SIFT Army Aviation Information Practice Test

A helicopter is

A type of rotorcraft

Helicopter turbine engines produce ___________ thrust per pound than piston engines

More

The four main forces working on a helicopter are

Lift, weight, thrust, drag

Helicopters typically have between ___ and ___ main rotor blades

2 and 6

Depending on the type of helicopter, main rotor system components can include

A stabilizer bar, upper/lower swashplates, counterweights, pitch horns, teeter/coning hinges, blade grips, pitch/scissor links, control rods

The function of the flybar is

To decrease crosswind thrust on the blades and enhance flight stability by keeping the bar stable as the rotor spins

Many helicopters have a horizontal stabilizer located _____

On the tail boom

The purpose of the tail rotor is:

To produce an anti-torque force acting perpendicular to the helicopter's longitudinal axis.

Wheels on _____ types of helicopters are _____

Some, retractable

A pilot controls a helicopter using:

Pedals, a collective, throttle, cyclic

From a physics perspective, the _____ force is deemed to act through a helicopter's _____

Total weight, center of gravity

When a pilot banks a helicopter, causing it to turn, _____

The machine's weight increases

In the case of helicopters, lift is produced by _____ moving through the air at a speed sufficient to create

Airfoils, a pressure differential

Thrust acts _____ to the aircraft's _____

Parallel, longitudinal axis

Profile drag consists of

Profile drag is usually defined as the sum of form drag(Shape of the object) and skin friction(imperfections)

Vortices produced by spinning rotor blades create

Induced drag

When plotted on a graph, L/DMAX is the point where the helicopter's _____

Total lift-to-drag ration is the greatest

A helicopter's potential energy is affected by

The aircraft's height above the ground

Which of the following factors affect the lift produced by spinning rotor blades

Airfoil coefficient of lift, air density, blade area

What happens when a helicopter's main rotor blades spin rapidly?

The upper and lower sides of each blade experience a difference in pressure

Newton's third law of motion applies to helicopters because

The spinning main rotor makes the aircraft try to spin in the opposite direction

When the pilot pushes the cyclic forward

The main rotor disk tilts forward

Multi-engine helicopters have

A throttle lever for each engine

When the pilot wants the helicopter's nose to move left or right he

Pushes on the corresponding pedal

For helicopters with a main rotor disk that spins counter-clockwise, the _____ airflow speed happens when each blade reaches the _____ position.

Maximum/ three o'clock (right)

On the advancing rotor blade, lift _____ and the blade _____

increases, moves upward

The angle between the _____ of a rotor blade and its direction of motion relative to the _____ is the angle of attack, which is _____ angle

Chord line, air, an aerodynamic

The angle of incidence is between the _____ line of each blade and the rotor system's _____

Chord, plane of rotation

When a helicopter engine _____, a clutch mechanism called a _____

fails, freewheeling unit automatically discinnects the engine from the main rotor, allowing it to spin freely

During an autororation in forward flight, the rotor disk takes in _____ air and the driven, driving and stall regions of each blade move _____ along its length but only on the _____ side of the dick

Upward flowing, outboard, retreating

Where there is too much lift, the main rotor blades will

Flap

Centrifugal force _____ spinning helicopter main rotor blades _____

Pulls, outward

If left uncorrected, greater lift produced by the advancing side of the rotor disk compared to the lift created by the disk's retreating side could make the helicopter _____

Uncontrollable

The driven region is _____ the blade tips and normally _____ percent of the radius

Nearest, 30

The _____ region is normally between a blade's _____ and _____ regions

Driving, stall, driven

Because of gyroscopic precession, if a wind gust applies a downward force on the left side of a helicopter's main rotor disk as it spins clockwise(as viewed from above), the movement response occurs at the _____ o'clock position

12

Helicopter's experience effective translational lift while transitioning to forward flight at approximately _____ to _____ knots

16, 24

Maximum ground effect occurs during a hover up to a height equal to _____ percent of the main rotor's diameter

100

A pilot can worsen a helicopter's pendular action by

Over-controlling the aircraft

The phenomenon of a helicopter sinking into its own downwash is called

Settling with power