Theory Of Flight Flashcards
(16 cards)
Describe airflow in relation to a body at rest or in motion?
When air moves past a stationary objects, the airflows interacts with the surface,creating pressure variation.
The Bernoulli’s principles explain that faster airflow over certain regions(the curved surface of an aerofoil )results in lower pressure,while slower airflows corresponds to higher pressure.
Define and explain Airflow over an aerofoil and around a fuselage structure?
Mechanics of lift Generation
1.As airflows over an aerofoil,it splits into two streams.One over the curved upper surface and one under the flatter lower surface.
2.The curved upper surface causes the air to accelerate,reducing(Bernoulli’s principles),while the lower surface experience slower airflow and higher pressure.The pressure differences generates lifts.
3.The angle of attack(angles between the chord lines of the wing and the oncoming airflow)influences the lift by a altering pressure distribution.
Airflows Around a Fuselage
1.Streamlining
The fuselage is designed to minimise drag by allow smooth airflows around it.A streamlined shape reduced pressure drag caused flow separation.
2.Presurre Distribution
Airflows accelerate over the curved top of the fuselage,creating a slightly pressure drop while slower airflows belows maintain higher pressure.
3.Interferences Effects
The interaction between wing and fuselage airflows can cause turbulence or drag,which designers aims to minimise for efficiency.
In summary,both aerofoil and fuselage design aim to optimise for lift generation (aerofoil)and drag reduction (fuselage)ensuring efficient flight performance.
Define and explain Free stream Flow as they affect aeroplane in flight?
Free stream flows refers to the undistributed airflow from an objects,such as aeroplane,where the velocity and pressure constant.
Effects on Airplane in Flight
1.Lift Generation
Free steam flows interacts with the aircraft wing.According to Bernoulli’s principles,as air flows faster over the curved top of the wing,pressure decrease, creating lift to counteract gravity.
2.Drag Force
The free-stream velocity also determines drag,which opposes motion.Engineer design wings and fuselage to minimise drag for efficiency.
Define and explain Laminar and Turbulent flows?
Laminar flows is smooth and orderly,within air moving in parallel layers without significant mixing or disturbance
Effects on Aircraft
a)Drag Reduction-Laiminar flows reduces skin friction drag,improving fuel efficiently and performance.
b)Stability-It provides a predictable aerodynamic environment,aiding in smoother flight
c)Limitation-Laminar flows is unstable and can transition to turbulance due to surface roughness to high Reynolds numbers.
Define and Explain Boundary layer as they affect an aeroplane in flight?
Boundary layers is a thin layer of air in contact with an aircraft surface such as its wings or fuselage,where the effects of viscosity are significant.It play a critical role in aerodynamic by influencing drag,lift and overall flight performance.
Effects in Flight
1.Drag
The Boundary layer contributes to skin friction drag,particularly in high-speed flight where it can account for up to half of total drag.
2.Lift
Flows separation in the boundary layers can reduced lift and increases drag,especially at high angles of attack,leading to stall conditions.
3.Flow separation
Adverse pressure gradient can cause the boundary layers to detach,disruption smooth airflows and degrading performance
Define and explain Relative flow as they affect an aeroplane in flight?
Relative flow is the velocity of the air Relative to the aircraft.It is the airflow that the aircraft encounters as it moves through the air.
Summary of Relative flow effects
1.Lift Generation-Lift is created by deflecting Relative airflow downward over the wing.
2.Drag Force-Drag is proportional to the square of Relative velocity at high speed.
3.Angle of attack-AOA affects lift production and is influenced by Relative flow.
4.Control Surface Effectiveness-Control surfaces rely on Relative airflow for Effectiveness.
In summary,Relative flow is crucial for understanding how aeroplane generate lift and experience drag during flight.It is influenced by airspeed,direction of flight,and air density,all of which are vital factors in maintaining controlled and efficient flight.
Define and explain Stagnation as they affect an aeroplane in flight?
In aerodynamic,stagnation refers to a point where the velocity of a fliud(such as air)becomes zero due to the presence of an object,like an airplane wing.
Effects of stagnation on Flight
Lift Generation and stall
1.Lift Generation
The position of the stagnation point affects how air flows over the wing,influencing lift.As the angle of attack increases,the stagnation point moves and if it reaches a point where air cannot follow the wing curvature,lift decrease,leading to a stall.
2.Stall
A stall occurs when the air flows detaches from the wing surfaces,resulting in a sudden loss of lift.This happens when the wing exceeds its critical angle of attack.
3.Icing
Ice Accumulation.In Icing conditions,ice tends to form at the stagnation point,which can be problematic if its not visible from the cockpit.As the angle of attack increases,the stagnation point moves further aft on the underside,potentially leading to rapid ice build up.
4.stall strip
Controlled stall.Stall strip’s are small devices on the wing that created a controlled stall by causing airflow to separate before the critical angle of attack is reached.
Stagnation point play a critical role in understanding how airplane generates lift and behave during flight.The movement of these point with changing angle of attack affect lift,generation,stall conditions,Icing risks,making essential consideration in aircrafts design and operation
Define and describe Up-wash and downwash as they affect aeroplane in flight.?
Upwash
Upwash refers to the upward movement of air ahead of an aerofoil or wing as it approaches the oncoming airflow.This phenomenon is closely related to the angle of attack and contributes to lift Generation by creating a pressure between the upper and lower surfaces of the wing.
Effects on Flights.
Upwash is beneficial during landing as it helps slow the aircraft by increasing drag.Howver,at high speeds,it can create additional drag,reducing efficiency.Upwash is also associated with wingtip vortices,which are formed due to pressure differences between the wing upper and lower surface.
Downwash
Downwash is the downward deflection of air behind an airfoil or wing.It occurs as a result of lift Generation,where air is deflected downward by the wing,creating a change in air direction.
Effects on Flight
Downwash affect the lift vector by tilting it backwards,which result in induced drag.This drag increases with the size of wingtip vortices,which are stronger at higher angles of attack or with heavier,slower aircraft.Downwash also influence the safety of flight by creating turbulent that can affect following aircraft.
In summary,upwash and downwash are interconnected phenomenon that significantly impact an airplane performance by influencing lift Generation,drag creation and overall fliud dynamics.
Define and explain vortices as they affect an aeroplane in flight?
Vortices, often referred to as Vortices in informal contexts,are swirling patterns of air that forms around the aircraft,particularly at the wingtips.These Vortices play a significant role in aerodynamic,affecting an airplane performance during flight.
Effects of Vortices on Flights
1.Induced Drag
Vortices are major contributors to induced drag,which is the drag created by the deflection of air downward behind the wing.This drag increases with larger wingtip vortices,which are more produced at higher angle of attack or with heavier,slower aircraft.
2.Wake Turbulence.
Vortices form the primary component of wake Turbulence,poising a hazard to following aircraft.The strength and persistent of these Vortices depends on factors like aircraft size,weights,and speed.
3.Lift Generation
While Vortices are a by-product of lift Generation,they also affect the efficiency of lift by altering the airflow around the wing.
4.Energy Dissipation
The energy used to create and maintain Vortices comes from the aircraft itself,contributing to increased drag and reduced efficiency.
In summary,Vortices are critical in understanding aerodynamic performance,as they influence drag,wake Turbulence and lift efficiency.While the term Vortices is not standard in aerodynamic,its likely refers to these swirling around the aircraft.
Specify the effects of ice,snow and frost on an aeroplane both on the ground and in flight?
On Ground.
Even thin layer of ice,comparable to coarse sandpaper,can disrupted airflow over the wing,reducing lift up to 30% and drag to 40%
-This degradation can prevent aircraft from achieving sufficient lift take off,increasing stall speed and risk asymmetrical stall
-Ice Accumulation on control surfaces may lead to roll or pitch instability during liftoff.
In Flight
-Lift Reduction
Ice alter the wing shape,reducing lift and increasing stall speed.The critical angle of attack is reached earlier,risking stall at higher speed
-Drag Increases
Ice protruding increases drag significantly,requiring more power to maintain speed and reducing speed efficiency.
-Weight Increase
Accumulated Ice weight,further degradation performance.
-Control issues
Ice on control surfaces or asymmetrical Accumulation can cause handling difficulties,vibration,or even structural damage if Ice break off and impact engine or other compartment.
-No warning
Thin ice layer may cause abrupt flow separation without prior aerodynamic warning,complicating recovery.
Proper de-icing procedures are critical to mitigate risk.
Describe the basic operation of an aerofoil section when subjected to laminar and turbulent airflow?
Explain Camber,their interaction with related forces,and their effects on the flight characteristics of an aeroplane
Camber is defined as the convexity of an airfoils from the leading edges to trailing edges.
1.Interaction with Related Force
The camber shapes creates a pressure differences between upper and lower surfaces of the airfoil.As air travels,faster over the curved surface,it reduces pressure above the wing,generating lift according to Bernoulli’s principles.
-The amount of lift produced is also influenced by the angle of attack(AOA) and airspeed.Increased camber generally allows for greater lift at lower speed.
2.Drag
While cambered airfoil enchance lift,they can also increases drag compared to symmetrical design.This drag arises from the airfoil separation at higher angle of attack and increased surface area exposed to oncoming air.
3.Weight
Lift must counteract weight for stable flight.A well-designed camber airfoil ensures that sufficient lift is generated to support the aircraft weight,particularly during takeoff and landing phases when maximum lift is critical.
Effects on Flight Characteristics
Cambered airfoil typically have lower critical angle of attack before stalling compared to symmetrical ones.This means they can generate more lift at angle of attack but may stall more easily if AOA become too steep.
In summary,camber significantly influences an aircraft aerodynamic by affecting lift Generation,drag Characteristics,and overall flight performance.
Gyroscopic Effects
Gyroscope effects stem from the Angular momentum of rotating objects such as an airplane propeller or turbine.When torque is applied to alter the orientation of these objects,they resists the changes and exhibits precession, aligning their Angular momentum with the applied torque. This phenomenon significantly impact airplane performance during manuers,stability and control.
During turns,gyroscopic precession can cause the airplane nose to pitch up or down,depending on the turn directional propeller rotation.
For instance, a clockwise-rotating propeller may cause the nose to rise during a left turn and dip during a right turn.Pilot must manage these effects using control surfaces like elevators and rudder to ensure flight,especially rapid manuers.
Lateral stability
Is an aircraft ablity to maintain or return, to level flight around its longitudinal axis when distributed primarily affecting its rolling motion.This stability ensures that the wing remains balanced during flight.
1.Diherdarl Angle-Wings angled upwards increases lift on the lower wing during roll disturbance, aiding in returning to level flight.
2.Sweepback-Sweept-back wing generate more lift on the side-facing the airflow during a slideslip,enhancing stabilisation.
3.Kneel Effects-The fuselage and vertical stability act like a kneel,resisting rolling motion.
4.Weight Distribution-Proper Distribution prevents excessive rolling tendencies, enchanging stability.
Lateral stability positively impacts,aircraft performance by improving smoothness and safety, reducing the pilot workload during turbulence.However excessive stability can hinder manuersability,which is not ideal for aerobatic or fighter aircraft.
