EMBRAER ERJ170 200LR near San Antonio, TX — 2016-12-04

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 narrative

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.

Analysis

Primary failure mode

Mechanical failure

First missed decision gate

Crew could have opted to land at MMTY instead of diverting to KSAT after initial gear warning.

NTSB coding

• Landing gear collapse · Landing-landing roll

Evidence available

• FDR / data
• 4 docket documents

Docket documents4

• Flight Data Recorder Specialist's Factual Reportfdr
• Flight Data Recorder Specialist's Factual Report - Attachment 1fdr
• Computed Tomography Specialist's Factual Reportreport
• Materials Laboratory - Factual Reportreport

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