Continental Aerospace Technologies issued mandatory instructions on February 13 to owners of various piston engines, including models in the 360, 470, 520, and 550 series, to inspect crankshaft assemblies with less than 200 hours in service for a possible assembly defect that could cause engine failure.
The mandatory service bulletin issued February 13 requires piston removal to inspect crankshaft counterweight retaining rings for proper installation and correct a “potential assembly error” that affects about 2,000 crankshaft assemblies (installed and otherwise), Continental noted in the bulletin.
“It is possible one or more counterweight retaining rings were not properly seated in the crankshaft counterweight groove,” the bulletin states. “This condition could allow the counterweight to depart from the crankshaft during engine operation resulting in catastrophic engine damage.”
A 24-page appendix to the eight-page bulletin lists affected engine and crankshaft serial numbers. The inspection costs are covered under warranty, and Continental detailed eligibility requirements that vary according to whether the affected crankshaft assembly has been installed, and by model and the number of cylinders required to be removed to complete the inspection. (Up to 22 labor hours are covered for six-cylinder engines from which three cylinders must be removed and reinstalled to complete the inspection, for example.) Continental detailed a procedure to obtain warranty reimbursement.
The service bulletin may become legally binding if the FAA incorporates it into an airworthiness directive.