On September 7, 1982, a Cessna 421C (registration N6868D) operated by R. Harris Russo was involved in an aviation accident near St. Louis, MO. Investigators recorded the probable cause as: The propeller de-ice ammeter was shorted to the instrument panel after being relocated to that position prior to the flight. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During flight in icing conditions near St. Louis, activation of the propeller de-ice system produced flames from the instrument panel. The pilot shut off the system, and the aircraft landed safely. Investigation found a shorted ammeter that had been relocated.
Incident Summary
A pilot reported that while flying near St. Louis, the aircraft encountered icing conditions. The propeller de-ice system was activated. Upon turning on the system, flames shot out from the lower right corner of the pilot's instrument panel, where the propeller de-ice ammeter is located. The pilot immediately turned off the propeller de-ice switch, and the flames ceased. The aircraft subsequently landed without further incident.
Examination Findings
Post-flight examination of the propeller de-ice ammeter revealed that it was shorted to the instrument panel. It was determined that the ammeter had been moved to that location on the instrument panel prior to the flight.
Probable cause
The propeller de-ice ammeter was shorted to the instrument panel after being relocated to that position prior to the flight.