Casualties unknown

Dual Hydraulic System Failures and Flap Malfunction During Cruise Flight (N473AC)

Los Angeles, CA, US

On June 27, 1985, a Boeing 737-247 (registration N473AC) was involved in an aviation accident near Los Angeles, CA. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards
Boeing 737-247
Photo: San Diego Air & Space Museum Archives / Public domain, via Wikimedia Commons

During cruise, the 'B' hydraulic system low oil level lamp illuminated. While addressing it, the 'A' system failed. The flight continued but trailing edge flaps could not be lowered due to another malfunction; a safe landing was made.

Incident Overview

According to the captain's statement, a low oil level warning lamp for the 'B' hydraulic system illuminated while the aircraft was in cruise flight. As the captain completed the failure checklist and configured the 'B' system into standby rudder condition—which supplies hydraulic pressure only to the rudder—the 'A' hydraulic system subsequently failed.

Flight Continuation and Landing

The flight continued to its intended destination. Upon arrival, the crew found that the trailing edge flaps could not be lowered. The source attributes this to another malfunction. Despite the flap issue, the aircraft landed without incident.

System Details

The aircraft's hydraulic systems are designed with redundancy. The 'B' system standby rudder condition is a degraded mode that limits hydraulic power to the rudder. The failure of the 'A' system after the 'B' system was reconfigured resulted in a loss of hydraulic pressure for other systems, including flap operation.

No further details about the aircraft type, registration, operator, or date are provided in the source.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X36809. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.