AEROLAB FINALS Flashcards
4 forces of flight
LIFT
DRAG
WEIGHT
THRUST
An airplane like all bodies have
mass, with the aicraft positioned in the
ground, it has only the force of the
acceleration due to gravity acting upon it.
Weight
Before an airplane can leave the
ground and fly the force “weight: must be
surpassed or balanced by a force which
acts upwards called
Lift
To generate lift, the airplane must
be propelled forward through air by a force
called thrust. Provided by its engine(s).
Thrust
From the very moment the airplane
moves forward, the air pushing against the aircraft relatively resists the motion, and is
called
Drag
force that resists the forward motion of an object
moving through a medium.
Drag
Forms of drag
PRASITE DRAG
INDUCED DRAG
is comprised of all the forces that work to
slow an aircraft’s movement.
it is the drag that is not
associated with the production of lift.
Parasite Drag
is an inevitable
consequence of lift and is produced by the passage
of an airfoil through the air. This only proves that
there is no system that does work in a mechanical
sense can be 100% efficient.
induced drag
This
type of drag is the aerodynamic
resistance due to the contact of moving air with the surface of an object, and in this particular
case that object would be an aircraft.
Skin Friction Drag
This layer of air extending from the surface (in
direct contact) to the point where no viscous effect is noticeable is known as the
Boundary Layer
The position of the transition point is dependent
upon a number of factors. Some of these factors are:
Surface Condition
Adverse Pressure GRadient
this factor is when The thin laminar layer is extremely sensitive to surface irregularities. Any roughness on the skin of a leading portion of an aircraft will cause transition to
turbulence at that point and the thickening, turbulent boundary layer will spread out
fanwise down-stream causing a marked increase in skin friction drag.
Surface Condition
in this factor A laminar layer cannot exist when pressure is rising in the
direction of the flow. On a curved surface, such as an airfoil, the transition point is
usually at, or near to the point of maximum thickness. Because of the adverse pressure
gradient existing on a curved surface the transition point will be further forward than if
the surface was flat.
Adverse Pressure Gradient
is the next portion of the parasite drag, generated by the aircraft due to its
shape and the airflow around it. When the air has to separate to move around a moving
aircraft and its components, it eventually rejoins after passing the body.
Form Drag
Form drag is the easiest to reduce when designing an aircraft, as the solution
for this conundrum is to just ______ as many parts as possible.
Sream Line
is
the measure of streamlining.
Streamlining
is the combination of skin friction and form drag.
Profile Drag
drag that is observed when two surfaces meet at
perpendicular angles.
Interference Drag
used to reduce interference drag
Fairings
Parasite drag formula
D= 1/2 Rho V^2 Cd S
Factors Affecting Parasite Drag
Indicated Airspeed
Configuration
Airframe Contamination
If the Indicated Air Speed is doubled the parasite drag will be ____ times greater,
Fourtimes
,however if it is halved, the value of parasite drag will be ____
of its previous value.
Quarter
Parasite drag varies directly in proportion to the frontal area presented to
the airflow, also known as the ______
Parasite Area
is an inherent component, a rather undesirable by-product of
lift.
Induced Drag
The lower the Indicated Air Speed
(IAS), the higher the Angle of Attack (α
- the stronger the vortices. The stronger the vortices
repeat: The lower the Indicated Air Speed
(IAS), the higher the Angle of Attack (α
- the stronger the vortices. The stronger the vortices
the stronger the vortices. The stronger the vortices - the greater the induced drag.
repeat: the stronger the vortices. The stronger the vortices - the greater the induced drag.
Factors that affect induced Drag
Speed of the aircraft
size of the lift force
aspect ratio of the wing
Coefficient of induced drag formula
Cdi= Cl^2/ pi AR e
where AR = b^2 / S
. Factors to consider if one decides to continue the increase of Aspect
Ratio
Excessive Wind bending Moment
Reduced Rate of Roll
Reduced Ground Clearance in roll during take off
Methods of reducing induces drag
Wing end plate
Tip tanks
Winglet
Shape of the winglet
