Principles of Flight Flashcards
Static Pressure?
Can be thought as the pressure exerted by the air of atmosphere itself - it is the same in all directions and surrounds a stationary object just as it surrounds a moving object.
Dynamic Pressure?
is a pressure caused by the movement of an object through the air or the flow or air past an object.
How does a pressure constant work
Static Pressure + Dynamic Pressure is a constant, in other words if dynamic pressure increases, static pressure decreases. This happens for example at the narrowest part of a venture as air moves through
Aerofoil?
Cross sectional area of a wing
The Chord line?
Straight line through the edge to the trailing edge.
The camber of an aerofoil?
Curvature.
Angle at which lift acts relative to airflow?
90 degrees.
Angle of attack?
The angle between the chord line of the aerofoil and the relative airflow.
Centre of pressure?
The point at which the force of lift appears to act. The distribution of lift changes with the angle of attack.
As the angle of attack increases?
The centre of pressure moves forward.
What is the coefficient of lift?
Measure of the lift generation properties of an aerofoil. As angle of attack increases, the coefficient of lift increases until a certain point (critical staling angle) beyond which the coefficient of lift reduces rapidly.
Coefficients of drag?
A measure of the drag generation properties of an object such as an aerofoil. (or aircraft)
Wake Turbulence?
Generated by a wing moving through the air, in particular at the wingtips where the airflow from under and over the wing surfaces meet and form a vortex.
Which type of aircraft create the most wake turbulence?
The larger, heavier and slow flying aircraft create the most wake turbulence.
Parasite drag?
Term used for drag caused by moving an object through the air
The ground effect?
This occurs when the aircraft wing is close to the surface (within a height equivalent of one wing span) ground effect modifies the airflow around the wing so that induced drag is reduced and as a result both lift and airspeed will increase, up to a certain point.
The Stall?
Occurs when smooth airflow over the wing breaks down and the airflow separates from the wing - this leads to a marked loss of lift and a significant increase in drag.
When does the stall occur?
When the wing reaches the critical angle of attack once the angle is reached the wing will stall regardless of airspeed.
Lift Augmentation: trailing edge flap?
reduces stall speed and increases both lift and drag. A wing stalls at a shallower stalling angle of attack when flaps are extended.
Lift Augmentation: Leading edge slots or slats?
re-energise airflow over the wing, and the wing stalls at steeper greater angle of attack if the wing has slots or slats.
the Boundary layer?
Layer of air closest to the surface of a moving object is the boundary layer.
where does thin Laminar boundary occurred?
leading edge of the wing where the fluid first meets the object.
Where does turbulent boundary occur?
further along the wing as the surface boundary thickens. Creates more drag, however it is less prone to separating from the surface.
Static stability?
a measure of how readily an aircraft returns towards its original attitude, following a disturbance
dynamic stability?
Measure of how easily the restoring motion caused by static stability is damped out so that the aircraft settles back at its original attitude.
positive stability?
returns aircraft to original position.
neutral stability?
disturbance gets no worse
negative stability?
disturbance increases.
differential ailerons?
going up aileron moves through a greater angle than the down-going aileron.
where are the limiting load factors?
Aircraft’s flight manual / pilots operating handbook
Flight load limits: Normal?
3.8
Flight load limits: Utility?
4.4
Flight load limits: Aerobatic?
+6
V-n envelope manoeuvring envelope?
used to set up the limiting factors and airspeeds of the aircraft.
V-a airspeed (design manoeuvring speed)
Max speed at which a full and abrupt movement of a flying control can be made without causing structural damage.
Slipstream effect?
the spiral corkscrew motion of the propeller slip stream (propwash) creates a force in the vertical tail in particular which yaws the aircraft to the left if the propeller is rotating clockwise.
Torque reaction?
The airframe will try to roll in the opposite direction to the propeller rotation, so there will be a rolling motion to the left if the propeller rotates clockwise.
Asymmetric blade effect
P-factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller, that is responsible for asymmetrical relocation of the propeller’s centre of thrust when aircraft is at a high angle of attack. creating more thrust on one side. The propeller rotates clockwise, there is yaw to the left.
gyroscopic effect?
Rotating blades create a gyroscope. Direction of the force is dependant on where the aircraft is pitched up down left or right.
equation straight and level flight?
lift = weight and thrust = drag
glide performance calculation?
lift/drag ratio. 10:1 means that the aircraft will travel 10 feet or metres horizontally for every 1 foot or metre vertically.
in a 60 degree banked turn the load factor is
2
The force that acts perpendicular to the wings in a balanced turn is?
The total lift force
Flying controls are mass balanced in order to?
prevent control flutter.
A slat or slot on the leading edge of the wing will?
re-energise the airflow over the wing’s surface, delaying airflow separation.
Yawing is a rotation about the?
Normal axis
adverse yaw can be minimised by:
Differential ailerons
The fin on an aeroplane?
Increases directional stability
The angle between the chord line of an aerofoil section and the relative airflow is the:
Angle of attack
Up to the stalling angle of attack. as the angle of attack is increased:
Coefficient of lift increases
as the stalling angle of attack is approached, where would a pilot normally expect the airflow to start separating from the wing?
From the trailing edge upper surface.
What is the most common reason for design modifications on the wing tip shape?
to reduce induced drag.
If an aircraft starts to slip towards a lowered wing, and no corrective action is made by the pilot, the most likely result is?
a spiral decent with increasing bank angle and rate of decent.
Horizontal tailplane is designed to
increase longitudinal pitch stability
aircraft is at 6000ft and glide range is 6 miles?What is ratio?
6:1
in steady climb in a single engine aircraft, the prop is rotating clockwise, slipstream effect will tend to make the aircraft:
Yaw to the lift
Indicated stall speeds are …………….. at all altitudes.
same
In a steady climb on a constant heading:
thrust is greater then drag.
To prevent flutter, the control surfaces can be fitted with?
a mass balance
In general, as the airspeed increases on an aircraft (in terms of drag)
Parasite drag increases, induced drag decreases.
The maximum coefficient of lift occurs?
at around the stalling angle of attack+, beyond which it falls sharply
Regarding airflow in the immediate vicinity of an aircraft’s wing in normal cruising flight, which of the following statements is correct?
Airflow above the wing will be faster than the free airflow
During a level, balanced turn, load factor can be defined as:
Lift divided by weight.
When an elevator is moved up, the attached simple trim tab will move:
Remain at a constant angle relative to the elevator.
An aircraft wing will stall at a fixed:
Angle of attack.
Which of the following conditions will cause an increased stall airspeed?
load factor increased, heavy icing of the wing.
if an aircraft is flying at an airspeed faster than Manoeuvring speed (Va) and full up elevator is rapidly applied, the most serious likely result is:
structural damage or failure
In relation to ground Effect, a high wing aircraft, when compared to a low wing aircraft, is most likely to:
Experience ground effect at lower hight
An aircraft is disturbed from its trimmed attitude, the aircraft then continues to oscillate at a constant rate and magnitude:
Neutral dynamic stability
roll, is rotation of the aircraft around it’s:
Longitudinal axis
To achieve the theoretical max glide range, and assuming nil wind an aircraft should be flown at:
The minimum drag airspeed.
Line is drawn through an aerofoil section, from the leading edge to the trailing edge:
chord
as the angle of attack is increased, the centre of pressure of the wing:
Moves forward.
to remain in straight and level flight and in trim as airspeed increase, it is the most likely that:
the elevator will be deflected down further.
when the rudder pedals are operated in-flight, the initial effect is:
yaw around the vertical (normal) axis
In general terms Induced drag……… with …….. airspeed?
increases with decreasing airspeed
the secondary effect of rudder is
Roll in the same direction as yaw
Compared with a zero flap setting, the use of trailing edge flap leads to a:
Reduced stalling angle of attack
in level flight an aircraft stalls at 60 knots. In 60 degrees angle of bank turn what would you expect the stalling speed to be.
85knt
If aircraft is disturbed from its trimmed attitude, a tendency to return back towards its original attitude is measure of the aircraft’s
static stability
term that describes aerofoils curvature section?
camber
The limiting airspeed known Va represents:
The max speed at which it is safe to violently operate aerofoils without causing structural damage
As air flows through the venturi?
the minimum static pressure occurs at the narrowest section.
For conventional light aircraft wing, at around 4 degrees angle of attack the wing can be expected to achieve
the max lift/drag ratio
What is true about a fixed pitch propeller?
blade or pitch angle is the angle between the blade chord line and the plane of rotation,
Blade angle reduced from root to tip
Ice on rotating propeller blades will reduce efficiency and may cause vibration.
What is most likely to occur as a result of an aircraft on take-off climbing out of ‘ground effect’
An increase in induced drag, reduction in lift
Normal limiting load factor for operation in the utility category is?
4.4
Which way is a propeller spinning if the effect if slipstream and asymmetric blade effect will cause yaw to the left?
clockwise
What conditions would reduce stall airspeed?
Altitude and flap setting are reduced
With reference to an aircraft wing, what is washout?
An increasing angle of incidence from the wingtip to the wing root.
A Frise aileron will:
increase the drag of the descending wing.
