H60 IPC Applied Aerodynamics
What does it take to change the direction of an object that is moving?__________________
A force
Referring to the lift equation, how can a helicopter pilot effectively change V2
An increase or decrease in rotor RPM
Which type of pressure results from the motion of a fluid (air)
Dynamic pressure.
his action occurs in a fully articulated rotor system but does not occur in a semi-rigid system
Hunting / lead and lag
In steady state forward flight (pilot is cyclic feathering) max down flap velocity occurs at the _________ position and max down flap displacement occurs at the __________ position
3 o'clock, 12 o'clock
Which of the following best describes a vector?
A vector is a graphic representation of a quantity that must be described using both magnitude and direction
Hunting
Absorbs stresses produced from blade flapping
If the forces of weight, lift, drag and thrust are not in balance the aircraft will _________ in the direction of the stronger force until the forces are again in balance
Accelerate
If the forces of weight, lift, drag and thrust are not in balance the aircraft will _________ in the direction of the stronger force until the forces are again in balance.
Accelerate.
What is the relationship between the amount of lift produced by the advancing and retreating blades in straight and level unaccelerated flight?
Advancing and retreating blades are creating equal lift.
How do we compensate for the lateral drift encountered with single main rotor helicopters
All of the answers. Through cyclic inputs of the pilot. A slight lateral tilt in the main transmission. Through inputs from any of a number of different on board mechanical and electrically automated compensation devices
Referring to the lift equation, how can a helicopter pilot effectively change V2 ?
An increase or decrease in rotor RPM.
In reference to the lift equation, which part of the lift equation specifically relates to angle of attack for a given airfoil? L=CL * S * 1/2p * V2
CL
Which of the following is true of a non symmetric airfoil?
Can produce useable lift even at negative angles of attack
Which of the following is true of a non symetric airfoil?
Can produce useable lift even at negative angles of attack.
What causes the left wheel or left skid to hang lower than the right on an american helicopter which has a fully articulated rotor system?
Compensation for translating tendency
Cyclic feathering
Controls the attitude of the main rotor system.
Collective feathering
Controls the overall lift production of the main rotor system.
What is the primary cause of dissymmetry of lift?
Differential wind flow velocities on the advancing and retreating halves of the rotor system.
On the airfoil segment below, draw and label vectors to depict rotational relative wind, induced flow, resultant relative wind, lift, drag and total aerodynamic force.
Draw the airfoil Model with all forces acting upon it.
Which type of pressure results from the motion of a fluid (air)?
Dynamic pressure.
Identify the contributing factors to advancing blade compressibility
High airspeeds and gross weight, low air density, high G maneuvers, turbulence, high rotor RPM, and low temperatures.
If you were able to control the temperature, humidity and pressure in the environment you were operating in, what combination of the mentioned conditions would you desire to produce maximum lift from an airfoil?
High pressure, Low temp, Low humidity
How will an updraft affect the angle of attack
Increase angle of attack
How will an updraft affect the angle of attack?
Increase angle of attack.
Ground effect causes the relative wind to be more horizontal, the lift vector to be more vertical, and the ________ _______ to be reduced
Induced drag
This type of drag is directly effected by the angle of attack and the production of lift
Induced drag
Which of Newton's Laws would explain the resistance a body offers to change of motion?
Inertia.
Which of the following would be a good example of Acceleration?
Initiating either of the following; an increase or decrease in velocity, or a change in altitude
If the tip path plane is perpendicular to the mast __________ is occurring
No flapping
Which type of airfoil encounters large center of pressure changes as angles of attack are varied?
Non symmetric; A-symmetric airfoil
In-ground effect altitudes increase the efficiency of the rotor system. This occurs when the helicopter is operating at heights no greater than
One rotor diameter
This type of drag is effected by the surface condition of the fuselage
Parasite drag
In a single rotor helicopter (counter-clockwise rotation), if the pilot ignores the abnormal vibrations and control feedback, and continues to aggressively maneuver and/or accelerate the aircraft into a retreating blade stall condition, the aircraft will then:
Pitch up and roll left
If not compensated for, the combined effects dissymmetry of lift and the transverse flow effect would cause the helicopter to _____________________ and ___________________________ as the helicopter transitions from a hover to forward flight.(counter clockwise rotating rotor system)
Pitch up at the nose , roll right
During autorotation, at a controlled rate of descent, the helicopter converts _______ energy based on the weight and altitude of the aircraft to _______ energy of the rotor system
Potential, kinetic
What accounts for approximately 75% of the aerodynamic forces produced by an airfoil?
Pressure differential
This type of drag is directly effected by the type, design and number of rotor blades in your rotor system
Profile drag
This type of drag is directly effected by the type, design and number of rotor blades in your rotor system.
Profile drag
Air in motion with respect to a body in it: the velocity or direction of the air in motion with respect to a body, usually the air outside the region affected by the body i.e. the free stream. The wind may arise from the motion of the body, the motion of the air or from the motion of the body and the air. Choose the term below that most closely relates to this statement
Relative wind
Air in motion with respect to a body in it: the velocity or direction of the air in motion with respect to a body, usually the air outside the region affected by the body i.e. the free stream. The wind may arise from the motion of the body, the motion of the air or from the motion of the body and the air. Choose the term below that most closely relates to this statement.
Relative wind
The resultant of lift and drag on the rotor system as a whole is referred to as which of the following?
Resultant lift.
What is defined as "the summation of all the lift produced by all the segments of all the rotor blades?"
Resultant lift.
he resultant of lift and drag on the rotor system as a whole is referred to as which of the following?
Resultant lift.
High forward airspeed, high gross weight, low rotor RPM, high-density altitude, high G-maneuvers, and turbulent air are conditions conducive to
Retreating blade stall
The angle of incidence is the angle between the chordline and the _______ _______ _______, and the angle of attack is the angle between the chordline and the _______ _______ _______.
Rotational relative wind, Resultant relative wind
_______ _______ _______ is created by the rotation of the rotor blades, which when modified by the induced flow rate becomes the _______ _______ _______, the only wind that the airfoil acts upon.
Rotational relative wind, resultant relative wind
Which of the definitions below best describes a scalar?
Scalars are quantities that can be described by magnitude or size alone.
What is defined as "a condition of powered flight where the helicopter will settle within its own downwash?"
Settling with power
If a roll rate is encountered on takeoff, to prevent the possibility of dynamic rollover, the pilot should:
Smoothly reduce collective therefore reducing the rate at which thrust is applied.
Which of the following best describes the point upon an airfoil where the velocity decreases to zero, which results in the highest static pressure area
Stagnation point
Which of the following best describes the point upon an airfoil where the velocity decreases to zero, which results in the highest static pressure area.
Stagnation point
Identify the three blade regions associated with autorotation
Stall, driving, driven.
Which type of pressure describes the weight of a column of air pushing upon a surface?
Static pressure
What are the effects of excessive blade coning?
Stress on blades and blade roots.
The tendency for the fuselage of a helicopter to remain stationary as you transition from a hover to forward flight is most closely related to which one of Newton's laws of motion
The Law of Inertia
What is the dominating factor in regard to advancing blade compressibility
The speed of sound
Flapping
The up and down movement of the blades as they rotate, this action aids in the compensation for dissymetry of lift.
What do we call the lateral drift caused by canceling the turning moment that occurs about the mast?
Translating tendency
What is defined as "the increased rotor efficiency resulting from directional flight?"
Translational lift
A cyclic increase in the pitch angle of the blade over the tail of the helicopter will result in a(n) ________ at the 3 o'clock position.
Up flap displacement
What conditions must exist for settling with power to occur?
Vertical or near-vertical descent of at least 300 feet per minute. Airspeed less than ETL. Rotor system using 20-100% of power available, with insufficient power to arrest descent.
When discussing Bernoulli's principle, or mass flow rate, the ________ of air passing any given point, per unit of time, is equal throughout the tube
Volume
When discussing Bernoulli's principle, or mass flow rate, the ________ of air passing any given point, per unit of time, is equal throughout the tube.
Volume
Listed below are various applications of Newton's laws of motion. To the right of each example identify which of Newton's laws applies. a. Torque effect.. _______________ b. The resistance a body puts up to a change to its motion is. ______________ c. Directly proportional to the force and inversely proportional to the mass.
a. Action/reaction b. Inertia c. Acceleration
At what point in the confined system below do we find the: a. highest dynamic pressure? ____________ b. highest velocity? _________ c. lowest static pressure? ______________ d. highest static pressure? __________ e. highest total pressure? ___________
a. b b. b c. b d. d e. Total energy is equal at all points in the confined system.
An increase in the induced flow velocity, at a constant pitch angle will ____________ the angle of attack.
decrease
If the pilot moves the cyclic forward, the rotor system will respond with a corresponding __________ in the angle of incidence at the _________ position.(this rotor system rotates counter clockwise
decrease, 3 o'clock
If the pilot moves the cyclic forward, the rotor system will respond with a corresponding __________ in the angle of incidence at the _________ position.(this rotor system rotates counter clockwise)
decrease, 3 o'clock
The velocity of air (_________________) must increase if the same volume of air, per unit of time, is to pass through the constriction.
dynamic pressure
As subsonic airflow passes through a constriction in a confined system, dynamic pressure _________________, static pressure ___________________ while total pressure _________________.
dynamic pressure increases, static pressure decreases, and total energy remains constant.
As subsonic airflow passes through a constriction in a confined system, dynamic pressure will __________, static pressure will _______________ while total pressure will __________________.
increase / decrease / remain constant
As a helicopter transitions from a hover to normal cruise flight, the average angle of attack of the blades____________ without a change to collective pitch. This is due to a reduction of
increases, induced flow
As a helicopter transitions from a hover to normal cruise flight, the average angle of attack of the blades____________ without a change to collective pitch. This is due to a reduction of _____________ ___________ velocity
increases, induced flow
As airspeed increases, differential velocities and phase lag will cause the nose of the helicopter to _______ _____ (without augmentation systems) the pilot will need to apply additional ______ ______ .
pitch up, foward cyclic
With the increase in velocity there must be a reduction in another component of energy, that being (_______________) if total energy is to remain constant.
static pressure
