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Boeing 777 Airworthiness Directive Includes Flap Bearings
The U.S. Federal Aviation Administration has issued an Airworthiness Directive covering Boeing 777 aircraft in service worldwide.
The AD, "results from reports of excessive wear of the pins, bushings, and bearings, and corrosion at the joints of the outboard trailing edge flap supports."
Loss of the trailing edge flap, "and possible loss of control of the airplane," could occur, so the FAA issued the AD, "to prevent wear and corrosion at the flap support joints."
Under scrutiny are airframes 1 through 546, and which have accumulated more than 6,000 flight cycles without a related teardown inspection -- although a necessarily wider variety of other operating conditions are covered. It extends a Boeing service notice (777-27A0071) issued in mid-2006.
Underscoring the precision under which modern jets operate, measuring flap component freeplay in excess of 0.02" is enough to trigger component inspection and potential replacement.
Japan Air Lines, in its related comments to the FAA, demonstrated a far more detailed approach than even the suggested measurement and replacement intervals. The FAA ultimately determined JAL had more information, and kept shorter-term inspection logs about its fleet, than most operators could properly utilize; the AD's simpler inspection information and intervals were kept in place.
Ultimately, the 777s will need to have new flap pins, ball sets, bushings and bearings installed -- at a total cost of more than $10 million.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 6003.2Z bearing | 17 | 35 | 10 |
| 6003.2RS bearing | 17 | 35 | 10 |