On September 22, 1982, a Cessna 177RG (registration N52716) operated by Cascade Flight School Inc. was involved in an aviation accident near Cashmere, WA. Investigators recorded the probable cause as: A slight oil leak from the left rear rocker cover allowed oil to drop onto a heated exhaust shroud, producing smoke that was ingested into the cockpit through a defroster vent under certain conditions. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During descent at 7,500 feet, smoke entered the cockpit from the instrument panel. Investigation revealed an oil leak from the left rear rocker cover onto a heated exhaust shroud, producing smoke ingested via a defroster vent.
Incident Description
While descending through 7,500 feet, the pilot observed smoke entering the cockpit from the area of the instrument panel. Attempts were made to isolate the source by shutting off various electrical components, but the smoke continued to appear intermittently until the aircraft reached its intended destination.
Investigation Findings
Subsequent investigation revealed that a slight oil leak from the left rear rocker cover allowed oil to drip onto a heated exhaust shroud. The oil on the hot surface produced smoke, which was then ingested into the cockpit through a defroster vent under certain conditions. The investigation did not identify any other contributing factors.
Probable cause
A slight oil leak from the left rear rocker cover allowed oil to drop onto a heated exhaust shroud, producing smoke that was ingested into the cockpit through a defroster vent under certain conditions.