An instructional YouTube video by Kenny Keller explaining causes, risks, and immediate actions for low rotor RPM and blade stall in helicopters (mentions R22 and R44). The presenter outlines how RPM decay reduces lift, prompts increased collective (raising drag), and can lead to blade stall and structural failure if RPM is not promptly restored; he also advises adding throttle and lowering collective when RPM falls below the green arc.
Chapters
This video is in response to two of our online customers that have requested training requested an online class on rotor RPM decay, one flying in R22 and one flying R44. So we're going to have an online class where we can get in and people can join in and we can kind of get the discussions going. But I wanted to put out a quick video to kind of COVID the basics that you can use for review and to listen to and think about the different elements of Low rotor RPM and RPM decay Low rotor RPM during an auto rotation might result in a less than successful maneuver. However, if rotor RPM decays to the point at which all the rotor blades stall, the result is usually fatal, especially when it occurs at altitude. It can occur in a number of ways, such as simply rolling the throttle the wrong way, pulling more collective pitch than power available, or when operating at a high density altitude. When the rotor RPM decreases, the blades produce less lift, so the pilot feels it necessary to increase collective pitch to stop the descent or increase the climb. As the pitch increases, drag increases, which requires more power to keep the blades turning at the proper rpm. When power is no longer available to maintain RPM and therefore lift, the helicopter begins to descend. This changes the relative wind and further increases the angle of attack. At some point the blades unless RPM is restored. As main rotor RPM decays, centrifugal force continues to lessen until the lift force opens, overcomes the centrifugal forces and folds or breaks the blades and the result is disastrous. Even though there is a safety factor built into most helicopters, anytime rotor RPM falls below the green arc and there is power, simultaneously add throttle and lower the collective. If in forward flight.
