Theory Of Flight Flashcards
Laminar Flows
This occurs when air moves in a smooth,parallel layers with minimal mixing,resulting in low velocity and orderly motion.It reduces drag over an airflow,enhancing fuel efficiently and allowing for higher crusing speeds.Aircraft wings are often designed to maximised laminar flows,but it is sensitive to surface irregularities and higher speeds,which can lead to a transition to turbulent flow.
Turbulent Flow
In contrast,turbulent flow is chaotic,characterised by eddies and mixing of air layers,typically at higher velocities or when the Reynolds number exceed a critical threshold.This type of flows increases drag due to higher energy dissipation,requiring more thrust and reducing efficiency.However,it can improve lift by developing flow separation under certain conditions.Excesssive turbulence can lead to instability and increased fuel consumption.
Relative flow
Relative flow refers to the direction and speed of airflow in relation to an aircraft motion, which is essential for understanding aerodynamic forces like lift and drag.It is always parallel and opposite to the aircraft flight path and helps determine the wings angle of attack.The angle of between the wings chordline and the oncoming airflow, lift acts perpendicular to this airflow, changing with the aircraft orientation Understanding Relative airflow is crucial for pilots to effectively control the aircraft and maintain stable flight conditions.
Stagnation
Stagnation in aerodynamic refers to the point where airflow velocity drops to zero due to an objects,like an airfoil.This Stagnation point is vital as it affects air movement around the wing,influencing lift and stall behaviour.
1.Lift Generation
The stagnation point shifts with angle of attack,impacting lift.At high angles,it can lead to airflow separation and potential stalling.
2.Stall Behaviour
Stall strip help manage stall by promoting early airflow separation near the wing root,providing a warning before a full stall occurs.
3.Icing
The stagnation point is prone to ice formation in Icing conditions, particularly at higher angle of attack.
Downwash and Upwash
Downwash is the downward deflection of air behind an aircraft wing,essentially for generating lift.It occur due to the pressure differences created as airflow over and under the wings,increasing the angle of attack and inducing drag,which can adversely affect lift.
The term upwash is not recognised in aerodynamic, however refers to the upward air deflection in front of the wing,contributing to lift,understanding both upwash and downwash is important for comprehending airflow around an aircraft wing.
Vortices
Vortices in aviation are circular patterns of rotating air formerly primarily at the wingtip due to lift generation.These wing tip Vortices arises from the pressure differences between the wings upper and lower pressure and creating a helical motion.Vorticles contribute to induced drags,a major component of total drag and lead to downwash. The downward deflection of air the wing.Their strength is influenced by factors such as wing speeds,lift and wing design.
Specify the aerodynamic effects of ice,snow and frost on an aeroplane both on the ground and in flight?
In Flight
1.Lift Reduction
These contaminants can decrease lift up to 30%,impairing the wing performance.
2.Drag Increase
Drag may rise by 40%,leading to higher fuel consumption and diminished performance.
3.Stall Characteristics
Increased stall speed and buffet complicate control.
On Ground
1.Control Surface Impairment
Ice can jam control surfaces hindering manuerablity.
2,Engine Performance
Ice ingestion can damage engines,causing vibration and reduces thrust.
3.Runaway Visibility
Frost on windshield can obscure Visibility during critical flight phases
4.Instrument Malfunction
Ice on pitot-static ports disrupt instrument reading.
5.Ground handling
Ice creates slippery surfaces,impacting safety.
De-icing is essential to mitigate these effects for safe flight operations.
Describe the flat plate effects on an objects in an airstream?
A flat plate in an airstream generates minimal lift and significant drag
1.Drag
The flat plate has a high drag coefficient of about 1.28due to its shape,which disrupt airflow and creates turbulence, unlike a streamlined airflow with a Cd of approximately 0.045.
2.Flow Separation
Airflow around the edges of the flat plate,causing flow separation that increases drag and turbulence.
3.Lack of lift
The plate does not create a significantly pressure between its upper and lower surfaces,resulting lift.
Specify the effects of changes
Angle of attack on the pressure distribution around an aerofoil.
Changing the angle of attack of an aerofoil significantly impact pressure distribution. An increased angle generally enhances lift by creating a larger pressure differences between the upper and lower surfaces, raising lower surface pressure and lowering upper surface pressure, which also increases induced drag.As the angle increases, flows over the surface accelerate, resulting in a lower-pressure region that aids lift Generation.However,beyond a certain angle(around 12 to 17 degrees) flows separation can occur leading to stall,which causes a sudden loss of lift and notable rise in drag.
B.Angle of attack on centre of pressure movement?
The movement of the centre of pressure in response to changes in the angle of attack varies by airflow type.For symmetric airfoils,the COP remains stable at about 25% of the chord length from the leading edges,regardless of the angle of attack, as long as the flows stay attached.In cambered airfoils,the COP shifts forward with increasing angle of attack, meaning the quarter-chord point at higher angles and influenced by camber at lower angles.For reflex-cambered airfoils,the COP moves forward with decreasing angle of attack, possibly exceeding the quarter-chord point.The movement of the COP affects aircraft stability, and the aerodynamic centre play a role in mitigating these effects.These airflow significantly influences the COP location at various angle of attack
C.Fitness Ratio
The term finesses ratio is more relevant to streamlined bodies like fuselage than to airfoils. However, when considering it interm of airfoils thickness to chord ration,changes can impact aerodynamic performance.
D.Increased thickness /Chord Ratio
Leads to higher drag due to thickness profile that disrupt airflow,but can enhance structure benefits and stall characteristics by delaying flow separation.
The shape of an airflow is crucial for maximising lift and minimising drag,typically featuring a curved upper surfaces and a flatter lower surface,with design varying for subsonic,transonic,or supersonic flight.For instance subsonic airfoils have a rounded leading edge,while supersonic are more angular.
The aspect ratios,defined as the ratio of a wing span to its chord length,play a significantly role in performance.A higher aspect ratios means a longer,narrower wing,which reduces drag and enhances efficiency at lower speeds.Airfoil with higher aspect ratios behaves more like two-dimensional flows,thereby minimising wingtip vortex effects.
Describe the relationship between lift,weight, thrust and drag and the factors affecting these relationship?
The relationship between lift,weight, thrust and drag is essential for understanding aircraft dynamic.
Key force in Flight
1.Lift is the upward force generated by the airfoils as air flows over and under its surface,acting perpendicular to the relative wing.
2.Weight
The downward force due to gravity,which must be countered by lift for level flight.
3.Thrust.
The forward force from engine or propeller that must overcomes drag to move the aircraft forward.Insteady flight,thrust equal drag.
4.Drag
The resistance forces opposing thrust,caused by airflow disruption around the aircraft, influenced by airspeed,airfoil shape,and surface roughness.
Factors Affecting Relationship
1.Angle of Attack
The angle between the wings chordline and the airflows,significantly impact lift and drag
2.Airspeed
Increased speed enhances lift due to higher airflow velocity over the wing.
3.Airfoil shape(camber)
The curvature of the airfoil affects airflows,influencing lift and drag.
4.Surfaces Roughness
The condition of the airfoil surface can increaes drag by dissrupting smooth airflows.
5. Altitude
Changes in air density with altitude affects lift and thrust,requiring operational adjustments.
In summary,stable flight requires lift to equals weight and thrust to equal drag,with pilots managing those relationships through adjustments in angle of attack speed and other factors.
Chord and Chordline
The chord and chordline are essential aerodynamics concepts that significantly affects an aircraft flight characteristics.The chord is the straight line connecting the leading and trailing edges of an airfoils,with its length varying along its wingspan-typically longer at the root than at the tip.The chord line is imaginary line alone the chord,serving as a reference for measuring aerodynamic parameters like the angle of attack, which is the angle between the chord line and relative wind.
The angle of attack directly influences lift generation,as AOA increases,lift increases until a critical point leads to stall.Higher AOA also increases drag,while the shape of the airfoil and the chord length affect drag force.The centre of pressure shift with change in AOA,impacting stability and control.The interaction between lift and centre of gravity determines pitch stability, with proper CG placement ensuring balanced flight.
Mean Aerodynamic chord
Mean Aerodynamic Chord is a critical concept in aerodynamic concept in aerodynamic,concerning and the design and of the stability of the wing.It represents the average chord length of a wing,that is typical tapered and swept,providing a simplified model to analyse aerodynamic properties.
Interacted with Force
1.Lift
Generated by the wing,lift acts perpendicular to the relative wing and influenced by the factors like airspeed,wingarea,and angle of attack.The centre of lift typically align MAC,affecting stability and control.
2.Weight
The gravitational force acting down must be balanced by the lift for level flight.The distribution of weight relative to the MAC pitch impact stability,if CG is forward of MAC,it creates a nose down moments,enhancing stability.
3.Thrust and Drag
Thrust propel the aircraft forward while drag oppose this moments.
For Stable flight,thrust must equal to drag.
Effects on Flight Characteristics
1.Stablity
A well-postioned CG relative to MAG ensure stable flight.If CG moves too far forward or aft of MAG,it can lead to undesirable pitching moments-causing a nose dive or excessive climb.
2.Control
Drag Coefficient
The drag coefficient is essential for understanding aerodynamic drag force on an aircraft, significantly affecting its flight characteristics.Drag opposes an aircraft motion and consist of several components.
1.Component Drag
Results from air viscosity over the aircraft surface.
2.Presurre Drag.
Caused by pressure differences due to the aircraft shape and flow separation
3.Induced Drag
Linked to lift generation,it increases with lift and is mainly due to vortices at the wingtips.
4.Aerodynamic Efficiency
The lift to drag ratio indicates an aircraft aerodynamic Efficiency.A higher L/D ratio signifies better performance and fuel economy during cruise flight.
5.Mininum Drag Speed
There is a specific speed where mininum drag occurs.Flight below this speed increases induced drag,while flying above it raises profile drag.
6.Performance during flight phases
Managing drag is crucial during takeoff and landing to avoid stalling due to higher induced drag at lower speed.At cruising speeds,minimising profile drag is vital for fuel efficiency.
In summary,understanding the drag coefficient and its interaction with aerodynamic force is crucial for optimizing flight performance, fuel efficiency and safety throughout different flight phases.
Axes of an Aeroplane(Longitudinal,lateral,Vertical)
1.Longitudinal Axis(Rolls)
This axes runs from the nose to the tail,rotation around it,known as roll,involves one wing rising while the other descends, altering the bank angle.Ailerons control will by changing lift distribution,exchanging manuerabliity during turns by potentially loads factors on the wings.
2.Lateral Axis(Pitch)
Running from wingtip to wingtip,rotation around this Axis is called pitch.A positive pitch raise the nose and lowers the tails,controlled by elevators on the horizontal stabilisers.Pitch affects altitude and climbs rates,excessive pitch can lead to stall,while insufficient pitch may hinder optimal climb.
3.Vertical Axis(Yaw)
This Axis runs vertically through the centre of gravity. Rotation around it is termed yaw moving the nose to the right.The rudder controls yaws,directing aircraft nose left or right.Yawing is critical for coordinating turns,but excessive yaw can cause adverse yaw,complicating maneuvers.
Define the Centrifugal and Centripetal force?
Centripetal force-This real force acts towards the centre of a circular path and is generated by the horizontal component of lift when the airplane banks to turn,keeping it on its curved trajectory.While Centrifugal force-This is a fictitious force that appears to act outwards from the centre of rotation due to inertia.It describes the sensation experienced by pilots and passengers during turns but is not real force in an inertia frame of reference.
Gravitational Force
In the context of an aeroplane in flight,gravitational force or weight,is a downward force that pulls aircraft towards the earth centre.It is one of the four primary forces acting on an aeroplane along with thrust,drag,and lift.The magnitude of this force depends on the mass of the aircraft,including its structure,fuel and payload.To counteract gravity and maintain flight,an airplane must generate sufficient lift,which is an upward force perpendicular to the direct of the motion.
Define the Sideslip as they relate to an aeroplane in flight?
In aerodynamics,a sideslip is an intention manuers where an aircraft moves sideways relative to its direction of motion,while maintaining its heading.This is achieved by banking into the wind and using opposite rudder input to prevent turning.The sideslip is commonly used during crosswind landings to keep the aircraft aligned with the runaway centreline,ensuring that the nose points in the same direction as the track over the ground.The sideslip angle measures the deviation of the aircraft centreline from the relative wing direction.
Skidding
In aviation,a skidding turn is an uncoordinated flight manuers where the aircraft’s nose is yawned towards the inside of the turn.This occurs when too much rudder is applied relative to the bank angle,causing the aircraft to slide sideways aways from the centre of the turn.The centrifugal force exceeds the horizontal component of lift,leading to a lateral movement outward from the turn.Skidding turns are considered dangerous because they can leads to a loss of control and increases the risks of entering a span,especially if the aircraft stalls.
Define the wing loading as they relate to an aeroplane in flight?
Wing loading is a measure in aviation that quantifies the weight an aircraft wing must support per unit area.It is calculated by dividing the total weight of the aircraft.(including fuel,passengers,cargo )by the total wing area,and is typically expressed in kilograms per square meter or pounds per square foot.
Specify the effects on wing loading and stalling speed of change in Angle of attack?
Wing Loading
1.Increase wing load
As the bank angle increases,the lift require to maintain altitude and perform the turn also increases.This results in higher wing loading because the aircraft must generate more lift to counteract both its weight and the centripetal force needed to turn.
2.Load factors.
The load factors increases with angle bank,which is a measure of the apparent weight or the force the wing must support.This is calculated using the formula.L=nW,where L is lift,and W is weight.
Stall Speed
Stall speed increases.The stall speed increases with bank angles due to the increased load factors.The relationships is given by Vst=Vs.
Bank and stall speed.For example,at 45degress bank,the stall speed is about 19% higher than in straight and level flight,and is 60 degrees,it is about 41% higher.
Practical Implications
1.Increased drag.Higher bank angle also increase drag,requiring more power to maintain airspeed.
2.Pilot Consideration.
Pilots must be aware of these change to avoids stall,especially in steep turns or when manuersability at low speed.
Specify the effects on wing loading and stalling speed of changes in thrust,weight, aerodynamic resultant?
Increases in wing loading
Thrust
While increasing thrust does not directly wing loading (the ratio of weight to wing areas),it allows for higher speeds,necessitating adjustment in the wings angle of attack to maintain lift.Increases thrust can also reduced the likelihood of stalling by boosting airspeed.
Weight.
An increase in weight raises wing loading,leading to higher stalling speeds and decreased manuersability.A heavier aircraft requires a greater angle of attack to generate lift,further increasing stalling speed.
Aerodynamic Resultant (lift and Drag).The aerodynamics Resultant influences lift generation. Higher lift demands,such as during turns,increases the effective weight on the wings,raising stalling speed.Additionally changes in lift and drag can affect stalling by modifying the wings angle of attack and lift coefficient.
Increased can lower airspeed,heightening the risk of stalling. Overall,thrust and weight can simultaneously impact stalling speed,while wing loading also plays a crucial role in manuersability.
Specify the effects of Ground speed and relate them to aeroplane?
Ground speed in aviation refers to the speed of an aircraft relative to earth surface,crucial for navigation and flight planning.It is calculated by adding the wind speed component in the direction of flight to the aircraft true airspeed.Ground speed is essential for determining flight duration and route planning,as it accounts for wind effects such as headwinds and tailwinds.
In airplane operations,ground speed is distinct for airspeed,which measure speed relative to the surrounding air mass.Understanding ground speed helps pilot manage fuel,select optimal routes and ensure safety flight operations.
Define true air speed and relate them to aeroplane operations?
True air speed is the speed of an aircraft relative to the air it is flying through,unadjusted for wind effects.It is calculated by correcting indicated Airspeed (IAS) for altitude and temperature variations,providing a more acurate measure of an aircraft speed through the air masses.
In airplane operations,TAS is crucial
1.Navigation..Acurate flight planning and route optimisation.
2.Performance Calculation..Determining fuel efficiency and flight duration.
3.Safety..Ensuring safe operation from other aircraft and obstacle.
4.Efficency..Optimisation flight paths to minimise fuel consumption and maximise speed over ground when combined with wing factors.
Define indicated air speed and related them to aeroplane operations?
Indicated Airspeed speed is the speed of an aircraft shown on its speed indicator,which measures the dynamics pressure differences between the pitot and static pressure. IAS is crucial in airplane operations for several reasons.
1.Flight Control-IAS is used for critical flight manuers like takeoff,landings,and stall speed as these speed remain constant regardless of altitude or temperature.
3.Safety IAS is essential for maintaining safe flight regimes,such as adhering to speed limits below certain altitude.
2.Performance Monitoring-It serves as a primary reference for flight performance monitoring and operational decision making.
However, IAS must be corrected for altitude and temperature to obtain True Airspeed (TAS)which reflects,the aircraft actual speed through the air.
