Airworthiness Directive · Amendment 39-21190 · Horizontal stabilizer structure
Aviat Aircraft Inc.
This AD applies to Aviat Aircraft Inc., Models A-1, A-1A, A-1B, A-1C-180, and A-1C-200 airplanes, all serial numbers, certificated in any category.
The FAA is adopting a new airworthiness directive (AD) for all Aviat Aircraft Inc. Models A-1, A-1A, A-1B, A-1C-180, and A-1C-200 airplanes. This AD requires repetitive inspections of the forward horizontal stabilizer support assembly and the rear horizontal stabilizer support tube and reporting information to the FAA. This AD was prompted by field reports of complete failure of both the forward support assembly and the rear support tube due to fatigue. The FAA is issuing this AD to address the unsafe condition on these products.
For airplanes with 400 or more hours time-in-service (TIS), do the following inspection within 30 days after September 1, 2020 (the effective date of this AD) or within 20 hours TIS after September 1, 2020 (the effective date of this AD), whichever occurs first. For airplanes with less than 400 hours TIS, do the following inspections within 30 days after accumulating 400 hours TIS or within 20 hours TIS after accumulating 400 hours TIS, whichever occurs first. After the initial inspection, repeat the inspections at intervals not to exceed 12 months or 100 hours TIS, whichever occurs first.
(1) Below and just aft of the horizontal stabilizer leading edge, remove each inspection hole cover if installed, or cut out the inside of each inspection ring if not cut out, on both sides of the fuselage. You do not need to remove the stabilizer support assembly. Locate the forward horizontal stabilizer support assembly. Using a light and a mirror or a borescope, inspect the stabilizer support assembly for cracks in the large tube portion of the assembly. Pay particular attention to the toe of the welded bushings where the stabilizer support assembly is bolted to the fuselage frame.
(i) If no cracks are found, install inspection hole cover, part number (P/N) 61659 and mounting screws, P/N 59146.
(ii) If any cracks are found, before further flight, replace the stabilizer support assembly with the same part-numbered part, either P/N 35086-501 or P/N 38086-501 as applicable. Replace both self-locking nuts with self-locking nuts that have zero hours TIS. Replacing the forward stabilizer support assembly requires removal and reinstallation of other horizontal stabilizer components. Replace all self-locking nuts with self-locking nuts that have zero hours TIS upon reinstallation of these components.
(2) Inspect the rear horizontal stabilizer support tube weld joints for corrosion and damage in accordance with the Instructions, steps 1.a. and 1.b., of Aviat Aircraft Inc. Service Bulletin No. 28, Revision A, dated April 2, 2015. If there is any corrosion or damage on a weld joint, before further flight, repair the weld joint and install a repair tube inside the stabilizer support tube as depicted in the figure on page 3 of Aviat Aircraft Inc.
Service Bulletin No. 28, Revision A, dated April 2, 2015. Repairing the rear horizontal stabilizer support tube requires removal and reinstallation of other horizontal stabilizer components. Replace all self-locking nuts with self-locking nuts that have zero hours TIS upon reinstallation of these components.
If a crack is found during any inspection required by paragraph (g) of this AD, within 10 days, report the following information to the FAA at the address listed in paragraph (l) of this AD:
(1) Aircraft Make and Model
(2) Aircraft N-number
(3) Aircraft Serial Number
(4) Total hours TIS
(5) Total takeoff and landing cycles (if known)
(6) Aircraft used for Tow operations? Yes or No
(7) If the Aircraft is used for Tow operations, report heaviest Glider Max Gross takeoff weight or banner maximum weight.
(8) Describe the crack location(s) and report the length of the crack(s) in the forward horizontal stabilizer support assembly, rear horizontal stabilizer support tube, or both.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
