Amateur-built ZODIAC 601XL N577M accident near Grady, Arkansas

Probable cause

The loss of engine power due to a lack of ignition resulting from a broken alternator wire.

NTSB analysis

The sport pilot was conducting a cross-country flight when the experimental amateur-built airplane experienced a loss of engine power; the pilot then conducted a forced landing to a field, and the airplane sustained substantial damage. Postaccident examination of the airplane revealed a broken wire to the airplane's alternator; this specific wire supplied electrical power to the alternator field coil. Because the wire was broken, the alternator was rendered inoperative. The pilot would not have been able to detect the broken alternator wire without removing the engine cowl, which is not normally part of a pilot's preflight examination.

The airplane's engine had been modified to use an ignition system that operated from the airplane's electrical system, which included a battery and the alternator to maintain the battery's charge. Once the alternator field wire had broken, the ignition system relied completely on the airplane battery's reserve power as the source of ignition power. Once the battery power was depleted, the ignition system could not operate, and the engine lost power due to the lack of ignition.

Text from the NTSB. Open the NTSB docket for CEN17LA313 for the full record.