Rotorcraft Flying Handbook Key Terms

Technical terms and definitions related to rotorcraft flight and mechanics.

Blade Flap

Upward or downward movement of rotor blades during rotation.

Payload

Term for passengers, baggage, and cargo.

Blade Feathering

Rotation of the blade around the spanwise axis.

Blade Lead or Lag

Fore and aft movement of blade in the plane of rotation.

Axis-of-Rotation

Imaginary line about which the rotor rotates.

Tip-Path Plane

Imaginary circular plane outlined by rotor tips.

Aircraft Pitch

Movement of helicopter about its lateral axis.

Load Factor

Load that the main rotor system supports.

Aircraft Yaw

Movement of the helicopter about its vertical axis.

L/Dmax

Maximum ratio between total lift and total drag.

VNE

Speed beyond which aircraft shouldn't be operated.

Centrifugal Force

The apparent force that an object moving along a circular path exerts on the body constraining the object.

Centripetal Force

The force that attracts a rotating body toward its axis of rotation.

Lift

The upward force created by the effect of airflow as it passes around an airfoil.

Relative Wind

The wind moving past the airfoil.

Cyclic Pitch Control

Controls the pitch of main rotor blades.

Antitorque Pedals

Controls the thrust of the tail rotor blades.

Throttle

Controls the power of the engine.

Collective Pitch Control

Controls the pitch angle of all main rotor blades.

Chip Detector

A warning device that alerts you to any abnormal wear in a transmission or engine.

VNE

The speed beyond which an aircraft should never be operated.

VOR

Ground-based navigation system consisting of very high frequency omnidirectional range stations.

Chip Detector

A warning device that alerts you to any abnormal wear in a transmission or engine.

GPS

A satellite-based radio positioning, navigation, and time-transfer system.

IFR

Rules that govern the procedure for conducting flight in weather conditions below VFR weather minimums.

Rotorcraft Flying Handbook

Designed as a technical manual for applicants who are preparing for pilot certificates

Center of pressure

Imaginary point on the chord line - aerodynamic forces concentrated.

Thrust

The force that propels the helicopter through the air.

Drag

The force that resists the movement of a helicopter through the air.

Load factor

ratio of the load supported by the main rotor system to the actual weight of the helicopter and its contents

Weight

Force that pulls object toward center of earth

Disc loading

ratio of weight to the total main rotor disc area/ helicopter weight by the rotor disc area

Never-exceed speed

The speed beyond which an aircraft should never be operated

Profile Drag

Develops from the frictional resistance of the blades passing through the air.

Induced Drag

Generated by the airflow circulation around the rotor blade as it creates lift

Parasite Drag

Is present any time the helicopter is moving through the air

Magnus Effect

air circulation in the airstream

Bernoulli’s Principle

creating differential pressure on the airfoil

Coriolis Effect

The tendency of a rotor blade to increase or decrease its velocity in its plane of rotation due to mass movement

Gyroscopic precession

The resultant action or deflection of a spinning object when a force is applied to this object

Translating Tendency

The tendency of a helicopter to drift in the same direction as antitorque rotor thrust

Steady-State Flight

A condition when an aircraft is in straight- and-level, unaccelerated flight, and all forces are in balance

Electrical Systems

An overpressure control may be incorporated to prevent excessive voltage, which may damage the electrical components.

Lift

Most of the lift is the result of decreased pressure above the blade, rather than the increased pressure below it.

Torque

The tendency of the helicopter to turn in the opposite direction of the main rotor rotation

Antitorque Rotor

a variable pitch, antitorque rotor or tail rotor

Fully Articulated Rotor System

Blades are allowed to flap, feather, and lead or lag independently of each other

NOTAR

Air jet lift supplies approximately two-thirds of the lift necessary to maintain directional control

Rigid Rotor

the blades cannot flap or lead and lag, but they can be feathered

Coanda Effect

low-pressure air that is forced into the tailboom by a fan mounted within the helicopter

Controllable Rotating Nozzle

horizontal slots

Angle of attack

is the angle between the blade chord line and the direction of the relative wind.

Tail Rotor

A variable pitch, antitorque rotor or tail rotor

Fenestron

another form of antitorque rotor is the fenestron or 'fan-in-tail' design

NOTAR

alternative to the antitorque rotor

Landing Gear

The most common landing gear is a skid type gear

Powerplant

A typical small helicopter has a reciprocating engine, which is mounted on the airframe

Collective Pitch Control

Changes the pitch angle of all main rotor blades simultaneously, or collectively

Throttle Control

Regulate engine r.p.m.

Cyclic Pitch Control

Tilts the main rotor disc by changing the pitch angle of the rotor blades in their cycle of rotation

Antitorque Pedals

Control the pitch, and therefore the thrust, of the tail rotor blades

Purpose of the tail rotor

To counteract the torque effect of the main rotor

Translating Tendency

The tendency of a single main rotor helicopter to drift in the same direction as antitorque rotor thrust

Powered flight

Acted upon by the four aerodynamic forces lift, weight, thrust, and drag

Induced Flow

Rotational relative wind

Dissymmetry of lift

transverse flow effect

collective pitch control

Changes the pitch angle of all main rotor blades simultaneously

throttle

Regulate engine r.p.m.

cyclic pitch control

Tilts the main rotor disc by changing the pitch angle of the rotor blades in their cycle of rotation

collective pitch control

Changes the angle of attack of each blade

correlator

A mechanical connection between the collective lever and the engine throttle

antitorque pedals

Used to make heading changes while hovering

aerodynamic loads

When you bank a helicopter while maintaining a constant altitude

The higher the loading

disc loading changes

Aircraft Yaw

Vertical axis

Weight

a known, fixed value, such as the weight of the helicopter, fuel, and occupants

Aircraft Pitch

The movement about its lateral, or side to side axis

span

The distance from the rotor hub to the blade tip

Main Rotor Transmission

To reduce engine output r.p.m. to optimum rotor r.p.m.

Clutch

Turbine engines do not require it, as the gas producer turbine is essentially disconnected from the power turbine.

Freewheeling Unit

This allows the main rotor to continue turning at normal in-flight speeds

Stability Augmentation System

A force trim system

fenestron

A series of rotat- ing blades shrouded within a vertical tail

cyclic pitch control

It changes the pitch of each blade as a function of where it is in the plane of rotation

cyclic control

They decrease the pitch angle of the rotor blade approximately 90° before it reaches the direction of cyclic displacement

piston helicopters

The throttle is the pri- mary control for r.p.m

selective method

This handbook adopts a selective method and concept to flying helicopters and gyroplanes.

Sideward flight

The vertical or lift compo- nent is still straight up and weight straight down, but the horizontal or thrust component now acts sideward with drag acting to the opposite side.

Purpose of Antitorque Pedals

To control the heading of the helicopter

fenestron

A series of rotor blades shrouded within a vertical tail

The rotor disc tilts

To move the helicopter in the direction of tilt

NOTAR

Low-pressure air that is forced into the tailboom

Tail Rotor

A variable pitch, antitorque rotor

Solidity Ratio

Used to measure the potential for a rotor system to provide thrust

Tail Rotor Thrust

Used to control the helicopters yaw

Straight Climbs

Constant Airspeed

Flapping Hinge

Designed to compensate for dissymetry of lift

Lead- Lag Hinge

Allows the blade to move back and forth

Rigid Rotor System

the blades, hub, and mast are rigid with respect to each other

Anti-Icing System

Electrical control