Mast Bumping and Uncommandend Right Roll

1. LTjg SANTAGATI DARIO

4. … .Gravitational acceleration…G-force …Apparent Weight… - All objects on earth are subject to the gravitational force. - In normal conditions this gravitational force is equal (by convention) to 1 g positive. - During manouvered flight, depending on the type of manouver performed, the g- force which we are subject to,changes (both positive and negative)  APPARENT WEIGHT. - If we perform a 60 ° turn, we will be subject to a force equal to 2 g’s positive (the APPARENT WEIGHT will be equal to twice the normal).

5. -Mast Bumping- Mast Bumping is generally caused by pilot cyclic overcontrol in a condition where the helicopter is subject to NEGATIVE or LOW g’s. It might also occur when flying in turbulent air or when landing on a slope.

6. -Mast Bumping- The Mast Bumping occurs when the rotor head impacts the main rotor shaft. It affects a particular rotor type  2 Bladed Semi-Rigid  R22/R44, Bell47, Bell 206, and Bell205/212 

7. -Mast Bumping- The rotor head literally strikes the mast causing damage or even detachment. This is caused by excessive flapping generated when flying outside the helicopter‘s operating envelope.

10. Fact  The only force in play at this point will remain the one generated by the tail rotor thrust Fact  The pilot will still have rotor disc control by the use of cyclic, but not fuselage control, because the moment between HRT and CG will be zero, there will be no force capable to induce roll COMMANDED by the pilot. Low/Negative Gs CONDITIONS

11. The lack of aerodynamic forces capable of balancing the tail rotor thrust will result in: - Left Yaw - Right Roll - Lack of authority of the Lateral Cyclic command Low/Negative Gs CONDITIONS

13. At some point, the rotor head will eventually hit the rotor mast, the shaft’s torque load in addiction of the rotor’s movement, will lead to damage or total detachment of the rotor shaft itself. Low/Negative Gs CONDITIONS