Great article by Robert Craymer of Covington Aircraft.
See related blog post, Emergency AD Grounding the 350/300 Fleet and Others Powered by -67s
An emergency Advisory Directive (AD) has been issued by the FAA. They are following the lead of Transport Canada and EASA (Transport Canada Emergency AD CF-2024-05). A corresponding category 1 service bulletin (A14574) has also been issued by Pratt and Whitney Canada. To highlight what this means as far as importance Pratt & Whitney Canada has only issued 3 other category 1 service bulletins, the last one being in 2014.
All of this information is applicable to the following engine models: All PT6A-64, PT6A-66, PT6A-66A, PT6A-66B, PT6A-66D, PT6A-66T, PT6A-67, PT6A-67A, PT6A-67AF, PT6A-67AG, PT6A-67B, PT6A-67D, PT6A-67F, PT6A-67P, PT6A-67R, PT6A-67RM, PT6A-67T engines.
This AD and service bulletin indicate that they must be complied with prior to the next flight. For most engine owner/operators this will mean a review of the AD and determining applicability. The inspection/replacement of the affected parts is specifically targeted to a batch of blades made from a specific batch of raw materials.
The parts affected are the second stage power turbine blades (PT2). These blades all have individual serial numbers on each blade and for new engines the blade serial numbers should be listed in the logbook on the serialized component list. If you have had your PT2 blades replaced within the last 50 hours of operation, then the installing maintenance provider should have provided or be able to identify for you the serial numbers of the blades that were installed.
This is the key information that you are looking for. The group of serial number affected blades are listed in the service bulletin (A14574). If you find these blades in your engine please contact someone within the Pratt & Whitney Canada network. You can contact your field service manager or the Designated Overhaul Facility that you work with. I have personally been assured by Pratt & Whitney Canada that parts will not be an issue as they know the number of blades affected and have set aside the replacements.
The majority of engines out there won’t be affected by this AD. All that needs to be done is a review of the information and to make a logbook entry stating that the AD is not applicable to your engine. This step does need to be done prior to your next flight. Get with your maintenance provider and please insure that you do this. It will keep you out of trouble if an inspector does a review of your logs.
I am advising everyone to be aware and review this AD to make sure that you are covered.
Robert Craymer's articles are published as Craymer’s Counsel. He has worked on PT6A engine and PT6A powered aircraft for the past three decades, including the last 25+ years at Covington Aircraft. As a licensed A&P mechanic, Robert has held every job in an engine overhaul shop as well as being an instructor of PT6A Maintenance and Familiarization courses for both pilots and mechanics. Robert has been elected to the NAAA board as the Allied-Propulsion Board Member.