Amateur-built LANCAIR EVOLUTION N3WB incident near San Carlos, California

Probable cause

The collapse of the nose landing gear (NLG) due to the separation of the right trunnion pin from the NLG strut as a result of reverse-bending fatigue.

NTSB analysis

The pilot reported that, during the landing roll, the nose landing gear (NLG) began to shimmy, which quickly became severe. The pilot applied back pressure on the control stick to reduce the weight on the NLG; however, the NLG collapsed about 2 to 3 seconds later. The airplane then skidded on the runway for about 1,000 ft before coming to a stop upright.

A postincident examination of the NLG revealed that the right trunnion pin had separated at the base of the pin where it connected to the NLG strut arm. The fracture surface had unified crack fronts, consistent with fatigue crack progression. The fatigue cracks initiated from multiple origins on opposite sides of the trunnion pin, consistent with reverse-bending fatigue. Although the reverse bending could have resulted from the exceedance of the lateral limits of the tow bar parameters during ground towing operations, it could not be determined if such an exceedance occurred before the incident. The event that precipitated the reverse bending could not be determined.

Text from the NTSB. Open the NTSB docket for WPR15IA105 for the full record.