AD 51-21-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Cessna Aircraft Company | 120 | Airworthiness Directives; CESSNA Model 120 and 140 Airplanes |
| aircraft | Cessna Aircraft Company | 140 | Airworthiness Directives; CESSNA Model 120 and 140 Airplanes |
| aircraft | Cessna Aircraft Company | 140A | Airworthiness Directives; CESSNA Model 120 and 140 Airplanes |
Unsafe Condition
Rudder rib flanges may have kinks or cracks just aft of the rudder horn fitting, leading to rib breakage and loss of rudder control.
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Required Actions
Inspect the bottom rib of the rudder for kinks or cracks. Replace the bottom rib assembly with Cessna P/N 0433106 if damage is found, including installing steel reinforcing channel P/N 0433131 with specified rivets. If no damage, install the steel reinforcing channel only using existing rivet holes.
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Compliance Time
prior to December 1, 1951
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Affected Aircraft
Cessna Model 120 and 140 Aircraft, Serial Numbers 8001 to 10650, Inclusive, and/or any other serial numbers not having Steel Reinforcing Channel Cessna P/N 0433131 or equivalent installed.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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