20251031019199A

Aircraft was on a test flight after a progressive inspection. While cycling the landing gear in flight, a large hydraulic leak was noticed by the mechanic in the cabin. The sequential gear system had reported by lights that the left main gear was down and locked. The pilot turned the aircraft over to the copilot, and went to the cabin to manually extend the gear. He visually checked the left main gear, but did not verify that it was locked, as it had reported locked down on the instrument panel. After performing the manual extension on the right main gear and nose gear, the pilot returned to the flight deck, and the aircraft circled and made an approach for landing. Almost immediately after touchdown, the left main gear began to collapse as the hydraulic actuator bled off pressure, as it was not in fact locked. Not having the power to regain airspeed and lift off, the throttles were left at idle. The left wing continued to drop, and made contact with a taxiway sign, destroying the sign, flexing the left wing enough to deform the skin and airframe, and tore through the bottom of the wing into the internal structure. The damage on the top of the wing is from leading edge all the way back to and including the left aileron. When the keel of the seaplane's hull contacted the ground, there was some deforming of the skin, with no obvious structural damage.

Due to recent change of right main gear hydraulic actuator, waiting on maintenance records from owner. Will amend and update as necessary upon receipt.

5 Feb 2026 update:

Maintenance records show proper procedures followed during rebuild and replacement of gear actuator and sequencing valve. Inspection of hydraulic line shows an improper flare angle and shape for the fitting installed on the sequencing valve. The curving flare indicates improper torquing of the b-nut to the fitting. Original parts are "ac" fittings, flared to 45 degrees. Manufacturer switched to "an" fittings, flared to 37 degrees, by the end of the 1950'S.