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This video is Part 1 of 2 covering Dynamic Rollover in helicopters. Dynamic Rollover is defined as the point at which a helicopter will roll over despite pilot inputs. Before jumping into dynamic Rollover, however, its best to understand static rollover first. Static Rollover is the point where any object rolls over from a stationary or static position. This can be anything from a table to a chair to a car or even a helicopter. Any object with a center of gravity (CG) above the ground can statically rollover. All this requires is a pivot point and to exceed the critical angle. The pivot point is just a point where an object has made contact with the ground and can then pivot from that point. The critical angle determines which direction an object will fall or rotate. In the first example I demonstrate how a table will fall either left or right depending on which side of the pivot point the CG is over. This same concept applies to a helicopter in a static condition.
If you were to tip a helicopter over just like a table, there would be a point where the helicopter would fall over on its side despite not having any more force being applied on it. That's the point where the critical angle is exceeded. Now if the helicopter were to be moving it would no longer be in a static position. It would be dynamic. Thus it would be subject to dynamic rollover due to its momentum creating a rolling motion once a pivot point was encountered. This rolling motion reduces its critical angle and makes it easier for a helicopter to roll over. This is due to Newton's law of motion stating that an object in motion will continue to stay in motion. The momentum of the helicopter translates into a rolling motion when a pivot point is introduced. This reduces the critical angle and instead of rolling over at say 15 degrees, now it may only take 5-10 degrees of roll angle to make the helicopter tip over on its side.
This wraps up the first video. Make sure to check out Part 2 ( • Dynamic Rollover in He... ) to see causes, physical and human factors, as well as avoidance of Dynamic Rollover
As always, safe flying!
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If you're just getting started and want more information, pictures, and more explanations, I'd recommend reading the Rotorcraft Flying Handbook - amzn.to/2ifPlnZ
If you've already got a basic understanding, and want to further your professional helicopter education with advanced helicopter concepts, I'd recommend reading Cyclic and Collective, by Shawn Coyle - amzn.to/2ifQGLx