What happened
On November 4, 2008, a Beechcraft BE-76 Duchess, registration CS-DCS, was conducting a routine flight training mission involving successive takeoffs and landings at the Aeródromo Municipal de Cascais. After completing three successful circuits, the crew prepared for a fourth landing. During this approach, the crew failed to extend the landing gear.
The error was only identified when the air traffic control tower alerted the crew to the gear's position. The instructor pilot immediately attempted a go-around by applying full power. However, because the aircraft was already at a low altitude and low airspeed, the propellers struck the runway surface. The impact caused significant deformation to the propeller blade tips and induced severe vibrations in both engines. Due to the intensity of the vibrations, the pilot was forced to reduce power and complete the landing on the belly of the aircraft.
Both the instructor and the student pilot were uninjured. The aircraft sustained damage to the lower fuselage, the nose gear doors, and the wing trailing edge near the root, along with the damaged propellers.
The investigation
The GPIAAF investigation examined the flight history, the aircraft's maintenance status, and the crew's performance. The investigation established that the crew was properly qualified and the aircraft was airworthy with a valid certificate of airworthiness. The investigation focused on why the landing gear omission went undetected during the approach and why the cockpit warning systems failed to alert the crew.
Findings
- The primary cause of the incident was the omission of the landing gear extension.
- The crew failed to properly execute and verify procedures through the use of checklists.
- The "routine effect" and accumulated fatigue from performing repetitive flight maneuvers contributed to a state of semi-consciousness, where the crew performed tasks automatically without active verification.
- The visual warnings for the landing gear were not recognized, potentially due to sunlight interference.
- The audible landing gear warning horn was deactivated at the time of the incident, removing a critical layer of redundancy.
- High wind conditions (310/36kts) were present during the approach.