AD 93-14-21
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-400 Series | Airworthiness Directives; BOEING Model 747-400 Series Airplanes |
| aircraft | The Boeing Company | 747-400D Series | Airworthiness Directives; BOEING Model 747-400 Series Airplanes |
Unsafe Condition
Depressurization of hydraulic system number one or four could cause airplane systems to enter ground operating mode while in flight, potentially affecting system operation and safety.
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Required Actions
Revise the AFM by inserting Operations Manual Bulletin 93-5 and including AD requirements; install a system providing full pitot and total air temperature heat per Boeing Alert Service Bulletin 747-30A2069.
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Compliance Time
Within 15 days after the effective date of this AD for AFM revisions and within 60 days after the effective date for installing the pitot and total air temperature heat system.
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Affected Aircraft
All Model 747-400 series airplanes, 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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