TFE731-20/40/60 front frames have been found with corrosion, resulting in unplanned removals. No criteria or repairs currently exist to solve this issue. The root cause was found to be the lack of anodized coating on the frame.
Design changes have been introduced into production to improve corrosion resistance. Honeywell developed a nondestructive testing (NDT) inspection process and updated the Light Maintenance Manual (LMM) and Heavy Maintenance Manual (HMM) to include inspection criteria.
Service Bulletin TFE731-72-5217 was issued in August 2011.
The field plan was approved by the FAA in September 2012 and the program was completed in January 2013.