Section 1.1 Flashcards
Define Flight Mechanics
The science of predicting and controlling aircraft motion.
Pg. 1
What are the three forces/moments exerted on an aircraft in flight?
- Aerodynamic forces/moments
- Propulsive forces
- Gravity
Pg. 1
The aerodynamic forces and moments acting on any arbitrary body moving through the atmosphere originate from what two sources?
- The pressure distribution over the body’s surface.
- The shear stress distribution over the body’s surface.
Pg. 1
What is the most commonly used coordinate system used in flight mechanics?
The Cartesian aerodynamic coordinate system (CACS).
Pg. 1
With respect to the CACS, describe the orientation of the x-axis relative to the aircraft.
The x-axis lies parallel to the chord and points in the general direction of airflow.
Pg. 1
With respect to the CACS, where is the origin typically located?
At the leading edge, or the front of the body.
Pg. 1
With respect to the CACS, what is the orientation of the y-axis?
Pointing upward relative to the Earth.
Pg. 1
With respect to the CACS, describe the z-axis orientation.
Pointing left to right along the span.
Pg. 1
For the rolling moment l (little L), the positive direction is ____.
Right wing down.
Pg. 2
For the yawing moment (n), the positive direction is _____.
Nose rotates right.
Pg. 2
For the pitching moment (m), the positive direction is _____.
Nose up.
Pg. 2
What is the meaning of section force and section moment?
The forces and moment per unit span.
Pg. 2
How is section force and section moment defined in terms of notation in the book?
With a tilde ~ over the top of the variable.
Pg. 2
The resultant aerodynamic force acting on a 2D airfoil is completely specified in terms of ______. These two equivalent descriptions of the resultant aerodynamic force are related to each other through ______.
- Either life and drag or axial and normal force.
- The angle of attack.
Pg. 3
The axial force (A) is often _____ even though the angle of attack may be small.
Negative.
Pg. 4
The resultant aerodynamic force (RAF) and moment acting on a body must have the same effect as _____.
The distributed loads.
Pg. 4
The resultant moment (RM) will depend on _______.
Where the RAF is placed.
Pg. 4
What are the two special locations along the chord of special interest?
The center of pressure (xcp) and the aerodynamic center (xac).
Pg. 5
What is the definition of the center of pressure (COP)?
The point about which the moment produced by a distributed load is zero.
Pg. 5
What is the definition of the aerodynamic center (AC)?
The point about which the change in the resultant moment (RM) is invariant with respect to the angle of attack.
Pg. 5
How are derivatives annotated in the textbook?
A two-letter subscript with a comma between the two letters.
Pg. 6
True or False
The location of the center of pressure varies considerably with angle of attack for chambered airfoils.
True
Pg. 7
True or False
The location of the aerodynamic center (AC) carries very little with respect to angle of attack.
True
Pg. 7
Downard deflection of the elevator is _____.
Positive
Pg. 9
Deflection of the rudder to the left is _____.
Positive.
Pg. 9
Deflection of the rudder to the right is ____.
Negative.
Pg. 9
When is aileron deflection positive?
The right aileron is deflected down and the left aileron is deflected up (roll left).
Pg. 9
What is the Von Karman line?
The boundary between Earth’s atmosphere and space. It is the altitude where aerodynamic forces no longer provide support to maintain S&L flight.
Lecture Notes
