AD 2001-12-14
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Boeing | 747-400 | Airworthiness Directives; Boeing Model 747-400 Series Airplanes |
Unsafe Condition
Miswiring of diodes in the heating system of the pitot static probes can lead to reduced power, causing ice accumulation on the probes, which may result in erroneous airspeed or altitude indications to the flight crew.
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Required Actions
Inspect the pitot static probe heating system using a multimeter to verify continuity, absence of diodes, and diode orientation between relay sockets. If miswiring is detected, rewire the system prior to further flight.
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Compliance Time
Within 15 months after the effective date of the AD.
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Affected Aircraft
Boeing Model 747-400 series airplanes, as listed in Boeing Alert Service Bulletin 747-30A2078, Revision 1, dated November 16, 2000, certificated in any category.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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