On August 18, 1988, a Bellanca 8KCAB (registration N7699S) operated by Head, Hardy L. was involved in an aviation accident near Miami, FL. Investigators recorded the probable cause as: A cracked muffler shroud allowed air to contact the firewall, leading to overheating of cabin insulation and smoke production. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A personal flight experienced smoke in the cockpit during normal cruise. The pilot shut off electrical systems, secured the engine, and landed on a grass strip. The aircraft landed long, overran the runway, and nosed over. Examination revealed a cracked muffler shroud.
Incident Summary
During a personal flight in normal cruise conditions, the pilot reported that the cockpit filled with smoke. In response, the pilot turned off the electrical system and secured the engine. The pilot then attempted a precautionary landing on a grass strip. During the landing, the aircraft touched down long, overran the runway, and nosed over.
Investigation Findings
Examination of the aircraft revealed that the muffler shroud had a crack. This crack allowed air normally used for cabin heat to come into contact with the firewall. As a result, the insulation on the inside of the cabin overheated, producing the smoke that filled the cockpit.
Probable cause
A cracked muffler shroud allowed air to contact the firewall, leading to overheating of cabin insulation and smoke production.