AD 99-11-05
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
Cracking found in power control unit (PCU) secondary servo valve slides could lead to failure of the secondary slide and consequent rudder hardover and reduced controllability.
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Required Actions
Conduct repetitive displacement tests of the secondary slide in the dual concentric servo valve of the rudder PCU. Replace the valve assembly with a modified valve assembly if necessary. Perform initial compliance within 16 months of effective date and subsequent tests every 24,000 flight hours.
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Compliance Time
Initial compliance within 16 months of effective date; subsequent tests every 24,000 flight hours.
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Affected Aircraft
All Boeing Model 737 series airplanes (737-100, 200, 200C, 300, 400, 500 series).
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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