Accident Description
During a flight following maintenance on the left main landing gear actuator and its flexible hoses, the pilot encountered a hydraulic system anomaly shortly after takeoff. At approximately 1,000 feet above ground level, the main landing gear failed to retract, and the hydraulic pressure gauge indicated zero pressure. The pilot selected the gear down, received three green landing gear indication lights, operated the hydraulic emergency hand pump, and initiated a return to the departure airport.
Flight Details
While using the emergency hand pump during the return, the pilot observed some pressure, up to 800 psi. He then moved the emergency hand pump selector valve to the "brakes only" position to enable stopping the airplane upon landing. However, he reported that no pressure was generated when pumping the emergency hand pump after selecting this position. On final approach, the pilot slowed the airplane to approximately 85 miles per hour. After touchdown, he attempted to pump the emergency hand pump for braking but achieved no braking action. Unable to stop, the airplane departed the runway and collided with a ditch beyond the departure end.
Post-Accident Findings
Following recovery of the airplane, the emergency hand pump selector valve was not found in the "brakes only" position. Subsequent testing with the selector set to "brakes only" revealed that the emergency hand pump did produce hydraulic pressure. According to the airplane's Maintenance Manual, the emergency hand pump selector valve, located between the pilot and co-pilot seats, directs hand pump pressure to either the brake system or the normal hydraulic system. With the selector in the "brakes only" position, pressure is directed solely to the wheel brake system and nose steering cylinder, and this pressure is not indicated on the hydraulic pressure gauge.