41001 thru incorporating a retrofitted LA nose strut,

Transcription

1 Service Newsletter SNL08-15 TITLE LA NOSE STRUT ASSEMBLY SEALS REPLACEMENT TO Cessna Distributors, Service Stations MODELS AFFECTED Model 300/LC40-550FG Serial Numbers thru incorporating a retrofitted LA nose strut 350/LC42-550FG 400/LC41-550FG thru incorporating a retrofitted LA nose strut, and On thru incorporating a retrofitted LA nose strut, and On DISCUSSION The purpose of this Service Newsletter is to provide instructions for replacing seals in the part number LA Nose Strut Assembly. MATERIAL AVAILABILITY The part below is available from Cessna Parts Distribution through an appropriate Cessna Service Station. Part Number Description Qty/Airplane LA SEALKT Nose Strut Seal Kit 1 To obtain satisfactory results, procedures specified in this publication must be accomplished in accordance with accepted methods and prevailing government regulations. Cessna Aircraft Company cannot be responsible for the quality of work performed in accomplishing the requirements of this publication. Cessna Aircraft Company, Product Support, P.O. Box 7706, Wichita, Kansas 67277, U.S.A. (316) Facsimile (316) COPYRIGHT 2008

2 Material Information The materials and equipment below will be necessary: NAME NUMBER MANUFACTURER USE Hydraulic Fluid MIL-H-5606-G Procure Locally For servicing strut Locitite 242 Procure Locally For locking and sealing threads of strut caps and Schrader valve Rod Seal Installation Tool (1 ½ inch) 1 ¼ - 3 inch Pin Type Spanner Wrench Procure Locally Procure Locally To install two piece Polypack Z seal To remove strut dust cap Holding Fixture Fabricate Locally To secure strut to work bench for ease of assembly Instructions 1. Prepare the airplane for maintenance. A. Make sure that all switches are in the OFF/NORM position. B. Disconnect electrical power from the airplane. (1) Disconnect the airplane battery. (2) Disconnect external electrical power. C. Attach maintenance warning tags to the battery and external power receptacle that have "DO NOT CONNECT ELECTRICAL POWER - MAINTENANCE IN PROGRESS" written on them. 2. Remove Strut Assembly from the nose gear per instructions in Chapter 32 ( ) of the applicable airplane model Maintenance Manual. 3. Prepare several shop cloths and plastic sheet on work surface. 4. Refer to Figure 1 and 2 as necessary to disassemble and reassemble the nose strut. CAUTION: WEAR SAFETY FACE SHIELD WHEN RELEASING GAS PRESSURE IN STRUT SNL08-15 Page 2

3 WARNING: REMOVAL OF THE AN7-6A BOLT WITHOUT DE-PRESSURIZING THE STRUT COULD CAUSE SERIOUS INJURY. 5. Relieve strut pressure by depressing the Schrader valve core. 6. Remove hex bolt on top of strut and replace O-Ring (2-013). 7. Pour out hydraulic fluid. 8. Invert strut assembly. For ease of assembly; secure strut to work bench using a locally fabricated holding fixture shown in Figure Unscrew strut dust cap and slide up shaft assembly, using pin spanner wrench. 10. Remove locking key with a 3/32 inch Allen Wrench. 11. Using a 2 inch wrench, unscrew damping sleeve from tube assembly. 12. Slowly rotate and pull up on the damping sleeve and shaft assembly until hydraulic fluid is noticeable. Wrap a shop cloth around tube assembly to mitigate the spillage of fluid. 13. Pour out hydraulic fluid from around the damping sleeve. 14. Remove damping sleeve and shaft assembly from tube assembly. 15. Remove centering cam-shaft and Damping Piston by removing shoulder bolt using a 5/32 inch Allen Wrench. 16. Remove black vane and shaft key from shaft assembly. 17. Remove damping sleeve from shaft assembly. 18. Remove strut dust cap from shaft assembly and replace dust seal (DS1500). 19. Remove valve core from Schrader valve body. WARNING: FLOATING PISTON WILL EXIT SHAFT ASSEMBLY AT HIGH VELOCITY. FAILURE TO SAFELY COMPLY WITH STEP 20 MAY CAUSE SERIOUS INJURY AND/OR DAMAGE TO THE PISTON. 20. Invert shaft assembly over soft table and using an air chuck, apply air pressure to Schrader valve to force out the floating piston from shaft assembly. 21. Prepare two quad rings (Q4226) by cutting thru to measured lengths. Damping sleeve seal, cut to inches to inches. Vane seal, cut to inches to inches. 22. Replace both Nitrile quad seals (Q4226) from vane and damping sleeve. 23. Replace O-ring (2-029), and two piece Polypack Z seal ( ) from inside of damping sleeve (see Figure 1), ensure lip faces toward shoulders. For ease of assembly, use a Rod Seal Installer tool (1 1/2 inches, procure locally), to install the two piece Polypack Z seal. 24. Replace O-ring (2-226) from outside of damping sleeve (see Figure 1). 25. Replace O-ring (2-135) and Bronze Teflon Bearing Tape from Damping Piston. 26. Replace both Nitrile Quad rings (Q4212) from floating piston. 27. Remove Schrader valve body and replace O-ring (2-010). 28. Clean and inspect all parts to ensure serviceability. SNL08-15 Page 3

4 29. Install Schrader valve body in shaft assembly; apply Loctitie 242 on threads of Shrader valve body. Torque to 50 to 60 LBS-IN. 30. Insert Floating piston into shaft assembly approximately 2 inches down. 31. Install valve core into Schrader valve body, tighten until snug. 32. Install strut dust cap onto shaft assembly. 33. Install damping sleeve over shaft assembly. 34. Install Centering cam-shaft and Damping Piston by applying Loctite 242 on threads of shoulder bolt, Head of the bolt is on the same side of the shaft assembly as the Schrader valve. Torque to 50 to 60 LB. -IN. 35. Install black vane and shaft key on tube assembly. 36. For ease of assembly; secure tube assembly to work bench using a holding fixture described in Figure Insert damping sleeve and shaft assembly into tube assembly until approximately 1/4 inch of quad seal on black aluminum vane is still visible; ensure bearing tape is installed on the damping piston. 38. Fill damping sleeve around both sides of black vane with MIL-H-5606-G hydraulic fluid. Let set and top off hydraulic fluid. 39. Finish installing shaft assembly and damping sleeve assembly into tube assembly and screw into tube assembly until shoulder of damping sleeve is level with tube assembly and locking key lines up. 40. Install locking key; apply Loctite 242 on threads of locking key screw. Torque to 10 to 15 LB.-IN. 41. Screw down dust cap; apply Loctite 242 on threads of dust cap and tighten snug with spanner wrench. 42. Service nose strut assembly per instructions in Chapter 12 ( ) of the applicable airplane model Maintenance Manual. 43. Install the strut assembly into the airplane nose gear per instructions in Chapter 32 ( ) of the applicable airplane model Maintenance Manual. 44. Make appropriate airplane logbook entries. * * * * * * * SNL08-15 Page 4

5 Figure 1. Damping Sleeve Assembly. SNL08-15 Page 5

6 Figure 2. Nose Strut core assembly. SNL08-15 Page 6

7 Figure 3. Strut Assembly Holding Fixture. SNL08-15 Page 7