The catapult effect on a mobile elevating work platform (MEWP) occurs when stored energy or an impact to the MEWP’s superstructure causes a whiplash effect, which travels through the boom to the platform. 

Remember: The catapult effect can also occur when driving in the stowed position, so make sure occupants wear personal fall protection equipment (PFPE) connected to the designated anchor point at all times. Occupants must always use a full body harness and an adjustable restraint lanyard, adjusted as short as possible, when using boom-type MEWPs.

Ref: TE-1106-0822-2-en