Figure 3-6. Monoplane (left) and biplane (right).
Aileron
Fuel tank
Wing tip
Wing flap
Ribs
Stringers
Spar
Skin
Figure 3-7. Wing components.
Attached to the rear, or trailing edges, of the wings are two
types of control surfaces referred to as ailerons and flaps.
Ailerons extend from about the midpoint of each wing
outward toward the tip, and move in opposite directions to
create aerodynamic forces that cause the airplane to roll.
Flaps extend outward from the fuselage to near the midpoint
of each wing. The flaps are normally flush with the wing’s
surface during cruising flight. When extended, the flaps move
simultaneously downward to increase the lifting force of the
wing for takeoffs and landings. [Figure 3-8]
Alternate Types of Wings
Alternate types of wings are often found on aircraft. The
shape and design of a wing is dependent upon the type of
operation for which an aircraft is intended and is tailored
to specific types of flying. These design variations are
discussed in Chapter 5, Aerodynamics of Flight, which
provides information on the effect controls have on lifting
surfaces from traditional wings to wings that use both flexing
(due to billowing) and shifting (through the change of the
aircraft’s CG). For example, the wing of the weight-shift
control aircraft is highly swept in an effort to reduce drag
and allow for the shifting of weight to provide controlled
flight. [Figure 3-9] Handbooks specific to most categories
of aircraft are available for the interested pilot and can be
found on the Federal Aviation Administration (FAA) website
at www.faa.gov.
Plain flap
Basic section
Split flap
Slotted flap
Fowler flap
Slotted Fowler flap
Figure 3-8. Types of flaps.
Figure 3-9. Weight-shift control aircraft use the shifting of weight
for control.
Horizontal stabilizer
Rudder
Elevator
Vertical stabilizer
Trim tabs
Figure 3-10. Empennage components.
Empennage
The empennage includes the entire tail group and consists
of fixed surfaces, such as the vertical stabilizer and the
horizontal stabilizer. The movable surfaces include the
rudder, the elevator, and one or more trim tabs. [Figure 3-10]
The rudder is attached to the back of the vertical stabilizer.
During flight, it is used to move the airplane’s nose left
and right. The elevator, which is attached to the back of the
horizontal stabilizer, is used to move the nose of the airplane
up and down during flight. Trim tabs are small, movable
portions of the trailing edge of the control surface. These
movable trim tabs, which are controlled from the flight deck,
reduce control pressures. Trim tabs may be installed on the
ailerons, the rudder, and/or the elevator.
A second type of empennage design does not require an
elevator. Instead, it incorporates a one-piece horizontal
stabilizer that pivots from a central hinge point. This type of
design is called a stabilator and is moved using the control
wheel, just as the elevator is moved. For example, when a
pilot pulls back on the control wheel, the stabilator pivots so
the trailing edge moves up. This increases the aerodynamic
tail load and causes the nose of the airplane to move up.
Stabilators have an antiservo tab extending across their
trailing edge. [Figure 3-11]
The antiservo tab moves in the same direction as the trailing
edge of the stabilator and helps make the stabilator less
sensitive. The antiservo tab also functions as a trim tab to
relieve control pressures and helps maintain the stabilator in
the desired position.
Figure 3-12. Types of landing gear: floats (top), skis (middle), and
wheels (bottom).
Antiservo tab
Stabilator pivot point
Figure 3-11. Stabilator components.
Landing Gear
The landing gear is the principal support of the airplane when
parked, taxiing, taking off, or landing. The most common type
of landing gear consists of wheels, but airplanes can also be
equipped with floats for water operations or skis for landing
on snow. [Figure 3-12]
Wheeled landing gear consists of three wheels—two main
wheels and a third wheel positioned either at the front or rear
of the airplane. Landing gear with a rear mounted wheel is
called conventional landing gear.
Airplanes with conventional landing gear are sometimes
referred to as tailwheel airplanes. When the third wheel is
located on the nose, it is called a nosewheel, and the design
is referred to as a tricycle gear. A steerable nosewheel or
tailwheel permits the airplane to be controlled throughout all
operations while on the ground. Most aircraft are steered by
moving the rudder pedals, whether nosewheel or tailwheel.
Additionally, some aircraft are steered by differential braking.
The Powerplant
The powerplant usually includes both the engine and the
propeller. The primary function of the engine is to provide
the power to turn the propeller. It also generates electrical
power, provides a vacuum source for some flight instruments,
and in most single-engine airplanes, provides a source of
heat for the pilot and passengers. [Figure 3-13] The engine
is covered by a cowling, or a nacelle, which are both types
of covered housing. The purpose of the cowling or nacelle
is to streamline the flow of air around the engine and to help
cool the engine by ducting air around the cylinders.
The propeller, mounted on the front of the engine, translates
the rotating force of the engine into thrust, a forward acting
force that helps move the airplane through the air. A propeller
is a rotating airfoil that produces thrust through aerodynamic
action. A high-pressure area is formed at the back of the
propeller’s airfoil, and low pressure is produced at the face of
the propeller, similar to the way lift is generated by an airfoil
used as a lifting surface or wing. This pressure differential
develops thrust from the propeller, which in turn pulls the
airplane forward. Engines may be turned around to be pushers
with the propeller at the rear.
There are two significant factors involved in the design
of a propeller that impact its effectiveness. The angle of a