ASN Wikibase Occurrence # 359232
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| Date: | Friday 17 March 1995 |
| Time: | 11:50 LT |
| Type: |  Beechcraft 1900C |
| Owner/operator: | Alpha Aviation |
| Registration: | N1568W |
| MSN: | UC-64 |
| Year of manufacture: | 1989 |
| Total airframe hrs: | 11711 hours |
| Engine model: | P&W PT6A-65B |
| Fatalities: | Fatalities: 0 / Occupants: 19 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | Los Angeles, CA -
 United States of America
|
| Phase: | Approach |
| Nature: | Unknown |
| Departure airport: | Mammoth Lakes, CA |
| (KLAX) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
WHILE ON FINAL APPROACH, THE AIRPLANE EXPERIENCED A RAPID, UNCOMMANDED ROLL TO THE LEFT WHEN THE 35-DEGREE FLAP SETTING WAS SELECTED. THE PILOT WAS ABLE TO COUNTER THE ROLL BY APPLYING FULL OPPOSITE AILERON AND LANDED WITHOUT FURTHER INCIDENT. AN EXAMINATION REVEALED THAT THE WING FLAPS HAD BEEN FULLY EXTENDED IN THE AFT DIRECTION, BUT THAT THE INBOARD TRAILING EDGE OF THE LEFT OUTBOARD FLAP HAD BEEN FORCED UPWARD ABOUT 3 INCHES. THE INBOARD AFT FLAP TRACK ROLLER BEARING ASSEMBLY, INCLUDING THE ATTACHING BOLT AND WASHER, HAD PULLED THROUGH THE SKIN OF THE FLAP TRACK HINGE BRACKET. AN ANALYSIS OF THE FAILED PARTS BY BEECH REVEALED THAT THE OUTER ROLLER WAS LOOSE ON THE BEARING AND COULD BE SHIFTED AXIALLY. A CIRCULAR WEAR PATTERN MATCHING THE DIAMETER OF THE OUTER ROLLER FLANGE WAS FOUND ON THE PORTION OF FLAP TRACK HINGE BRACKET WHICH HAD PULLED OUT. BEECH CONCLUDED THAT THE BEARING OUTER ROLLER HAD SHIFTED ON THE ROLLER ELEMENT BEARING AND ALLOWED THE OUTER ROLLER FLANGE TO WEAR AGAINST THE SIDE OF THE FLAP HINGE BRACKET UNTIL THE BEARING ASSEMBLY WAS PULLED OUT. THE FAILED FLAP TRACK HINGE BRACKET AND BEARING ASSEMBLY IS CONTAINED WITHIN THE INTERIOR OF THE FLAP STRUCTURE.
Probable Cause: AN AXIAL SHIFT OF THE OUTER BEARING ROLLER FOR AN UNDETERMINED REASON, RESULTING IN EROSION AND FAILURE OF THE FLAP TRACK HINGE BRACKET/BEARING ASSEMBLY. FACTORS RELATING TO THE INCIDENT WERE: THE ROLLER BEARING AND ASSOCIATED BRACKET ASSEMBLY WITHIN THE INTERIOR OF THE FLAP STRUCTURE COULD NOT BE ADEQUATELY INSPECTED WITHOUT DISASSEMBLY; AND LACK OF INSPECTION CRITERIA IN THE MANUFACTURER'S MAINTENANCE MANUAL CONCERNING FLAP ROLLER/HINGE BRACKET ASSEMBLIES.
Accident investigation:
 |
|
Sources:
NTSB LAX95IA142
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Mar-2024 08:23 | ASN Update Bot | Added |
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