Cessna 210 N6575X accident near Florence, Oregon

Probable cause

The failure of the hydraulic power pack, which prevented the extension of the landing gear and resulted in a partial gear-up landing.

NTSB analysis

The pilot reported that the landing gear actuator had been rebuilt and that all ground tests were uneventful. During the takeoff for the maintenance test flight, the landing gear retracted normally. However, when selected to the extend position for landing, the left and right main landing gear would not extend. The nosewheel landing gear did extend and lock in the down position. The pilot's numerous attempts to raise or lower the main landing gear were unsuccessful. The pilot initiated a partial gear-up landing, and, during the landing, the left horizontal stabilizer struck the runway. Multiple attempts to retract or extend the landing gear during postaccident examinations were unsuccessful. During functional tests of the hydraulic power pack, the power pack extended the landing gear; however, it did not extend or retract the flaps. In addition, the power pack did not retract the landing gear or build up any pressure with the hand pump. Further examination of the hydraulic pack revealed that the No. 1 thermal relief valve lost pressure after it was relieved and that four poppet assemblies did not hold pressure.

Text from the NTSB. Open the NTSB docket for WPR14LA059 for the full record.