On June 10, 1984, a Hiller UH-12E (registration N93431) was involved in an aviation accident near Merrimac, WI. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft experienced an inflight explosion at about 75 feet above ground level during landing approach, leading to a crash and fire. The aircraft had prior electrical issues with generator overheating and irregular voltage. Post-accident examination revealed a voltage regulator fault causing continuous battery charging, generator overheating, and a battery explosion.
Incident Overview
An aircraft crashed and burned after an inflight explosion occurred at approximately 75 feet above ground level as it approached to land. The aircraft had previously experienced electrical problems, including generator overheating and irregular voltage outputs on two prior occasions. Following repairs, the pilot was advised to pull the generator circuit breaker if any hot smell was detected.
Post-Accident Examination
Examination of the aircraft after the accident revealed a condition of the voltage regulator that would have caused continuous charging of the battery. The generator showed signs of overheating. The battery had exploded away from the wreckage, with its terminal poles melted off.
Electrical System History
The aircraft's electrical system had a history of malfunctions. The pilot had been informed after repairs that pulling the generator circuit breaker was the appropriate action if a hot odor was noticed. This suggests an awareness of potential overheating issues within the electrical system.