AD 56-27-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sierra Hotel Aero, Inc. | Navion B | Airworthiness Directives; Navion B Type Aircraft |
Unsafe Condition
Cylinder head and oil temperature values can exceed established limits due to engine cooling tests revealing overheating risks from Reading Aviation Service Inc. or Hackenberg Sales and Service downdraft cooling kit installations.
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Required Actions
Remove the Reading Aviation Service Inc. or Hackenberg Aviation Sales Service downdraft cooling kit and return to original Ryan cooling configuration, or modify the kit per Reading Aviation Service Inc. Service Bulletin No. 1 dated July 26, 1956.
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Compliance Time
not later than July 1, 1957
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Affected Aircraft
Sierra Hotel Aero, Inc. Navion B Type Aircraft equipped with Reading Aviation Service Inc. or Hackenberk Sales and Service Downdraft Cooling Kit installations.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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