Thank you for your comments, Gouli. No, I do not advocate making any extreme yanking-type movements of the cyclic. But any delay at all in applying aft cyclic can be critical because this is the ONLY control movement that will lead to stopping and reversing the falling rotor rpm. The movement should be as instant as possible and done so there is no doubt that positive g's are being applied to the airframe.
When drive to the rotor system is lost, the rotor rpm begins to fall instantly and the reduction of lift causes the nose of the helicopter to fall, or pitch forward. This in turn acerbates the problem of air coming through the rotor from top to bottom. This along with the drag of the blades and gearbox, etc., is causing the rotor rpm to fall. Add to this the negative g's applied by lowering the lever which also increases the downward pitch of the airframe and rotor, and you can see where this is going.
Applying aft cyclic quickly is the ONLY way to reverse this chain of events.
THIS is the critical situation that Cyclic Back addresses.
Two posters have said that aft cyclic should not be applied during a climb. A vertical climb, no, but in every other type of climb, YES! Why? Because indicated airspeed is of NO VALUE AT ALL at the moment power is lost. The ONLY airspeed that matters at that moment is the airspeed over the wings, which, of course, means the rotor blades. Cyclic Back done in time will catch the rotor rpm before it drops to the critical point. NOW you have a flying machine and can then dial in whatever airspeed you'd like, but be careful when nosing over because the rotor rpm you've just saved will disappear in a heartbeat if you push over aggressively. Keep an eye on the rotor tach as you lower the nose to gain speed.
In the case of the two law-enforcement accidents I investigated, the pilots said they lowered the lever the moment the engine failed and then immediately applied forward cyclic to gain airspeed. Both of these accidents happened when the helicopters were on a routine climb at about 400 ft. agl and somewhere between 60 and 80 knots. The rotor blades were barely turning when the ships hit the ground. Damage to the blades was "downward" bending, not damage associated with the blades turning and hitting something hard. Both ships burned. Both crews survived but barely. One blade from one accident showed NO DAMAGE AT ALL per the NTSB report. And both ships crashed badly on the left side, the pilot's side.
The application of aft cyclic in time would have given both pilots a controllable helicopter all the way to touchdown. But instead they were just along for the ride. This was not pilot error! They had never heard about Cyclic Back. Both were high time and one was former military.
Pete Gillies