Cessna 337 N107BL accident near Baldwin City, Kansas

Probable cause

The loss of hydraulic accumulator pressure for reasons that could not be determined, which prevented the propeller from unfeathering, and the pilot's improper decision to attempt a go-around, which resulted in an off-airport landing and the airplane impacting trees and a fence. Contributing to the accident was the loss of tension at the flap switch pivot, which prevented it from holding position.

NTSB analysis

The commercial pilot was conducting a local flight to practice single-engine maneuvers. After taking off and climbing the airplane to 3,500 ft, he shut down the rear engine and feathered the propeller. After performing some turns and climbs, the pilot attempted to unfeather the propeller and restart the engine but was unsuccessful. He returned to the airport to set up for a single-engine approach. During the approach, the pilot realized that the flaps were no longer in the full-flap setting and that a landing on the grass runway was going to be close, so he chose to perform a go-around. However, as the pilot began to go around, he realized that the airplane could not maintain altitude. He maneuvered the airplane for an off-airport landing to a nearby field, during which the airplane struck small trees and a fence and sustained substantial damage to the left wing and fuselage.

The rear engine propeller had a remote hydraulic accumulator that assisted in unfeathering the propeller and was normally serviced to 120 pounds per square inch (psi). During an annual inspection that took place 4 flight hours before the accident flight, it was noted that the pressure was slightly low. During postaccident examination, the accumulator pressure was 85 psi. It is likely that a nitrogen leak occurred between the time the accumulator was last serviced and the time of the accident; however, the reason for the nitrogen leak could not be determined. Further, the flap switch was not holding position due to a loss of tension at the flap switch pivot, which is likely why the flaps were not in the full-flap setting as reported by the pilot.

Text from the NTSB. Open the NTSB docket for CEN18LA246 for the full record.