EngineeringClicks

Main Parts of an Airplane and their Functions

Although aircrafts have evolved a lot since the WWI, the major components of an aircraft have remained same.  The location, size and type of the components may vary from a Cessna 172 to Boeing 727, however the primary functionality of the components remains same.

Major parts of an Airplane

 

Powerplant

Flight Instruments.  First row, from left to right 1) Air speed indicator, 2) Altitude indicator, 3) Altimeter Second row, from left to right 4) Turn Coordinator, 5) Compass & 6) Vertical speed indicator . Image source: CC BY-SA 3.0

The powerplant, perhaps the most important of components, is a combination of both the engine and the propeller. The primary function of an engine is to generate the power necessary to run the propeller. In modern aircrafts, the powerplant is also used to generate electrical power necessary for operating all the electrical components i.e. flight instruments, and heat the cabin as the temperature goes down by ~10 degrees/1000m elevation.

In earlier small sized aircrafts the engine was positioned in the front of the fuselage. However, with the advent of commercial flying and transportation, the need for ever larger aircrafts has increased. Massive aircrafts demand considerable lift and thrust force and now need multiple powerplants. As a consequence the engine has been shifted to the either side of a fuselage to accommodate multiple powerplants. Nacelle is the part that covers the engine under the wing and it streamlines the flow of air for efficient combustion of fuels. The propeller, which is mounted on the front of the engine, converts the power developed by engine into forward thrust.

Image source: CC BY-SA 4.0

Airplane fuselage

The fuselage includes the cockpit, for pilots and the cabin, for passengers.  It will often have additional space for cargo depending upon the type of aircraft. The construction of the fuselage will vary on different types of aircraft. Materials ranging from wood to welded steel tubes were used to make the fuselage during WW II. Today, to reduce weight and increase strength, hydroformed aluminium tubes are used to make the fuselage in modern small sized aircrafts. You will also find that the fuselage of the airplane is generally covered with aluminium sheets.

Types of airplane fuselage

Truss

In the truss fuselage structure the loads are not uniformly distributed through-out the body. Further more, this type of structure offers minimum cabin space. To uniformly distribute the forces, a monocoque or semi-monocoque chassis is used to make modern aircrafts as depicted in the image below.

The monocoque & semi-monocoque design

The monocoque skin is used to support loads. This structure can be very strong but cannot tolerate dents/deformation of the surface. For example, you can exert considerable force to the ends of an aluminium can without causing any damage. But, if you damage it through the sides it will collapse. As a consequence the monocoque chassis can be used for smaller aircrafts. However, it is not suitable for mammoth commercial aircrafts as they are subjected to bending (and sagging) loads, demanding tremendously high shell thickness.

Modern aircrafts use a combination of monocoque and truss chassis (stringers) to overcome the problems associated with the monocoque and truss chassis.

Wings

Image source: Thierry Dugnolle [CC0], from Wikimedia Commons

Image source: NASA derivative work: Retama [Public domain], via Wikimedia Commons

 

The wings are aerofoils attached to each side of the fuselage to generate lift. As the air particles passes through the wing, the shape of the wing creates differential pressure. The angle of wing is varied (or separate flaps attached on wings) either to change the magnitude of lift force or to control the speed and lift while taking off and landing. Here is a simulation indicating the change in lift force according to the angle. The force is 0 at symmetric aerofoil and increases with the angle. The lift force increases gradually and reaches a peak at ~15 degrees. After 15 degrees the air particles are separated from the wing and the aircraft will stall.

Empennage

The empennage consists of fixed surfaces such as the vertical stabilizer and the horizontal stabilizer and movable surfaces such as the rudder and the elevator.

Image source: Pearson Scott Foresman [Public domain], via Wikimedia Commons

Stabilizers

The stabilizers’ job is to provide stability to the airplane on both vertical and horizontal planes:-

The rudder

The rudder is a movable part of vertical stabilizer and it helps the aircraft maintain the position of the nose while negotiating a curve. Interestingly the rudder isn’t used for turning, it is used for stabilizing the aircraft while turning. The aircraft turns by banking its wings at a specified angle depending upon the curve.

The elevators

The elevators contribute to the pitch stability and they also help in changing the angle of attack of an aircraft. When elevator moves up an increased downward force, produced by up elevator, forces the tail down and the nose up. Whereas when the elevator moves down, a decreased downward force at the tail causes the tail to rise and the nose to lower.

Landing Gear

As fellow pilots would say, one wishes to be in the air forever but eventually life happens. Landing gear is the part of an aircraft which allows the aircraft to land and takeoff again. It is the principle support of the airplane when parked, taxiing, taking off, or landing. The most common type of landing gear consists of wheels, but landing gears can also be floats for water operations, or skis for landing on snow.

The landing gear consists of three wheels—two main wheels and a third wheel positioned either at the front or rear of the airplane.  A steerable third wheel allows the pilot to perform all operations while on the ground.

Cessna Landing Gear