13. PRINCIPLES OF FLIGHT – AEROPLANES

PRINCIPLES OF FLIGHT
PRINCIPLES OF FLIGHT — AEROPLANES
SUBSONIC AERODYNAMICS
Basics, laws and definitions
Laws and definitions
List the international system of units of measurement (SI) for mass, acceleration, weight, velocity, energy, density, temperature, pressure, force, wing loading, and power.
Define ‘mass’, ‘force’, ‘acceleration’, and ‘weight’.
State and interpret Newton’s three laws of motion.
Explain air density.
List the atmospheric properties that effect air density.
Explain how temperature and pressure changes affect air density.
Define ‘static pressure’.
Define ‘dynamic pressure’.
State the formula for ‘dynamic pressure’.
Describe dynamic pressure in terms of an indication of the energy in the system, and how it is related to indicated airspeed (IAS) and air density for a given altitude and speed.
State Bernoulli’s equation for incompressible flow.
Define ‘total pressure’ and explain that the total pressure differs in different systems.
Apply Bernoulli’s equation to flow through a venturi stream tube for incompressible flow.
Describe how IAS is acquired from the pitot static system.
Describe the relationship between density, temperature, and pressure for air.
Explain the equation of continuity and its application to the flow through a stream tube.
Define ‘IAS’, ‘CAS’, ‘EAS’, and ‘TAS’.
Basics of airflow
Describe steady and unsteady airflow.
Explain the concept of a streamline and a stream tube.
Describe and explain airflow through a stream tube.
Explain the difference between two- and three‑dimensional airflow.
Aerodynamic forces on aerofoils
Describe the originating point and direction of the resultant force caused by the pressure distribution around an aerofoil.
Resolve the resultant force into the components ‘lift’ and ‘drag’.
Describe the direction of lift and drag.
Define the ‘aerodynamic moment’.
List the factors that affect the aerodynamic moment.
Describe the aerodynamic moment for a symmetrical aerofoil.
Describe the aerodynamic moment for a positively and negatively cambered aerofoil.
Define ‘angle of attack’ ().
Shape of an aerofoil section
Describe the following parameter of an aerofoil section: leading edge.
Describe the following parameter of an aerofoil section: trailing edge.
Describe the following parameter of an aerofoil section: chord line.
Describe the following parameter of an aerofoil section: thickness-to-chord ratio or relative thickness.
Describe the following parameter of an aerofoil section: location of maximum thickness.
Describe the following parameter of an aerofoil section: camber line.
Describe the following parameter of an aerofoil section: camber.
Describe the following parameter of an aerofoil section: nose radius.
Describe a symmetrical and an asymmetrical aerofoil section.
Wing shape
Describe the following parameter of a wing: span.
Describe the following parameter of a wing: tip and root chord.
Describe the following parameter of a wing: taper ratio.
Describe the following parameter of a wing: wing area.
Describe the following parameter of a wing: wing planform.
Describe the following parameter of a wing: mean geometric chord.
Describe the following parameter of a wing: mean aerodynamic chord (MAC).
Describe the following parameter of a wing: aspect ratio.
Describe the following parameter of a wing: dihedral angle.
Describe the following parameter of a wing: sweep angle.
Describe the following parameter of a wing: wing twist, geometric and aerodynamic.
Describe the following parameter of a wing: angle of incidence.
Remark: In certain textbooks, angle of incidence is used as angle of attack (α). For Part-FCL theoretical knowledge examination purposes, this use is discontinued, and the angle of incidence is defined as the angle between the aeroplane longitudinal axis and the wing-root chord line.
Two-dimensional airflow around an aerofoil
Streamline pattern
Describe the streamline pattern around an aerofoil.
Describe converging and diverging streamlines, and their effect on static pressure and velocity.
Describe upwash and downwash.
Stagnation point
Describe the stagnation point.
Describe the movement of the stagnation point as the α changes.
Pressure distribution
Describe pressure distribution and local speeds around an aerofoil including effects of camber and α.
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Centre of pressure (CP) and aerodynamic centre (AC)
Explain CP and AC.
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Drag and wake
List two physical phenomena that cause drag.
Describe skin friction drag.
Describe form (pressure) drag.
Explain why drag and wake cause loss of energy (momentum).
Influence of angle of attack (α)
Explain the influence of α on lift.
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The lift coefficient (CL) – angle of attack () graph
Describe the CL–α graph.
Explain the significant points:
— point where the curve crosses the horizontal axis (zero lift);
— point where the curve crosses the vertical axis (α = 0);
— point where the curve reaches its maximum (CLMAX).
Coefficients
General use of coefficients
Explain why coefficients are used in general.
The lift coefficient (CL)
Explain the lift formula, the factors that affect lift, and perform simple calculations.
Describe the effect of camber on the CL– graph (symmetrical and positively/negatively cambered aerofoils).
Describe the typical difference in the CL– graph for fast and slow aerofoil design.
Define ‘CLMAX’ (maximum lift coefficient) and ‘CRIT’ (stalling ) on the graph.
Describe CL and explain the variables that affect it in low subsonic flight.
Drag
Describe the two-dimensional drag formula.
Discuss the effect of the shape of a body, cross‑sectional area, and surface roughness on the drag coefficient.
Three-dimensional airflow around an aeroplane
Angle of attack (α)
Define ‘angle of attack’ (α).
Remark: For theoretical knowledge examination purposes, the angle-of-attack definition requires a reference line. This reference line for 3D has been chosen to be the longitudinal axis and for 2D the chord line.
Explain the difference between the α and the attitude of an aeroplane.
Streamline pattern
Describe the general streamline pattern around the wing, tail section, and fuselage.
Explain and describe the causes of spanwise flow over top and bottom surfaces.
Describe wing tip vortices and their contribution to downwash behind the wing.
Explain why wing tip vortices vary with α.
Describe spanwise lift distribution including the effect of wing planform.
Describe the causes, distribution and duration of the wake turbulence behind an aeroplane.
Describe the influence of flap deflection on the wing tip vortex.
Describe the parameters that influence wake turbulence.
Induced drag
Explain the factors that cause induced drag.
Describe the approximate formula for the induced drag coefficient (including variables but excluding constants).
Describe the relationship between induced drag and total drag in straight and level flight with variable speed.
Describe the effect of mass on induced drag at a given IAS.
Describe the means to reduce induced drag:
— aspect ratio;
— winglets;
— tip tanks;
— wing twist;
— camber change.
Describe the influence of lift distribution on induced drag.
Describe the influence of downwash on the effective airflow.
Explain induced and effective local α.
Explain the influence of the induced α on the direction of the lift vector.
Explain the relationship between induced drag and:
— speed;
— aspect ratio;
— wing planform;
— bank angle in a horizontal coordinated turn.
Explain the induced drag coefficient and its relationship with the lift coefficient and aspect ratio.
Explain the influence of induced drag on:
— the CL–α graph, and show the effect on the graph when comparing high- and low‑aspect ratio wings;
— the CL–CD (aeroplane polar), and show the effect on the graph when comparing high- and low-aspect ratio wings;
— the parabolic aeroplane polar in a graph and as a formula [CD = CPD + kCL2], where CD = coefficient of drag and CPD = coefficient of parasite drag.
Describe the CL–CD graph (polar).
Indicate minimum drag on the graph.
Explain why the CL–CD ratio is important as a measure of performance.
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Total drag
Total drag in relation to parasite drag and induced drag
State that total drag consists of parasite drag and induced drag.
Parasite drag
Describe the types of drag that are included in parasite drag.
Describe form (pressure) drag and the factors which affect its magnitude.
Describe interference drag and the factors which affect its magnitude.
Describe friction drag and the factors which affect its magnitude.
Parasite drag and speed
Describe the relationship between parasite drag and speed.
Induced drag and speed
(Refer to 081 01 04 03)
Total drag
Explain the total drag–speed graph and the constituent drag components.
Indicate the speed for minimum drag.
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Variables affecting the total drag–speed graph
Describe the effect of aeroplane gross mass on the graph.
Describe the effect of pressure altitude on:
— drag–IAS graph;
— drag–TAS graph.
Describe speed stability from the graph.
Describe non-stable, neutral, and stable IAS regions.
Explain what happens to the IAS and drag in the non-stable region if speed suddenly decreases and why this could occur.
Ground effect
Influence of ground effect
Explain the influence of ground effect on wing tip vortices, downwash, airflow pattern, lift, and drag.
Describe the influence of ground effect on induced  and the coefficient of induced drag (CDi).
Explain the effects of entering and leaving ground effect.
Effect on stalling angle of attack (αCRIT)
Describe the influence of ground effect on αCRIT.
Effect on lift coefficient (CL)
Describe the influence of ground effect on the effective  and CL.
Effect on take-off and landing characteristics of an aeroplane
Describe the influence of ground effect on take‑off and landing characteristics and performance of an aeroplane.
Describe the difference in take-off and landing characteristics of high- and low-wing aeroplanes.
The relationship between lift coefficient and speed in steady, straight, and level flight
Represented by an equation
Explain the effect on CL during speed increase/decrease in steady, straight, and level flight, and perform simple calculations.
Represented by a graph
Explain, by using a graph, the effect on speed of CL changes at a given weight.
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CLMAX augmentation
Trailing-edge flaps and the reasons for their use in take-off and landing
From the given relevant diagrams, describe or identify the following types of trailing-edge flaps:
— split flaps;
— plain flaps;
— slotted flaps;
— Fowler flaps.
Describe how the wing’s effective camber increases the CL and CD, and the reasons why this can be beneficial.
Describe their effect on:
— the location of CP;
— pitching moments (due to wing CP movement);
— stall speed.
Compare their influence on the CL– graph:
— indicate the variation in CL at any given ;
— indicate their effect on CLMAX;
— indicate their effect on critical ;
— indicate their effect on the  at a given CL.
Compare their influence on the CL–CD graph:
— indicate how the (CL/CD)MAX differs from that of a clean wing.
Explain the influence of trailing-edge flap deflection on the glide angle.
Describe flap asymmetry:
— explain the effect on aeroplane controllability.
Describe trailing-edge flap effect on take-off and landing:
— explain the advantages of lower-nose attitudes;
— explain why take-off and landing speeds/distances are reduced.
Explain the effects of flap-setting errors, such as mis-selection and premature/late extension or retraction of flaps, on:
— take-off and landing distance and speeds;
— climb and descent performance;
— stall buffet margins.
Leading-edge devices and the reasons for their use in take-off and landing
From the given relevant diagrams, describe or identify the different types of leading-edge high‑lift devices:
— Krueger flaps;
— variable camber flaps;
— slats.
Describe the function of the slot.
Describe how the wing’s effective camber increases with a leading-edge flap.
Explain the effect of leading-edge flaps on the stall speed, also in comparison with trailing-edge flaps.
Compare their influence on the CL– graph, compared with trailing-edge flaps and a clean wing:
— indicate the effect of leading-edge devices on CLMAX;
— explain how the CL curve differs from that of a clean wing;
— indicate the effect of leading-edge devices on αCRIT.
Compare their influence on the CL–CD graph.
Describe slat asymmetry:
– describe the effect on aeroplane controllability.
Explain the reasons for using leading-edge high‑lift devices on take-off and landing:
— explain the disadvantage of increased nose-up attitudes;
— explain why take-off and landing speeds/distances are reduced.
Vortex generators
Explain the purpose of vortex generators.
Describe the basic operating principle of vortex generators.
State their advantages and disadvantages.
Means to reduce the CL–CD ratio
Spoilers and the reasons for their use in the different phases of flight
Describe the aerodynamic functioning of spoilers:
— roll spoilers;
— flight spoilers (speed brakes);
— ground spoilers (lift dumpers).
Describe the effect of spoilers on the CL– graph and stall speed.
Describe the influence of spoilers on the CL–CD graph and lift-drag ratio.
Speed brakes and the reasons for their use in the different phases of flight
Describe speed brakes and the reasons for using them in the different phases of flight.
State their influence on the CL–CD graph and lift–drag ratio.
Explain how speed brakes increase parasite drag.
Describe how speed brakes affect the minimum drag speed.
Describe their effect on rate and angle of descent.
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Aerodynamic degradation
Ice and other contaminants
Describe the locations on an aeroplane where ice build-up will occur during flight.
Explain the aerodynamic effects of ice and other contaminants on:
— lift (maximum CL);
— drag;
— stall speed;
— CRIT;
— stability and controllability.
Explain the aerodynamic effects of icing during take-off.
Deformation and modification of airframe, ageing aeroplanes
Describe the effect of airframe deformation and modification of an ageing aeroplane on aeroplane performance.
Explain the effect on boundary layer condition of an ageing aeroplane.
HIGH-SPEED AERODYNAMICS
Speeds
Speed of sound
Define ‘speed of sound’.
Explain the variation of the speed of sound with altitude.
Explain the influence of temperature on the speed of sound.
Mach number
Define ‘Mach number’ as a function of TAS and speed of sound.
Influence of temperature and altitude on Mach number
Explain the absence of change of Mach number with varying temperature at constant flight level and calibrated airspeed.
Explain the relationship between Mach number, TAS and IAS during climb and descent at constant Mach number or IAS, and explain variation of lift coefficient, α, pitch and flight-path angle.
Explain:
— risk of exceeding the maximum operation speed (VMO) when descending at constant Mach number;
— risk of exceeding the maximum operating Mach number (MMO) when climbing at constant IAS;
— risk of a low-speed stall at high altitude when climbing at a too low Mach number.
Compressibility
State that compressibility means that density can change along a streamline, and that this occurs in the high subsonic (from Mach 0.4), transonic, and supersonic flow.
State that compressibility negatively affects the pressure gradient, leading to an overall reduction of the CL.
State that Mach number is a measure of compressibility.
Describe that compressibility increases low‑speed stall speed and decreases αCRIT.
Subdivision of aerodynamic flow
List the subdivision of aerodynamic flow:
— subsonic flow below compressibility;
— subsonic flow above compressibility;
— transonic flow;
— supersonic flow.
Describe the characteristics of the flow regimes listed above.
Explain why some transport aeroplanes cruise at Mach numbers above the critical Mach number (MCRIT).
Shock waves
Definition of shock wave
Define a ‘shock wave’.
Normal shock waves
Describe a normal shock wave with respect to changes in:
— static temperature;
— static and total pressure;
— velocity;
— local speed of sound;
— Mach number;
— density.
Describe a normal shock wave with respect to orientation relative to the wing surface.
Explain the influence of increasing Mach number on a normal shock wave, at positive lift, with respect to:
— strength;
— position relative to the wing;
— second shock wave at the lower surface.
Explain the influence of  on shock-wave intensity and shock-wave location at constant Mach number.
Effects of exceeding the critical Mach number (MCRIT)
Critical Mach number (MCRIT)
Define ‘MCRIT’.
Explain how a change in , aeroplane weight, manoeuvres, and centre-of-gravity (CG) position influences MCRIT.
Effect on lift
Describe the behaviour of CL versus Mach number at constant .
Explain the consequences of exceeding MCRIT with respect to CL and CLMAX.
Explain the change in stall indicated airspeed (IAS) with altitude.
Discuss the effect on αCRIT.
Explain the advantages of exceeding MCRIT in aeroplanes with supercritical aerofoils with respect to:
— speed versus drag ratio;
— specific range;
— optimum altitude.
Effect on drag
Describe wave drag.
Describe the behaviour of CD versus Mach number at constant .
Explain the effect of Mach number on the CL–CD graph.
Describe the effects and hazards of exceeding MDRAG DIVERGENCE, namely:
— drag rise;
— instability;
— Mach tuck;
— shock stall.
State the relation between MCRIT and MDRAG DIVERGENCE.
Effect on pitching moment
Discuss the effect of Mach number on the CP location.
Describe the overall change in pitching moment above MCRIT and explain the ‘tuck under’ or ‘Mach tuck’ effect.
State the requirement for a Mach trim system to compensate for the effect of the CP movement and ‘tuck under’ effect.
Discuss the aerodynamic functioning of the Mach trim system.
Discuss the corrective measures if the Mach trim fails.
Effect on control effectiveness
Discuss the effects on the effectiveness of control surfaces.
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Means to influence critical Mach number (MCRIT)
Wing sweep
Explain the influence of the angle of sweep on:
— MCRIT;
— effective thickness/chord change or velocity component perpendicular to the quarter chord line.
Describe the influence of the angle of sweepback at subsonic speed on:
— CLMAX;
— efficiency of and requirement for high-lift devices;
— pitch-up stall behaviour.
Discuss the effect of wing sweepback on drag.
Aerofoil shape
Explain the use of thin aerofoils with reduced camber.
Explain the main purpose of supercritical aerofoils.
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Explain the advantages and disadvantages of supercritical aerofoils for wing design.
Vortex generators
Explain the use of vortex generators as a means to avoid or restrict flow separation caused by the presence of a normal shock wave.
Stall, Mach tuck, and upset prevention and recovery
The stall
Flow separation at increasing α
Define the ‘boundary layer’.
Describe the thickness of a typical laminar and turbulent boundary layer.
Describe the properties, advantages and disadvantages of the laminar boundary layer.
Describe the properties, advantages and disadvantages of the turbulent boundary layer.
Define the ‘transition point’.
Explain why the laminar boundary layer separates easier than the turbulent boundary layer does.
Describe why the airflow over the aft part of a wing slows down as the α increases.
Define the ‘separation point’ and describe its location as a function of α.
Define αCRIT.
Describe in straight and level flight the influence of increasing the α and the phenomenon that may occur regarding:
— the forward stagnation point;
— the pressure distribution;
— the CP location (straight and swept-back wing);
— CL;
— CD and D (drag);
— the pitching moment (straight and swept-back wing);
— buffet onset;
— deterrent buffet for a clean wing at high Mach number;
— lack of pitch authority;
— uncommanded pitch down;
— uncommanded roll.
Explain what causes the possible natural buffet on the aeroplane in a pre-stall condition.
Describe the effectiveness of the flight controls in a pre-stall condition.
Describe and explain the normal post-stall behaviour of a straight-wing aeroplane.
Describe the effect and dangers of using the controls close to the stall.
Describe the deterrent buffet.
Explain the occurrence of the deterrent buffet and why this phenomenon is considered to be a stall limit.
The stall speed
Explain VS0, VS1, VSR, and VS1G.
Solve VS1G from the lift formula given varying CL.
Describe and explain the influence of the following parameters on stall speed:
— CG;
— thrust component;
— slipstream;
— wing loading;
— mass;
— wing contamination;
— angle of sweep;
— altitude (for compressibility effects, see 081 02 03 02).
Define the ‘load factor n’.
Explain why the load factor increases in a turn.
Explain why the load factor increases in a pull-up and decreases in a push-over manoeuvre.
Describe and explain the influence of the ‘load factor n’ on stall speed.
Explain the expression ‘accelerated stall’.
Remark: Sometimes, accelerated stall is also erroneously referred to as high-speed stall. This latter expression will not be used for Subject 081.
Calculate the change of stall speed as a function of the load factor.
Calculate the increase of stall speed in a horizontal coordinated turn as a function of bank angle.
Calculate the change of stall speed as a function of the gross mass.
The initial stall in spanwise direction
Explain the initial stall sequence on the following planforms:
— elliptical;
— rectangular;
— moderate and high taper;
— sweepback or delta.
Explain the purpose of aerodynamic and geometric twist (washout).
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Explain the influence of fences, vortilons, saw teeth, vortex generators, and strakes on engine nacelles.
Stall warning
Explain why stall warning is necessary.
Explain when aerodynamic and artificial stall warnings are used.
Explain why CS-23 and CS-25 require a margin to stall speed for take-off and landing speeds.
Describe:
— buffet;
— stall strip;
— flapper switch (leading-edge stall-warning vane);
— angle-of-attack vane;
— angle-of-attack probe;
— stick shaker.
Describe the recovery after:
— stall warning;
— stall;
— stick-pusher actuation.
Special phenomena of stall
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Explain the difference between power-off and power-on stalls and recovery.
Describe stall and recovery in a climbing and descending turn.
Describe the pitch-up effect on a swept wing aeroplane and also an aeroplane with a T-tail.
Describe super stall or deep stall.
Describe the philosophy behind the stick-pusher system.
Describe the factors that can lead to the absence of stall warning and explain the associated risks.
Describe the indications and explain the consequences of premature stabiliser stall due to ice contamination (negative tail stall).
Describe when to expect in-flight icing.
Explain how the effect is changed when retracting/extending lift-augmentation devices.
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Explain the effect of a contaminated wing on the stall speed and αCRIT.
Explain the hazards associated with airframe contamination when parked and during ground operations in winter conditions, and the aerodynamic effects when attempting a take-off.
Explain de-icing/anti-icing holdover time and the likely hazards after it has expired.
Describe the aerodynamic effects of heavy tropical rain on stall speed and drag, and the appropriate mitigation in such conditions.
The spin
Explain how to avoid spins.
List the factors that cause a spin to develop.
Describe an ‘incipient’ and ‘developed’ spin, recognition and recovery.
Describe the differences in spin attitude with forward and aft CG.
Buffet onset boundary
Mach buffet
Explain shock-induced separation, and describe its relationship with Mach buffet (high speed buffet) and Mach tuck.
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Buffet onset
Explain the concept of buffet margin, and describe the influence of the following parameters on the concept of buffet margin:
— ;
— Mach number;
— pressure altitude;
— mass;
— load factor;
— angle of bank;
— CG location.
Explain how the buffet onset boundary chart can be used to determine:
— manoeuvrability;
— buffet margin.
Describe the consequences of exceeding MMO: light buffet, buffet onset.
Explain ‘aerodynamic ceiling’ and ‘coffin corner’.
Explain the concept of the ‘1.3g’ buffet margin altitude.
Find (using an example graph):
— buffet free range;
— aerodynamic ceiling at a given mass;
— load factor and bank angle at which buffet occurs at a given mass, Mach number, and pressure altitude.
Explain why descent increases the buffet free range.
Situations in which buffet or stall could occur
Explain why buffet or stall occurs
Explain why buffet or stall could occur in the following pilot-induced situations, and the methods to mitigate them:
— inappropriate take-off configuration, detailing the consequences of errors associated with leading-edge devices;
— steep turns;
— go-around using take-off/go-around (TOGA) setting (underslung engines).
Explain why buffet or stall could occur in the following environmental conditions at low altitude, and how to mitigate them:
— thunderstorms;
— wind shear and microburst;
— turbulence;
— wake turbulence;
— icing conditions.
Explain why buffet or stall could occur in the following environmental conditions at high altitude, and how to mitigate them:
— thunderstorms in the intertropical convergence zone (ITCZ);
— jet streams;
— clear-air turbulence.
Explain why buffet or stall could occur in the following situations, and how to mitigate them:
— inappropriate autopilot climb mode;
— loss of, or unreliable, airspeed indication.
Recognition of stalled condition
Recognition and explanation of stalled condition
Explain why a stalled condition can occur at any airspeed, or attitude or altitude.
Explain that a stall may be recognised by continuous stall-warning activation accompanied by at least one of the following:
— buffet, that can be heavy;
— lack of pitch authority;
— uncommanded pitch down and uncommanded roll;
— inability to arrest the descent rate.
Explain that ‘stall warning’ means a natural or synthetic indication provided when approaching the stall that may include one or more of the following indications:
— aerodynamic buffeting;
— reduced roll stability and aileron effectiveness;
— visual or aural clues and warnings;
— reduced elevator (pitch) authority;
— inability to maintain altitude or arrest a rate of descent;
— stick-shaker activation.
STABILITY
Static and dynamic stability
Basics and definitions
Define ‘static stability’:
— describe/identify a statically stable, neutral, and unstable condition (positive, neutral, and negative static stability), and
— explain why aeroplanes are statically stable.
Explain manoeuvrability.
Explain the relationship between static stability and manoeuvrability.
Define ‘dynamic stability’:
— describe/identify a dynamically stable, neutral, and unstable motion (positive, neutral, and negative dynamic stability);
— describe/identify periodic and aperiodic motion.
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Precondition for static stability
Explain an equilibrium of forces and moments as the initial condition for static stability.
Sum of forces
Identify the forces considered in the equilibrium of forces.
Sum of moments
Identify the moments about all three axes considered in the equilibrium of moments.
Discuss the effect of sum of moments not being zero.
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Static and dynamic longitudinal stability
Methods for achieving balance
Explain the stabiliser as the means to satisfy the condition of nullifying the total sum of the moments about the lateral axis.
Explain the influence of the location of the wing CP relative to the CG on the magnitude and direction of the balancing force on the stabiliser.
Explain the influence of the indicated airspeed on the magnitude and direction of the balancing force on the stabiliser.
Explain the use of the elevator deflection or stabiliser angle for the generation of the balancing force and its direction.
Explain the elevator deflection required to balance thrust change as a function of engine position.
Static longitudinal stability
Discuss the effect of the CG location on pitch manoeuvrability and longitudinal stability.
Neutral point
Define ‘neutral point’.
Explain why the location of the neutral point is only dependent on the aerodynamic design of the aeroplane.
Factors affecting neutral point
Describe the location of the neutral point relative to the locations of the aerodynamic centre of the wing and tail.
Location of centre of gravity (CG)
Explain the influence of the CG location on the static longitudinal stability of the aeroplane.
Explain the CG forward and aft limits with respect to:
— longitudinal control forces;
— elevator effectiveness;
— stability.
Define ‘static margin’.
The Cm– graph
Describe the Cm– graph with respect to the relationship between the slope of the graph and static stability.
Factors affecting the Cm– graph
Explain:
— the effect on the Cm– graph of a shift of CG in the forward and aft direction;
— the effect on the Cm– graph when the elevator is moved up or down;
— the effect on the Cm– graph when the trim is moved;
— the effect of the wing contribution;
— the tail contribution.
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The stick force versus speed graph (IAS)
Explain how a pilot perceives stable static longitudinal stick force stability regarding changes in:
— speed;
— altitude;
— mass distribution (CG location).
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The manoeuvring stability/stick force per g
Define the ‘stick force per g’, and describe that the stick force increases linearly with increase in g.
Explain why:
— the stick force per g has a prescribed minimum and maximum value;
— the stick force per g decreases with pressure altitude.
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Factors affecting the manoeuvring stability/stick force per g
Explain the influence on stick force per g of:
— CG location;
— trim setting.
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Dynamic longitudinal stability
Describe the phugoid and short-period motion in terms of period, damping, variations (if applicable) in speed, altitude, and α.
Explain why the short-period motion is more hazardous than the phugoid.
Describe ‘pilot-induced oscillations’.
Explain the effect of high altitude on dynamic stability.
Describe the influence of the CG location on the dynamic longitudinal stability of the aeroplane.
Static directional stability
Definition and effects of static directional stability
Define ‘static directional stability’.
Explain the effects of static directional stability being too weak or too strong.
Sideslip angle
Define ‘sideslip angle’.
Identify β as the symbol used for the sideslip angle.
Yaw-moment coefficient Cn
Define the ‘yawing-moment coefficient Cn’.
Define the relationship between Cn and β for an aeroplane with static directional stability.
Cn–β graph
Explain why:
— Cn depends on β;
— Cn equals zero for that β that provides static equilibrium about the aeroplane’s normal axis;
— if no asymmetric engine thrust, flight control or loading condition prevails, the equilibrium β equals zero.
Identify how the slope of the Cn–β graph is a measure for static directional stability.
Identify how the slope of the Cn–β graph is affected by altitude.
Factors affecting static directional stability
Describe how the following aeroplane components contribute to static directional stability:
— wing;
— fin;
— dorsal fin;
— ventral fin;
— angle of sweep of the wing;
— angle of sweep of the fin;
— fuselage at high α;
— strakes.
Explain the reduction in static directional stability when the CG moves aft.
Static lateral stability
Definition and effects of static lateral stability
Define ‘static lateral stability’.
Explain the effects of static lateral stability being too weak or too strong.
Bank angle Ø
Define ‘bank angle Ø’.
The roll-moment coefficient Cl
Define the ‘roll-moment coefficient Cl’.
Contribution of sideslip angle (β)
Explain how without coordination the bank angle (Ø) creates sideslip angle (β).
The Cl–β graph
Describe the Cl– graph.
Identify the slope of the Cl– graph as a measure for static lateral stability.
Identify how the slope of the Cl–β graph is affected by altitude.
Factors affecting static lateral stability
Explain the contribution to the static lateral stability of:
— dihedral, anhedral;
— high wing, low wing;
— sweep angle of the wing;
— ventral fin;
— vertical tail.
Dynamic lateral/directional stability
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Tendency to spiral dive
Explain how lateral and directional stability are coupled.
Explain how high static directional stability and low static lateral stability may cause spiral divergence (unstable spiral dive), and under which conditions the spiral dive mode is neutral or stable.
Describe an unstable spiral dive mode with respect to deviations in speed, bank angle, nose low-pitch attitude, and decreasing altitude.
Dutch roll
Describe Dutch roll.
Explain:
— why Dutch roll occurs when the static lateral stability is higher than static directional stability;
— the conditions for a stable, neutral or unstable Dutch roll motion;
— the function of the yaw damper;
— the actions to be taken when the yaw damper is not available.
Describe how the asymmetric nature of shock waves on both wings, at high Mach numbers, can lead to Dutch roll.
Effects of altitude on dynamic stability
Explain that increased pressure altitude reduces dynamic lateral/directional stability.
CONTROL
General
Basics — The three planes and three axes
Define:
— lateral axis;
— longitudinal axis;
— normal axis.
— Define:
— pitch angle;
— bank angle (Ø);
— yaw angle.
Describe the motion about the three axes.
Name and describe the devices that control these motions.
Camber change
State that camber is changed by movement of a control surface and explain the effect.
Angle-of-attack (α) change
Explain the influence of local α change by movement of a control surface.
Pitch (longitudinal) control
Elevator/all-flying tails
Explain the working principle of the elevator/all-flying tail and describe its function.
Downwash effects
Explain the effect of downwash on the tailplane α.
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Location of centre of gravity (CG)
Explain the relationship between elevator deflection and CG location to produce a given aeroplane response.
Explain the effect of forward CG limit on pitch control.
Moments due to engine thrust
Describe the effect of engine thrust on pitching moments for different engine locations.
Yaw (directional) control
The rudder
Explain the working principle of the rudder and describe its function.
State the relationship between rudder deflection and the moment about the normal axis.
Describe the effect of sideslip on the moment about the normal axis.
Rudder limiting
Explain why and how rudder deflection is limited on CAT aeroplanes.
Roll (lateral) control
Ailerons
Explain the functioning of ailerons.
Describe the adverse effects of aileron deflection.
(Refer to Subjects 081 05 04 04 and 081 06 01 02)
Explain why some aeroplanes have inboard and outboard ailerons.
State that the outboard ailerons are locked beyond a given speed to prevent:
— over-control;
— exceeding structural limitations;
— aeroelastic phenomena (flutter, divergence and aileron reversal).
Describe the use of aileron deflection in normal flight, flight with sideslip, crosswind landings, horizontal turns, flight with one-engine-inoperative.
Define ‘roll rate’.
List the factors that affect roll rate.
Describe flaperons and aileron droop.
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Spoilers
Explain how spoilers can be used to control the rolling movement in combination with or instead of the ailerons.
Adverse yaw
Explain why the use of ailerons induces adverse yaw.
Means to avoid adverse yaw
Explain how the following reduce adverse yaw:
— Frise ailerons;
— differential aileron deflection;
— rudder aileron cross-coupling;
— roll spoilers.
Roll/yaw interaction
Explain roll/yaw interaction
Explain the secondary effect of roll.
Explain the secondary effect of yaw.
Means to reduce control forces
Aerodynamic balance
Describe the purpose of aerodynamic balance.
Describe the working principle of the horn balance.
Describe the working principle of the internal balance.
Describe the working principle and application of:
— balance tab;
— anti-balance tab;
— spring tab;
— servo tab.
Artificial means
State the differences between fully powered controls and power-assisted controls.
Describe power-assisted controls.
Describe the advantages of artificial feel in fully powered control.
Fly-by-wire (FBW)
Control laws
Explain which parameters may be controlled in level flight with the pitch control law.
Explain the advantages of using the CG position in the FBW system.
Explain what type of flight-degraded control laws may be available in case of failure.
Explain what are hard and soft protections.
Trimming
Reasons to trim
State the reasons for using trimming devices.
Explain the difference between a trim tab and the various balance tabs.
Trim tabs
Describe the working principle of a trim tab including cockpit indications.
Stabiliser trim
Describe the working principle of a stabiliser trim including the flight deck indications.
Explain the advantages and disadvantages of a stabiliser trim compared to a trim tab.
Explain the relationship between CG position, take-off trim setting, and stabiliser trim position.
Explain the effect of errors in the take-off stabiliser trim setting on the rotation characteristics and stick force during take-off rotation.
Discuss the effects of jammed and runaway stabiliser.
Explain the consequences of a jammed stabiliser during take-off, landing, and go-around.
LIMITATIONS
Operating limitations
Flutter
Describe the phenomenon of flutter and how IAS and mass distribution affects the likelihood of flutter occurrence.
Describe the use of mass balance to alleviate the flutter problem by adjusting the mass distribution:
— wing-mounted engines on pylons;
— control surface mass balance.
Explain what is the flight envelope free of flutter.
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Landing gear/flap operating
Describe the reason for flap/landing gear limitations.
Define ‘VLO’.
Define ‘VLE’.
Explain why there is a difference between VLO and VLE in the case of some aeroplane types.
Define ‘VFE’ and describe flap limiting speeds.
Describe flap design features, procedures and warnings to prevent overload.
VMO, VNO, and VNE
Define ‘VMO’, ‘VNO’, and ‘VNE’.
Explain the significance of VMO, VNO and VNE, and the differences between these airspeeds.
Explain the hazards of flying at speeds above VNE and VMO.
MMO
Define ‘MMO’ and state its limiting factors.
Manoeuvring envelope
Manoeuvring–load diagram
Describe the manoeuvring–load diagram.
Define limit and ultimate load factor, and explain what can happen if these values are exceeded.
Define ‘VA’, ‘VB’, ‘VC’, and ‘VD’.
Identify and explain the varying features on the VN diagram:
— load factor ‘n’;
— speed scale, equivalent airspeed;
— equivalent airspeed envelope;
— 1g stall speed;
— stall boundary (refer to 081 03 01 02).
Describe the relationship between VMO or VNE and VC.
State all the manoeuvring load-factors limits applicable to CS-23 and CS-25 aeroplanes.
Explain the relationship between VA and VS in a formula, and calculate the values.
Explain the significance of VA and the adverse consequences of applying full, abrupt nose-up elevator deflection when exceeding VA.
Factors affecting the manoeuvring–load diagram
State the relationship of mass to load-factor limits and accelerated stall speed boundary limit.
Calculate the change of VA with changing mass.
Explain why VA loses significance at higher altitude.
Define ‘MC’ and ‘MD’.
Gust envelope
Gust–load diagram
Recognise a typical gust–load diagram, and state the minimum gust speeds in ft/s, m/s and kt that the aeroplane must be designed to withstand at VB to VC and VD.
Discuss considerations for the selection of VRA.
Explain the adverse effects on the aeroplane when flying in turbulence.
Factors affecting the gust–load diagram
Describe and explain the relationship between the gust–load factor and the following: lift–curve slope, aspect ratio, angle of sweep, altitude, wing loading, weight, wing area, equivalent airspeed (EAS), and speed of vertical gust.
(Note: For examination purposes, the ECQB questions will not be calculation based.)
PROPELLERS
Conversion of engine torque to thrust
Explain conversion of aerodynamic force on a propeller blade
Explain the resolution of aerodynamic force on a propeller blade element into lift and drag or into thrust and torque.
Describe how propeller thrust and aerodynamic torque vary with IAS.
Relevant propeller parameters
Describe the geometry of a typical propeller blade element at the reference section:
— blade chord line;
— propeller rotational velocity vector;
— true airspeed vector;
— blade angle of attack;
— pitch or blade angle;
— advance or helix angle.
Define ‘geometric pitch’, ‘effective pitch’, and ‘propeller slip’.
Remark: For theoretical knowledge examination purposes, the following definition is used for geometric pitch: the theoretical distance a propeller would advance in one revolution at zero blade angle of attack.
Describe how the terms ‘fine pitch’ and ‘coarse pitch’ can be used to express blade angle.
Blade twist
Define ‘blade twist’.
Explain why blade twist is necessary.
Fixed pitch and variable pitch/constant speed
List the different types of propellers:
— fixed pitch;
— adjustable pitch or variable pitch (non-governing);
— variable pitch (governing)/constant speed.
Discuss the advantages and disadvantages of fixed-pitch and constant-speed propellers.
Discuss climb and cruise propellers.
Explain the relationship between blade angle, blade angle of attack, and airspeed for fixed and variable pitch propellers.
Describe and explain the forces that act on a rotating blade element in normal, feathered, windmilling, and reverse operation.
Explain the effects of changing propeller pitch at constant IAS.
Propeller efficiency versus speed
Define ‘propeller efficiency’.
Explain and describe the relationship between propeller efficiency and speed (TAS) for different types of propellers.
Explain the relationship between blade angle and thrust.
Effects of ice on propeller
Describe the effects and hazards of ice on a propeller.
Engine failure
Windmilling drag
Describe the effects of an inoperative engine on the performance and controllability of an aeroplane:
— thrust loss/drag increase;
— influence on yaw moment during asymmetric power.
Feathering
Explain the reasons for feathering a propeller, including the effect on the yaw moment, performance and controllability.
Design features for power absorption
Propeller design characteristics that increase power absorption
Name the propeller design characteristics that increase power absorption.
Diameter of propeller
Explain the reasons for restricting propeller diameter.
Number of blades
Define ‘solidity’.
Describe the advantages and disadvantages of increasing the number of blades.
Propeller noise
Describe how propeller noise can be minimised.
Secondary effects of propellers
Torque reaction
Describe the effects of engine/propeller torque.
Describe the following methods for counteracting engine/propeller torque:
— counter-rotating propellers;
— contra-rotating propellers.
Gyroscopic precession
Describe what causes gyroscopic precession.
Describe the effect on the aeroplane due to the gyroscopic effect.
Slipstream effect
Describe the possible effects of the rotating propeller slipstream.
Asymmetric blade effect
Explain the asymmetric blade effect (also called P factor).
Explain the influence of direction of rotation on the critical engine on twin-engine aeroplanes.
Consideration of propeller effects
Describe, given direction of propeller rotation, the propeller effects during take-off run, rotation and initial climb, and their consequence on controllability.
Describe, given the direction of propeller rotation, the propeller effects during a go-around and their consequence on controllability.
Explain how propeller effects during go-around can be affected by:
— high engine performance conditions and their effect on the VMC speeds;
— loss of the critical engine;
— crosswind;
— high flap setting;
FLIGHT MECHANICS
Forces acting on an aeroplane
Straight, horizontal, steady flight
Describe the forces that act on an aeroplane in straight, horizontal, and steady flight.
List the four forces and state where they act on.
Explain how the four forces are balanced, including the function of the tailplane.
Straight, steady climb
Define ‘flight-path angle’ ().
Describe the relationship between pitch attitude,  and α for zero-wind and zero-bank conditions.
Describe the forces that act on an aeroplane in a straight, steady climb.
Name the forces parallel and perpendicular to the direction of flight.
— Apply the formula relating to the parallel forces (T = D + W sin ).
— Apply the formula relating to the perpendicular forces (L = W cos ).
Explain why thrust is greater than drag.
Explain why lift is less than weight.
Explain the formula (for small angles) that gives the relationship between , thrust, weight, and lift–drag ratio, and use this formula for simple calculations.
Explain how IAS, α, and  change in a climb performed with constant vertical speed and constant thrust setting.
Straight, steady descent
Describe the forces that act on an aeroplane in a straight, steady descent.
Name the forces parallel and perpendicular to the direction of flight.
— Apply the formula for forces parallel to the direction of flight (T = D – W sin ).
— Apply the formula relating to the perpendicular forces (L = W cos ).
Explain why lift is less than weight.
Explain why thrust is less than drag.
Straight, steady glide
Describe the forces that act on an aeroplane in a straight, steady glide.
Name the forces parallel and perpendicular to the direction of flight.
— Apply the formula for forces parallel to the direction of flight (D = W sin ).
— Apply the formula for forces perpendicular to the direction of flight (L = W cos ).
Describe the relationship between the glide gradient and the lift–drag ratio, and calculate glide range given:
— initial height;
— L–D ratio;
— glide speed and wind speed.
Define VMD (speed for minimum drag) and explain the relationship between α, VMD and the best lift–drag ratio.
Explain the effect of wind component on glide angle, duration, and distance.
Explain the effect of mass change on glide angle, duration, and distance, given that the aeroplane remains at either the same airspeed or at VMD.
Explain the effect of configuration change on glide angle and duration.
Describe the relation between TAS, gradient of descent, and rate of descent.
Define VMP (speed for minimum power) and describe that the minimum rate of descent in the glide will be at VMP, and explain the relationship of this speed to the optimum speed for minimum glide angle.
Discuss when a pilot could elect to fly for minimum glide rate of descent or minimum glide angle, and why speed stability or headwinds/tailwinds may favour a speed that is faster or slower than the optimum airspeed in still air.
Steady, coordinated turn
Describe the forces that act on an aeroplane in a steady, coordinated turn.
Resolve the forces that act horizontally and vertically during a coordinated turn
(tan).
Describe the difference between a coordinated and an uncoordinated turn, and describe how to correct an uncoordinated turn using turn and slip indicator or turn coordinator.
Explain why the angle of bank is independent of mass, and that it only depends on TAS and radius of turn.
Resolve the forces to show that for a given angle of bank the radius of turn is determined solely by airspeed (tan).
Calculate the turn radius of a steady turn given TAS and angle of bank.
Explain the effects of bank angle on:
 load factor (LF = 1/cos);
 α;
 thrust;
 drag.
Define ‘angular velocity’.
Define ‘rate of turn’ and ‘rate-1 turn’.
Explain the influence of TAS on rate of turn at a given bank angle.
Calculate the load factor and stall speed in a turn given angle of bank and 1g stall speed.
Explain situations in which turn radius is relevant for safety, such as maximum speed limits on departure or arrival plates, or outbound speed categories on approach plates, and the implications/hazards of exceeding given speeds.
Describe the hazards of excessive use of rudder to increase the rate of turn in a swept-wing aeroplane.
Asymmetric thrust
Jet-engined and propeller-driven aeroplanes
Describe the effects on the aeroplane of asymmetric thrust during flight, for both jet‑engined and propeller-driven aeroplanes.
Explain critical engine, and explain, for a propeller-driven aeroplane, the effect of the direction of propeller rotation.
Explain the effect of steady, asymmetric flight on a conventional (ball) slip indicator/turn indicator.
Explain the effect of a crosswind on asymmetric flight.
Balanced moments about the normal axis
Explain the yaw moments about the CG.
Explain the change to the yaw moment caused by the effect of air density on thrust.
Describe the changes to the yaw moment caused by engine distance from CG.
Describe the methods to achieve directional balance following engine loss.
Forces parallel to the lateral axis
Explain:
— the force on the vertical fin;
— the fuselage side force due to sideslip (using wing-level method);
— the use of bank angle to tilt the lift vector (in wing-down method).
Explain the flight hazards at VMC:
— α;
— side slip;
— loads on the fin;
— α on the fin.
Explain the effect on fin α due to sideslip.
Influence of aeroplane mass
Explain why controllability with one-engine-inoperative is a typical problem arising from the low speeds associated with low aeroplane mass.
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Minimum control speed (VMC)
Define ‘VMC’.
Describe how VMC is determined.
Explain the influence of the CG location.
Minimum control speed during approach and landing (VMCL)
Define ‘VMCL’.
Describe how VMCL is determined.
Explain the influence of the CG location.
Minimum control speed on the ground (VMCG)
Define ‘VMCG’.
Describe how VMCG is determined.
Explain the influence of the CG location.
Influence of density
Describe the influence of density on thrust during asymmetric flight.
Explain why VMC, VMCL and VMCG reduce with a reduction in thrust.
Significant points on a polar curve
Identify and explain
Identify and explain the significant points on a polar curve.

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