Cessna 337 N86507 accident near Atlanta, Georgia

Probable cause

An area of pitting and corrosion on the surface of the aluminum hydraulic line connecting the emergency handle/pump to the electric hydraulic pump, which resulted in a loss of hydraulic pressure and the pilot’s inability to extend the landing gear.

NTSB analysis

The private pilot was conducting a cross-country, personal flight. He stated that, while on approach to the destination airport, he was unable to extend the landing gear. He declared an emergency and attempted to pump the landing gear down via the emergency gear-extension handle to no avail. He then observed a large puddle of red hydraulic fluid on the floorboards near the hydraulic pump. The pilot realized that he would not be able to extend the gear and conducted a gear-up landing, which resulted in substantial damage to the lower fuselage.

Postaccident examination of the airplane revealed that the hydraulic reservoir was nearly empty. When the emergency handle was activated, a stream of hydraulic fluid sprayed from the surface of the aluminum hydraulic line connecting the emergency handle/pump to the electric hydraulic pump that was mounted under and behind the pilot's instrument panel. Magnified visual examination of the leaking hydraulic line revealed an area of corrosion and pitting on the aluminum surface, which likely resulted in a loss of hydraulic pressure and the pilot's inability to extend the landing gear.

Text from the NTSB. Open the NTSB docket for ERA18LA176 for the full record.