AD 91-09-17
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 737-300 Series | Airworthiness Directives; BOEING Model 737-300 and -400 Series Airplanes |
| aircraft | The Boeing Company | 737-400 Series | Airworthiness Directives; BOEING Model 737-300 and -400 Series Airplanes |
Unsafe Condition
Separation of the outboard flap from the airplane due to improper bolts or nuts securing the track forward support fitting of the inboard tracks.
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Required Actions
Inspect bolts and nuts securing the track forward support fitting of the inboard tracks to determine their part numbers and material. Replace bolts with Boeing part numbers BACB30LE6, BACB30LE7, BACB30US6, or BACB30US7 if incorrect. Replace nuts with A286 CRES steel Boeing part number BACN10HR if incorrect. Inspections must be done visually or via eddy current as per Boeing Alert Service Bulletin 737-57A1202.
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Compliance Time
Within the next 30 days after August 25, 1989 (for bolt inspections), or within the next 1,500 cycles or 6 months after August 6, 1990 or the effective date of this amendment (for nut inspections), whichever occurs first. Replacement must be done prior to further flight if non-compliant parts are found.
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Affected Aircraft
Boeing Model 737-300 and -400 Series airplanes, line numbers 1001 through 1769 and 1771, as listed in Boeing Alert Service Bulletin 737-57A1202, Revision 1.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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