On May 28, 1997, a Piper PA-31-350 (registration N491SC) was involved in an aviation accident near Greeley, CO. Investigators recorded the probable cause as: unlatching of the left outboard engine cowling latches for undetermined reason(s), which allowed the left engine cowling to separate inflight and strike the vertical stabilizer. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise, the left engine cowling began to loosen and separated, striking the vertical stabilizer. Postaccident inspection revealed outboard latches were unlocked, while inboard latches were locked.
Incident Description
The pilot reported that while in cruise flight, he observed the left front portion of the left engine cowling starting to come loose. After receiving clearance from air traffic control, he initiated a diversion to the nearest suitable airport. Shortly thereafter, the left cowling completely separated from the aircraft and struck the vertical stabilizer.
Postaccident Inspection
Postaccident inspection disclosed that the outboard cowling latches were in the unlocked position, while the inboard latches were in the locked position. A portion of the cowling remained attached via the inboard latches. The pilot stated that he checked the cowling latches during his preflight inspection and they were all in the locked position. Orange stripes had been painted across the latches to visually indicate locked and unlocked positions.