When a crankshaft is built up by shrink fitting, reference marks are made to show the correct relative position of web and journal. These marks should be inspected during crankcase inspection. If for some reasons, the web slips with respect to the journal then it is termed as “Slippage.”
Common causes for slippage are:
- If starting air is applied to the cylinder when they contain water or fuel inside the unit or when the turning gear is engaged.
- If an attempt is made to start the engine when the propeller is constrained by for example ice or log.
- If during operation the propeller strikes a sunken object.
- If the engine comes to a rapid unscheduled halt.