AD 56-22-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hamilton Standard | Propeller Blades | HAMILTON STANDARD Applies to all Hamilton Standard Aluminum Alloy Propeller Blades |
Unsafe Condition
Omission of EC776 cement as a prime coat under BB1007 in the cement sequence for adhering rubber accessories to Hamilton Standard aluminum blades has resulted in corrosion of the blade area under these parts. Fatigue cracking has occurred in 6,507 blades on DC-4 type aircraft, believed to originate from such corrosion.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Remove adhered rubber parts from all aluminum blades with fluid deicing boots, electric blade heaters, deicer troughs, or slip ring mounts (except blades with known EC776 application history). Inspect and rework uncovered areas per Service Bulletin No. 385. Use Service Bulletin No. 385B for anodize inspection facilities. Return blades with excessive corrosion/cracks to Hamilton Standard.
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Compliance Time
Compliance required for 6507 blades before July 1, 1957; all other blades before January 1, 1958.
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Affected Aircraft
Hamilton Standard Aluminum Alloy Propeller Blades with fluid deicing boots, electric blade heaters, deicer troughs, or slip ring mounts, including blades that formerly incorporated these rubber parts without EC776 application.
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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