AD 90-06-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 737-100 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200C Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-300 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-400 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-500 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-600 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-700 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-800 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
Unsafe Condition
Undetected APU fire due to improper installation or configuration of Walter Kidde APU fire detectors in the APU compartment.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Placard the APU as inoperative within 3 days after the effective date. Within 5 days after placarding, inspect to determine if a Walter Kidde APU fire detector with a perforated shield is installed. If discrepancies are found, replace the detector within 5 days and submit a report within 10 days after inspection.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the specified timeframes: 3 days for placarding, 5 days for inspection after placarding, 5 days for replacement if needed, and 10 days for reporting discrepancies after inspection.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
All Model 737 series airplanes equipped with Walter Kidde APU fire detection systems that either have not yet had an initial 'C' check or had an APU replaced since the last 'C' check.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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