What happened
On October 28, 2018, a Diamond DA20, registration N653DC, was performing a personal flight in cruise flight at approximately 6,500 feet mean sea level when the engine experienced a partial loss of power. The pilot reported that the engine speed decreased to 1,000 rpm. After attempting remedial actions to restore power without success, the pilot selected a field for a forced landing because no airport was reachable within gliding distance.
The pilot declared an emergency and secured the engine prior to the landing. The aircraft struck terrain, resulting in substantial damage to the wings, fuselage, and empennage. The horizontal stabilizer and elevator were separated from the tail section, though the tail remained attached by cables. The pilot and passenger were not injured.
At the time of the accident, weather conditions were visual meteorological conditions (VMC) with clear skies and winds from 240 degrees at 6 knots.
The investigation
An FAA inspector confirmed that the flight control surfaces remained connected from the cockpit through the airframe, with all fractures showing signs of overload failure. Fuel samples showed no evidence of water or debris.
Following the accident, the engine was sent to a manufacturer for testing. While the engine ran roughly in a test cell, it would not run continuously. Investigation revealed that both magnetos and both ignition harnesses required replacement to achieve a successful run.
Disassembly of the right magneto revealed extreme wear on the distributor gear bushing, with debris from the bushing and gear block coating internal components. The distributor gear and drive gear were found to be loose in their mounts. Additionally, both ignition harnesses exhibited damage consistent with over-tightening at terminal b-nuts and clamp sites, as well as chafing, which caused high-energy spark to leak through the leads.