Embraer ERJ170 200LR N161SY incident near San Antonio, Texas

Probable cause

A failure of the nose landing gear down lock spring which precluded normal downlock operation of the nose landing gear. The spring failure was due to the presence of too much retained austenite which led to the formation of progressive cracking and subsequent failure of the spring.

NTSB analysis

Based on the material laboratory examinations, the area around the failure point contained higher than allowable levels of retained austenite. The presence of too much retained austenite subsequently resulted in the formation of intergranular cracking. The intergranular cracking resulted in the formation of progressive cracking, which caused the separation and subsequent failure of the downlock spring. After the failure, the spring became lodged in the nose landing gear yoke, which prevented the nose gear from achieving a down and locked position. Without the NLG being fully down and locked, as the weight of the aircraft during landing was transferred to the nose and main landing gear, the NLG subsequently retracted back into the nose gear wheel.

Text from the NTSB. Open the NTSB docket for ENG17IA005 for the full record.