Mast bumping and it's tragic consequences

I got my helicopter rating in Robinsons. I think most people who have experienced mast bumping have died...

The Robinson, just like any aircraft, has to be flown within its limitations. That's all there is to it. Go outside the limitations, and bad things can happen.

 

What is the problem? Fuselage not stiff enough?

 

No, the problem is that if you have a two bladed teetering rotor system (which many helicopters do, think Bell Jet Ranger among others), typically in a positive G configuration, the rotor blades bend upwards as they hold the weight of the helicopter.

In a negative G situation, the rotor blades will bend down... now, as they are bent down, if you push forward on the cyclic (stick), the tail rises and the rotor disc tips and the blades chop the tail boom off. At that point, it's basically game over.

Negative G conditions and semi-rigid rotor systems, especially two bladed ones, are simply a no go. If you do end up in that situation, you recover smoothly and gently, just as you would in an airplane in an overspeed condition.

Every aircraft has a proven performance envelope, and if you get far enough outside of that envelope, bad things will happen.

 

Scary.

 

I remember in my R22 training 30 years ago, being told that it required zero G (or less, maybe even -1) and full deflection of the controls. That's a very unusual circumstance.

 

My very first lesson in the R-22 was preceded by a fair amount of mandatory ground instruction regarding this phenomenon and how to avoid it.