AD 91-20-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | Airworthiness Directives; BOEING Model 747-100 and -200 Series Airplanes |
Unsafe Condition
Cross connection of the engine nacelle fire extinguishing plumbing during maintenance could lead to failure of the fire extinguishing system to function properly.
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Required Actions
Conduct an inspection of the engine fire extinguishing system plumbing within 10 days after October 24, 1989, and after any maintenance that could cause mis-plumbing, following Boeing SB 747-26A2094, Rev 1. Correct discrepancies before further flight. Modify the system plumbing within 18 months after November 7, 1991, per Boeing SB 747-26-2162 to terminate repetitive inspections.
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Compliance Time
Within 10 days after October 24, 1989; within 18 months after November 7, 1991
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Affected Aircraft
Boeing Model 747-100 and -200 series airplanes manufactured prior to January 1, 1981, equipped with GE CF6-45/50 or Pratt & Whitney JT9D-70 engines, as listed in Boeing SB 747-26-2162.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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