What happened
On March 19, 1998, a Beechcraft BE58P, registration HB-GPC, was conducting a scheduled flight from Basel to Altenrhein under IFR conditions. During the approach to Altenrhein, the pilot deployed the first stage of flaps and attempted to extend the landing gear. However, the gear failed to deploy, and the cockpit indicators remained dark.
Following the failure, the pilot proceeded to fly toward Zurich to reach visual flight conditions, where emergency procedures could be executed. The pilot attempted to manually extend the gear using the onboard hand crank. Despite various efforts—including maneuvering the aircraft to create positive G-loads and even using a fire extinguisher to strike the lever—the gear remained retracted. The nose gear door mechanism was found to be jammed. Ultimately, the pilot decided to perform an emergency landing on Runway 14 at Zurich Airport. The airport fire service prepared a foam carpet to mitigate fire risks. The aircraft landed with the gear up, resulting in one injury to the pilot and damage to the propeller, fuselage underside, antennas, and landing gear doors.
The investigation
Investigators examined the aircraft's maintenance history and the mechanical state of the landing gear system. The aircraft had undergone a 100-hour inspection approximately 1,400 flight hours prior to the accident, during which the landing gear motor brushes had been inspected and found to be in good condition.
Upon recovery, the aircraft was placed on supports, revealing that while the landing gear could be manually extended and locked, the electric motor was non-functional. A detailed inspection of the motor brushes showed that while one brush was normal, the second brush had a detached copper lead. The spring associated with this brush had overheated and shrunk due to electrical current flowing through it.
Findings
- The investigation determined that a material defect caused the copper lead to detach from one of the motor brushes.
- This defect caused the electrical current to flow through the spring, leading to overheating and loss of tension.
- Because the spring lost its tension, the motor could no longer stop once the landing gear reached its limit, causing it to continue running until it hit a mechanical stop.
- The motor forced the nose gear door mechanism beyond its normal position, resulting in a bent and jammed linkage that prevented manual extension via the hand crank.
- The pilot's decision to perform the emergency landing on a prepared foam carpet was appropriate and minimized the risk of fire and further damage.