AD 91-09-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 737-300 Series | Airworthiness Directives; BOEING Model 737-300, -400 and -500 Series Airplanes |
| aircraft | The Boeing Company | 737-400 Series | Airworthiness Directives; BOEING Model 737-300, -400 and -500 Series Airplanes |
| aircraft | The Boeing Company | 737-500 Series | Airworthiness Directives; BOEING Model 737-300, -400 and -500 Series Airplanes |
Unsafe Condition
Damage to the circuits within the Flight Instrument Accessory Unit, Integrated Flight Systems Accessory Unit, or Inertial Navigation System Battery Monitor Module, and surrounding equipment due to lack of a 2-ampere thermal circuit breaker between the crew call horn drive circuitry and the crew call horn.
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Required Actions
Install a modification to add a 2-ampere thermal circuit breaker between the crew call horn drive circuitry and the crew call horn, following applicable Boeing Service Bulletins or an approved alternative method. Compliance may be adjusted with FAA approval.
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Compliance Time
within the next 180 days after the effective date of this AD, unless previously accomplished
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Affected Aircraft
Boeing Model 737-300, -400, -500 series airplanes prior to line position 2000, and specific serial numbers of Model 707, 727, and 737-200 series airplanes as listed in the AD.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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