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081 04 01 00 Static and dynamic stability
081 04 01 01 Basics and definitions
— describe/identify a statically stable, neutral, and unstable condition (positive, neutral, and negative static stability).
(02) Explain manoeuvrability.
(03) Explain why static stability is the opposite of manoeuvrability, and why CAT aeroplanes are designed to be statically stable.
(04) Define ‘dynamic stability’:
— describe/identify a dynamically stable, neutral, and unstable motion (positive, neutral, and negative dynamic stability);
— describe/identify periodic and aperiodic motion.
(05) Explain what combinations of static and dynamic stability will return an aeroplane to the equilibrium state after a disturbance.
081 04 01 02 Precondition for static stability
(01) X Explain an equilibrium of forces and moments as the initial condition for the concept of static stability.
081 04 01 03 Sum of forces
(01) X Identify the forces considered in the equilibrium of forces.
081 04 01 04 Sum of moments
(01) Identify the moments about all three axes considered in the equilibrium of moments.(02) Discuss the effect of sum of moments not being zero.
081 04 02 00 Intentionally left blank
081 04 03 00 Static and dynamic longitudinal stability
081 04 03 01 Methods for achieving balance
(02) 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.
(03) Explain the influence of the indicated airspeed on the magnitude and direction of the balancing force on the stabiliser.
(04) Explain the use of the elevator deflection or stabiliser angle for the generation of the balancing force and its direction.
(05) Explain the elevator deflection required to balance thrust changes.
081 04 03 02 Static longitudinal stability
(01) Discuss the effect of the CG location on pitch manoeuvrability and longitudinal stability.
081 04 03 03 Neutral point
(01) X Define ‘neutral point’.(02) X Explain why the location of the neutral point is only dependent on the aerodynamic design of the aeroplane.
081 04 03 04 Factors affecting neutral point
(01) Describe the location of the neutral point relative to the locations of the aerodynamic centre of the wing and tail.
081 04 03 05 Location of centre of gravity (CG)
(01) Explain the influence of the CG location on the static longitudinal stability of the aeroplane.(02) Explain the CG forward and aft limits with respect to:
— longitudinal control forces;
— elevator effectiveness;
— stability.
(03) Define ‘static margin’.
081 04 03 06 The Cm–α graph
(01) X Describe the Cm–α graph with respect to the relationship between the slope of the graph and static stability.081 04 03 07 Factors affecting the Cm–α graph
(01) Explain:— the effect on the Cm–α graph of a shift of CG in the forward and aft direction;
— the effect on the Cm–α graph when the elevator is moved up or down;
— the effect on the Cm–α graph when the trim is moved;
— the effect of the wing contribution and how it is affected by the CG location;
— the effect of the fuselage contribution and how it is affected by the CG location;
— the tail contribution;
— the effect of aerofoil camber change.
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081 04 03 10 The stick force versus speed graph (IAS)
— speed;
— altitude;
— mass.
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081 04 03 12 The manoeuvring stability/stick force per g
(02) Explain why:
— the stick force per g has a prescribed minimum and maximum value;
— the stick force per g decreases with pressure altitude at the same indicated airspeed.
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081 04 03 14 Factors affecting the manoeuvring stability/stick force per g
— CG location;
— trim setting.
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081 04 03 16 Dynamic longitudinal stability
(02) Explain why the short-period motion is more hazardous than the phugoid.
(03) Describe ‘pilot-induced oscillations’.
(04) Explain the effect of high altitude on dynamic stability.
(05) Describe the influence of the CG location on the dynamic longitudinal stability of the aeroplane.
081 04 04 00 Static directional stability
081 04 04 01 Definition and effects of static directional stability
(02) Explain the effects of static directional stability being too weak or too strong.
081 04 04 02 Sideslip angle
(01) Define ‘sideslip angle’.(02) Identify β as the symbol used for the sideslip angle.
081 04 04 03 Yaw-moment coefficient Cn
(01) X Define the ‘yawing-moment coefficient Cn’.(02) X Define the relationship between Cn and β for an aeroplane with static directional stability.
081 04 04 04 Cn–β graph
(01) X 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.
(02) X Identify how the slope of the Cn–β graph is a measure for static directional stability.
(03) X Identify how the slope of the Cn–β graph is affected by altitude.
081 04 04 05 Factors affecting static directional stability
(01) 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.
(02) Explain why both the fuselage and the fin contribution reduce static directional stability when the CG moves aft.
081 04 05 00 Static lateral stability
081 04 05 01 Definition and effects of static lateral stability
(02) Explain the effects of static lateral stability being too weak or too strong.
081 04 05 02 Bank angle Ø
(01) X Define ‘bank angle Ø’.
081 04 05 03 The roll-moment coefficient Cl
(01) X Define the ‘roll-moment coefficient Cl’.
081 04 05 04 Contribution of sideslip angle (β)
(01) Explain how without coordination the bank angle (Ø) creates sideslip angle (β).
081 04 05 05 The Cl–β graph
(01) X Describe the Cl–β graph.(02) X Identify the slope of the Cl–β graph as a measure for static lateral stability.
(03) X Identify how the slope of the Cl–β graph is affected by altitude.
081 04 05 06 Factors affecting static lateral stability
(01) Explain the contribution to the static lateral stability of:— dihedral, anhedral;
— high wing, low wing;
— sweep angle of the wing;
— ventral fin;
— vertical tail.
081 04 06 00 Dynamic lateral/directional stability
081 04 06 01 Intentionally left blank
081 04 06 02 Tendency to spiral dive
(02) 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.
(03) Describe an unstable spiral dive mode with respect to deviations in speed, bank angle, nose low-pitch attitude, and decreasing altitude.
081 04 06 03 Dutch roll
(01) Describe Dutch roll.(02) Explain:
— why Dutch roll occurs when the static lateral stability is large compared to static directional stability;
— the condition 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.
(03) State the effect of Mach number on Dutch roll.
081 04 06 04 Effects of altitude on dynamic stability
(01) Explain that increased pressure altitude reduces dynamic lateral/directional stability.