regional gliding school stability stability is the tendency of an airplane in flight to remain in...
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![Page 1: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/1.jpg)
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Regional Gliding School
Stability• Stability is the tendency of an airplane in
flight to remain in straight, level, upright flight and to return to this attitude if displaced, without corrective action by the pilot.
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Regional Gliding School
Static Stability• The initial tendency of an airplane when
disturbed to return to its original position.
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Regional Gliding School
Dynamic Stability• The overall tendency of an airplane to
return to its original position, following a series of damped out oscillations.
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Regional Gliding School
Stability may be:• Positive
– meaning the airplane will develop forces or moments that tend to restore it to its original position.
• Neutral – meaning the restoring forces are absent and the
airplane will neither return from its disturbed position, nor move further away.
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Regional Gliding School
Stability may be:• Negative
– meaning it will develop forces or moments that tend to move it further away. Negative stability is Instability.
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Regional Gliding School
Longitudinal Stability• Longitudinal Stability is pitch stability or
stability around the lateral axis of the airplane.
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Regional Gliding School
Two factors influence longitudinal stability
• The Horizontal Stabilizer • When a disturbance increases the angle of attack on
the wings, the nose goes up and the tail down. As the stabilizer moves down it meets the air at a greater angle of attack, obtains more lift and tends to restore the aircraft to straight and level flight.
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Regional Gliding School
Two factors influence longitudinal stability
• Center of Gravity• C of G is very important in achieving longitudinal
stability. If the airplane is loaded with the C of G too far aft, the airplane will have a nose up rather than a nose down attitude. The inherent stability will be lacking and even though putting the elevator down may correct the situation, control of the airplane in the longitudinal plane will be difficult and maybe impossible.
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Regional Gliding School
Confirmation Stage
NOTE: You must use the buttons in the Confirmation Stage
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Regional Gliding School
A
B
C
D
Static stability
Neutral stability
Dynamic stability
Let's try a few review questions on Theory of Flight:
Question #1 - When the restoring forces are absent and the airplane will neither return from its disturbed position, nor move further away is known as?
Positive stability
Theory of FlightTheory of FlightStabilityStability
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Flying Scholarship Program
![Page 13: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/13.jpg)
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Flying Scholarship Program
![Page 14: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/14.jpg)
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Flying Scholarship Program
![Page 15: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/15.jpg)
Flying Scholarship Program
That answer is correct.
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Regional Gliding School
Stability may be:• Positive
– meaning the airplane will develop forces ormoments that tend to restore it to its originalposition.
• Neutral – meaning the restoring forces are absent and the
airplane will neither return from its disturbedposition, nor move further away.
![Page 16: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/16.jpg)
Regional Gliding School
A
B
C
D
Longitudinal
Lateral
Vertical
Let's try a few review questions on Theory of Flight:
Question #2 - Longitudinal stability is pitch stability around or about what axis?
Normal
Theory of FlightTheory of FlightStabilityStability
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Flying Scholarship Program
![Page 18: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/18.jpg)
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Flying Scholarship Program
![Page 19: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/19.jpg)
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![Page 20: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/20.jpg)
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Regional Gliding School
Longitudinal Stability• Longitudinal Stability is pitch stability or
stability around the lateral axis of theairplane.
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Regional Gliding School
Lateral Stability• Lateral stability is stability around the
longitudinal axis or roll stability.
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Regional Gliding School
Lateral stability is achieved through:
• Dihedral• The Dihedral Angle is the angle that each wing
makes with the horizontal. When a wing is displaced, a flow of air will strike the down going wing at a higher angle of attack with a resultant increase in lift.
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Regional Gliding School
Lateral stability is achieved through:
• Keel Effect• Most high wing airplanes are laterally stable simply
because the wings are attached in a high position on the fuselage and because the weight is therefore low. When the airplane is disturbed and one wing dips, the weight acts as a pendulum returning the airplane to its original attitude.
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Regional Gliding School
Lateral stability is achieved through:
• Sweepback• When the aircraft is disturbed and a wing dips, the
lower frontward wing is exposed to more airflow. This will result in an increase in lift in the front ward wing.
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Regional Gliding School
Directional Stability• Directional Stability is stability around the
vertical or normal axis. The most important feature that affects directional stability is the vertical tail surface, that is, the fin and rudder.
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Regional Gliding School
The Fin
• An airplane has the tendency always to fly head on into the relative wind. If the airplane yaws away from its course, the airflow strikes the vertical tail surface from the side and forces it back to its original line of flight.
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Regional Gliding School
AXIS MOTION CONTROL STABILITYLongitudinal Rolling Ailerons Lateral
Stabilityaround theLongitudinalAxis.
Lateral Pitching Elevators LongitudinalStabilityaround theLateral Axis.
Normal Yawing Rudder DirectionalStabilityaround theNormalAxis.
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Regional Gliding School
Confirmation Stage
NOTE: You must use the buttons in the Confirmation Stage
![Page 29: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/29.jpg)
Regional Gliding School
A
B
C
D
Keel effect
Centre of gravity
Horizontal stabilizer
Let's try a few review questions on Theory of Flight:
Question #3 - Name a type of lateral stability?
Fin
Theory of FlightTheory of FlightStabilityStability
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![Page 31: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/31.jpg)
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![Page 32: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/32.jpg)
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Flying Scholarship Program
![Page 33: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/33.jpg)
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That answer is correct.
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Regional Gliding School
Lateral stability is achieved through:
• Keel Effect• Most high wing airplanes are laterally stable simply
because the wings are attached in a high position onthe fuselage and because the weight is therefore low.When the airplane is disturbed and one wing dips,the weight acts as a pendulum returning the airplaneto its original attitude.
![Page 34: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/34.jpg)
Regional Gliding School
A
B
C
D
Directional
Lateral
Longitudinal
Let's try a few review questions on Theory of Flight:
Question #4 - What stability is around or about longitudinal axis?
Normal
Theory of FlightTheory of FlightStabilityStability
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Flying Scholarship Program
![Page 36: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/36.jpg)
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![Page 37: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/37.jpg)
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![Page 38: Regional Gliding School Stability Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this](https://reader035.vdocuments.site/reader035/viewer/2022062511/551b18e45503462e578b5ec2/html5/thumbnails/38.jpg)
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That answer is correct.
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Regional Gliding School
Lateral Stability• Lateral stability is stability around the
longitudinal axis or roll stability.
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Regional Gliding School
Congratulations!!
You have now completed the Stability lesson of the Theory of Flight Module. Of course, this lesson is always available to you for future reference if required.
You are now ready to move along to the next Theory of Flight lesson you have not completed or to any other module you wish. You can advance to the Self Test Module if you feel ready to challenge the final exam.
Good Luck!
Theory of FlightTheory of FlightStabilityStability