Questions and Answers
What is a helicopter?
A type of rotorcraft
Helicopter turbine engines produce ___________ thrust per pound than piston engines.
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What are the four main forces working on a helicopter?
Lift, weight, thrust, drag
Helicopters typically have between ___ and ___ main rotor blades.
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What components can be included in a helicopter's main rotor system?
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What is the function of the flybar?
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Where is the horizontal stabilizer located on many helicopters?
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What is the purpose of the tail rotor?
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Wheels on _____ types of helicopters are _____
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What controls does a pilot use to operate a helicopter?
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From a physics perspective, the _____ force acts through a helicopter's _____
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What happens when a pilot banks a helicopter to turn?
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Lift is produced by _____ moving through the air at a speed sufficient to create?
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Thrust acts _____ to the aircraft's _____
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Profile drag consists of?
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What do vortices produced by spinning rotor blades create?
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When plotted on a graph, L/DMAX is the point where the helicopter's _____ is the greatest.
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A helicopter's potential energy is affected by?
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Which factors affect the lift produced by spinning rotor blades? (Select all that apply)
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What happens when a helicopter's main rotor blades spin rapidly?
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Why does Newton's third law of motion apply to helicopters?
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What happens when the pilot pushes the cyclic forward?
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What do multi-engine helicopters have?
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When the pilot wants the helicopter's nose to move left or right, what does he do?
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For helicopters with a main rotor disk that spins counter-clockwise, the _____ airflow speed happens when each blade reaches the _____ position.
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On the advancing rotor blade, lift _____ and the blade _____
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The angle between the _____ of a rotor blade and its direction of motion relative to the _____ is the angle of attack, which is _____ angle.
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The angle of incidence is between the _____ line of each blade and the rotor system's _____
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When a helicopter engine fails, what mechanism automatically disconnects the engine from the main rotor?
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During an autorotation in forward flight, what type of air does the rotor disk take in?
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Where there is too much lift, what will the main rotor blades do?
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What does centrifugal force do to spinning helicopter main rotor blades?
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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 _____
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The driven region is _____ the blade tips and normally _____ percent of the radius.
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The _____ region is normally between a blade's _____ and _____ regions.
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Because of gyroscopic precession, if a wind gust applies a downward force on the left side of a helicopter's main rotor disk, the movement response occurs at the _____ position.
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Helicopters experience effective translational lift while transitioning to forward flight at approximately _____ to _____ knots.
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Maximum ground effect occurs during a hover up to a height equal to _____ percent of the main rotor's diameter.
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What can worsen a helicopter's pendular action?
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What is the phenomenon of a helicopter sinking into its own downwash called?
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Study Notes
Helicopter Basics
- A helicopter is classified as a type of rotorcraft.
- Turbine engines in helicopters produce more thrust per pound compared to piston engines.
Forces Involved
- The four main forces acting on a helicopter are lift, weight, thrust, and drag.
Rotor Blade Characteristics
- Helicopters commonly have between 2 and 6 main rotor blades.
- Main rotor system components may include stabilizer bars, swashplates, and control rods.
- Flybars help reduce crosswind thrust and improve flight stability.
Flight Control and Mechanisms
- Many helicopters feature a horizontal stabilizer located on the tail boom, enhancing stability.
- The tail rotor's primary purpose is to generate an anti-torque force perpendicular to the helicopter’s longitudinal axis.
- Pilots use pedals, a collective, a throttle, and cyclic to control the helicopter.
Aerodynamic Principles
- The total weight of a helicopter acts through its center of gravity, influencing balance.
- Banking causes an increase in the helicopter's perceived weight.
- Lift is produced by airfoils moving at a speed that creates a pressure differential.
Thrust and Drag
- Thrust acts parallel to the aircraft's longitudinal axis, essential for forward movement.
- Profile drag comprises form drag and skin friction, impacting the aircraft's performance.
- Vortices from spinning rotor blades result in induced drag.
Energy and Performance
- A helicopter's potential energy is contingent on its altitude above the ground.
- Factors affecting lift from rotor blades include airfoil coefficient of lift, air density, and blade area.
Rotor Blade Mechanics
- Rapid spinning of blades causes pressure differences across the upper and lower sides, generating lift.
- Newton's third law indicates the opposite spin of the aircraft caused by the main rotor’s rotation.
Operational Maneuvers
- Pushing the cyclic forward tilts the main rotor disk, influencing movement direction.
- Multi-engine helicopters utilize a throttle lever for each engine.
- Left or right movements of the helicopter’s nose are controlled by corresponding pedals.
Rotor Blade Dynamics
- In helicopters with counter-clockwise spinning rotors, maximum airflow occurs as blades reach the three o'clock position.
- During forward flight, the rotor disk takes in upward flowing air, affecting its driving and stall regions.
Mechanical Failures
- In the event of an engine failure, a freewheeling unit disconnects the engine from the rotor, allowing it to spin freely.
Flight Conditions
- Excessive lift leads to blade flapping, which can alter flight dynamics.
- Centrifugal force pulls rotor blades outward during operation.
- Unchecked lift discrepancies between advancing and retreating sides can cause uncontrollable flight.
Blade Regions and Effects
- The driven region is closest to blade tips, typically within 30% of the rotor radius.
- The driving region lies between the stall and driven regions, essential for rotor efficiency.
Gyroscopic Precession
- A gust of wind affecting the left side results in movement response at the 12 o'clock position due to gyroscopic precession.
Translational Lift and Effects
- Effective translational lift is experienced during forward flight between 16 to 24 knots.
- Maximum ground effect occurs during hover when at a height equal to 100% of the rotor diameter.
Pilot Control Challenges
- Over-controlling a helicopter can exacerbate pendular movements, making stability harder to achieve.
- Settling with power occurs when a helicopter sinks into its own downwash, affecting performance during landing and hovering.
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Description
Test your knowledge of helicopter aviation with this informative practice quiz. Covering key concepts such as rotorcraft definitions, engine thrust comparisons, and forces acting on helicopters, this test is perfect for aviation enthusiasts and professionals alike. Improve your understanding of helicopter mechanics and terminology.