AD 70-04-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 737-100 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200C Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-300 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-400 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-500 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-600 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-700 Series | BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-800 Series | BOEING Model 737 Series Airplanes |
Unsafe Condition
Failure of the APU bleed air duct or failure of the APU fire extinguisher bottle to discharge safely, or exposure to an overheat condition following ground operation of the pneumatic system with bleed air from the APU or external ground service.
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Required Actions
Install specific placards in the cockpit and adjacent to the pneumatic ground service connection. Check the cockpit bleed air wing-body overheat system and master caution light prior to further flight if overheat conditions exist. Inspect and replace cracked APU bleed air ducts per specified service bulletins. Remove and replace the APU fire extinguisher container with a specific part number as per service bulletins.
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Compliance Time
Within 25 hours time in service after the effective date of this directive for placards; within 50 hours time in service after the effective date for duct inspection, and thereafter every 500 hours time in service.
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Affected Aircraft
Boeing Model 737 series airplanes including 737-100, 737-200, 737-200C, 737-300, 737-400, 737-500 series.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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