What happened
On the morning of March 11, 2007, a PIPER PA-28RT 201T, registration EC-EZY, was preparing for a dual instructional flight at Cuatro Vientos Airport in Madrid. The flight crew initially struggled to start the engine, eventually requiring an external battery to successfully initiate the engine run.
Shortly after takeoff from runway 28, the aircraft experienced a sudden and complete failure of its electrical system, which also resulted in the loss of all radio communications. The crew, realizing the extent of the failure, decided to return to the airport following standard communications failure procedures. During the approach, air traffic controllers used visual light signals to communicate with the aircraft. The crew observed a flashing green light, which they misinterpreted as a warning that the landing gear was not properly configured.
Despite attempts by the student pilot to extend the landing gear, the gear remained retracted. The aircraft subsequently performed a belly landing on runway 10. While the crew escaped without injury, the aircraft sustained significant damage to the propeller and the underside of the fuselage.
The investigation
The CIAIAC investigation focused on the simultaneous failure of the aircraft's electrical components and the crew's inability to deploy the landing gear. Technical examinations of the aircraft revealed that the alternator's slip clutch was failing, allowing excessive slippage and preventing the alternator from generating electricity to recharge the battery. Furthermore, the installed battery was found to be in a severely degraded state, unable to maintain the required discharge rate for emergency operations.
Investigators also examined the landing gear extension process. While the hydraulic system was functional, the investigation suggested the crew may have failed to properly execute the emergency gravity extension procedure, possibly due to a lack of familiarity with the locking pin mechanism or the absence of the correct Airplane Flight Manual (AFM) in the cockpit.
Findings
- The primary cause of the electrical failure was the simultaneous failure of the alternator coupling and the depleted state of the battery.
- The alternator was unable to recharge the battery because the engine-driven coupling slipped at a much lower torque than required by service bulletins.
- The battery was in an inoperable condition, showing physical defects and an inability to support electrical loads for the necessary duration.
- The landing gear remained retracted because the crew likely failed to properly release the locking pin during the emergency extension attempt.
- The crew's interpretation of the tower's flashing green light contributed to the landing configuration error.
Safety action
- A safety recommendation was issued to the FAA to modify the PIPER PA-28RT 201T flight manual to explicitly include instructions regarding the locking pin in the emergency gear extension procedures.