Adverse Aerodynamic Conditions Affecting All RC Helicopters

Whether you fly the real thing or a slightly scaled down RC version, all pilots should have knowledge of the following adverse conditions affecting the aerodynamics of their helicopter.  First, however, a common misconception to clarify… Chopper = Motorcycle & Copter = Helicopter.

The first adverse aerodynamic condition is known as Settling with Power. Settling with power is a state of flight in which a helicopter settles into its

rc helicopter

own rotor downwash.  Generally this condition results at a near zero airspeed, whenever the helicopter is descending at a rate of 300 fpm (feet per minute) or greater, whenever the aircrafts engine power being produced is between 20 to 100%, and/or when there is insufficient additional power available to stop the descent of your helicopter. Should your aircraft find itself in this adverse condition you might notice your control inputs becoming less effective (sluggish / sloppy / etc). In addition, your aircraft will quickly lose altitude (high sink rate) and there will be a noticable main rotor vibration (rumbling).  In order to recover from Settling with Power, simply increase your RC Helicopters forward airspeed (altitude permitting of course); you may also need to reduce your aircraft’s collective setting.

The second adverse aerodynamic condition is known as Retreating Blade Stall. This is a condition of high speed flight where your RC Helicopters retreating main rotor blade exceeds its critical angle and stalls while flapping to correct for dissymmetry of lift. Several contributing factors of Retreating Blade Stall include operating your aircraft at high speeds (near Vne), when there is an increased loading of the rotor disc (high gross weight / high density altitude, low rotor RPM), and while operating your RC Helicopter in turbulent weather or while making abrupt maneuvers. Should your aircraft find itself in Retreating Blade Stall circumstances, the aircraft itself will begin to vibrate (buffet), as well as begin to pitch up and roll to the left (depending on the direction your main rotor blade is spinning). As an RC Helicopter pilot, you must immediately reduce the collective, reduce forward airspeed of the helicopter, carefully reduce the maneuver, and increase rotor RPM if possible.