Aviation & Pilots Forum
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Location: Anchorage, AK
Accident Number: ANC20LA059
Date & Time: June 8, 2020
Registration: N3188M
Aircraft: Piper PA 12
Injuries: 2 None
Flight Conducted Under: Part 91: General aviation - Instructional
On June 8, 2020, about 0945 Alaska daylight time, a float-equipped Piper PA-12 airplane, N3188M, sustained substantial damage when it's rudder structurally failed in flight about 8 miles north of Anchorage, Alaska. The flight instructor and private pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
According to the flight instructor, they departed Lake Hood Airport (PALH) and proceeded to Twin Island Lake (about 8 nm northwest of PALH), where upon arrival, they conducted a normal landing. After departing, they climbed to about 500 ft above ground level (agl) before turning a left crosswind traffic pattern leg. While on the left crosswind leg, the airplane yawed abruptly to the right and the private pilot indicated that the controls felt strange. The flight instructor assumed control of the airplane and noticed drastically diminished control about the vertical axis. In addition, a significant downward elevator pressure (forward control yoke) was required. In an effort to aid in directional control the water rudders were deployed. Uncertain that he could make a 180° turn and return to Twin Island Lake due to the poor directional control, he elected to return to PALH where emergency services were available and conducted an uneventful landing.
An initial examination of the rudder revealed that the vertical spar tube separated just above the upper hinge point and the top portion of the rudder folded over the horizontal stabilizer tail brace wires.
The rudder has been retained for further examination by the National Transportation Safety Board (NTSB) Materials Laboratory.
Two wild guesses of mine are possibly the upper hinge tube on the rudder having some welding done and the heat screwing with the local temper of the metal making it brittle, or possibly the weight of that light up top being just perfect for some resonance with the engine’s vibrations. Or hell, some other weird thing.Scudrunner wrote: ↑Wed Feb 03, 2021 3:39 amHate to speculate but perhaps something was missed on re assembly or damaged during rebuild and not caught. Don't know enough about the cub structures I suppose.
