Wing configuration: - Dihedral wings, Anhedral wings, High wings and
Low wings
By
Kartik
Chaturvedi; K.Chetan Rao; Rohit De; Vishal Vishnukumar
Dihedral Wings
Introduction:
The
upward angle made by the wing along the span with the horizon is called a
dihedral or dihedral angle. The wings that are configured with this angle are
called a Dihedral Wings.
So why is the dihedral angle
added to the wing configuration?
If the airplane rolls in any direction, the
plane starts banking in the opposite direction, which means the nose of the
airplane also swings in the opposite direction. This is because
when you bank an airplane in any direction, the lift force acting on it will
tilt in the same direction as the bank. So, when that happens, the airplane
starts slipping in the same direction.
This phenomenon (known as adverse yaw) also
happens because the wing rotating upward experiences more drag than the wing
rotating down. Consequently, the airplane rotates because one wing has more
lift than the other. We know that lift requires work and this effect shows
itself as increased induced drag. Thus, the wing with the greatest lift has the
greatest drag.
A
dihedral adds stability because the adverse yaw results in a net reduced angle
of attack on the upper wing, and an increased angle of attack on the lower wing, producing slightly
more lift. So
now because the wings are tilted up slightly, a portion
of the relative wind strikes the underside of the low wing, pushing it back up
toward wings-level.
ADVANTAGES
AND DISADVANTAGES:
· If you have a
straight-wing aerial vehicle, there's no force that can bring the airplane back
to wings-level itself. This problem is solved by using dihedral wing.
· Airplane with more
dihedral is more stable, even during turbulence in air.
· Main disadvantage
of more dihedral angle is that it results in decreased roll rate and increased
drag.
Anhedral wings
Anhedral
is a type of wing configuration where two wing spans were bended downwards with
same angle and it is used basically in fighter aircrafts where maneuverability
is more important, this type of wings meets this criterion as it decreases the
stability thereby improving the maneuverability and this type of wings are also
used in big aircraft carriers like Antonov 225 which is very heavy so in order
to roll the aircraft more fluid force means difference between the lift of two
wingspans should be very high and by using dihedral wings it will take more
time to roll because of its high wing stability so because of this reason to
increase the roll rate anhedral wings are used as it has comparatively lower
stability and due to its lower stability it can roll the aircraft much faster
hence having high roll rate.
High wing: -
High wing aircraft
are aircraft whose wings are mounted above the fuselage. The wings on high wing
aircraft tend to be little dihedral or anhedral. There is clear, unobstructed
view of the ground. There is more ground clearance for avoiding low obstacles
and the pilots can easily detect the fuselage. The high wings resist some of
the sunlight from entering into the cockpit. This means welcome shade and
cooler cockpit temperatures during hot summer days. Shorter landing distance
due to lessened impact of ground effect. Gravity helps fuel flow from the tank
to engine without the need for a fuel pump. Inherently stable since the center
of mass is situated below the center of lift. Usable work and storage space
under wings when plane is in a hangar. Easier to get in and out of no walking
on the wings. Wings provide protection from sun, rain and snow when
loading/unloading and when sitting around the plane at air shows or fly-ins.
Easier to chock and un-chock main wheels. Some of the disadvantages are, during
a rough landing, the fuselage takes the brunt of the force without the wings to
help absorb the impact. The raised fuel tank location means you will probably
need to use a ladder during refueling. Obstructed view on base to final turn.
Restricted visibility of aircraft above the pilot. Heavier weight due to the
need for separate landing gear spars and wing spars. Longer and heavier landing
gear with narrower and less stable track. More sensitive to crosswind and
turbulence on and near the ground.
Low wing: -
In
low wing aircrafts, the wings are attached at the bottom of the aircraft
fuselage. This configuration can be extensively seen in almost all the modern-day
passenger aircrafts. Low wing aircrafts are preferably used for performance-based
flying and in flights where good maneuverability is desired
Advantages
§
Safer during emergency landings and gear up
landings as wings will absorb some of the impact rather than all the force
being concentrated on the fuselage as with a high wing aircraft
§
In an emergency water landing, the low wings can
float on the surface for several minutes. This allows time to evacuate.
§
The fuel tank is easy to reach and fill from the
ground
§
Shortened take off distance thanks to enhanced
ground effect
§
Better overhead views of the sky
§
Clear view on base to final turn
§
May be lighter weight because the same spar is used
for landing gear and wings
§
Can accommodate a shorter, more widely spaced main
gear which improves stability during taxiing (especially in high winds) and is
less prone to structural failure
Disadvantages
- The wing’s
proximity to the ground means that the pilot must be extra careful to
avoid even low obstacles like tie-downs or taxiway lights that a high wing
aircraft can just glide over.
- The wings block a
pilot’s view of the ground
- It takes more
effort to inspect the underside of the wings, so pilots are more likely to
skip over this important part of the pre-flight check
- The wings can
reflect sunlight back into the cockpit making it even hotter on a summer
day
- Fuel pumps are
needed to transport fuel from the tank to the engine since it is moving
uphill
- Reduced rudder and
elevator effectiveness since wing blocks airflow to tail during take-off,
landing, and at high angle of attack (AoA).
