ASN Wikibase Occurrence # 370277
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| Date: | Thursday 19 October 2006 |
| Time: | 01:00 LT |
| Type: |  Boeing 737-790 |
| Owner/operator: | Alaska Airlines |
| Registration: | N614AS |
| MSN: | 30343/439 |
| Year of manufacture: | 1999 |
| Engine model: | General Electric CFM56SER |
| Fatalities: | Fatalities: 0 / Occupants: 5 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Los Angeles, CA -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Los Angeles International Airport, CA (LAX/KLAX) |
| MMX | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During cruise flight, just after entry into foreign airspace, the flight crew was alerted to a System B hydraulic failure, and they decided to return to, and land in the United States (US). Upon re-entry to US airspace, the flight crew declared an emergency and requested to land at the departure airport. On final approach, about 5 minutes after selecting flaps to 15 and lowering the landing gear, the flight crew was alerted to the System A hydraulic quantity gage, that had dropped to 0 pounds per square inch (psi). At this point both System A LOW PRESSURE LIGHTS illuminated and the airplane went into the manual reversion mode. The flight crew indicated that the airplane was difficult to control; however, they landed uneventfully at the airport. Maintenance personnel for the airline, and the airplane manufacturer, inspected the hydraulic systems. They noted that the initiating event was a failed engine driven pump. The secondary event was a cracked hydraulic line that failed due to fatigue. A metallurgical examination revealed the fatigue fracture initiated at the toe of the welding root where they were able to locate a crack that had propagated through half the perimeter. The airframe manufacturer redesigned the affected tube, part number 272A4451-87, a titanium tube, with part number 272A4451-200, a stainless steel tube.
Probable Cause: A complete failure and depressurization of both hydraulic systems due to two separate events: 1) the failure of a engine driven pump on the 'A' system, and 2) the fatigue fracture and failure of a hydraulic line on the 'B' system.
Accident investigation:
 |
|
Sources:
NTSB LAX07IA014
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 25-Mar-2024 08:56 | ASN Update Bot | Added |
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