Originally Posted by
helithree
In 30 fps videos the 4-bladed rotors usually appear turning the opposite direction...
Exactly - discussing blade turning direction is a complete red herring! Even going back years we see movies with stage coach, trains and vehicle wheels going backwards. Videos of the EC155 online, with the Nr selected to Hi (vertical take off and landings) show the blades completely stationary! In this example we see them going backwards and forwards and stationary, at different rpms:
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