Aeronautical Terms Defined
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Wing dihedral and polyhedral are two important design features of aircraft wings
that affect their stability and maneuverability. Here is a discussion on
the definitions, effects, and applications of these two features.
Wing dihedral refers to the upward angle at which the wings are mounted on the
fuselage of an aircraft. When the wings are angled upward, the tips are higher than
the roots, creating a V-shape. This design helps to increase stability and prevent
the aircraft from rolling, especially during turns.
The angle of dihedral can vary, but it typically ranges from 2 to 10 degrees.
The amount of dihedral required depends on the type of aircraft and its intended
mission. For example, gliders and small single-engine aircraft typically have a
higher degree of dihedral to provide more stability, while high-performance fighter
jets have a lower degree of dihedral to provide more maneuverability.
Wing polyhedral refers to a more complex design feature, where the wings are
angled upwards at different amounts. The purpose of wing polyhedral is to improve
stability, especially during turns. Unlike wing dihedral, which angles the wings
in a single direction, wing polyhedral angles the wings in different directions,
creating a more complex wing shape.
This design feature is common on gliders and light aircraft, but it is also used
on larger aircraft, including airliners, to provide improved stability during turns
and turbulence. The amount of polyhedral required also depends on the type of aircraft
and its intended mission.
Effects of Wing Dihedral and Polyhedral
Wing dihedral and polyhedral both have a significant effect on the stability
and maneuverability of aircraft. In general, a higher degree of dihedral or polyhedral
provides more stability, while a lower degree provides more maneuverability.
Dihedral provides stability by making the aircraft more resistant to rolling,
especially during turns. The upward angle of the wings creates a self-righting moment
that helps to prevent the aircraft from rolling, which is especially important during
turns and turbulence.
Polyhedral provides stability in a similar manner, but with a more complex design.
The different angles of the wings create a more complex set of lifting forces, which
helps to improve stability, especially during turns.
Applications of Wing Dihedral and Polyhedral
Wing dihedral and polyhedral are used in a wide range of aircraft, from gliders
and light aircraft to airliners and military aircraft. The amount of dihedral or
polyhedral required depends on the type of aircraft and its intended mission.
For example, gliders and light aircraft typically have a higher degree of dihedral
or polyhedral to provide more stability, while high-performance fighter jets have
a lower degree to provide more maneuverability. Airliners use a moderate amount
of dihedral or polyhedral to provide a balance between stability and maneuverability.
Anhedral is a term used to describe the downward angle of the wings on an
airplane relative to the horizon. An airplane with anhedral wings has wings that
are tilted downwards at the outer tips. The opposite of anhedral is dihedral,
which refers to wings that are tilted upwards at the outer tips.
Anhedral is often used in aircraft design to improve stability and reduce the
risk of a spin or uncontrolled roll. By tilting the wings downwards, the wings
present a smaller surface area to the oncoming air, reducing the risk of a stall
or loss of control. Additionally, the downward tilt of the wings helps to dampen
any rolling motion, improving stability and control.
Anhedral is commonly used in light aircraft and regional jets, where
stability and control are critical considerations. In contrast, high-performance
military and racing aircraft often have dihedral wings to improve stability and
handling during high-speed turns and maneuvers.
Posted February 4, 2023