AD 90-21-13
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-300 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400D Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400F Series | BOEING Model 747 Series Airplanes |
Unsafe Condition
Damage to hydraulic and pneumatic systems and flight deck/cabin air contamination
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Required Actions
Modify the hydraulic system in the number 2 and 3 struts in accordance with Boeing Service Bulletin 747-29-2051, Revision 1. An alternate means of compliance or adjustment may be used if approved by the FAA Manager. Special flight permits may be issued under FAR 21.197 and 21.199.
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Compliance Time
within the next 4,000 flight hours or 12 months after the effective date of this AD, whichever occurs first
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Affected Aircraft
Model 747 series airplanes, line position 001 through 331, identified in Boeing Service Bulletin 747-29-2051, Revision 1, dated August 8, 1980, certificated in any category
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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