Transcript Airplane Axes - 180 Mosquito

Theory of Flight
Airplane Axes
Lesson 2.3
Sep 2012
Reference
From the Ground Up
Chapters 2.1.3, 2.1.4:
The Axes of an Airplane, Stability
Pages 23 – 26
Introduction
• There are three axes around which an
airplane moves. Each run through the C
of G, are controlled by the pilot, and are
stabilized by features in the aircraft.
Outline
• Airplane Axes
• Balanced Controls
• Stability
Airplane Axes
Lateral Axis
(wing tip to wing tip)
Longitudinal Axis
(nose to tail)
Vertical (or Normal) Axis
(vertical through C of G)
Longitudinal Axis
Movement around: Roll
Controlled by: Ailerons
Attitude: Left/Right Bank
Lateral Axis
Movement around: Pitch
Controlled by: Elevator
Attitude: Nose Up/Down
Vertical Axis
Movement around: Yaw
Controlled by: Rudder
Attitude: Nose Left/Right
Balanced Controls
• Control surfaces sometimes balanced to help
pilot move them and reduce flutter
• Inset Hinge/Horn Balance
– Part of control surface in front of hinge
– Airflow helps pilot to move it
• Mass Balance
– Streamlined mass in front of control surface hinge
– Reduces flutter
Balanced Controls
Horn Balance
Mass Balance
Stability
• Stability
– 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 pilot
• Inherent Stability
– Stability from design features of an aircraft
– Affected by weight and C of G
Stability
Static Stability
Initial tendency to return to original position
Dynamic Stability
Overall tendency to return to
original position, after series
of oscillations
Straight flight disturbed
by upward gust of wind
Stability
Neutral Stability
Aircraft continues in disturbed position
Negative Stability (AKA Instability)
Aircraft moves further away from
disturbed position
Positive Stability
Aircraft returns to original position
Straight flight disturbed
by upward gust of wind
Longitudinal Stability
= Pitch Stability = Stability around Lateral Axis = Corrects unwanted pitch
Horizontal Stabilizer
Airflow hitting stabilizer pushes aircraft
back to original position if disturbed
Longitudinal Stability
Center of Gravity
C of G affects nose up/down tendencies
if too far rear/forward of C of P
* Airplane must never be tail-heavy, or
unable to recover from stalls
Lateral Stability
•
Lateral Stability = Roll Stability = Stability around Longitudinal Axis
•
Dihedral
– Angle that each wing makes with horizontal
– If wing is displaced downwards, airplane slips into that direction
causing more airflow to down going wing and lifting it
•
Keel Effect
– High-wing aircraft have weight below wings acting as pendulum to
return aircraft to original position if wing displaced
•
Sweepback
– If aircraft is disturbed and a wing dips, lower frontward wing is
exposed to more airflow
– This creates more lift in frontward wing, thus picking it up
Lateral Stability
Keel Effect:
Directional Stability
= Stability around vertical/normal axis = Corrects unwanted yaw
Vertical Stabilizer
Airflow hitting vertical stabilizer pushes aircraft
back to straight flight when disturbed
Directional Stability
Sweepback
Airflow hitting one wing is more perpendicular to relative airflow,
creating more drag and pushing it back
Next Lesson
2.4 - Theory of Flight
Flight Performance
From the Ground Up
Chapters 2.1.5, 2.1.6, 2.1.7:
Flight Performance Factors, Airspeed
Limitations, Mach Number
Pages 26 - 33