AD 91-21-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | DC-9-81 (MD-81) | Airworthiness Directives; MCDONNELL DOUGLAS DC-9-80 Series Airplanes |
| aircraft | The Boeing Company | DC-9-82 (MD-82) | Airworthiness Directives; MCDONNELL DOUGLAS DC-9-80 Series Airplanes |
| aircraft | The Boeing Company | DC-9-83 (MD-83) | Airworthiness Directives; MCDONNELL DOUGLAS DC-9-80 Series Airplanes |
| aircraft | The Boeing Company | DC-9-87 (MD-87) | Airworthiness Directives; MCDONNELL DOUGLAS DC-9-80 Series Airplanes |
Unsafe Condition
In-flight electrical shorting of the Sundstrand Data Control management control units (MCU), part numbers 960-0511-001, -002, or -003, could cause the MCU battery to burst and blow the MCU case open, damaging other aircraft systems in the electrical and electronics compartment.
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Required Actions
Remove Sundstrand MCU part numbers 960-0511-001, -002, or -003 in accordance with McDonnell Douglas Alert Service Bulletin A31-39. Operators using the MCU to record maintenance data must obtain FAA approval for an alternative recording method. MCUs may be replaced with FAA-approved part number 960-0511-011.
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Compliance Time
within 15 days after the effective date of this AD, unless previously accomplished
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Affected Aircraft
MCDONNELL DOUGLAS DC-9-80 series airplanes equipped with Sundstrand Data Control management control units (MCU), part numbers 960-0511-001, -002, or -003
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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