Chapter 3: Helicopter Flight Controls

Question 1

Collective Pitch Control

Answer 1

• Operated w/ left hand
• Changes pitch angle of main rotor blades simultaneously(collectively)
• Increase in collective=increase in pitch angle of all main rotor blades
• Adjustable friction control helps to prevent inadvertent pitch inputs
  
  • Increase pitch=increase AOI=Increase Drag=rotor RPM decreases
  • In order to maintain a constant rotor rpm, which is essential in helicopter operations, a proportionate change in power is required to compensate for the change in drag. This is accomplished with the throttle control or governor, which automatically adjusts engine power.’

Question 2

Throttle Control

Answer 2

• Regulates engine rpms.
• Governor system usually maintains desired rpm instead of manual throttle inputs

Question 3

Governor

Answer 3

• Device that senses rotor and engine rpm and makes necessary adjustments to keep a constant/safe rotor rpm

Question 4

Correlator

Answer 4

• Mechanical connection between collective and engine throttle.
• When collective is raised, power is auto increased.
• Maintains rpm close to desired value but still requires throttle adjustment for fine tuning

Question 5

Cyclic Pitch control

Answer 5

• Controls forward/rearward, left and right flight
• Total lift force is always perpendicular to the tip-path plane of main rotor
• Cyclic purpose is to tilt tip-path plane in direction of desired horizontal direction
• Rotor disc tilts in same direction as cyclic input
• An increase in pitch angle increases AOA;
  
  • cyclic is moved forward, the AOA decreases as the rotor blade passes the right side of the helicopter and increases on the left side resulting in maximum downward deflection of the rotor blade in front of the helicopter and maximum upward deflection behind it, causing the rotor disk to tilt forward.

Question 6

Anti Torque Pedals

Answer 6

• control the pitch and therefore the thrust of the tail rotor blades or other antitorque system
• Newtons Third Law
• Pedals control pitch angle increase/decrease of tail rotor putting heli in longitudinal trim
• Pedals are connected to pitch change mechanism on tail rotor gearbox
• A vertical fin or stabilizer is used in many single-rotor helicopters to help aid in heading control. The fin is designed to optimize directional stability in flight with a zero tail rotor thrust setting
• At speeds above translational lift, the pedals are used to compensate for torque to put the helicopter in longitudinal trim so that coordinated flight can be maintained
• Thrust of tail rotor depends on pitch angle of blades.
  
  • Positive pitch angle= move tail to right
  • Negative pitch angle=move tail to left
  • Max positive pitch angle is greater than negative b/c main purpose is to counter torque of main rotor/fuselage

Question 7

Manifold Pressure and RPM adjustments

Answer 7

• In piston helicopters, the collective pitch is the primary control for manifold pressure, and the throttle is the primary control for rpm. However, the collective pitch control also influences rpm, and the throttle also influences manifold pressure; therefore, each is considered to be a secondary control of the other’s function. Both the tachometer (rpm indicator) and the manifold pressure gauge must be analyzed to determine which control to use

If RPM is And manifold pressure is Solution

1) low Low increase throttle increases MP and RPM
2) low High lower collective decreases MP and increase RPM 3) high Low raise collective increase MP and decreases RPM
4) High high reduce throttle decreases MP and RPM