Retreating blade stall symptoms in a helicopter typically include:
- nose-up pitching, vibration, and a roll toward the retreating blade side as the retreating blade loses lift capacity
- immediate loss of all rotor thrust resulting in an uncontrollable descent regardless of the pilot control actions taken
- a smooth and gradual reduction in forward speed with no vibration or unusual control response from the pilot input
Explanation from PART66Online
At high forward speed the retreating blade meets a slow relative airflow at a high angle of attack and stalls, and its development is felt as a low frequency vibration, pitching up of the nose and a roll toward the retreating blade side. It builds up progressively, and the first step in recovery is usually to lower the collective, so it is neither an instant loss of all rotor thrust nor a smooth slowing with no vibration.
kenguan76 asked · 7h ago
I don't understand why in answer A. and in the explanation it states that there will be a "roll to the advancing blade side".
If the retreating blade stalls, the effect should be felt 90deg later which is the rear of the helicopter, thus the pitch up.
If there is any roll I would assume it will be to the left side since the right side (advancing blade) has not stalled.
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