Service Bulletin No. 34

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SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 1 Husky Service Bulletin No. 34 P.O. Box 1240 Afton, WY 83110 USA Tel: 307-885-3151 Fax: 307-885-9674 e-mail: aviat@aviataircraft.com DATE: 25 SEP 2020 SUBJECT: Stabilizer Support Assembly REVISION: C AIRCRAFT MODELS AFFECTED: A-1, A-1A, A-1B, A-1C-180 & A-1C-200 ALL AIRCRAFT SERIAL NUMBERS ARE AFFECTED (CERTIFIED IN ANY AIRWORTHINESS CATEGORY) PURPOSE To inform aircraft owners and operators of the affected aircraft models and serial numbers listed above of a Mandatory Requirement to perform an inspection of the Stabilizer Support Assembly. DESCRIPTION The stabilizer support assembly, part numbers 35086-501 or 38086-501, are attached to the fuselage structure with AN bolts and serves as one attachment point for the horizontal stabilizer assembly. Aviat Aircraft Inc. has received reports from the field involving broken stabilizer support assemblies. The broken stabilizer support assemblies were discovered during pre-flight inspections of the aircraft. Aircraft involved had more than 1200 hours of operating time. COMPLIANCE "Inspect the stabilizer support assembly for cracks per paragraph (f) of AD 2020-16-06”. TABLE OF CONTENTS Purpose, Description, Compliance, and Table of Contents.............………...1 Accomplishment Instructions ………………........…….………………........2- 8 Compliance Letter ..…...………….…………………………………..………….9 SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 2 Husky Service Bulletin No. 34 *NOTE: • Only FAA certified mechanics are to perform the instructions in this service bulletin. • It is the responsibility of owner/operator to have only FAA certified mechanics perform this work. • Complete and send Aviat Aircraft, Inc. the compliance letter to the address provided. ACCOMPLISHMENT INSTRUCTIONS Step 1. An FAA authorized mechanic must perform this aircraft inspection to determine if the stabilizer support assembly is broken or has cracks that could lead to a failure. Step 2. Locate the stabilizer support assembly as shown in figure 1. The use of illustrated parts catalog (IPC) section on tail surface installation can be helpful with disassembly and reinstallation. Figure 1, Stabilizer Support Assembly, fabric removed for clarity. Tube 30800-111 SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 3 Husky Service Bulletin No. 34 Figure 2, Inspection access hole cover LH side Step 3. Remove adjacent inspection hole cover located just behind and below the horizontal stabilizer assembly leading edge. There are inspection holes on both right and left sides of the fuselage. Either hole can be used to gain access to the stabilizer support assembly. See figure 2. To remove the hole cover, remove two PK screws and slide the hole cover forward to release the mounting tabs on the back side of the hole cover. With the hole cover removed you will have access to the stabilizer support assembly mounted to the fuselage. SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 4 Husky Service Bulletin No. 34 Figure 3 Uncut inspection ring If the inspection ring is not cut out as shown in figure 3 then the inspection ring will need to be cut out to gain access to inspect the stabilizer support assembly. Figure 4, Cut out inspection ring To cut out the inspection ring, use a sharp knife such as an exacto knife and cut out the inside portion of the inspection ring as shown in figure 4. An inspection hole cover P/N 61659 and mounting screws P/N 59146 x 2 can be purchased from Aviat Aircraft Inc. SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 5 Husky Service Bulletin No. 34 The stabilizer support assembly does not need to be removed to perform the required inspection. With visual aids such as light and a mirror or a borescope, inspect the stabilizer support assembly for cracks in the large tube portion of the assembly. Figure 5, Typical crack location Cracks reported originated at the toe of the welded bushings, see figure 5. Inspect both the right end, left end, and the forward and rear sides of the stabilizer support assembly tube in the area shown in figure 5 for the presence of cracks. If no signs of a broken or cracked stabilizer support assembly is discovered during the inspection replace the inspection hole cover in reverse order as removed or install a new hole cover and record this initial inspection in the aircraft’s logbook. Complete and return the compliance letter to Aviat Aircraft Inc. at the address provided. If a broken or cracked stabilizer support assembly is discovered during this inspection, it must be replaced. The following pages of this service bulletin describes the removal and replacement of the stabilizer support assembly. SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 6 Husky Service Bulletin No. 34 Figure 6, Tail fairings removed and AN3 attach bolts shown Step 4. To replace a stabilizer support assembly, start by removing the stabilizer tail fairings. Horizontal stabilizer tail fairings are located on the top and the bottom of the horizontal stabilizers at the fuselage. See figure 6. To remove the tail fairings top and bottom, remove the PK screws holding the fairings to the horizontal stabilizers. SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 7 Husky Service Bulletin No. 34 Figure 7, Stabilizer strut assembly Next remove the stabilizer strut assemblies from the horizontal stabilizers and fuselage. Figure 8 Step 5. Remove the AN4 bolt holding the elevator assembly to the horizontal stabilizer. See figure 8. Note: elevators must be supported from the bottom side as the elevators are still attached to the control system. Next remove the two AN3 bolts holding each horizontal stabilizer to the fuselage. See figure 6. The horizontal stabilizers can now be removed from the fuselage by pulling them off the mounting tube at the fuselage. SERVICE BULLETIN NO. 34 Aviat Aircraft Inc. 8 Husky Service Bulletin No. 34 Figure 9, AN4 Bolts, fabric removed for clarity Step 6. With the inspection hole cover opened, the horizontal stabilizers taken off and