What happened
On February 8, 2006, a Cessna P210N Centurion, registration D-ECPM, departed Marina di Campo Airport for a local flight. Shortly after takeoff and following the retraction of the landing gear, the pilot experienced a total electrical failure. The pilot declared an emergency via portable radio and maintained an altitude of 2,000 feet while attempting to manually extend the landing gear.
Despite performing more than 65 manual pump cycles—exceeding the emergency procedure requirements—the gear failed to lock in the extended position. Due to the electrical failure, the flaps were also inoperable. The pilot proceeded to land on runway 34 at 82 knots with the gear in an unsecure state. Upon touchdown, the gear partially retracted, causing the aircraft to veer left and depart the runway, eventually coming to rest in a roadside ditch. The pilot sustained no injuries, but the aircraft suffered substantial damage to the fuselage, wings, empennage, and propeller.
The investigation
The ANSV investigation focused on the dual failure of the electrical system and the manual gear extension mechanism. Technical examinations of the electrical system revealed two simultaneous faults: a disconnected cable between the battery contactor and the master switch, and an alternator failure. Microscopic analysis showed the cable connection was extremely fragile, with only about 10% of the original cross-section remaining intact, likely due to damage from tools during maintenance.
The alternator failure was attributed to overheating of the stator, leading to insulation loss and a short circuit. Investigators found that the alternator had been upgraded to a higher amperage version (95A), and the presence of an air conditioning unit restricted cooling efficiency. Furthermore, while a specific longer belt was previously used to prevent tension issues, the aircraft was found to be using a worn, standard-specification belt that was not properly documented in the maintenance logs.
Regarding the landing gear, while specific tests could not be replicated, investigators hypothesized that a partial hydraulic leak or insufficient pressure prevented the gear from locking during the manual extension attempt.
Findings
- The primary cause was the simultaneous occurrence of an electrical system failure and the failure of the manual landing gear extension mechanism to lock the gear in place.
- The electrical failure was caused by a combination of a faulty connection (likely caused during recent maintenance) and an alternator malfunction.
- Maintenance deficiencies were identified, specifically regarding the improper installation of a worn belt and inadequate documentation of recent maintenance tasks.
- The alternator's susceptibility to overheating was exacerbated by the installation of an upgraded high-amperage unit and the physical obstruction caused by the air conditioning system.