AD 94-04-13
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Twin Commander Aircraft LLC | 500 | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 500-A | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 500-B | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 500-S | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 500-U | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 520 | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 560 | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 560-A | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 560-E | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
| aircraft | Twin Commander Aircraft LLC | 560-F | Airworthiness Directives: Twin Commander Aircraft Corporation 500, 600, and 700 Series Airplanes |
Unsafe Condition
Failure of the wing structure caused by cracks in the lower front spar cap.
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Required Actions
Inspect the wing front spar lower cap at left and right Wing Station 24 in accordance with specified service bulletins. Replace the spar cap if cracks are found prior to further flight, using designated procedures from Twin Commander Custom Kit No. CK-145 or manufacturer instructions. Compliance may be adjusted via approved alternative methods.
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Compliance Time
Initially within the next 50 hours time-in-service (TIS), or 500 hours after spar cap replacement, whichever is later. Repetitive inspections at intervals not exceeding 500 hours TIS.
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Affected Aircraft
All serial numbers of Twin Commander models: 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680FL(P), 680FL, 680T, 680V, 680W, 681, and 720.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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