AD 90-21-21
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-300 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400D Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400F Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
Unsafe Condition
Potential for an engine fire due to a fuel leak caused by aluminum pneumatic duct brackets, P/N 69B94023-1, in the outboard struts.
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Required Actions
Replace aluminum pneumatic duct brackets (P/N 69B94023-1) with steel brackets (P/N 69B94023-2) in accordance with Boeing Service Letter 747-SL-54-32.
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Compliance Time
Within the next 60 days or 450 hours time-in-service after the effective date of this AD, whichever occurs first
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Affected Aircraft
Model 747 series airplanes equipped with General Electric CF6-45 and CF6-50 engines, as listed in Boeing Service Letter 747-SL-54-32 dated December 4, 1989.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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