I second the fortunate son, turbine wind up/wind down for take off and landing. However, may I propose the “pew pew” sound with sparks from said abused, mistreated and inaccurately represented god of the sky? Oh, don’t forget the masses of beepers, horns and alarms. May I suggest you travel on a simulator recurrency trip (with a Trapper type who apparently “invented” helicopters (but their knowledge is secret) ) to gain the amazing multilayered cacophony of sounds.