B318

OTHER: Flight Dynamics - Control (Response)

Overview:

	General Information, related primarily to intermeshing helicopters.
	Specific Information:	Related to the SynchroLite	Related to the UniCopter

Helicopter Control for Different Configurations:

(1)
(1)		INTERMESHING
		L.R. COLLECTIVE
		L.R. CYCLIC
		L.R. CYCLIC
		L.R. DIFF. CYCLIC & Q_RI ≠ Q_L& RUDDER (2)
		Q_RI = Q_L

Borrowed from Rotary-Wing Aerodynamics

The Kaman Huskie uses both differential collective pitch and opposed longitudinal cyclic together. The Flettner used differential torques (differential collective pitch change) and rudder and only the rudder could give steering during autorotation. For ideas on Intermeshing yaw control see the following section on this page.

Possible Solution to Yaw Problems on Intermeshing Configuration:

See what Kellett wanted to do; OTHER: Helicopter - Outside - Intermeshing - Kellett XR-8 & XR-10

Consider combining this with; Variable Vertical Fin Concept (VVF)

Control Inputs:

Collective [θ₀] ~ zero harmonic pitch control

Longitudinal Cyclic [θ_1s] ~ first harmonic pitch control

Lateral Cyclic [θ_1c] ~ first harmonic pitch control

Pedals [θ_0T]

Remote Velocity [V] (forward component only for intermeshing?)

Control Systems: [Source ~ RWP5 p.92]

Rate Control System:

Attitude Control System:

Control Analysis:

Control Sensitivity:

Defined in three ways.

= control power / rotor damping

= (control moment / stick displacement) / (damping moment / angular velocity)

= angular velocity / stick displacement

Small helicopters with conventional control systems are subjected to high control sensitivity. The height of the rotor and the offset of the flapping hinges do not effect control sensitivity because they change the control power and rotor damping in proportion. This can lead to pilot-induced lateral oscillations. The Bell stabilizer bar and the Hiller paddles are incorporated to reduce the control sensitivity. The Robinson's delta3 is, no doubt, used for the same reason.

The, possibly out of date, military specification MIL-H-8501, Nov. 5, 1952 states that the requirement for the rate of roll per inch of stick displacement (often referred to as "sensitivity") be less than 20º per second.

Control Forces:

The general requirements for good control forces are; low friction, low vibration, and logical control force transients.

A means for trimming the control forces in steady flight is also required.

Control Vibration:

Ref; UniCopter - Vibration - Rotor Induced - Control

Control Vector:

The single rotor helicopter has four components: main rotor collective, longitudinal cyclic, lateral cyclic and tail rotor collective.

The intermeshing has:

	Port	Starboard
Collective
Longitudinal cyclic
Lateral cyclic
Empennage

Control Derivatives:

General Notes:

Pedals and Yaw:

The pedal causes a yaw in the same direction as does an airplane's rudder or its foot brakes. I.e. in all cases, the application of left pedal results in the craft turning to the left.

Items:

OTHER:

	Name	Item
	OTHER: Flight Dynamics - Control - MIL-H-8501-A	0938
	OTHER: Flight Dynamics - Control - Comparative Cyclic Moments	1215
	OTHER: Flight Dynamics - Control - Independent Root & Tip Control Concept	1096
	OTHER: Flight Dynamics - Control - Twin Vertical Stabilizers	1322
	OTHER: Flight Dynamics - Control - Yaw Control for Twin Rotor Configurations	1184

Related Web Pages at This Site:

	OTHER ~ Flight Dynamics - Rotor Hub - Cyclic Control for a Simple Ultralight Helicopter
	SynchroLite ~ Trim, Stability & Control - Stability & Control
	UniCopter ~ Trim, Stability & Control - Control
	SynchroLite ~ Control - Flight
	Dragonfly ~ Control - Flight
	UniCopter ~ Control - Flight

Last Revised: May 17, 2010