Aero 2: Stalls & Drag Flashcards
Total Drag
The sum of parasite drag and induced drag
Parasite Drag
All drag not associated with the production of lift.
Form Drag
Drag resulting from the airflow separation over a surface and the low pressure wake created
Is a component of Parasite Drag
Friction Drag
Drag arising from friction forces at the surface of an aircraft, due to the viscosity of the air
Is a component of Parasite Drag
Induced Drag
That portion of total drag resulting from the production of lift
Boundary Layer
The layer of airflow over the surface of an airfoil, which shows local airflow retardation caused by viscosity
Stall
A condition of flight in which an increase in AOA will result in a decrease in the coefficient of lift
Spin
An asymmetrical aggravated stall resulting in autorotation
Drag
The component of the aerodynamic force that is parallel to relative wind and acts in the same direction
What factors affect induced drag?
Lift
Weight
Air density
Velocity
Wing span
How can induced drag be minimized?
(1) Increasing density, velocity, or wingspan
(2) Install devices to impede airflow around the wingtip (spanwise airflow) such as winglets, missile rails, and wingtip tanks
L/Dᴍᴀx
The greatest ratio of lift to drag
L/Dᴍᴀx AOA
The most efficient AOA for that airfoil
Also known as max range
How does velocity change total drag?
As airspeed decreases to stalling speed, total drag increases due to induced drag increase.
As airspeed increases to terminal airspeed/velocity, total drag increases due to parasite drag increase.
On the total drag curve, which type of drag dominates at lower airspeeds?
Induced drag
On the total drag curve, which type of drag dominates at higher airspeeds?
Parasite drag
How can form drag be reduced?
By creating a more streamlined object
Form drag is easier to reduce than friction drag
How can friction drag be reduced?
(1) By using a glossy, flat finish on plane surfaces
(2) By removing protruding heads, any surface roughness, and irregularities
What types of flow are present with the boundary layer?
Laminar flow and turbulent flow
Laminar flow
Boundary layer airflow that is smooth/ unbroken (creates little friction)
Turbulent flow
Boundary layer airflow characterized by turbulent, unsteady airflow (creates more friction)
Which boundary airflow sticks to the boundary layer? Which does not?
Turbulent airflow sticks to the boundary layer. Laminar airflow separates from the boundary layer easily.
What is the difference between speeds for a power-on stall and a power-off stall?
Power-off stall speeds are higher because the engines are at idle
Higher stall speed means it’s easier to stall at a high speed (not good)
What must be present for an aircraft to spin?
(1) Aircraft must be stalled
(2) Yaw present
What is the relationship between the wings during a spin?
The inside wing is more stalled than the outside wing (due to higher AOA).
This causes the inside wing to have more drag than the outside wing.
How do you recover from a spin?
(1) Correct the stall by reducing excessive AOA
(2) Correct the yaw input by applying opposite rudder
PARE Procedure
What causes induced drag?
It is caused by air downwash that is created from wingtip vortices from spanwise airflow over the wings
Induced Drag Formula
Di = kL² / (ρV²b²)
How thick is the boundary layer?
About 1mm thick
Stall Equation
Vₛ= sqrt(2W/ρSCₗₘₐₓ)
