HEMS SPIFR Question  

Never heard of ATT mode otherwise known at attitude rentention?  Please tell me you are kidding.  Please get back in the books.  ATT mode is what you get when you turn the AP on.  Often called the outer loop or lower mode.  It's what allows you to fly SPIFR. Not to be confused with the upper modes. Most RFM's will say for IFR flight the Autopilot must be on and in the ATT mode.  I believe the EC135 says AP on and A TRIM on.  This is basic attitude retention.