L5_Introduction to Helicopters

helicopter

is an aircraft that is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades.

rotorcraft or rotary-wing

Helicopters are classified as _____ aircraft to distinguish them from fixed-wing aircraft because the helicopter derives its source of lift from the rotor blades rotating around a mast.

move forward

vertically

The primary advantages of the helicopter are due to the rotor blades that revolve through the air, providing lift without requiring the aircraft to _____.

This creates the ability of the helicopter to take off and land _____ without the need for runways.

congested or isolated

Helicopters are often used in _____ areas where fixed-wing aircraft are not able to take off or land.

The lift from the rotor also allows the helicopter to hover in one area and to do so more efficiently than other forms of vertical takeoff and landing aircraft, allowing it to accomplish tasks that fixed wing aircraft are unable to perform.

vertical flight

The earliest references for _____ came from China.

400 BC

bamboo flying toys (or Chinese top)

Since around _____. Chinese children have played with _____.

bamboo-copter

is spun by rolling a stick attached to a rotor.

The spinning creates lift, and the toy flies when released.

1480s

aerial screw

It was not until the early _____, when Italian polymath Leonardo da Vinci created a design for a machine that could be described as an "_____", that any recorded advancement was made towards vertical flight.

Leonardo da Vinci

It was not until the early 1480s, when Italian polymath _____ created a design for a machine that could be described as an "aerial screw", that any recorded advancement was made towards vertical flight.

1939

Vought-Sikorsky VS-300

In _____, Igor Sikorsky designed and flew the _____, the first viable American helicopter, which pioneered the rotor configuration used by most helicopters today.

Igor Sikorsky

In 1939, _____ designed and flew the Vought-Sikorsky VS-300, the first viable American helicopter, which pioneered the rotor configuration used by most helicopters today.

Sikorsky R-4

Igor Sikorsky modified the design into the _____, which became the world's first mass-produced helicopter in 1942.

Igor Sikorsky

designed the first successful helicopter incorporating the tail rotor into the design, upon which further designs were based.

1951

K-225 helicopter

In _____, at the urging of his contacts at the Department of the Navy, Charles H. Kaman modified his _____ with a new kind of engine, the turbo-shaft engine.

Charles H. Kaman

turbo-shaft

horsepower

In 1951, at the urging of his contacts at the Department of the Navy, _____ modified his K-225 helicopter with a new kind of engine, the _____ engine.

This adaptation of the turbine engine provided a large amount of _____ to the helicopter with a lower weight penalty than piston engines, heavy engine blocks, and auxiliary components.

K-225

On December 11, 1951, the _____ became the first turbine-powered helicopter in the world.

hover

low airspeed

time or work-intensive

Due to the unique operating characteristics of the helicopter its ability to take off and land vertically, to _____ for extended periods of time, and the aircraft’s handling properties under _____ conditions, it has been chosen to conduct tasks that were previously not possible with other aircraft or were too _____ or _____ to accomplish on the ground.

Helicopters are used for transportation, construction, firefighting, search and rescue, and a variety of other jobs that require its special capabilities.

helicopter rotor system

is the rotating part of a helicopter that generates lift.

main rotors

tail rotor

Rotor system may be mounted horizontally, as _____ are, providing lift vertically; it may be mounted vertically, such as a _____, to provide lift horizontally as thrust to counteract torque effect.

tilt rotors

horizontal

vertical

In the case of _____, the rotor is mounted on a nacelle that rotates at the edge of the wing to transition the rotor from a _____ mounted position, providing lift horizontally as thrust, to a _____ mounted position providing lift exactly as a helicopter.

nacelle

lift horizontally

lift exactly as a helicopter

In the case of tilt rotors, the rotor is mounted on a _____ that rotates at the edge of the wing to transition the rotor from a horizontal mounted position, providing _____ as thrust, to a vertical mounted position providing _____.

tail rotor

is a smaller rotor mounted vertically or near vertically on the tail of a traditional single-rotor helicopter.

tail rotor

either pushes or pulls against the tail to counter the torque.

main transmission

tail boom

The tail rotor drive system consists of a drive shaft powered from the _____ and a gearbox mounted at the end of the _____.

tail rotor

is powered by the helicopter's main power plant, and rotates at a speed proportional to that of the main rotor.

Hover

Forward Flight

2 Flight Conditions

Hover

means that it is in flight at a constant altitude, with no forward, aft, or sideways movement.

main rotor blades

In order to hover, a helicopter must be producing enough lift in its _____ to equal the weight of the aircraft.

Forward flight

a helicopter's flight controls behave more like those in a fixed-wing aircraft.

down

altitude

airspeed.

Forward Flight

Moving the cyclic forward makes the nose pitch _____, thus losing _____ and increasing _____.

up

Forward Flight

Moving the cyclic back makes the nose pitch _____, slowing the helicopter and making it climb.

1. collective pitch control

2. cyclic pitch control

3. antitorque pedals or tail rotor control

3 Major controls in a helicopter that the pilot must use during flight.

throttle control

In addition to these 3 major controls, the pilot must also use the _____, which is usually mounted directly to the collective pitch control in order to fly the helicopter.

collective pitch control (or simply “collective” or “thrust lever”)

is located on the left side of the pilot’s seat and is operated with the left hand.

collective pitch control (or simply “collective” or “thrust lever”)

is used to make changes to the pitch angle of the main rotor blades.

pitch angle

As the collective pitch control is raised, there is a simultaneous and equal increase in _____ of all main rotor blades; as it is lowered, there is a simultaneous and equal decrease in _____.

collective pitch control

The pilot uses _____ to rise vertically.

pitch angle

angle of incidence

Changing the _____ on the blades changes the _____ on each blade.

angle of incidence

With a change in _____ comes a change in drag, which affects the speed or revolutions per minute (rpm) of the main rotor.

increases

increases

increases

decreases

Decreasing pitch angle decreases both angle of incidence and drag, while rotor rpm increases.

As the pitch angle ____, angle of incidence _____, drag _____, and rotor rpm _____.

proportionate

throttle control or governor

In order to maintain a constant rotor rpm, which is essential in helicopter operations, a _____ change in power is required to compensate for the change in drag.

This is accomplished with the _____, which automatically adjusts engine power.

throttle

The function of the _____ is to regulate engine rpm.

twist grip

If the correlator or governor system does not maintain the desired rpm when the collective is raised or lowered, or if those systems are not installed, the throttle must be moved manually with the _____ in order to maintain rpm.

collective

If the correlator or governor system does not maintain the desired rpm when the _____ is raised or lowered, or if those systems are not installed, the throttle must be moved manually with the twist grip in order to maintain rpm.

throttle control

The _____ is much like a motorcycle throttle, and works in virtually the same way.

increases

decreases

Twisting the throttle control to the left _____ rpm; twisting the throttle to the right _____ rpm.

governor

is a sensing device that senses rotor and engine rpm and makes the necessary adjustments in order to keep rotor rpm constant.

throttle

In normal operations, once the rotor rpm is set, the governor keeps the rpm constant, and there is no need to make any _____ adjustments.

Governors

are common on all turbine helicopters and used on some piston powered helicopters.

correlator

is a mechanical connection between the collective lever and the engine throttle.

collective lever

When the _____ is raised, power is automatically increased; when lowered, power is decreased.

Correlator

this system maintains rpm close to the desired value, but still requires adjustment of the throttle for fine tuning.

collective pitch

throttle

In piston helicopters, the _____ is the primary control for manifold pressure, and the _____ is the primary control for rpm.

secondary control

However, the collective pitch control also influences rpm, and the throttle also influences manifold pressure; therefore, each is considered to be a _____ of the other’s function.

tachometer (rpm indicator) and the manifold pressure gauge

Both the _____ and the _____ must be analyzed to determine which control to use.

cyclic pitch control

is usually projected upward from the cockpit floor, between the pilot’s legs or between the two pilot seats in some models.

cyclic pitch control

This primary flight control allows the pilot to fly the helicopter in any direction of travel: forward, rearward, left, and right.

total lift force

is always perpendicular to the tip-path plane of the main rotor.

tip-path plane

The purpose of the cyclic pitch control is to tilt the _____ in the direction of the desired horizontal direction.

rotor disk

The cyclic controls the _____ tilt versus the horizon, which directs the rotor disk thrust to enable the pilot to control the direction of travel of the helicopter.

rotor disk

If the cyclic is moved forward, the rotor disk tilts forward; if the cyclic is moved aft, the disk tilts aft, and so on.

tilts in the same direction the cyclic pitch control is moved.

gyro

rigged

Because the rotor disk acts like a _____, the mechanical linkages for the cyclic control rods are _____.

increase

increases

decrease

decreases

An _____ in pitch angle _____ AOA; a _____ in pitch angle ____ AOA.

AOA

downward

upward

If the cyclic is moved forward, the _____ decreases as the rotor blade passes the right side of the helicopter and increases on the left side.

This results in maximum _____ deflection of the rotor blade in front of the helicopter and maximum ____ deflection behind it, causing the rotor disk to tilt forward.

antitorque pedals

located on the cabin floor by the pilot’s feet, control the pitch and therefore the thrust of the tail rotor blades or other antitorque system.

fuselage

Newton’s Third Law “For every action there is an equal and opposite reaction”.

This law applies to the helicopter _____ and its rotation in the opposite direction of the main rotor blades unless counteracted and controlled.

antitorque rotor or tail rotor

To make flight possible and to compensate for this torque, most helicopter designs incorporate an _____.

antitorque pedals

allow the pilot to control the pitch angle of the tail rotor blades.

antitorque pedals

are connected to the pitch change mechanism on the tail rotor gearbox and allow the pitch angle on the tail rotor blades to be increased or decreased.

tail rotor

is used to control the heading of the helicopter while hovering or when making hovering turns, as well as counteracting the torque of the main rotor.

Hovering turns

are commonly referred to as “pedal turns.”

tail rotor

tail rotor blades

The thrust of the _____ depends on the pitch angle of the _____.

This pitch angle can be positive, negative, or zero.

positive pitch angle

tends to move the tail to the right.

negative pitch angle

moves the tail to the left, while no thrust is produced with a zero pitch angle.

positive

negative

The maximum _____ pitch angle of the tail rotor is generally greater than the maximum _____ pitch angle available.

This is because the primary purpose of the tail rotor is to counteract the torque of the main rotor.

right

left

From the neutral position, applying right pedal causes the nose of the helicopter to yaw _____ and the tail to swing to the _____.

nose

tail

Pressing on the left pedal has the opposite effect: the ____ of the helicopter yaws to the left and the _____ swings right.

medium positive

With the antitorque pedals in the neutral position, the tail rotor has a _____ pitch angle.

tail rotor thrust

torque of the main rotor

In medium positive pitch, the _____ approximately equals the _____ during cruise flight, so the helicopter maintains a constant heading in level flight.

vertical fin or stabilizer

is used in many single-rotor helicopters to help aid in heading control.

vertical fin or stabilizer

is designed to optimize directional stability in flight with a zero tail rotor thrust setting.

A

A