Chapter 9

Question 1

Find the speed point corresponding to the maximum flight duration and maximum flight range
and draw it on the figure we provided.

Answer 1

max flight duration : min power required

max flight range: line from origin is tangential to power required curve

Question 2

Compare 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 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

Advancing tip compressibility effect, stall condition in the retreating side

Question 5

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

Answer 5

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.