Approximately 2,200 large-bore engines manufactured by Teledyne Continental Motors in 1998 are targeted in an emergency airworthiness directive (AD) to be released shortly. The AD is intended to eliminate a rash of crankshaft breakages caused by a manufacturing defect.
Seven crankshaft failures resulted in six on-airport landings and one off-airport landing that resulted in minor injuries. In all accidents, the crankshaft broke in the same place. After further research, Continental determined that the tool used to press counterweight bushings into the crank damaged a small number of the cranks produced between January 1, 1998, through December 31, 1998. The damage started a fatigue crack, which led to all-out failures after several hours in service.
TCM will release Critical Service Bulletin (CSB) 99-3 to owners of new or rebuilt 470-, 520-, and 550-series engines this week. The inspection process will involve removing cylinders one and three to allow visual and ultrasonic testing of the crankshaft’s trouble area. The inspection will cost anywhere from $700 to $900 for normally aspirated and turbocharged installations, respectively. Charges will be picked up by TCM’s warranty. The non-destructive testing part of the process will be performed by designated TCM representatives in the field.
Soon after the appearance of the CSB, the FAA is expected to release an emergency AD that will require owners to comply within 10 hours time in service if the engine has between 50 and 300 hours. If the engine has more than 300 hours, compliance time will be extended to 50 hours. Failures have been occurring at accumulated time in service of 85 hours to 175 hours. Those with more than 300 hours time in service are assumed to be undamaged, but TCM is taking no chances.
TCM also wanted to reassure owners that this rash of crankshaft problems has nothing to do with the ongoing issue of crankshafts built using the airmelt process versus the vacuum arc remelt (VAR) technique. Continental has set up a hotline for more information on the issue. Call 888/200-7565 or visit the Web site.
April 19, 1999