Narrative:
The crew noted that the nose and main body gear indicated up and locked after normal gear extension. The crew used the alternate gear extension procedure, which was unsuccessful. The aircraft landed on runway 25R with the nose and main body gear retracted when the flight reached the minimum fuel state. Examination of the aircraft revealed that the selector valve for the affected gear was in the up and locked position, and the bolt which connects the valve arm to the cockpit control cable system was missing. The bolt for the wing gear selector valve arm was found partially backed out; the nut and cotter pin were missing. The aircraft was delivered to United in January of 1990 and had 2,952 flight hours and 402 cycles. Detailed review of the maintenance records proved that United had not performed any maintenance on the landing gear system. A second alternate gear extension procedure involving de-energizing the hydraulic system for the affected gear is not published in the crew manuals, taught during initial training, nor available on any checklist.
PROBABLE CAUSE: "The failure of the manufacturer to ensure that the landing gear selector valves and their associated drum link assemblies were properly installed prior to delivery of the aircraft. A factor in the accident was the lack of information available to the crew concerning the secondary alternate gear extension procedure."
| Status: | Accident investigation report completed and information captured |
| Date: | Monday 27 August 1990 |
| Time: | 10:25 |
| Type: |  Boeing 747-422 |
| Operator: | United Airlines |
| Registration: | N174UA |
| MSN: | 24381/762 |
| First flight: | 1990-01-05 (8 months) |
| Total airframe hrs: | 2952 |
| Cycles: | 402 |
| Engines: | 4 Pratt & Whitney PW4056 |
| Crew: | Fatalities: 0 / Occupants: 20 |
| Passengers: | Fatalities: 0 / Occupants: 323 |
| Total: | Fatalities: 0 / Occupants: 343 |
| Aircraft damage: | Minor |
| Aircraft fate: | Repaired |
| Location: | Los Angeles International Airport, CA (LAX) ( United States of America)
|
| Phase: | Landing (LDG) |
| Nature: | International Scheduled Passenger |
| Departure airport: | Sydney-Kingsford Smith International Airport, NSW (SYD/YSSY), Australia |
| Los Angeles International Airport, CA (LAX/KLAX), United States of America |
The crew noted that the nose and main body gear indicated up and locked after normal gear extension. The crew used the alternate gear extension procedure, which was unsuccessful. The aircraft landed on runway 25R with the nose and main body gear retracted when the flight reached the minimum fuel state. Examination of the aircraft revealed that the selector valve for the affected gear was in the up and locked position, and the bolt which connects the valve arm to the cockpit control cable system was missing. The bolt for the wing gear selector valve arm was found partially backed out; the nut and cotter pin were missing. The aircraft was delivered to United in January of 1990 and had 2,952 flight hours and 402 cycles. Detailed review of the maintenance records proved that United had not performed any maintenance on the landing gear system. A second alternate gear extension procedure involving de-energizing the hydraulic system for the affected gear is not published in the crew manuals, taught during initial training, nor available on any checklist.
Probable Cause:
PROBABLE CAUSE: "The failure of the manufacturer to ensure that the landing gear selector valves and their associated drum link assemblies were properly installed prior to delivery of the aircraft. A factor in the accident was the lack of information available to the crew concerning the secondary alternate gear extension procedure."
Accident investigation:
 |
|
Classification:
Forced landing on runway
Sources:
» Aviation Week & Space Technology 3.9.90 (p.205)Photos
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Sydney-Kingsford Smith International Airport, NSW to Los Angeles International Airport, CA as the crow flies is 12026 km (7516 miles).
Distance from Sydney-Kingsford Smith International Airport, NSW to Los Angeles International Airport, CA as the crow flies is 12026 km (7516 miles).
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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