Reading about this propeller-related accident at RAF Henlow got my attention, because it amazes me that the pilot asked her passenger to vacate the aircraft whilst the propeller was still turning.
AAIB Bullentin Report available here.
The pilot had been told during training that, in order to protect the engine, she should not shut down immediately after start and so, instead, she reduced the power to idle before the passenger stepped onto the wing.
I remember being told during my own flying training (albeit on a Cessna 150) that if the 'Low Voltage' warning light remained lit, then the engine should immediately be shut down. I've not looked at a Piper checklist for sometime, but I believe that this is the same. Can shutting down the engine immediately after start cause damage to the engine, and how?