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Aircraft Accident During Go-Around in Severe Turbulence (N9559R)

Grass Valley, CA, US

On October 11, 1991, a Beech K35 (registration N9559R) operated by Mike Collishaw was involved in an aviation accident near Grass Valley, CA. Investigators recorded the probable cause as: THE INADVERTENT ENCOUNTER WITH A MICROBURST/DOWNBURST PHENOMENA ASSOCIATED WITH THUNDERSTORM ACTIVITY. A FACTOR IN THE ACCIDENT WAS THE FAILURE OF THE PILOT TO ADEQUATELY ASSESS THE WEATHER CONDITIONS DURING THE LANDING ATTEMPT. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-09-03Data APIEditorial standards

A pilot attempted a landing during squall line activity. On short final, the aircraft encountered severe turbulence and a downdraft. A go-around was initiated, but the wingtip struck the ground.

Pilot Account and Approach Conditions The pilot reported that, while approaching the airport, he observed squall line activity and elected to orbit until the weather improved. After visual conditions appeared to improve, he entered the landing pattern. On short final approach, the aircraft encountered severe turbulence and a downdraft. The pilot initiated a go-around, but the aircraft rolled violently and the wingtip struck the ground. ## Airport Attendant Observations An airport attendant stated that he was in the office where the weather observation instruments were located at the time of the accident. He reported that winds were 30 to 40 knots with sudden 180-degree changes in direction when the pilot attempted the approach. Thunderstorm clouds were visible in the distance, and the airport was experiencing intermittent heavy rain showers.

Weather

Frequently asked questions

What happened in the 11 Oct 1991 Beech K35 accident near Grass Valley, CA?

A pilot attempted a landing during squall line activity. On short final, the aircraft encountered severe turbulence and a downdraft. A go-around was initiated, but the wingtip struck the ground.

What aircraft was involved and where did it happen?

The accident on 11 Oct 1991 involved a Beech K35, registration N9559R, operated by Mike Collishaw, at Grass Valley, CA.

What was the probable cause of the accident?

THE INADVERTENT ENCOUNTER WITH A MICROBURST/DOWNBURST PHENOMENA ASSOCIATED WITH THUNDERSTORM ACTIVITY. A FACTOR IN THE ACCIDENT WAS THE FAILURE OF THE PILOT TO ADEQUATELY ASSESS THE WEATHER CONDITIONS DURING THE LANDING ATTEMPT.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X18322. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.