# Piper Service Bulletin 644: Revision E - Rights: © Piper. Filed by the FAA in regulations.gov docket FAA-2012-0983; AD 2013-10-04 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Piper Service Bulletin 644](https://openairdocs.org/service-documents/piper/sb-644.md) - Title as filed: U.S. DOT/FAA - SB 0644E - Pages: 6 - PDF: https://openairdocs.org/files/sha256/a2/15/a2155d7551cbbc97f23d92c79f13983545e23f299c54eb31c70192ff27e18fd8 - Page: https://openairdocs.org/service-documents/piper/sb-644/file/a2155d7551cb ## Text Some pages are OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 Service Bulletin 644E supersedes Service Bulletin 644D in its entirety and voids Service Bulletin 534 completely. Aircraft that have previously complied with Service Bulletin 664D are already in compliance with Service Bulletin 644E. Aircraft that have previously complied with Service Bulletin 534 must also comply with Service Bulletin 644E. SUBJECT: TURBOCHARGER EXHAUST COUPLING INSPECTION/REPLACEMENT REASON FOR REVISION: To add pressurized models PA-31P and PA-31P-350 and rescind SB 534. MODELS AFFECTED: SERIAL NUMBERS AFFECTED: PA-31 and PA-31-325 Navajo 31-2 through 31-8312019 PA-31-350 Chieftain 31-5001 through 31-8452021 PA-31-350 T -1020 31-8253001 thru 31-8553002 PA-31P Pressurized Navajo 31P-1 through 31P-7730012 PA-31P-350 Pressurized Mojave 31P-8414001 through 31P-8414050 NOTE: All further references to PA-31-350 below apply to both the Chieftain and T -1020 models. COMPLIANCE TIME: Part I. All aircraft within ten (10) hours of operation or at the next scheduled inspection, whichever occurs first, determine the type of turbocharger exhaust coupling installed. If Turbocharger Exhaust Coupling, Piper part number (P/N) 555-511 or 555-366 (segmented type), inspect every one-hundred (100) hours time-in-service (TIS). Replace turbocharger exhaust coupling at one-thousand (1000) hours TIS. NOTE: If Turbocharger Exhaust Coupling is Piper P/N 556-962 or 556-053, it is no longer an approved part and must be replaced with an approved exhaust coupling prior to further flight. Part II. At Owner/Operator’s discretion, or when required by PART I. Part III. Within the next ten (10) hours of operation or at the next regularly scheduled maintenance event, whichever occurs first. APPROVAL: The technical content of this Service Document has been shown to comply with the applicable Federal Aviation Regulations and is FAA approved. PURPOSE: Field reports indicate several service problems associated with turbocharger to tailpipe couplings. A field investigation into the cause has revealed that in many instances the recommended maintenance, inspection, and torquing procedures in this very important part of the exhaust system have not been followed. The failure of a turbocharger to tailpipe coupling may allow hot turbocharger exhaust gases to be expelled into the coupling area, creating a fire hazard. SERVICE NO. 644E BULLETIN PIPER CONSIDERS COMPLIANCE MANDATORY Piper Aircraft, Inc. 2926 Piper Drive Vero Beach, Florida, U.S.A. 32960 Date: May 9, 2012 (M) ATA: 8123 (OVER) ### Page 2 SERVICE BULLETIN NO. 644E PAGE 2 of 6 PART I of this Service Bulletin provides instructions for a more detailed inspection and torquing of the segmented type Turbocharger Tailpipe Coupling, Piper P/N 555-511 or 555-366, at each one-hundred (100) hours; requires the use of the revised One-Hundred Hour Inspection Forms; and requires that coupling be replaced at one-thousand (1,000) hours of coupling TIS. PART II announces the availability of a new, heavy-duty field tested turbocharger exhaust coupling that, when installed, relieves the Inspection Requirement of PART I and the one-thousand (1,000) hour mandatory replacement. NOTE: Compliance with PART II also relieves the one-thousand (1,000) hour replacement requirements called for in the PA-31 and PA-31-325 Navajo Service Manual, P/N 753-704; in the PA-31-350 Chieftain Service Manual, P/N 761-488; in the PA-31P Pressurized Navajo Service Manual, P/N 753- 770; and in the PA-31P-350 Pressurized Mojave Maintenance Manual, P/N 761-781. NOTE: The requirements for compliance with this Service Bulletin will vary according to the V-band Coupling part number that is installed on each engine. See TABLE 1 for a summary of these requirements. PART I. INSTRUCTIONS: Refer to the latest revision of the following Piper Aircraft Inspection Reports: 1. Within the next ten (10) hours of operation, determine type of turbocharger exhaust coupling installed: a. If single-piece type, Piper P/N 556-962 (PA-31, PA-31-325) or 556-053 (PA-31-350, PA-31P , PA-31P-350), replacement is required prior to further flight. Proceed to Part II. b. If segmented-type, Piper P/N 555-511 (PA-31, PA-31-325) or 555-366 (PA-31-350, PA-31P , PA-31P-350), proceed to Instruction 2 below, in accordance with Compliance Time, Part I. 2. Remove upper engine cowlings. 3. Remove turbocharger exhaust couplings. Inspect couplings for cracks, spreading of sides, and indication of exhaust pipe flanges bottoming in coupling. (Refer to Sketch “A” attached). Inspect coupling clamp bolt for bending, overstress and cracks. (Refer to Sketch “A”.) CAUTION: ANY TIME AN EXHAUST SYSTEM COMPONENT IS INSTALLED OR REMOVED, USE CAUTION NOT TO SPREAD OR FORCE THE COUPLING BEYOND ITS NORMAL OPEN POSITION. TO DO SO WILL EITHER DISTORT ITS SHAPE AND CAUSE AN INEFFECTIVE SEAL OR IT WILL DAMAGE THE METAL AND RESULT IN EVENTUAL FAILURE OF THE COUPLING. 4. Inspect turbocharger exhaust pipe flange area for proper mating of surfaces and for leaks. Inspect flanges for cracks and distortion. Carbon deposits should be removed from mating flanges before reassembly. 5. Should any parts of the above inspection reveal any of the described faults, the failed component(s) must be replaced before further flight. 6. Reinstall turbocharger exhaust pipe and coupling onto the tailpipe assembly and turbocharger. NOTE: Waste gate exhaust clamps should be loosened to facilitate installation of the exhaust pipe and insure proper alignment of exhaust flanges without unnecessary strain on exhaust system components. 7. Install coupling on exhaust flange and torque nut in accordance with Sketch “A” while tapping gently around the periphery with a soft mallet to distribute band tension. PA-31, PA-31-325 Piper Part No. 230-211 PA-31-350 Piper Part No. 230-764 PA-31P-350 Piper Part No. 230-1088 PA-31P Piper Service Manual P/N 753-770, Section III ### Page 3 SERVICE BULLETIN NO. 644E PAGE 3 of 6 PART II. INSTRUCTIONS: 1. Remove upper engine cowlings. 2. Remove turbocharger exhaust couplings and discard. 3. Inspect turbocharger exhaust pipe flange area for proper mating of surfaces and for leaks. Inspect flanges for cracks and distortion. Carbon deposits should be removed from mating flanges before reassembly. 4. Install new style exhaust couplings. (See MATERIAL REQUIRED.) NOTE: Waste gate exhaust clamps should be loosened to facilitate installation of exhaust pipe and insure proper alignment of exhaust flanges without unnecessary strain on exhaust system components. 5. Tighten couplings to torque value of 30 in-lbs minimum, 35 in-lbs maximum. Tap gently around the periphery with a soft mallet to distribute band tension. Recheck torque. 6. Secure and tighten waste gate exhaust clamps previously loosened per NOTE above. 7. Inspect couplings for positive clearance between safety latch and “T” bolt, and between coupling segments after final torque. See Sketch “B” attached. 8. Reinstall upper engine cowlings. 9. Make appropriate logbook entry of compliance with PART II of this Service Bulletin. 8. Turbocharger to tailpipe coupling with one-thousand (1,000) hours or more TIS must be replaced. (See MATERIAL REQUIRED.) NOTE: If a coupling has more than one-thousand (1,000) hours TIS, and if a new coupling is not immediately available, the existing coupling may be continued in use for up to an additional two-hundred (200) hours if the coupling is inspected for cracks every twenty-five (25) hours without removal with a 10X magnifying glass. This twenty-five (25) hour inspection requirement does not relieve the one-hundred (100) hour inspection requirement for couplings with Piper P/N 555-511 or 555-366. 9. Reinstall upper cowling. 10. Make appropriate logbook entry of compliance with PART I of this Service Bulletin. PART III. INSTRUCTIONS: 1. If Turbocharger Exhaust Couplings, Piper P/N 557-584 and 557-369 have been installed prior to the date of this publication and PART II has not been previously completed, comply with the following instructions. 2. Remove upper cowlings on left and right engines. 3. Inspect couplings for positive clearance between safety latch and “T” bolt, and between coupling segments, after final torque. See Sketch “B” attached. 4. Inspect couplings for security and that “T” bolt is not bottomed out. 5. If couplings are found to be distorted and/or bottomed out, replacement is required. (See MATERIAL REQUIRED.) 6. Reinstall upper cowlings on left and right engines. 7. Make appropriate logbook entry of compliance with PART III of this Service Bulletin. ### Page 4 MATERIAL REQUIRED: Two (2) each Couplings, Piper P/N 557-584 for PA-31 and PA-31-325. Two (2) each Couplings, Piper P/N 557-369 for PA-31-350, PA-31P , PA-31P-350. AVAILABILITY OF PARTS: Y our Piper Service Facility. EFFECTIVITY DATE: This Service Bulletin is effective upon receipt. SUMMARY: Please contact your Factory Authorized Piper Service Facility to arrange for compliance with this Service Bulletin in accordance with the Compliance Time indicated above. NOTE: Please notify the factory of any address/ownership corrections. Changes should include aircraft model, serial number, current owner’s name and address. Corrections and/or changes should be directed to: PIPER AIRCRAFT, INC. Attn: Customer Service 2926 Piper Drive Vero Beach, FL 32960 SERVICE BULLETIN NO. 644E PAGE 4 of 6 Aircraft Model Piper V-band Applicable Maintenance Action Summary Coupling P/N Sketch 556-962 n/a Replace prior to next flight. PA-31 Navajo 555-511 Sketch A Inspect every 100 hrs TIS. PA-31-325 Navajo Replace upon reaching 1,000 hrs TIS. Routine inspection per Service Manual 557-584 Sketch B instructions. Replace on condition. (no life limit) 556-053 n/a Replace prior to next flight. PA-31-350 Chieftain PA-31-350 T -1020 555-366 Sketch A Inspect every 100 hrs TIS. PA-31P Pressurized Navajo Replace upon reaching 1,000 hrs TIS. PA-31P-350 Pressurized Mojave Routine inspection per Maintenance 557-369 Sketch B Manual/Service Manual instructions. Replace on condition. (no life limit) Summary of compliance requirements for this Service Bulletin. Read the entire Service Bulletin to obtain complete instructions. TABLE 1 ### Page 5 (OCR) SERVICE BULLETIN NO. 644E PAGE 5 of 6 Inspect Tailpipe and Turbocharger Flanges for proper mating - Tailpipe COUPLING - Refer to Chart for correct P/N and Proper Torque VIEW LOOKING AFT AT TURBOCHARGER Inspect Turbocharger Flange for carbon Inspect Coupling Strap deposits, cracks for cracks, separation and distortion and distortion Inspect Coupling V Bands for cracks, separation from strap and distortion Inspect Coupling Bolt- for bends, distortion, cracks and thread damage Inspect Tailpipe Flange for carbon deposits, cracks and distortion Torque the coupling in accordance with this chart Model Clamp P/N Torque PA-31-350, PA-31P, PA-31P-350 555-366 (MVT68049-450M) 45-55 in-Ibf PA-31, PA-31-325 555-511 (MVT69861-377M) 40-50 in-Ibf SKETCH "A" ### Page 6 (OCR) SERVICE BULLETIN NO. 644E PAGE 6 of 6 After installation and Final Torque to 35 in-Ibs, Positive Clearance must be evident between Safety Latch and "T" Bolt Safety Latch "T" Bolt Retaining Strap Positive clearance V BAND CLAMPING DETAILS Torque the coupling in accordance with this chart Model Clamp P/N Torque PA-31-350, PA-31P, PA-31P-350 557-369 (NH1005798-10) 30-35 in-Ibf PA-31, PA-31-325 557-584 (NH1005834-10) 30-35 in-Ibf SKETCH "B" --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.