Helicopter Aerodynamics Flashcards
Define Newton’s first law
The law of inertia. An object in motion remains in motion until acted upon by an outside force. The same occurs with an object at rest
Define Newton’s second law
Law of acceleration, an object acted upon by a force will continue to accelerate in proportion to the magnitude of the force and the mass of the object
Define Newton’s third law Newton’s third law
Equal and opposite reaction. When an object receives a force it pushes back with an equal opposite force.
How does Newton’s first law act upon a helicopter?
Helicopter will continue to move unless acted upon by an outside force such as weight or drag.
How does Newton’s second law impact a helicopter?
The amount of lift or thrust required is proportional to the weight of the aircraft
How does Newton’s third law act upon an aircraft?
Tail rotor counteracts the main rotor torque effect
What is the definition of a scalar?
A scalar is a value with a magnitude only (Speed)
What is the definition of a vector?
Vectors have both magnitude and direction (Velocity)
What is the vector known as if it is the result of two separate vectors?
The resultant vector
The anti torque pedals control what in a helicopter?
The tail rotor which impacts yaw
The cyclic controls what two axes of motion in a helicopter?
Pitch and roll
What is known as the venturi effect?
Fluid velocity increases in direct proportion to the reduction of area of flow
What is Bernoulli’s principle?
As fluid velocity increases, the dynamic pressure also increases, so to keep total pressure constant static pressure must decrease
How does bernoulli’s principle act upon an airfoil?
As the air moves around the airfoil the dynamic pressure increases due to the increase in velocity above the airfoil resulting in a decrease in static pressure generating lift
The symbol CL corresponds to what in the lift equation?
A combination of angle of attack and wing shape
The symbol P corresponds to what in the lift equation?
Air density
The symbol V corresponds to what in the lift equation?
Airfoil speed
Symbol S corresponds to what in the left equation?
Wing surface area
Temperature lapse rate is defined as what?
2 degrees per every thousand feet
As humidity increases, what happens to overall air density?
Overall air density decreases resulting in a increase in density altitude
An airfoil is defined as what?
A surface body or structure designed to produce a lift or thrust force when subjected to an airflow
The front of the airfoil is known as what?
A leading edge
The rear of the airfoil is known as a what?
Trailing edge
A line from the leading edge to the trailing edge is known as what?
The chord
What line is the average between the upper surface and lower surface of the airfoil?
The camber line
What are the characteristics of a symmetrical airfoil?
Equal camber on each side of the cord, each half is a mirror image of the other.
What are some advantages of a symmetric airfoil?
Constant center of pressure, ease of construction, lower cost.
What are some disadvantages of a symmetric airfoil?
Less efficient at a given angle of attack, undesirable style characteristics