AD 2004-20-16
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Boeing | 747-200B | Airworthiness Directives; Boeing Model 747-200B, -200C, -200F, -300, -400, -400D, and -400F Series Airplanes; and Model 747SP Series Airplanes |
Unsafe Condition
Mineral build-up on the auxiliary power unit (APU) and engine fire shutoff switches could lead to failure of the switches to discharge fire suppressant in the affected area, resulting in an uncontrolled fire that could spread to the strut, wing, or aft body of the airplane.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Perform an initial functional test of the APU and engine fire shutoff switches within 18 months of the original certificate or within 90 days after the effective date of the AD. Repeat the functional test every 18 months. Replace any failed switch before further flight. Replace all APU and engine fire shutoff switches within 36 months of the AD's effective date and every 36 months thereafter. Operators may terminate repetitive requirements by deactivating the Lucas humidifier and replacing all switches.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 90 days after the effective date of the AD.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Boeing Model 747-200B, -200C, -200F, -300, -400, -400D, -400F, and Model 747SP series airplanes, as listed in Boeing Alert Service Bulletin 747-26A2274, Revision 1, dated January 9, 2003.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.