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Theory of Rotary Wing Flight
File Number 011-4260-12
Terms in this set (63)
Which of Newton's laws apply to torque effect? What does the law state?
For every action, there is an equal/opposite reaction.
Which of Newton's laws apply to "More power needed to obtain a desired RPM than is needed to maintain RPM"? What does the law state?
A body at rest will remain at rest and a body in motion will remain in motion at the same speed and in the same direction unless acted upon by some external force.
Which of Newton's laws apply to a greater load resulting in less acceleration?
Acceleration is directly proportional to the force and inversely proportional to mass.
If airflow atop the airfoil increases, static pressure will ___ and dynamic pressure will ___.
The rounded edge is ___. The ___ is the straight line between the edge and the tailing edge. The ___ ___ is the upper curvature. The ___ ___ is the lower shape. ___ is the length of the rotor blade from the point of rotation to the tip of the blade. The tapered edge is the ___ ___.
(Chord, Upper camber, Lower camber, Span, Trailing edge, Leading edge)
What are the two basic types of airfoils?
Define rotational relative wind as applied to an airfoil?
Parallel to and opposite to the flight path of an airfoil.
What is the definition of an airfoil?
Any system designed to produce lift when air is passed over it.
Which direction does rotational relative wind travel for rotation only? For rotation and up flapping? For rotation and airspeed? For Rotation and flapping down?
Straight into the airfoil
Diagonal and upward
Double arrows towards the airfoil
Diagonal and downward
What is the stalling angle of most airfoils?
BThe blade tip speed of the helicopter is 360 knots, airspeed is 100 knots. What is the relative velocity of positions A, B, C, D?
What is the relationship between lift and resultant relative wind?
Lift is perpendicular to resultant relative wind.
What is the relationship between drag and resultant relative wind?
Lift is in line with and is in the same direction as drag.
Which type of drag exists in the rotor tip vortexes? The lift and total aerodynamic force tilting rearward on the airfoil? Skin friction on the fuselage? Skin friction on the airfoil? Non streamlined fuselage?
What is induced, parasitic, and profile drag?
Results from producing lift
Drag created from the fuselage (any non-lifting components)
Caused by the frictional resistance of the rotor blades passing through the air.
Lift equal to weight and thrust to drag?
Lift equal to weight but thrust greater than drag?
Lift greater than weight and thrust greater than drag?
Lift equal to weight but drag greater than thrust?
Level unaccelerated flight
Level accelerated flight
Level decelerating flight
List three factors that determine air density?
Temperature, pressure, humidity
What relative combination of pressure, temperature, and humidity would produce the greatest lift about an airfoil?
The following are either semirigid or articulated rotor systems. Disc tilts relative to the hub. CH-47. Disc tilts relative to the mast. Opposite blades act as one unit. TH-67. Lead and lag (hunt).
What force supplies rigidly to the rotor blades?
List three causes of excessive blade coning.
Low rotor RPM
High gross weight
High "G" maneuvers
List three effects of excessive blade coning.
Loss of disc area
Loss of lift
Stress on blades
How is the angle of incidence measured in a rotary-wing aircraft?
The angle of incidence is measured between the chord of the airfoil and the rotational relative wind (plane of rotation)
Which control changes angle of incidence differentially around the rotor system?
Cyclic pitch control
What is the definition of angle of attack?
The acute angle between resultant relative wind and the chord of the airfoil.
List two possible effects when the blades in a rotor system are out of track.
Low frequency vertical vibrations
Why does the helicopter act as a pendulum?
The CG is located below the supporting elements.
With rotor systems which rotate counterclockwise, what is the direction in which the fuselage tends to yaw because of torque effect?
How is torque effect overcome in single rotor and tandem rotor systems?
Opposite rotating main rotor.
A pedal turn to the right requires more or less power than a pedal turn to the left.
List three methods used to overcome translating tendency in single rotor helicopters.
Rigging the cyclic
Tilting the mast
What type of vibration (high or low frequency) is associated with tail rotor out of track?
In US Army single rotor helicopters, if tail rotor thrust is to the right, which direction is the air flow through the tail rotor?
Which of the following are occurrences in articulated rotor systems or in both articulated and semirigid?
Collective feathering compensates for? Cyclic feathering compensates for? Hunting is? Rotation is? Flapping is?
Controls overall lift of the rotor system (vertical control)
Produces a lift differential in the rotor system (directional control)
Absorbs stresses produced by flapping
Produces relative wind
Overcomes dissymmetry of lift
What is the relationship of total force of the rotor system to the tip-path plane?
List two components of total force which result when the tip-path plane is tilted, and state the purpose of each component.
Lift opposes weight and acts vertically
Thrust opposes drag and acts horizontally
List 4 conditions that would promote "ground effect"
Altitude 1 rotor diameter or less
List six conditions that would result in the loss or apparent loss of ground effect.
Beginning of translational movement
Altitude greater than 1 rotor diameter
Hovering into a wind
Hovering into a wind
List three conditions necessary until settling with power.
Rate of decent of 300 fpm or greater
Rotor system using some of the available engine power (20-100%)
Airspeed below ETL
List 4 symptoms of settling with power.
High rate of decent
High power consumption
Loss of collective pitch effectiveness
List six flight situations that would be conductive to settling with power.
Attempting to hover above the hovering ceiling
Attempting to hover OGE within the hovering ceiling without maintaining altitude control
Steep powered approach in which airspeed is permitted to drop to nearly 0
List three corrective actions for settling with power.
Increase airspeed with cyclic
Reduce collective pitch
Adjust rotor RPM to normal operating range
ETL exists between what airspeed range?
What speed are low frequency vibrations associated with transverse flow effect likely to occur?
The vibration while going through transverse flow effect is caused by?
Imbalance of induced air drag between the front half and rear half of the rotor system.
While in flight you notice your airspeed is 10kts too fast. To decelerate, you...
Move cyclic aft.
You are flying straight and level at 1,500 feet and 90 kts. You desire to reduce airspeed to 60kts and maintain altitude, RPM, and heading. Which control movement is necessary?
Rear cyclic, lower collective, right pedal
List two purposes of cyclic pitch control.
Tilt of the tip-path plane.
Control dissymmetry of lift.
What method compensated for dissymmetry of lift?
Cyclic pitch control
In an articulated rotor system, assume that a blade flaps up. In which direction will the blades center of gravity move? Will the blade then lead or lag?
List 5 factors that would contribute to ground resonance.
Bad oleo struts
Bad drag dampers
Taxiing over uneven ground
Hard one-skid or wheel landing
List two corrective procedures in the event of ground resonance.
If operating RPM exists, get airborne.
If RPM does not exist, place firmly on ground, reduce throttle, and normal shutdown.
During autorotation, the main rotor blades continue turning in the same direction of powered flight because of thrust produced in the ___ region.
What are the names of the three blade regions during autorotation? What is their inclination? What type of force do they produce?
Driven - aft - drag
Driving - forward - thrust
Stall - aft - drag
What is the direct cause of all stalls?
Exceeding the circular angle of attact
What are the corrections for all stalls?
Reduce the angle of attack to a value less than the critical angle
List 5 factors, other than airspeed, which could contribute to a retreating blade stall.
High gross weight
Low air density
High G maneuvers
low rotor RPM
List three symptoms of retreating balde stall.
What immediate corrective actions should be initiated if a retreating blade stall occurs?
Reduce collective and regain control of the aircraft
What three conditions are necessary for dynamic rollover?
Exceed the critical angle
What are the physical factors associated with dynamic rollover?
Main rotor thrust
Tail rotor thrust
Slopped landing area
Low fuel causing CG to move forward
What are the human factors associated with dynamic rollover?
Failure to take timely action
Inappropriate control input
Loss of vertical reference.
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