What happened
On July 17, 2007, a Cessna 152, registration CS-AYU, was conducting a general aviation leisure flight over the Cascais Bay at an altitude of 1,000 feet. During the flight, the pilot observed smoke emanating from the radio panel caused by an electrical fire. In response to the emergency, the pilot deactivated all electrical systems, including the battery, and opened the windows to ventilate the cabin of smoke.
Due to the electrical failure, the aircraft was unable to maintain radio communications. The pilot proceeded directly to the final approach for runway 35 at Cascais Municipal Aerodeome (LPCS) without notifying the control tower. The aircraft landed on the runway, passing over another aircraft that was positioned for takeoff, creating a significant risk of collision. Following the landing, the pilot taxied to the end of the runway, stopped the aircraft in the overrun area, and evacuated the cabin along with the passenger.
The investigation
The GPIAAF investigation focused on the cause of the electrical fire and the subsequent loss of communication. Firefighters responded to the scene, but the fire had already extinguished itself by the time they arrived. Maintenance inspections revealed that a burnt voltage regulator had caused a power surge, leading to a short circuit and the resulting fire. Following the replacement of the regulator and affected radio units, and subsequent electrical insulation testing, the aircraft was returned to service.
Findings
- The primary cause of the incident was a voltage regulator failure that triggered a short circuit and an onboard fire.
- The pilot's emergency procedures regarding fire suppression and smoke evacuation were executed correctly.
- The decision to land at the nearest aerodrome was appropriate given the loss of electrical power and essential flight instruments.
- The pilot failed to follow standard flight procedures by operating near a controlled aerodrome without radio communications, which interfered with existing traffic and compromised safety.
- There was a lack of established local procedures for aircraft experiencing radio communication loss within the traffic zone of the aerodrome.
Safety action
- The GPIAAF issued a recommendation to NAV Portugal and the Administration of Cascais Municipal Aerodrome to develop and implement local procedures for handling aircraft that lose radio contact with the Control Tower within the traffic and maneuvering areas, in accordance with ICAO Annex 2 standards.