Accident Overview
On February 15, 2015, at approximately 1145 Pacific standard time, an EVO113 LLC Lancair Evolution, registration N3WB, sustained minor damage when the nose landing gear collapsed during the landing roll at San Carlos Airport (SQL), San Carlos, California. The commercial pilot and two passengers were not injured. The flight was a personal cross-country operation under 14 CFR Part 91 with an active instrument flight rules (IFR) flight plan. Visual meteorological conditions prevailed. The flight had departed Gillespie Field (SEE) in San Diego, California, at 1000 with SQL as the planned destination.
Pilot Report and Sequence of Events
According to a report submitted to the National Transportation Safety Board (NTSB) investigator-in-charge, the pilot stated that after touchdown on both main landing gear, the nose wheel was lowered and the power lever was retarded into the BETA position to slow the airplane. Immediately thereafter, a shimmy developed and quickly became severe. The pilot pulled back on the control stick to relieve pressure on the nose gear, but the nose gear collapsed about 2 to 3 seconds later. The airplane then skidded approximately 1,000 feet on the runway before veering right onto the adjacent grass, sliding another 70 feet and coming to rest upright. An examination of the airplane revealed no structural damage beyond the gear collapse.
Post-Accident Examination
At the NTSB investigator-in-charge's request, on March 3, 2015, a Federal Aviation Administration aviation safety inspector supervised the removal of the right hand bearing block (serial number 111-0003) and the nose landing gear strut (serial number 432-0008). These parts were shipped to the NTSB Materials Laboratory in Washington, D.C., for examination on March 17, 2015. The materials engineer reported that the nose landing gear strut was submitted with a separated right trunnion pin. The separation occurred at the base of the trunnion pin where it connected to the strut arm. The fracture surface had extensive damage that obscured most features, but two areas were identified as generally flat with a finely textured appearance and unified crack fronts consistent with fatigue crack progression. The fatigue cracking initiated from multiple origins on opposed sides of the trunnion pin, indicative of reversed bending fatigue. The fatigue cracks had propagated through approximately 35% of the cross-section from each side, with overstress separation covering the remaining 30%. The size and shape of the fatigue crack areas were typical of reversed bending fatigue in the presence of a severe stress concentration. The specific mode of operation (towing, takeoff, or landing) that precipitated the reverse bending was not determined during the investigation.
Aircraft Information
The airplane's Pilot's Operating Handbook states under the Landing Gear section: "Nose gear rotation is limited to 50 degrees either side of center."