ASN Wikibase Occurrence # 379259
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| Date: | Monday 11 June 1984 |
| Time: | 21:30 LT |
| Type: |  Boeing 747-122 |
| Owner/operator: | United Airlines |
| Registration: | N4712U |
| MSN: | 19757/67 |
| Year of manufacture: | 1970 |
| Total airframe hrs: | 45436 hours |
| Engine model: | P&W JT9D-3 |
| Fatalities: | Fatalities: 0 / Occupants: |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | San Francisco, CA -
 United States of America
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Honolulu, HI (HNL) |
| San Francisco, CA (SFO | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
JUST INSIDE THE OUTER MARKER, A 'LOUD BANG' WAS HEARD & LEFT AILERON INPUT WAS NEEDED TO CONTROL ACFT HEADING. THE LANDING WAS MADE WITHOUT INCIDENT UNTIL THE FLAPS WERE RAISED WHILE TAXIING & THE FLT ENGINEER REPORTED A #4 HYDRAULIC SYSTEM FAILURE. THE CAPT LOST BRAKES AND HAD TO UTILIZE STANDBY BRAKES. AT THIS TIME A SPLIT FLAP INDICATION WAS OBSERVED. INSPECTION REVEALED FLAP TRACK FRACTURED APRX 6 INCHES AFT OF THE FORWARD ATTACH POINT. THE FRACTURE INITIATEDON OUTBOARD FLANGE #1 BOLTHOLE WALL BECAUSE OF PITTING CORROSION. A PORTION OF THE FORE FLAP & A SMALL WING PANEL SEPARATED FROM THE ACFT. DURING FLAP RETRACTION AFTER LANDING, THE TRANSMISSION BALL NUT JAMMED. THE DRIVE TORQUE TUBE FRACTURED AT THIS TIME AND THE BROKEN END OF THE ROTATING TORQUE TUBE DAMAGED HYDRAULIC LINES, CAUSING A LOSS OF HYDRAULIC FLUID. AN ALERT SERVICE BULLETIN WAS ISSUED BY BOEING AFTER THIS INCIDENT & UNITED AIRLINES INITIATED A FLEET WIDE INSPECTION.
Probable Cause:
Accident investigation:
 |
|
Sources:
NTSB LAX84IA350
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 31-Mar-2024 17:26 | ASN Update Bot | Added |
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