# Aviat Mandatory Service Bulletin 33: No revision named - Rights: © Aviat. Filed by the FAA in regulations.gov docket FAA-2017-0418; AD 2019-10-06 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Aviat Mandatory Service Bulletin 33](https://openairdocs.org/service-documents/aviat/sb-33.md) - Title as filed: Service Bulletin No 33 Husky 11 11 2016 Released - Pages: 7 - PDF: https://openairdocs.org/files/sha256/4c/e4/4ce499a24b8f682a0c15c5d6a3df8da8bb71ff0aa5588be3c863b54e8a77d17b - Page: https://openairdocs.org/service-documents/aviat/sb-33/file/4ce499a24b8f ## Text Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 1 Husky Service Bulletin No. 33 P.O. Box 1240 Afton, WY 83110 USA Tel: 307-885-3151 Fax: 307-885-9674 e-mail: aviat@aviataircraft.com REVISION: Initial Release (IR) AIRCRAFT MODEL AFFECTED: HUSKY A-1C-180 & A-1C-200. AIRCRAFT SERIAL NUMBERS AFFECTED: 3181 – 3282 PURPOSE To inform aircraft owners and operators of affected aircraft listed above of a Mandatory Requirement to verify the Rapco fuel vent check valves part number RA1798-00-1 are operating properly as required for continued airworthiness. The instructions in this service bulletin are required until a long term solution is approved and published. This service bulletin does not apply to aircraft manufactured with Duke’s fuel vent check valves part number 1798-001 (red in color). DESCRIPTION Fuel vent check valves allow air into the tanks as fuel is consumed from the fuel tanks and prevents fuel from escaping the fuel tank. The check valve is an essential part in the fuel system. Aviat Aircraft Inc. has received a report from the field that involved the fuel tank vent check valves sticking resulting in fuel starvation to the engine which caused a forced landing of the aircraft. COMPLIANCE IMMEDIATE ACTION REQUIRED PRIOR TO NEXT FLIGHT AND PRIOR TO EACH FLIGHT THEREAFTER; VERIFY OPERATION OF RAPCO FUEL VENT CHECK VALVES. DATE: November 11, 2016 SUBJECT: RAPCO RA1798-00-1 FUEL VENT CHECK VALVE ### Page 2 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 2 Husky Service Bulletin No. 33 TABLE OF CONTENTS Purpose, Description, Compliance ………………….………....…….....………...1 Table of Contents …................................ ............................…...2 Part List & Accomplishment Instructions ……..………………… ….…………3 - 6 Figure 1 ……………………………………………………………………………….3 Figure 2 ……………………………………………………………………………….4 Figure 3 ……………………………………………………………………………….4 Figure 4 ………………………………………………………………………………. 6 Compliance Letter…..………………………………………………………………...7 ### Page 3 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 3 Husky Service Bulletin No. 33 ACCOMPLISHMENT INSTRUCTIONS AAI Parts Number Description Qty 40110 x 18” Hose 1 Step 1 The pilot (PIC) or a mechanic must perform this inspection and verification of proper operation of both fuel vent check valves, one installed in each wing, is mandatory before every flight for continued airworthiness. Verify the proper operation of the fuel vent check valve with use of the supplied hose attached to the fuel tank vent line a t the aft edge of the wing at the wing tip attach point as shown in figure 1. Figure 1. Fuel tank vent line and inspection ring. Step 2 Once the vent line is located per figure 1 , attach supplied hose to the wing vent line. The supplied hose should be pushed over the vent line to make a tight seal as shown in figure 2. Connect supplied hose here ### Page 4 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 4 Husky Service Bulletin No. 33 Figure 2. Supplied clear plastic test tube pushed onto the fuel vent line. Step 3 With the supplied hose attached per step 2, blow into the hose to tell if the vents are stuck as seen in figure 3. Using your mouth and not your lungs force air into the vent line. If you can blow and force air into the vent line then the check valve is operating properly. If no air can be forced into the vent line then the Rapco vent check valve is stuck. To demonstrate a stuck check valve simply block one end of the supplied hose and try to force air into it, you will sense the same obstruction as with a stuck Rapco fuel vent check valve. Figure 3. Testing fuel tank vent check valve. Air ### Page 5 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 5 Husky Service Bulletin No. 33 Step 4 If a stuck vent check valve is discovered in one or both wings, the vent line check valve must be removed from the aircraft and sent to Aviat Aircraft, Inc. *NOTE  Only FAA or CAA authorized repairman should perform the removal instructions in this service bulletin.  It is the responsibility of the owner/operator to have only FAA or CAA authorized repairman perform this work.  Complete and send Aviat Aircraft, Inc. compliance letter to the provided address. Step 5 For the removal of a stuck fuel vent check valve or valves, start by removing the attachment screws from the forward, rear and outboard sections of the fuel tank cover. Cut out the inspection access hole adjacent and below the check valve per figure 1. Next drain the fuel in accordance with aviation industry standards for draining fuel from an aircraft, Note: Be mindful static electricity buildup when draining fuel as static electricity can cause a spark that could ignite the draining fuel. Drain the fuel to approximately ¾ of a tank. Draining the fuel down to ¾ of a tank will assure no fuel will drain from the vent line when removing the affected check valve. Step 6 Using an 11/16 th inch wrench loosen the vent line from the check va lve and move the line for removal of the check valve. T o remove the check valve from the fuel use a 1 1/16 th wrench on the portion of the check valve closest the tank at the brass nipple. The brass nipple may be removed with the check valve. See figure 4. Step 7 Return the completed compliance letter to Aviat Air craft Inc. In the event a stuck Rapco fuel vent check valve is discovered during the initial inspection or thereafter, contact Al Humbert or Steve Anderson at Aviat Aircraft, Inc. at the telefax number/email address above and a replacement vent check valve(s) will be sent to you with a pre-paid and addressed label to return the stuck vent check valve(s) and the executed compliance letter. Do not unstick any stuck check valve. Step 8 If a stuck Rapco fuel vent check valve(s) is discovered and a replacement Rapco valve(s) sent, an approved mechanic must rein stall the new check valve using a thread sealant, such as fuel lube or equiva lent on both ends of the brass nipple before installation. Using a 1 - 1/16 wrench tighten the replacement valve by the hex thread on the check valve closest to the tank. Next install the vent line to the newly installed fuel vent check valve. Inspe ct to verify the check valve and vent line are properly tightened. Next install the supplied inspection hole cover by centering the hole cover over the cut out inspectio n hole that and drill the two mounting holes using a #40 drill bit and install th e two mounting screws. ### Page 6 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 6 Husky Service Bulletin No. 33 Step 9 Record in the aircraft’s log book the replacement of the stuck Rapco check valve(s) per this Service Bulletin. NOTE: The inspection procedures described in this s ervice bulletin for a stuck fuel vent check valve must be performed during each and every pre-flight inspection by the Pilot (PIC) or a mechanic. This pre-flight insp ection is required even after the installation of a replacement Rapco fuel vent check valve.” Figure 4. Removal of fuel tank vent check valve. Vent line compression fitting Check Valve Brass nipple ### Page 7 MANDATORY SERVICE BULLETIN NO. 33 Aviat Aircraft Inc. 7 Husky Service Bulletin No. 33 COMPLIANCE LETTER This is to certify that I have complied with Service Bulletin No. 33 on airplane: Model Number: Serial No: Registration Number: Were Rapco P/N RA1798-00-1 check valves installed? Yes:____ No:____ Were Duke P/N 1798-001 check valves installed? Yes:____ No.____ Were Rapco fuel check valves found to be operating properly? Yes:____ No:____ Were there non-operational (stuck) Rapco valve(s) discovered? Yes:____ No:____ How many the non-operational (stuck) Rapco valve(s) were removed and returned to Aviat Aircraft Inc. One:____ Two:____ Date:________________ Aircraft Hours:_____________ ____ FAA Authorized Repairman:__________________________ __ Certificate No.:___________________________________ _____ Signed:______________________________________________ Return completed compliance letter to Aviat Aircraft Inc. via fax at 307-885-9674 or email to engineering@aviataircraft.com after complying with Mandatory Service Bulletin No. 33 for the first time. In the event a stuck Rapco fuel vent check valve(s) is discovered during the initial inspection or thereafter, contact Al Humbert or Steve Anderson at Aviat Aircraft, Inc. at the telefax number/email address above and a replacement vent check valve(s) will be sent to you with a pre-paid and addressed label to return the stuck vent check valve(s). --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. 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