Field reports of fractured crankshaft gear retaining screws on Continental Motors Inc. IO-520, TSIO-520, IO-550, TSIO-550, and TSIOL-550-series reciprocating engines have prompted the FAA to issue a special airworthiness information bulletin (SAIB) alerting operators to the problem of engine “kickback” and how to inspect for resulting damage.
“Engine kickback can be identified by the propeller blades stopping abruptly or rotating backwards during the engine start sequence,” the SAIB says.
Light-weight propellers, a slow or sluggish starting rpm, or both were found to be contributing factors. The slow starts can be caused by “low battery voltage, an overheated starter, or high resistance in the starting circuit.”
The SAIB recommends that following a kickback event, starter system components be inspected for damage and replaced as needed. The inspection should include “rotating the starter adapter to ensure smooth rotation, free from binding or ratcheting.”
“If discrepancies are found during the rotational check,” the SAIB recommends “replacing the starter adapter and crankshaft gear retaining screws.”
The SAIB also recommends following CMI Service Bulletin SB16-6, dated October 19, 2016, when performing maintenance on the listed products.