Overview
The pilot reported an erratic RPM drop and a partial loss of power during a swath run. The event occurred while the helicopter was approximately 10 feet above trees and traveling at about 40 knots. The aircraft began losing airspeed and altitude.
Event Sequence
Following the power loss, the pilot executed an emergency landing. During this landing, the tail rotor and main rotor blades struck tree branches. The impact caused damage to the plexiglass and landing gear.
Investigation
During the subsequent investigation, the ignition harnesses were examined. The #4 and #6 lead assemblies, part number 10-720642, exhibited leakage at the sleeve assembly point, identified by Bendix part number 10-320473. A partial teardown of the engine revealed no other preimpact mechanical failure.