The condition known as dynamic roll-over is an uncontrolled rolling situation when a helicopter is in contact with the ground with only one skid or one wheel.
The Forces Involved in Dynamic Rollover
* Roll Component: This is the horizontal component of total rotor thrust about the point of ground contact of the skid/wheel.
* Weight of the aircraft: This component is positioned between the wheels/skids and opposes the roll component.
This is the angle where cyclic input will not be able to stop further roll. The roll component is too big and the opposing effect of gross weight is too small.
Factors Influencing the Critical Angle
Rate of Roll
The rate of roll during dynamic roll-over affects the critical angle. If the helicopter rolls into one direction with faster rates, the critical angle will be affected accordingly.
The tail rotor counteracts the torque effect created by the rotation of the main rotor by creating a lateral lift. During the dynamic roll, this thrust is added to or subtracted from the component encouraging roll. If the skid touching the ground is at the same side as the tail rotor thrust, this increases the total roll component and decreases the critical angle.
Crosswind from the opposite side of roll increases the total roll component and decreases the critical angle.
If the CG (Centre of Gravity) is not centered and deflected laterally to the side of the roll, the total cyclic input required to counter the roll increases and the critical angle decreases.
A lateral slope to the side of the roll decreases the margin for the critical angle.
A skid stuck to the ground (due to mud, ice or bush) can shift the center of gravity just enough to begin dynamic rollover.
Low altitude sideways flying
An onset occurrence of a rollover is common when a skid or wheel inadvertently contacts the ground or an obstruction, or an animal, while flying sideways.
When a dynamic rollover starts and no cyclic input can stop the roll: lower the collective smoothly to reverse the roll.
- VID 522050 - Creation
DATE OF SUBMISSION
- 12:46, 23 February 2021
- This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.
- The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.