The FAA has issued SAIB NE-17-11 (Special Airworthiness Information Bulletin) to inform airplane owners/operators, and certificated repair shops of available service instructions for identifying the causes of an engine kickback, and the recommended engine inspections after a kickback event, in airplanes equipped with certain Contintental Motors, Inc (CMI) IO-520 series, TSIO-520 series, IO- 550 series, TSIO-550 series, and TSIOL-550 series reciprocating engines operating with AVGAS.
The FAA has been receiving reports from the field of “fractured crankshaft gear retaining screws,” which they say were determined to be related to engine kickback events. According to the agency and CMI, an engine kickback can be identified by “the propeller blades stopping abruptly or rotating backwards during the engine start sequence.”
After extensive engine testing conducted by CMI, it was found that engine kickback during a failed engine start “can cause high instantaneous torque loads resulting in damage to engine components including the starter, starter adapter assembly, as well as the crankshaft gear and its retaining screws.” The agency noted that the two primary contributors (but not the only contributors) to the highest likelihood of a kickback are the installation of lower inertia (or light weight) propellers, and/or a slow or sluggish starting RPM. They also note that a slow starting RPM can be caused by “low battery voltage, an overheated starter, or high resistance in the starting circuit.”
The FAA recommends pilots take the following steps after a kickback event:
For any further information regarding SAIB NE-17-11 (which you can view here), the FAA says to contact aerospace engineer Scott Hopper:
And for service information, contact CMI at:
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