Pilot Report
On November 16, 2001, a pilot prepared to depart from his home airport, McCollum Field. During the engine runup, the left magneto was found inoperative. The pilot returned to the ramp, and his mechanic disconnected and then reconnected the magneto "P" leads, after which the left magneto began to work. The pilot departed McCollum Field and flew to Peachtree City, then to Tara Field in Hampton, Georgia.
When leaving Tara Field, the left magneto was again inoperative. The pilot called his mechanic, who advised disconnecting the "P" leads and flying home. With the "P" leads disconnected, the magnetos could not be checked during subsequent runup. During takeoff, the engine appeared to develop full power with normal exhaust gas temperature (EGT).
About five minutes after departure, the EGT pegged high, and one magneto appeared to quit. Approximately one minute later, the engine quit. Atlanta Approach provided radar vectors to the nearest airport, Peachtree City, but the pilot could not reach it. He performed a forced landing in a field with the landing gear down and full wing flaps extended. During rollout, the airplane collided with a drainage ditch, causing the landing gear to collapse and the airplane to slide to a stop.
Engine and Magneto Examination
Prior to running the engine after the accident, it was found that the "P" lead was disconnected from the right magneto and the spark retard lead was disconnected from the left magneto. The leads were reconnected, and the engine was started; only the right magneto operated. The engine was run to 1,500 RPM with a club propeller in the feathered position. No evidence of mechanical failure or malfunction of the engine assembly was found.
The magnetos were tested at the manufacturer's facilities. The left magneto condenser was inoperative, causing the magneto to not operate. The right magneto operated normally.
Manufacturer's Observations
Manufacturer personnel stated that with one magneto inoperative, the EGT becomes elevated due to inefficient burning in the cylinder, which carries over into the exhaust area. When the "P" lead is removed from these magnetos, they internally ground and become inoperative. Contamination can sometimes prevent immediate grounding when the "P" lead is removed, but they eventually ground and become inoperative.
The manufacturer personnel believed that with the spark retard disconnected on the left magneto and the "P" lead disconnected on the right magneto, both magnetos operated during takeoff because the left magneto's condenser was working at that time, and the internal grounding of the right magneto was temporarily prevented by contamination. Therefore, takeoff at full power was normal with both magnetos functioning. Then either the left magneto quit due to condenser failure, or the right magneto quit due to becoming internally grounded. The EGT increased and a small power loss occurred. Subsequently, the second magneto quit, resulting in complete engine failure.