What happened
The incident began when the pilot attempted to start the engine. During this process, the engine appeared to hang up in the middle of the compression stroke. After verifying that the magnetos were turned off, the pilot proceeded to manually rotate the propeller in an effort to free it. As soon as the propeller was moved, the engine started unexpectedly.
A non-pilot passenger seated in the right front position attempted to shut down the aircraft by manipulating the magneto switch. Despite this intervention, the aircraft continued to move forward for approximately 100 yards. It then rolled through a guardrail and nosed down into an adjacent canal.
The investigation
Post-acc examination of the aircraft revealed that the magneto switch was found in the 'both' position. The fuel mixture control was set to full rich, and the throttle was advanced. A subsequent check of the magnetos indicated no mechanical malfunction.