extension.
- The manufacturer has been contacted to explore piping the warning horn audio through the aircraft intercom to bypass the noise-cancelling effects of modern headsets.
- Air Traffic Controllers (ATC) have adopted best practices to inform crews during the approach phase if they observe the gear is not down.