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SIFT Army Aviation Information Practice Test

Key Concepts:

Terms in this set (40)

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
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