Pilot Debrief

Williams Yakovlev YAK 3UPW near Half Moon Bay, CA — 2010-03-22

Final reportWPR10LA173
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Date
2010-03-22
Location
Half Moon Bay, CA, USA
Airport
HAF
Aircraft
Williams Yakovlev YAK 3UPW
Registration
N153U
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Landing

Probable cause

The failure of left main landing gear actuator to lock in the down position due to low down-lock pressure as a result of a contaminated down-lock track and corroded down-lock balls.

NTSB narrative

Prior to landing the pilot observed 3 green lights indicating that the landing gear was down and locked. During the landing roll the left main landing gear collapsed, which resulted in substantial damage to the left wing and aileron. A Federal Aviation Administration inspector reported that a postaccident examination of the left main landing gear's pneumatic actuator revealed that the actuator's down-lock ball track was contaminated with dirt and that the steel down-lock balls were corroded. The combination of dirt in the actuator's down-lock track, the corroded down-lock balls, and the low down-lock pressure likely caused the gear to collapse.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have inspected landing gear condition before flight.

NTSB coding

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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