Aerodynamics (AA1290) Flashcards
What is center of gravity (Cg)?
-“3 axes intersect and all weight is concentrated”
-the point where the roll, yaw, and pitch axes intersect and from which all axes movements are measured
-the point where all weight is considered to be concentrated
What is aerodynamic center (AC)?
-“changes in lift occur”
-the point along the chord line of the wing, approx. 23-27% from the leading edge, around which the wing forces act through and all changes in lift effectively occur
What is Angle of Attack?
Angle between the wing’s chord line and the relative wind
What are the 4 primary forces acting on an aircraft?
Lift, Weight, Thrust, and Drag
How does weight act on the aircraft?
Weight acts through the aircraft’s CG towards the Earth (always perpendicular to the surface regardless of attitude)
What is lift and how does it act?
-Lift opposes the downward force of weight and acts perpendicular to the flight path
-Lift can be in any direction (not always upwards) based on aircraft attitude
-Wings generate most of the lift, but the horizontal stab and fuselage also generate some
What is drag and how is it formed?
-Drag is the rearward force that opposes thrust
-Drag results from the disruption of airflow and the production of lift
What is thrust?
-thrust is the acceleration and reaction force described in Newton’s 3rd law
-forward force that opposes drag
-assume thrust acts parallel to the longitudinal axis in the T-38C
What is aerodynamic force (AF)?
the combined effect of lift and drag in a single net force
Where does aerodynamic force come from and where does it usually point?
-aerodynamic force is the result of pressure and friction distribution over the wing
-direction and size varies, but generally points up and to the rear of the aircraft
When the aircraft is in stable, unaccelerated flight, the forces are?
balanced
What happens to the 4 forces in a turn?
-Lift: is being shared in a horizontal and vertical component (which decreases the amount available to oppose weight)
-Weight: remains the same
-Drag: ultimately increases b/c AoA must be increased to compensate for the decreasing vertical lift
-Thrust: must increase proportional to the turn to overcome the additional drag
What is the only force that does not change in size or direction when a climb is initiated?
Weight
How does the 4 forces get affected in a climb?
In a stabilized climb, lift is less than weight and thrust must increase to overcome
W: weight is now not only acting downward, but has a rearward component with drag (WD)
L: lift is still equal to the downward force of weight (WL)
T: Thrust must increase to overcome the addition of Wd
The steeper the climb angle, the (more/less) lift is required to maintain balanced flight.
Less lift.
It is the thrust force that increases to support the drag portion of weight (WD) that is not being supported by lift (L = WL)
What are the two components of weight in a power-on descent?
WL and WT (the thrust component of weight)
How are the 4 forces balanced in a power-on descent?
W: 2 components; WL and WT
L: is still opposing WL
D: equals T and WT
T: MUST be less than drag
In a power-on descent, ___ must be less than ____
thrust is less than drag (b/c D = T + WT)
In a wings-level, constant airspeed climb, lift is ____ weight
less than
In the flow of incompressible fluid, the sum of static pressure and dynamic pressure is ____
constant (which is why pressure and velocity are inversely related)
What are the two key factors that the pilot can control in the lift equation?
Velocity and Angle of Attack
What is the simplified “pilot’s lift equation”?
Lift = V^2 x AoA
What is stall angle of attack?
the AoA associated with the lift limit of the wing at a given airspeed (beyond this point results in a decrease in CL)
The aircraft always stalls at the same ___ regardless of ____
AoA, regardless of airspeed