What aircraft was involved and where did it happen?

The accident on null involved a aircraft, registration EI-CMT, at IE.

What was the probable cause of the accident?

The primary cause was insufficient battery voltage to excite the alternator field windings, exacerbated by a heavy electrical load and a poorly maintained master relay.

Electrical Failure Forces Emergency Landing in Piper Seneca

A private flight to Jersey was interrupted by a total loss of electrical power, communications, and radar shortly after departing Kerry Airport.

What happened

On 7 November 2007, a Piper PA-34-200T, registration EI-CMT, departed Kerry Airport on a private flight bound for Jersey. Shortly after takeoff, as the aircraft entered instrument meteorological conditions, the crew experienced a sudden and complete failure of all onboard electrical systems, including communications and weather radar.

Following the failure, the pilot initially flew south, attempting to find visual conditions to descend safely. During the flight, the pilot used a mobile phone to establish contact with Cork Air Traffic Control (ATC) after radio communications failed. The crew also noted that the nose undercarriage had become stuck at half-travel during the initial climb.

As the aircraft moved south of Clonakilty, the crew manually extended the landing gear using the emergency system. Shortly after this procedure, the electrical supply was suddenly restored. After confirming with ATC that the gear was properly locked, the pilot performed a fly-by of the Cork Tower to verify the undercarriage status and landed safely on runway 35.

The investigation

The investigation focused on why the electrical system failed and why the alternators were unable to maintain power. Testing revealed that the electric motor/hydraulic pack lacked sufficient battery voltage to operate the undercarriage pump effectively.

Upon inspecting the nose section, investigators found that the master relay had been modified during its service life with an epoxy adhesive applied to the main terminals for corrosion protection. While the relay appeared to function normally during testing, its condition was a primary focus. Further research into the aircraft's maintenance showed that the master relay had not been replaced during the aircraft's 30-year lifespan.

Findings

The aircraft suffered a total loss of onboard electrical power, communications, and radar systems shortly after takeoff.
The alternators were unable to maintain adequate busbar voltage.
Insufficient battery voltage prevented the excitation of the alternator field windings.
The degraded condition of the master relay, coupled with the high electrical load required to retract the undercarriage, acted as a significant contributing factor.