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 operation at Ponte de Sor Airfield in Portugal. During the landing phase, the aircraft experienced an abnormal contact with the runway due to the landing gear not being properly extended and locked.
The investigation
The GPIAAF investigation focused on the landing gear configuration and the procedures followed by the crew. The investigators examined the aircraft's maintenance records, the pilot's training history, and the Standard Operating Procedures (SOPs) of the operator. The investigation also reviewed similar historical events involving gear-up landings to identify patterns of pilot distraction or procedural deviations. The inquiry looked into the effectiveness of the landing gear warning horn and the potential for modern noise-canceling headsets to mask such auditory warnings.
Findings
- The primary cause of the incident was the landing gear being in the retracted position during touchdown.
- The crew failed to verify the landing gear position correctly during the approach.
- There was a lack of uniformity between the Pilot’s Operating Handbook (POH), the SOPs, and the aircraft checklists, which could lead to confusion during critical flight phases.
- Modern noise-canceling headsets used by the crew may have prevented the pilot from clearly hearing the landing gear warning horn.
- The investigation noted a trend of gear-up landings during instructional flights, often stemming from pilot distraction or the interruption of established flight patterns.
Safety action
Following the investigation, several safety improvements were implemented or proposed:
- The operator updated flight test forms to include specific checks for the landing gear warning horn and manifold pressure reference values.
- The landing gear warning horn test was integrated into the annual inspection requirements.
- A new operational placard was added to the instrument panel to remind pilots to verify the gear position.
- A visual warning (a "G" sign) was added to the flight display to trigger when the aircraft reaches the appropriate speed for gear extension.
- The training department implemented random written tests for instructors regarding SOPs and local procedures.
- The manufacturer was contacted to explore piping the warning horn audio through the aircraft intercom to ensure audibility despite noise-canceling technology.
- Air Traffic Controllers (ATC) adopted a practice of informing crews if they observe the landing gear is not down during the approach phase.