If you are dual qualified then there is no problem - I know a couple of engineers with pilot licences too.
A non-flying qualified engineer doing ground track and balance, so trying to take the readings from the kit whilst controlling the helicopter - what could possibly go wrong??? Oh yes, that picture shows exactly that!
I have ground run an aircraft that had just been adjusted to improve the track and balance - problem was the adjustment was in the wrong direction and an 18 inch track split became very apparent as I wound the rotors up - needless to say it was a quick shutdown.