Service Bulletin No. 632 Frequently Asked Questions

FAQs for Service Bulletin No. 632 Identification of Connecting Rods with Non-Conforming Small End Bushings

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  Service Bulletin No. 632 Frequently Asked Questions

Lycoming has received several questions regarding Service Bulletin No. 632 (Identification of Connecting Rods with Non-Conforming Small End Bushings), and we want to ensure that our customers receive accurate and timely information about their Lycoming engines.  We hope this FAQ will provide further clarification to those customers affected by Service Bulletin No. 632, but if you have any additional questions, please contact Lycoming Product Support at technicalsupport@lycoming.com, 1-800-258-3279 or 1-570-323-6181 (United States and Canada) or +1-570-323-6181 (Outside North America).

1. Why is Lycoming issuing Service Bulletin No. 632? 

As of the publication date of this FAQ, Lycoming has confirmed five reports of connecting rod failures that occurred during flight.These connecting rod failures can lead to an un-commanded, complete loss of engine power.Our present analysis indicates that these failures were due to a bushing becoming unseated from the small end of the connecting rod.

While Lycoming is not aware of any accidents or injuries related to this issue, we believe that it is necessary to recommend inspection of all potentially affected aircraft to identify and correct any non-conforming bushings that were not screened out during installation.

2. Why are the connecting rod bushings becoming unseated?

Lycoming has determined that a small percentage of the bushings manufactured by a sub-supplier during a specific time period were diametrically undersized, resulting in a tightness of fit below factory accepted tolerances.These non-conforming bushings may have a substantially lower push-in/pull-out force than conforming bushings and may be susceptible to unseating during normal engine operations.

3. If the push-in force is substantially lower, why wasn’t the non-conformance identified during installation?

Lycoming has received reports from a few third-party facilities that indicate they were able to detect some non-conformance in the suspect bushings and did not place them into service.However, Lycoming does not have sufficient information as to whether any third-party or repair or overhaul facility quality assurance measures were able to detect all non-conforming bushings prior to installation.

4. Why is Lycoming recommending inspection?

Despite evidence that some technicians could detect the non-conformity at installation, current data received from the field indicates that approximately 7% of the bushings from the defined time period do not exhibit an appropriate safety-margin, as measured by the field service tool recommended by Lycoming.

At Lycoming, the safety of our customers is our first priority, and while we continue to evaluate other methods for detecting non-conforming bushings, at this time data indicates that the detailed inspection set forth in Service Bulletin No. 632 remains the best way for ensuring that we meet that priority.

5. Why has Lycoming selected a 10-hour time-of-compliance?

Lycoming is concerned that mechanics may not identify bushing deterioration during oil filter checks at the recommended oil change intervals.  In addition, data indicates that once a bushing becomes unseated, it is difficult to predict the time until connecting rod failure.  In order to ensure the safety of our customers, Lycoming determined that a 10-hour time of compliance is appropriate. 

In addition, the limited available time-in-service information does not currently justify a longer compliance period.

6. How can I determine if my engine is affected?

If your engine is listed in Table 1 of Service Bulletin No. 632, it should be inspected.  In addition, if your engine has been overhauled or repaired in the field since November of 2015, you should contact your field maintenance provider to determine if an inspection is required.

7. Does Service Bulletin No. 632 affect all engines shipped from Lycoming engines?

No.  Most Lycoming engines are not affected by Service Bulletin No. 632.  Only the engines specifically listed in Table 1 of Service Bulletin No. 632 are affected.  In addition, engines repaired or overhauled by field service providers after November of 2015 may be subject to the Service Bulletin.  Please contact your Service Provider to determine if you must comply with Service Bulletin No. 632.

8. Do my connecting rods or bushings need to be replaced if they are subject to Service Bulletin No. 632?

Not necessarily.  Lycoming recommends replacement only if the inspection identifies a bushing that does not exhibit an appropriate safety-margin, as measured by the field service tool recommended by Lycoming.

9. What are the chances that the inspection will find that the bushing that requires replacement?

As a precaution, Service Bulletin No. 632 provides an inspection method that tests bushings at a much greater force than they would experience during normal engine operation.   Based on this conservative safety-margin, current data indicates that approximately 7% of bushings in the affected population will require replacement.

10. My engine is listed in Table 1 of Service Bulletin No. 632 and it is still under warranty.  What kind of support is Lycoming providing to me?

Lycoming will fully honor the terms of its Limited Warranty, including coverage for the cost of inspection, and, if necessary, replacement of any suspect connecting rods.For factory engines listed in Table 1 of Service Bulletin No. 632, Lycoming will cover costs of (a) parts; (b) labor; and (c) freight associated with the Service Bulletin.Specifically, Lycoming will cover the costs of the following parts associated with the inspection and any necessary repair:

  • Replacement connecting rods (if necessary);
  • A top overhaul gaskets set; and
  • A connecting rod bearings.

Lycoming Limited Warranty also includes the following allowances as set forth in the current Lycoming Removal and Installation Labor Allowance Guidebook (SSP-875):

Warranty Claim Allowances for Engines Listed in Table 1

Description

Max. Labor Allowance

Cylinder removal, inspection, and reinstallation of a 4-cylinder engine.

12 hours

Cylinder removal, inspection, and reinstallation of a 6-cylinder engine.

16 hours

Cylinder removal, inspection, and reinstallation of an 8-cylinder engine.

20 hours

Removal and reinstallation of each connecting rod that requires replacement pursuant to Service Bulletin No. SB-632A.

1 hour for each connecting rod

 

In addition, Lycoming will provide for the following additional labor allowances beyond our those provided by our Limited Warranty (if applicable):

Additional Labor Allowances for Engines Listed in Table 1

Description

Max. Labor Allowance

Additional labor allowance for any engine installed in a helicopter.

4 hours

Exhaust manifold removal and reinstallation of a 6-cylinder turbocharged engine

3 hours

Connecting Rod Bushing Press-Out Verification Procedure for all engines.

0.25 hours for each connecting rod

 

Finally, Lycoming provides for an allowance for standard freight. Please reference the terms of Service Bulletin No. 632 and your Limited Warranty for details.

11. My engine is listed Table 1 of Service Bulletin No. 632, but it is out of warranty.  What kind of support will Lycoming provide to me?

Even if your Lycoming factory engine is recently out of warranty, Lycoming is committed to standing behind its products.If your engine is listed in Table 1 of Service Bulletin No. 632 and you have it inspected in accordance with the Service Bulletin by July 17, 2018, Lycoming will provide you the same coverage as an in-warranty engine. 

12. My engine was field overhauled. I’ve checked with my overhaul provider, and my technician used a connecting rod assembly purchased within the timeframe listed in Table 2 of Service Bulletin No. 632.  What kind of support is Lycoming providing to me?

Lycoming is committed to honoring its Replacement Parts Limited Warranty.  Under that Limited Warranty, Lycoming will cover the replacement or repair any connecting rod assembly purchased as a spare part that requires replacement under Service Bulletin No. 632. In addition, because connecting rod assemblies come from Lycoming’s supplier with the bushings pre-installed, we’re extending our Limited Warranty as follows. 

The following additional parts associated with the inspection and any necessary repair:

  • A top overhaul gaskets set; and
  • A connecting rod bearings.

In addition, Lycoming will offer the following Additional Labor Allowances for connecting rod assemblies originally supplied as spare parts within the timeframes listed in Table 2 of Service Bulletin No. 632.

Additional Labor Allowances for Connecting Rod Assemblies

Supplied as Spare Parts Within the Timeframes Listed in Table 2

Description

Max. Labor Allowance

Cylinder removal, inspection, and reinstallation for first affected cylinder on engine.

6 hours for first cylinder

Cylinder removal, inspection, and reinstallation for each additional affected cylinder on engine.

2 hours for each additional cylinder

Connecting Rod Bushing Press-Out Verification Procedure for all engines.

0.25 hours for each connecting rod

Removal and reinstallation of each connecting rod that requires replacement pursuant to Service Bulletin No. SB-632A.

1 hour for each connecting rod

 

Finally, Lycoming will provide an allowance for standard freight.

13. My engine was field overhauled. I’ve checked with my overhaul provider, and my technician installed a spare bushing identified in Table 2 of Service Bulletin No. 632.  What kind of support is Lycoming providing to me?

Lycoming is committed to honoring its Replacement Parts Limited Warranty for any bushing affected by Service Bulletin No. 632.If inspection reveals that your engine requires a replacement connecting rod bushing, we’ll replace it pursuant to the terms of your Limited Warranty.Customers should check with their overhaul service provider for any additional warranties.

In addition, Lycoming is diligently working with overhaul and repair facilities whose customers are affected by Service Bulletin No. 632.Because each customer and repair facility is impacted differently, our Product Support teams are working tirelessly to address our customer’s concerns.

14. Who can perform the inspection and maintenance required by Service Bulletin No. 632?

Any FAA authorized and appropriately rated mechanic, maintenance technician or repair facility can perform the work noted in the Service Bulletin.

15. Are the ST-531 tools needed for inspection available?  Where do I get one?

Lycoming has developed a special tool to apply a pre-determined load to the side of the connecting rod bushing.  When the bushing press-out force is applied, which includes an appropriate safety margin, the technician checks for any movement of the bushing.  The ST-531 (Connecting Rod Bushing Press-Out Verification Tool) is available for purchase through any authorized Lycoming Distributor.

16. Are spare parts available?

Spare parts are available through any authorized Lycoming Distributor.  Lycoming continues to work with its suppliers to ensure that spare parts are available to support the needs of our fleet.  

17. I just received my new -S-85 connecting rod assembly and it doesn’t have a serial number or date code; is it okay to install?

Your licensed mechanic or repair facility is ultimately responsible for determining whether a part is okay to install.  Please note that not all -85 connecting rods will have a serial number and a date code. However, they are still an approved part to be installed into the engine. Be sure to check that you have the appropriate part number and weight (-S) before installing.

18. How do I file a warranty claim?

Please reference our warranty page for information on filing a warranty claim. 

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