Principles of Flight (POF)
Principles of Flight FS 15 Klasse:AV14 Dozent:Manfrian Weiteres Lernmaterial unter: www.tinyurl.com/av14fs15
Principles of Flight FS 15 Klasse:AV14 Dozent:Manfrian Weiteres Lernmaterial unter: www.tinyurl.com/av14fs15
Define the zero lift line
Consider a wing at an angle of attack such that lift is zero. With the wing in this orientation draw a line through the trailing edge parallel to the relative wind. That is the zero lift line.
Define the absolute angle of attack
The angle between the zero-lift line and the relative wind. \(\alpha_a=\alpha+|\alpha_{L=0}|\)
For an airfoil at \(\alpha_a=0\)
the point where \(M_{cg}=0\) is called
An airplane with this characteristic about the pitching moment is
This airplane is....
In general adding a fuselage to a wing shifts the aerodynamic center ....
In general adding a fuselage to a wing shifts the aerodynamic center forward, .... the lift curve slope
In general adding a fuselage to a wing contributes a ... increment to the moment about the aerodynamic center.
Two interference effects that influence the tail aerodynamics
1. The airflow at the tail is deflected downwards by the downwash due to the finite wing
2. Because of the retarding force of skin friction and pressures drag over the wing, the airflow reaching the tail has been slowed
the tail volume ratio is ...
the ratio between a volume wich defines the position and size of the tail and a volume which charaterizes the size of the wing.
the tail setting angle \(i_t\) must be ... to balance the airplane
if the center of gravity is at the neutral point ....
the airplane is statically neutral.
if the center of gravitiy is behind the neutral point
the airplane is statically unstable
if the center of gravitiy is infront of the neutral point
the airplane is statically stable
this is the ....
static margin
Define the elevator control effectivenes
It is the slope of the curve, Lift coefficient of the tail ploted versus the elevator downward deflection angle at a constant angle of attack.
it is always positive
what is the goal of elevator deflection
to maintain the airplane trimmed at different velocitys, and different angle of attacks.
By deflecting the elevator the moment coefficient curve gets shifted to the left or to the right.
if the elevator is defelcted downwards the \(C_m vs. \alpha_a\) curve is shifted to the ....
left
if the elevator is defelcted upwards the \(C_m vs. \alpha_a\) curve is shifted to the ....
right
Definition of Pressure
Pressure is the Force perpendicular to a surface per area
Pressure at sea level \(p_s =101325 N/m^2\)
Definition of density
Density is mass contained in a volume divided by that volume
Density at Sea level \(\rho_s=1.225 kg/m^3\)
0 Grad Celsius in Kelvin
273.15
speed is a ....
scalar
velocity is a .....
vector
A flow is incompressible if
\(V< ...m/s\)
100 m/s
What is an isentropic flow
An isentropic flow is adiabatic (no heat exchange) and reversible (no friction or other dissipative effects, production of entropy)
what is adiabatic
a prozess in which no heat is added or taken away
what is a reversible process
a process in which no entropy is produced (impossible)
A flow is incompressible if:
\(V< M....\)
Mach 0.3
Draw a converging nozzle that starts with sub sonic flow and ends with supersonic flow
.
In a stream tube with M< 1.0:
to accelerate the flow the crosssection Area must ....
decrease
In a stream tube with V> M 1.0:
to accelerate the flow the crosssection Area must ....
increase
In our course we asume that the flow through a sound wave is ....
if M=1.0 the flow is....
the flow is sonic
Normal shockwave:
What changes across the shockwave
Normal shockwave:
Across the shock wave the Mach number ....
Normal showck wave:
Across the shock wave the static pressure ...
Normal shockwave:
Across the shock wave the total pressure ...
The total energy of a air molecule across a shockwave, considering insentropic flow, does ....
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Lernkarten
\({Re_x}_{cr}\) is the ...
critical Reynoldys Number. It is the Reynolds number at \(x_{cr}\) where the boundary layer becomes turbulent
\(x_{cr}\) is ...
the critical value where the boundary layer becomes turbulent
Name the two major consequences of flow separation
1. drastic loss of lift
2. major increas in drag, caused by pressure drag due to separation
Name the two sources of drag due to viscous effect
1. Skin friction
2. pressure drag due to separation
Number 1
Leading edge
2
Thickness
3?
Mean camber line
4
Trailing edge
5
Chord line
6
chord
7
camber
The straight line connecting the leading and trailing edges is the ...
chord line
The distance between the leading and the trailing edge is the ...
chord , c
The ... ist the maximum distance between the ... and the ...
(airfoil)
camber, camber line, chord line
The moment about the aerodynamic center of an airfoil is ...
The quarter chord point is for low-speed subsonic airfoils close to the ...
aerodynamic center
\(c_L\) is a function of
shape of the airfoil, angle of attack, Reynolds-Number
angle of attack is the angel between the relative wind and ...
All airfoil with positive camber have a \(\alpha_{L=0}\) .... 0
1
\({c_L}_{max}\)
2
Stall
3
\(a_0\) Lift slope
4
stalling angle of attack
5
\(a_{L=0}\) zero lift angle of attack
The Reynolds number has a big influence when the airfoil is in ...
Profiles with positive camber have a ... \(c_{m,c/4}\)
Lift of an Airfoil is always to be considered as ....
Lift per unit span
Airfoil:
The Drag varies alot with different .... because ....
Reynold Numbers, the drag of a slender aerodynamic shape is mainly skin friction drag
The center of pressure is the point where ...
Which profile is the thickest?
The Prandtl-Glauert correction
takes the effects of compressibility between 0.7> \(M_{\infty}\)>0.3 into account
The critical Mach number for a wing decreases when
thicker airfoils have a ... \(M_{crit}\) than thin ones
\(c_p\) can by definition not be ....
Wing tip vortices are formed because
The pressure at the bottom of the wing is higher then on the top. Consequently there is some tendency for the air to flow around the wing tips
As the aspect ratio is increased
induced drag is ... for an elliptical wings
the effective angle of attack \(\alpha_{eff}\) is ... than the geometric angle of attack
Consider downwash
\(\alpha-\alpha_{eff} =....\)
the lift curve slope of a .... wing is ... than that of a ... wing
the lift curve slope of a finite wing is smaller than that of a infinite wing
