got it , thanks
what paid my attention was caused by 2 situations in the past
1. coming to land at the spot , not so fast , like 60-70 kts , low like 20-30 ft above the ground with a very little tailwind - intentions to do "spectacular" 180 turn as close to landing spot as possible , almost at the spot and land there . During that 180 turn , body starts to shake , NR drop , reacted like quick drop on collective to gain NR back - all ended good but heli shows it's edge on the limit's
2.coming to land 50-60 kts , descent angle like 4-5 degree , but descent "on power" , flare phase with cyclic move to the back to slow down but without reducing collective much , rather raising it up a little to reduce vertical speed - again NR dropped to the red ( very little , easy to recover but wondering about exact rotor aerodynamics in both cases )