AD 2026-04-05

final rule
Data completeness: 80%

Airworthiness Directives; The Boeing Company Airplanes

AD Number
2026-04-05
Status
final_rule
Effective Date
Product Category
aircraft
Docket
Docket No. FAA-2026-1332
FR Citation
91 FR 8708

Applicability

TypeManufacturerModelDetails
aircraft Boeing Company Airworthiness Directives; The Boeing Company Airplanes

Unsafe Condition

The BAT BUS SECT 2 circuit breaker (CB3062) on the standby power control unit (SPCU) tripping causes an unintended erroneous electrical ground signal to the smart ram air door actuators (SRADAs), which in turn causes both ram air deflector doors to extend (close), thus reducing cooling airflow to the air conditioning heat exchangers. The reduced airflow causes insufficient cooling of the hot bleed air, which causes both packs to supply excessively hot air to the cabin and flight deck.

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Required Actions

Revising the Operating Procedures section of the existing airplane flight manual (AFM) to provide the flightcrew with non-normal checklists if the BAT BUS SECT 2 circuit breaker in the SPCU trips.

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Compliance Time

Before further flight

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Affected Aircraft

The Boeing Company Model 737-8, 737-9, and 737-8200 airplanes.

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Source: Official FAA Source ↗

Retrieved: Apr 4, 2026

Rights: U.S. Government Public Domain

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