Ghengis,
The dreaded horseshoe vortex and the other artiifacts of LTE are almost as fake as crop circles.
The main wake spilling into the tail rotor causes about 5% reduction in thrust, easily seen and measured on most helos. The pilot sees it as a bit more pedal needed at that condition. Try it, just move forward at about 10 to 15 knots in the 1 to 2 oclock direction. You can hear a different noise from the tail, and the pedals will vibrate a bit. Usually, the left pedal will have to go forward a bit to hold the nose, or else a right yaw will develop. This is what most helos experience, not the dreaded LTE. The only tail rotors that cannot withstand the loss of this 5% are those that are so marginal that they cross the line to negative anti-torque margin when the interaction occurs.
Some facts:
Most single rotor helicopters with normal (powerful) tail rotors have never experienced LTE. Never in their service lives, with thousands of pilots. Never.
Most LTE events are experienced by one type/model of helicopter. About 95% of the LTE accidents worldwide are on this type, I know I did a survey of three years of worldwide accident data back when the maker of that one helo tried to get the FAA to insert that LTE drivel into every single rotor helo flight manual. If they had succeeded, then lawyers for that company would have been able to claim that the cause is common to all helos, instead of explainimnmg that the real reason is the poor residual yaw authority, which leaves little margin to cover minor variations in tail thrust.
That blurb in the first post of this thread is so pervasive that many incidents now being mislabled as LTE when they are actually due to over pitching - demanding too much power, causing rpm reduction and then loss of yaw control. Calling overpitching "LTE" is like saying that an airplane hit a cliff and stall was to blame because the wing was doing 0 mph right after impact.
Let me take you through the typical overpitching accident:
Pilot pulls main torque and hits engine power limits.
RPM reduces and main torque continues to increase (constant power is shown by increasing torque as rpm reduces, since power is torque times rpm.
Tail thrust is being reduced as rpm drops, since the tip speed is dropping, and max thrust is reduced by the square of the rpm (it is a v squared function).
As torque goes up, moore anti-torque is needed, even though power is constant. This eats more left pedal.
The pilot hits the pedal stops, rpm reduces more, torque goes up more and the right yaw develops.
Uh-oh....
Just dont call it LTE.
Good post Crab, BTW.