Accident: Boeing 737-8

Damage to the standby rudder power control unit connection to the vertical fin due to an extreme high wind event while the airplane was parked, which remained undetected and resulted in anomalous operation of the standby rudder power control unit. Contributing to the nondetection of the damage was 1) the improper accomplishment of the standby hydraulic system operational test by Southwest Airlines maintenance personnel; 2) the lack of a defined wind speed threshold, in the Boeing 737 aircraft maintenance manual, to perform the extreme high wind conditional inspection for parked and moored aircraft; and 3) the absence of an adequate process at Southwest Airlines to notify maintenance control when parked aircraft experience an extreme high wind event that may require the relevant conditional inspection.

NTSB docket DCA24LA206

• Oakland San Francisco Bay Airport (OAK)0 nm (0 km) southVoydar estimateGreat-circle distance and initial true bearing between the two airport reference points.Version voydar.air.great_circle v1
• Hayward Executive Airport (HWD)6 nm (11 km) south-eastVoydar estimateGreat-circle distance and initial true bearing between the two airport reference points.Version voydar.air.great_circle v1
• San Francisco International Airport (SFO)10 nm (18 km) south-westVoydar estimateGreat-circle distance and initial true bearing between the two airport reference points.Version voydar.air.great_circle v1