What happened
On April 1, 1996, a Cessna 402B, registration OH-CGA, was performing a B1/IFR flight inspection at Helsinki-Malmi Airport. The flight involved a sequence of maneuvers, including steep turns and simulated approaches, as well as a simulated single-engine condition where the pilot adjusted power to mimic the drag of a feathered propeller.
During the approach to runway 18, the crew intended to perform a low pass before returning for a final landing. Upon touchdown, an unusual noise was heard, and the aircraft descended lower than intended. The pilot initiated a go-around at 600 feet, which stabilized the flight. However, during the subsequent taxi, the crew discovered that the propeller blades on both engines had sustained significant damage, with the tips worn and bent backward by approximately 20 cm. Additionally, the ADF antenna mounting arms on both sides of the fuselage were damaged.
The investigation
The investigation focused on why the landing gear remained retracted despite the crew's belief that it had been deployed. Testing of the landing gear system confirmed that the mechanism, warning lights, and microswitches were all functioning normally.
Investigators examined the cockpit controls and found that the landing gear selector switch in this aircraft type has three positions: up, neutral, and down. The neutral position is easily reached because the lever moves into it without resistance. The investigation established that the lever had likely been left in this neutral position, which keeps the gear retracted but does not trigger the landing gear warning lights. While the landing gear warning horn did activate, the crew likely failed to notice it due to the use of noise-attenuating headsets and potential radio communications.
Findings
- The primary cause of the damage was the failure to ensure the landing gear was fully extended due to the selector lever being left in a neutral position.
- High workload during the approach, compounded by the simulated single-engine configuration and the introduction of a new approach procedure, contributed to the error.
- The crew failed to consult the checklist during the approach phase.
- The pilot's failure to read the checklist likely would have prevented the accident.
- The pilot's decision to accept the flight inspection despite the observed performance deficiencies and the resulting damage was noted as an unprofessional practice.