Service Bulletin 492A supersedes Service Bulletin 492. Aircraft that have previously complied with Service Bulletin 492 are already in compliance with Service Bulletin 492A. Service Bulletin 492A voids Service Letter 694 and Service Bulletin 430.
**REASON FOR REVISION** : SB492A removes obsolete information about Turbine Tailpipe Coupling part numbers. **SUBJECT** : **TIGO-541-E1A EXHAUST SYSTEM MODIFICATION**

**MODELS AFFECTED** : **SERIAL NUMBERS AFFECTED** : PA-31P Pressurized Navajo 31P-1 to 31P-7400222 Inclusive, 31P-7400224 to 31P7630004 Inclusive, 31P-7630006 and 31P-7630007; (reference MATERIAL REQUIRED, below for individual modification kit/aircraft serial number applicability). **COMPLIANCE TIME** : At the next regularly scheduled inspection interval (100 hour, annual or Programmed Inspection Event), not to exceed the next 100 hours of operation.

**APPROVAL** : The technical content of this Service Document has been shown to comply with the applicable Federal Aviation Regulations and is FAA approved.

**PURPOSE** : Throughout the operational life of the Pressurized Navajo, the TIGO-540-E1A exhaust system has been periodically refined and upgraded through a continuing program conducted jointly by the powerplant manufacturer - Lycoming, and Piper Aircraft to extend the service life of the exhaust system in general, and to alleviate specific reported conditions involving various exhaust system components. Thorough inspection procedures, in addition to required parts replacements were stressed in order to detect and replace unserviceable component attachments (couplings, clamps and brackets), vibration-induced tailpipe/exhaust pipe cracks, etc. This service bulletin provides instructions and material (in addition to related reference data--see attached Lycoming publications) to consolidate and incorporate the latest exhaust system refinements on the above referenced aircraft. New material includes new exhaust transition couplings, new isolator assemblies, new support brackets, new exhaust manifold retainer assembly (reference Lycoming Service Bulletin No. 393C) and transition couplings replacement requirements, (reference Lycoming Service Bulletin No. 395). New materials are of heavy duty construction, designed to extend exhaust system component service life and reduce system maintenance/component parts replacements, as well as prevention of hazardous engine compartment conditions (fire hazard, etc.) resulting from exhaust system component failures. 

# SERVICE **NO.** 

## 492A 

# BULLETIN
**PIPER CONSIDERS COMPLIANCE MANDATORY**  **Piper Aircraft, Inc.** 2926 Piper Drive Vero Beach, Florida, U.S.A. 32960

Date: May 29, 2012 (M)

ATA: 7800 (OVER)**SERVICE BULLETIN NO. 492A PAGE 2 of 3** 

**INSTRUCTIONS** : Prior to compliance activity, it is advisable to refer to the following service releases:

**Source Type**  **Number Topic**  **Date** Piper Service Bulletin 462A Tailpipe Support Bracket Installation 11/3/75 Lycoming Service Bulletin 393C Exhaust Slip Joint Modification 2/6/76 (attached) Lycoming Service Bulletin 395 Exhaust Transition Coupling Replacement 3/5/76 (attached) Lycoming Service Instruction 1320 Tightening Procedure-Exhaust Manifold Components 3/7/75 (attached)

1. Refer to attached sketch/instruction sheet (Figure 1) which illustrates the exhaust system components to be installed or replaced (references: Piper Service Bulletin No. 462A, Lycoming Service Bulletin Nos. 393C and 395 attached. When reattaching turbine tailpipe to tailpipe support bracket, proceed as follows: Position existing tailpipe support clamp around tailpipe and support bracket. Deflect upper end of bracket approximately 1/8 inch away from turbine housing and tighten clamp so as to preload the tailpipe flange against the turbine flange. Torque clamp nut to 25 – 35 in-lbs. 2. Reference attached Lycoming Service Instructions No. 1320 Exhaust Manifold Components Tightening Procedures. 3. Inspect complete exhaust system for cracks, exhaust leakage evidence, looseness at joints, etc; correct as required. 4. Make appropriate log book entry indicating compliance with this service bulletin; be sure to record compliance with other service releases referred to in this release.
**MATERIAL REQUIRED** : 1. One (1) each per aircraft (i.e., both engines) Piper kit P/N 761-045, Tailpipe Isolator Replacement, applies to the following aircraft configurations:
a. Serial numbers 31P-1 to 31P-7400216 inclusive if Piper kit P/N 760-837 has been previously installed per Piper Service Letter 694; and b. Serial numbers 31P-7400217 to 31P-7400222 inclusive, 31P-7400224 to 31P-7630004 inclusive, 31P7630006 and 31P-7630007. 2. One (1) each per aircraft (i.e., both engines) Piper kit P/N 761-046, Tailpipe Support Installation (contains new turbine tailpipe to wastegate tailpipe isolators), and one (1) each per aircraft (i.e., both engines) Piper kit P/N 761-047, Tailpipe Isolator Replacement (contains new isolators to replace existing turbine tailpipe to exhaust transition isolators); both kits required for aircraft serial numbers 31P-1 to 31P-7400216 inclusive if Piper kit P/N 760-837 has NOT been previously installed per Piper Service Letter 694. 3. Per Piper Service Bulletin 462A - one (1) each per aircraft Piper kit P/N 760-974, Tailpipe Support Bracket Installation applicable to aircraft serial numbers 31P-1 to 31P-7630009 that have not yet complied with Service Bulletin 462A. 4. Refer to Lycoming Service Bulletins 393C and 395 for related material requirements.**SERVICE BULLETIN NO. 492A PAGE 3 of 3** 

**AVAILABILITY OF PARTS** : Your Piper Service Facility.

**EFFECTIVITY DATE** : This Service Bulletin is effective upon receipt.

**SUMMARY** : Please contact your Factory Authorized Piper Service Facility to make arrangements for compliance with this Service Bulletin in accordance with the compliance time indicated.
**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 

### Figure 1 Tailpipe Support Bracket & Clamp (Ref: Piper Service Bulletin 462A)

Turbine Tailpipe Turbine Housing

Exhaust Transition Assembly New Isolator Assembly (Contained in Piper Kits 761-045 and 761-047) Exhaust Slip Joint Retainer (Ref: Lycoming Service Bulletin 393C)
Exhaust Pipe

Exhaust Transition Coupling Replacement (Ref: Lycoming Service Bulletin 395) Exhaust Slip Joint Retainer (Ref: Lycoming Service Bulletin 393C)

New Isolator Assembly (Contained in Piper Kits 761-045 & 761-046) Wastegate Tailpipe**SERVICE BULLETIN NO. 492A DATED: May 29, 2012**  

### BULLETIN SUPPLEMENT - PROCEDURAL OPERATING INFORMATION

**MATERIAL ALLOWANCE** : N/A

**LABOR ALLOWANCE** : N/A

**DISPOSITION OF PARTS IN STOCK** : N/A

**DISPOSITION OF PARTS REPLACED** : N/A