Accident Details
On December 13, 2012, at approximately 1409 Alaska standard time, a tailwheel-equipped Cessna 150C (registration N1901Z) was substantially damaged while landing at Juneau International Airport, Juneau, Alaska. The airplane was operating as a visual flight rules (VFR) instructional flight under Title 14 CFR Part 91. The student pilot and the airline transport rated flight instructor (CFI) were not injured. Visual meteorological conditions prevailed; no flight plan was filed.
According to the CFI, the flight originated at Juneau International Airport for local practice of stop-and-go landings. At the time of the accident, he was demonstrating a short-field, three-point landing. The touchdown was normal, but during the landing roll, a gust of wind pushed the airplane, causing it to turn right. The CFI applied left brake to correct the turn, and the left main landing gear broke. As the broken gear leg dug into the runway, the airplane pivoted 180 degrees to the left, and the left wing struck the runway. Substantial damage occurred to the left wing and fuselage.
Investigation Findings
Examination of the fractured left main landing gear leg revealed a crescent-shaped fracture on the upper forward surface, consistent with fatigue cracking. The remaining fracture surface exhibited a coarse grainy appearance, clear chevron markings, and a shear lip, indicating an overstress fracture. Corrosion damage and grinder marks were present on the surfaces of the left landing gear leg.
Maintenance History
The CFI, who is also a certificated airframe and powerplant (A&P) mechanic, stated that during the annual inspection in August, he observed corrosion on the main landing gear legs. The corrosion was ground off using a hand-held grinder, and Zinc Chromate Primer was applied.
The Cessna 100 Series Service Manual, Section 5-5A, specifies that corrosion on landing gear springs should be removed by light sanding, blending the damage into the adjacent area in an approximate 20:1 ratio.
Weather Conditions
The closest weather reporting facility is Juneau International Airport. At 1353, an aviation routine weather report (METAR) reported: wind calm, visibility 10 statute miles, light rain, few clouds at 2,000 feet, broken clouds at 3,900 feet, broken clouds at 5,000 feet, temperature 36°F, dew point 32°F, altimeter 29.44 inHg.