What happened
On 2 March 2006, a Piper PA-3CO-200T Seneca II, registration HB-LOG, departed Egelsbach, Germany, for a flight to Locarno, Switzerland. Shortly after takeoff, the pilot transitioned from visual to instrument flight rules. Approximately 17 minutes into the flight, the pilot noticed low battery voltage warnings. Within 30 minutes of this initial warning, the aircraft suffered a total failure of the electrical power supply.
As the electrical system failed, the aircraft's cabin heating also ceased, causing the cockpit side windows to ice up. The pilot, anticipating a loss of radio contact, notified air traffic control of his intention to proceed to Locarno rather than Lugano. Due to the loss of the transponder and radio communications, the aircraft's path became difficult to monitor, prompting the Swiss Air Force to initiate a "hot mission" escort. Two F-5 Tiger aircraft first intercepted the aircraft, followed later by an F/A-18 patrol. The pilot of HB-LOG did not realize he was being intercepted by military fighters and landed safely in Locarno without further incident.
The investigation
The investigation examined the technical state of the aircraft, the pilot's actions, and the communication chain between air traffic control and the military. Investigators found significant evidence of water penetration and condensation within the aircraft. The electrical system, specifically the power distribution components, showed considerable corrosion. Furthermore, a terminal on the master switch for the wire leading to the left alternator switch had broken off. The investigation also noted that several required maintenance tasks were overdue and that the aircraft's flight manual and emergency checklists were positioned in the rear seats, making them difficult for the pilot to access during the emergency.
Findings
- The aircraft's electrical system was in a poor technical condition due to corrosion and water ingress.
- The right alternator switch was found in the OFF position following the incident.
- The pilot did not follow the troubleshooting charts or emergency procedures outlined in the aircraft flight manual (AFM).
- The pilot did not carry a handheld VHF/COM radio, which would have aided communication during the failure.
- Information regarding the pilot's change of destination from Lugano to Locarno was not consistently forwarded by ground control units.
- The pilot did not perceive the presence of the intercepting F-5 or F/A-18 aircraft during the flight.