AD 2004-22-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Boeing | 747-400 | Airworthiness Directives; Boeing Model 747-400, -400D, and -400F Series Airplanes Equipped With General Electric (GE) or Pratt & Whitney (P&W) Series Engines |
Unsafe Condition
Inadvertent commanded shutdown of the engine bleed air distribution systems due to an erroneous air supply control test unit (ASCTU) command, which could cause depressurization of the airplane and subsequent ice build-up on the engine inlets during descent, leading to ingestion of ice into the engine(s) and consequent loss of thrust on one or more engines.
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Required Actions
Remove the existing ASCTU, perform wiring changes between the wire integration unit (WIU) and ASCTU, conduct resistance tests, and install a new or reworked ASCTU. Post-installation tests must be conducted before further flight.
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Compliance Time
Within 18 months after the effective date of this AD.
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Affected Aircraft
Boeing Model 747-400, -400D, and -400F series airplanes equipped with GE or P&W series engines, as listed in Boeing Service Bulletin 747-36A2136, Revision 2, dated May 13, 2004.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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