C9

Question 1

Here is the x3 rotorcraft and its power consumption figure. This helicopter can fly at a higher forward
speed compared to the traditional helicopter

Compared to the trimmed collective pitch of this vehicle and the vehicle sharing the same size
but without the wing system in hover and high-speed forward flight.

Answer 1

The trim collective pitch of X3 would be higher in the hover but lower in the high-speed flight.

Question 2

Here is the x3 rotorcraft and its power consumption figure. This helicopter can fly at a higher forward
speed compared to the traditional helicopter

Indicate the reason why this vehicle ground effect is lower than the single-rotor helicopter
configuration.

Answer 2

The rotor wake is affected by the wing system, and therefore the airflow momentum that can
hit the ground would be reduced.

Question 3

Here is the x3 rotorcraft and its power consumption figure. This helicopter can fly at a higher forward
speed compared to the traditional helicopter

What are the two main reasons related to the rotor that limits the helicopter’s maximum flight
speed?

Answer 3

Advancing tip compressibility effect, stall condition in the retreating side

Question 4

Here is the x3 rotorcraft and its power consumption figure. This helicopter can fly at a higher forward
speed compared to the traditional helicopter.

Why this helicopter can fly at a higher speed compared to the traditional single-rotor-with-
tail rotor configuration?

Answer 4

The wing and propeller will offload the rotor in the high-speed flight. Thus, the compressibility effect and the stall condition will be delayed to a higher speed range