Safety Notice SN024 – TaperLock Bushing/Hub Set Screws

SAFETY NOTICE SN024                                                  January 17, 2019 Download PDF TaperLock Bushing/Hub Set Screws The set screws installed in the TaperLock hub and bushing on the transmission output and provided with the Tail Rotor Driveshaft Kit should be replaced with AN74-A4 drilled head bolts and secured with safety wire. The set screws are out of sight inside the orange flex coupling when installed, making frequent inspection impractical. Even when secured with LocTite, the set screws can back out as the glue degrades over time.  When the set screws allow the inner hub to loosen, it is subject to vibration and will likely break.  Depending on which coupling fails, this will either break the connection between the flex coupling and the output shaft or the tail rotor driveshaft. Either event will be extremely dangerous in flight, with a loss of tail rotor authority at the very least. Please either secure these bolts from your usual supplier or contact the factory.  We strongly suggest you add the inspection of these bolts to your annual condition inspection as well.