Retreating Blade Stall
- Josh Rogne
- Nov 14, 2022
- 2 min read
Updated: Nov 16, 2022
Understand the aerodynamics during retreating blade stall
Retreating blade stall is one of the major contributing factors that limits helicopters forward airspeed. Let's say that the helicopter is flying at 100 knots, and the rotor is spinning at 400 knots. That means that the advancing blade is experiencing a total of 500 knots of wind while the retreating blade is only experiencing 300 knots.
This results in a different amounts of lift being created by each blade, to compensate for this the advancing blade flaps up, and the retreating blade flaps down. When the advancing blade flaps up, this reduces the angle of attack. When the retreating blade flaps down, this increases the angle of attack. We refer to this as dissymmetry of lift.
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