POF
T1
T1
WIth a turbofan ngines have no critical engine except the outher ones at a 4-engined aeroplane. By a crosswind T/O which one is the critical one?
the engine one on the windward side is the critical engine
3 options how to fly after an engine failure (small aircraft)
1.=> keeping the wings level => Rudder + aileron towards good engine=> The ball is centered => sideslip greates a large amount of drag
2. bank towards the good engine => ONLY AILERON => Rudder neutral => sideslip greates a large amount of drag
3. slighz bank and moderate rudder towards goo engine => straight ahead with minimum drag => no sideslip
=> minimum drag, no sideslip ====> the ball of the turn and slip indicator is not centered, but there is no sideslop => Bank angle max. 5 degrees
how to fly after engine failure big aircraft
a) larger power surplus
b) jet aeroplanes is linked with spoiler deflection which increases drag
=> then rudder is applied to teh side of teh operating engine which keeps aileron input at almost zero with the spoilers retracted => sideslip towards the side with the dad engine
VMCG
Minimum controlled speed on the ground => Flaps T/O
VMCA
Minimum controlled speed in the air => Flaps T/O, Gear up
VMCL
Minimum controlled speed for landing
Why is an aft, why a forward C.G. limit established?
aft: stability fwd: controllability
The static margin is equal to the distane between:
the CG and the NP
When the CG is close to the forward limit:
very hight stick forces are require for pitch because the aircraft is very stable
Dihedral angle is:
the upward and outward inclination of the main planes to the horizontal datum
helix angle
angle between the rotational speed and relative speed
pitch angle propeller
Angle between rotational speed and chord line
reference point propeller
where the resultant thrust force of a bald acts
Geometric pitch
distance a propeller should advance in one revolution
propeller: feather position
lowest drag for the aeroplane => 90 degrees => used on a failed engine of a multi-engine aeroplane to keep draw as slow as possible
propeller: Cruise pitch
between coarse (high pitch) and fine (low pitch)
propeller: Ground fine
the thrust is approximately zero => aeroplane is not moving
propeller: full reverse
max reverse thrust
propeller: Why is the pitch angle high at the root and low at the blade tip ?
to maintain the optimum AOA from the blade root to the blade tip
If teh aircraft is properöy loaded the CG, the neutral point and the manouvre point will be in the order given, forward to aft?
CG, neutral point, manoeuvre point
accelerate
beschleunigen
equidistant
gleich weit entfernt
obtain
erhalten
increase
zunehmen
dynamischer Druck
1/2 * p(Roh) * v^2
Lift in Newton
dynamischer Druck (1/2 * Roh * v^2) * s (Fläche) * CI (Koeffizient)
Kraft F in N
influence that causes a body to undergo a certain change in movement. ⇒ F (N) = m(kg)* a(m/s^2)
Arbeit (W)
Work (W)= Force x Distance Unit = Joule (J)
Leistung (P)
Power = Force x Velocity Unit = Watt
Gravitationskraft:
9.81 m/sec2
shape of an airfoil
Profil eines Flügels
Vektor:
Vektor: Grösse, welche auch durch ihre Richtung bestimmt ist
Weight:
Weight: the gravitational force onto a body. ⇒ In N
Mass:
Mass: the resistance that a body exhibits in response to a force which acce-lebrates or slows down the body Masse ⇒ Materie in a body
Acceleration
Acceleration: The rate at which the speed of an object changes = Beschleunigung ⇒ a = F / m
Coanda Effekt:
Coanda Effekt: ein strömendes Fluid mit Kontakt mit einer gebogenen Ober-fläche hat die Neigung der Biegung der Oberfläche zu folgen
Dichte (p) =
Masse pro Volumen = Mit zunehmender Höhe = Dichte nimmt ab è Hohe Temperatur + hoher Airport = selten gut p (N/m2) = p (kg/m3) * Rair * T(K) Rair = 287
atmospheric pressure =
weight of air column / area
totaler Druck
• Totaler Druck (pt): statischer (q)+ dynamischer Druck (ps)
Das Trägheitsgesetz = Gerade aus fliegen
Jeder Körper verharrt in Ruhe oder behält eine gleichförmige, geradlinige Bewegung bei, solange keine äussere Kraft auf ihn einwirkt, oder die äusse-ren Kräfte im Gleichgewicht sind d.h. sich gegenseitig aufheben
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Lernkarten
Variable Pitch and fixed pitch Propeller; Wann ist die Efficiency gleich, wo nicht?
1. At the design point = Efficiency same 2. AT lower or higher air speed: Variable pitch propeller Efficiency is higher
advantage of fixed pitch propeller
Lower weight and less expensive
On which station teh propeller produce the lowest drag ?
feather position => 90 Grad
Why is the propeller blade twisted?
different relative wind directions requires twist to achieve the same AOA
4 propeller effects
1. Torque reaction
2. Corkscrew effect or slipstream effect
3. Gyroscopic abtion of the propeller
4. Asymmetric thrust of the propeller
1. Torque reaction of the propeller
=> Actio = reactio
Propeller treis to rotate teh airplane in the opposite direction
=> can be eliminated by using: a) counter-roatating propeller (left propeller left, right P right) b)contra-rotatoîng ( 2 Propeller an der selben Achse wo in unterschiedlicher Richtungen drehen)
1. Torque reaction of the propeller im Flug => Compensation in flight?
=> Left wing has to create more lift
a) different Angle of Incident
b) different size
c) different aileron deflection
2. Corkscrew effect or slipstream effect of the propeller => Wann ist diese am stärksten? == >Result?
air stream behind the propeller into a corkscrew-kind of rotation => Am stärksten wenn: a) when the forward speed is low b) RPM is high ==> Yaw to the left and a small roll moment to the right
3. Gyroscopic abtion of the propeller
The resulting force temporarily pushes ahed at 90 Grad in the direction of the rotation and in the direction of the application
4. Asymmetric thrust of the propeller => P-factor
=> Hight AOA sonst passiert nichts, weil sonst the propeller blade isn't moving downwards
=> Führt dazu: a higher Thrust bei den Blades, welche nach unten laufen (rechtsdrehen die Blades wenn sie links sind (von Vorne))
=> a asymmetric thrust => yaw to the left
Which aeroplanes have a large torque effect
light weight aeroplanes with high torque engines
How can we the slipstream effect compensated in cruise flight?
No compensation by pilot: aeroplane design is compensating
3. Gyroscopic abtion of the propeller => Putching up: ?
bild
3. Gyroscopic abtion of the propeller => ywaing to teh left ==> ?
Bild
3. Gyroscopic abtion of the propeller => ywaing to teh left ==> ?
Bild
The angle of attack of a fixed pitch propeller blade increases when:
RPM increases and forward velocity decreases.
Asymmetric propeller blade effect is mainly induced by:
the inclination (Neigung) of the propeller axis to the relative airflow.
Force
Unit: N (F) force is an influence that causes a body to undergo a certain change in movement, direction or geometric properties
weight
the gravitational force onto a body => weight = mass x g
Mass
The resistance that a body exhibits in response to a force which accelerates or slows down the body.
Newton
m x a = F
Density
Masse per Volume
atmospheric pressure
weight of air column / area
statischer Druck
potential energy and acts in all directions
dynamischer Druck
acts only in the direction of the flow and expresses the kinetic energy P= air density v= m/s^2 statischer Druck in Pa
=>\(x = {1\over 2} * p * v^2 \)
Bernoulli says that an ideal and incompressible airflow is based on the assumption that
the total energy of a flow remains constant along a stream tube => v * A = constant !!!
hPa in Pa
700 hPa = 70'000 Pa
convergence
zusammenlaufen
low speed aerofoil => camber and wehere?
4% (4/100 of the chord length) and located 40% aft the leading edge
How might habe a negative camber?
the stabilizer might have a negative camber
Angle of Incident is a ....
Angle of Incident is a constant for a specific airplane ==> chosen that the airplane is horizontally aligned during cruise flight
Angle between the relative airflow and the horizon is the
climb angle
where occurs the min. static pressure on a aerofoil?
at the point where the streamlines are closest together
How generates the lift?
difference in static pressure between bottom and upper surfaces creates the aerodynamic forces.
The critical angle of attack at which a given aircraft stalls is dependent on the
design of the wing
In general terms lift is a result of
A reduction of pressure over the wing.
The lift force, acting on an aerofoil
is mainly caused by suction on the upperside of the aerofoil.
When an aeroplane is flying at an airspeed which is 1.3 times its basic stalling speed, the coefficient of lift as a percentage of the maximum lift coefficient (CLmax) would be
59%.
Dynamic pressure is
If density is kept constant, the dynamic pressure increases proportionally with
The square of the velocity.
