Hi again zorab64,
We always do the wash with the engine at idle - fire's not gone out yet. Big pain in the butt, as we can't keep the aircon on
(although we leave the sandfilter running). When the wind around the hangars has the usual Kuwait-afternoon gust-spread we do follow the instructions in finest Minglish - ie other engine to Flight while the engine being washed is at Ground, changing-over engines at Flight to minimise the vibration-band risk.
Another area where the 206/7s on the MD902 were far easier to look after than the 135T - comp-wash there is a single-person job during the daily, no fuss no bother.
Haven't heard anything back from Eurocopter about the fact that switching off the Gen to carry out the trend-monitoring in-flight checks involves the sandfilters going off, in direct contradiction to what the Sect 9 says about them remaining on at all times. On a previous type, if the EAPS blowers failed then all the crap that they were sweeping out of the way of the intakes was liable to get ingested in one big lump. Not exactly best practice.