Aircraft wing configuration- High wing aircraft

High wing aircraft


Image from:-en.wikipedia.org

Aircraft are classified based on various ways. Aircraft are also classified according to their wings configuration. There are three types of wing configuration
2.Mid wing aircraft
3.High wing aircraft

In previous post we learnt about low wing aircraft for previous posts on low wing aircraft Click here. So today we are going to learn about High wing aircraft.

High wing aircraft

Aircraft having wings attached at the top of the fuselage are known as High Wing aircraft. Generally almost all the cargo aircrafts have a High Wing configuration.


Advantages of High wing aircraft

  • Better visibility for the passengers sitting at the side of wings unlike low wing aircraft.
  • Lots of space available for ground staff to do maintenance of the aircraft whereas low wing aircraft blocks the space.


 Disadvantages of High wing aircraft

  • It blocks the visibility of pilot while turning.
  • Refueling is a tedious task due to the height of the wing.

Examples of High wing aircraft

1.Antonov An-225

2.Airbus CASA C295
Image from:-www.flickr.com

3.Boeing globemaster C17


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What are contrails?

Contrails

Have you ever seen something in sky which looks similar to the picture below.

Image From:-en.wikipedia.org

Here's the explanation for this....

Those white streaks planes leave behind are actually artificial clouds. They're called contrails, which is a shortened version of the phrase “condensation trail."Airplane engines produce exhaust, just like car engines do. As hot exhaust gases escape from a plane, the water vapor in the fumes hits the air. At heights of 26,000 feet or more, the air is extremely cold. The cold air causes the water vapor to condense. This means the water vapor turns into tiny water droplets or even freeze into tiny ice crystals before eventually evaporating. This condensed water vapor and mixture of ice crystals make up the cloud-like trails you see in the sky.

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Aircraft wing configuration- Low wing Aircraft

Low wing aircraft


Image from:-en.wikipedia.org

There are various types of aerial vehicles. Aircraft are one of the them. Aircrafts are classified based on various criteria. One of the criteria of classification is based on the position of its wings. Aircraft are classified as 
1.Low wing aircraft

So today we are going to talk about low wing aircrafts.

What is this?

Have you ever seen this in the sky? click here for the explanation of this thing.
Image From:-en.wikipedia.org

Low Wing Configuration

Low wing aircrafts are aircrafts whose wings are attached at the bottom of the aircraft fuselage. Now a days almost all the passenger aircraft have a low wing configuration.

Advantages of Low Wing Configuration

  •  The wings are attached at the bottom of fuselage so it is easy to refuel the aircraft.
  • Low wing configuration aircraft have a better visibility above and at the sides of the aircraft.
  • Low wing config causes better ground effect which increases lift and reduces drag of the aircraft when it is nearer to the earth's surface.
  • It supports the landing gears.

Disadvantages Low wing Configuration

  • Passengers visibility gets blocked.
  • Lack of space for movement on ground for ground staff at the time of aircraft maintainance.

Examples for low wing aircraft

1.Airbus A380
Image From:-en.wikipedia.org

2.Boeing 787
Image From:-en.wikipedia.org

What is this?

Have you ever seen this in the sky? click here for the explanation.
Image From:-en.wikipedia.org

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Why are aircraft windows round?

Why are aircraft windows round?


Airbus A380 Aircraft round windows
Round Aircraft windows - Wikimedia

Ever wondered why aircraft windows are always round in shape?
Aircraft windows were not always in round shape. In the 1950's, the de Havilland Comet aircraft of British Airways had square windows.

de havilland comet square windows
de Havilland Comet square windows - Wikimedia

This aircraft crashed killing all 56 people in total. The crash of this aircraft taught a very important lesson about the shape of aircraft windows to aircraft engineers.

British Airways Aircraft crash
British Airways Aircraft crash - Wikimedia

As we go higher, atmospheric pressure decreases but the air pressure inside the aircraft is adjusted so that passengers can feel comfortable during the flight. So this means that the air pressure inside the aircraft cabin is higher than the air pressure outside. Hence the high air pressure applies force on the fuselage in the outward direction which causes stress in the fuselage.

In a case of square windows, this stress gets concentrated at corners, where edges of square windows meet at 90° causing damage to the fuselage. Also for any other shape with an angle in it, the force will concentrate on the angles. So we need the shape of the aircraft windows such that there are no angles. So the circle is the apt shape. But oval shape windows are used in a Aircraft as they give a better view of the scenery to passengers.

In such windows, stress is distributed uniformly all over the circumference. So the stress won't concentrate at a single point. And hence it won't damage the fuselage.

Check out this video!




So this is the reason that all aircraft have rounded windows.
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Types of drag on aircraft

Types of drag

Types of drag
Drag - Wikimedia

Drag:-

Drag is one of the four aerodynamic forces that act on a plane. For more information on aerodynamic forces click here. Drag is a restrictive force which opposes the motion of an aircraft. There are various types of drag depending upon their sources

Types of drag

  • Parasite drag
  • Form drag or pressure drag
  • Skin friction drag
  • Profile drag
  • Interference drag
  • Lift induced drag
  • Wave drag
ADetailed explanation of each type of drag is given below

1. Parasite drag
Parasite drag is a drag produced due to the motion of an object through a fluid. With respect to aviation, the object is an aircraft and the fluid is the atmospheric air. Parasite drag occurs due to air molecules. Parasite drag is classified as form drag or pressure drag, skin friction drag and interference drag.

2. Form drag or pressure drag
Form drag - Wikimedia
Form drag is produced due to the shape of the object moving through the fluid. It depends on the cross section of an object. An object with a larger cross section and blunt shape will have a larger form drag whereas an object with a smaller cross section area and a sharper shape will have a lesser form drag.

How is form drag reduced?
It can be reduced using smaller cross section area for making wings and by using aerodynamic shape for an aerofoil.

3. Skin friction drag
Skin friction drag is a drag produced due to friction between an object (aircraft) & fluid (atmospheric air). The rough surface will have high skin friction drag and conversely a smooth surface will have less skin friction drag.

How is skin friction drag reduced?
Making the aircraft skin smooth will reduce skin friction.

4. Profile drag
Profile drag is a sum of the form drag & skin friction drag.

5. Interference drag
Interference drag is produced due to the interference of two or more airflows having different speeds. And this drag is produced by the interference of different aircraft parts, that is, due to a mixture of airflow around wing and the airflow around the fuselage.

How interference drag is reduced?
This can be reduced by keeping the angle between these two below 90 degrees

6. Lift Induced drag

Lift induced drag
Lift induced drag
Lift is another aerodynamic force. It is a force which keeps an aircraft in the air and its magnitude is equal to the weight of the aircraft during stable flight. The direction of lift is perpendicular to the oncoming airflow towards the aircraft. Lift induced drag, as the name suggests, is a drag produced due to lift. At slower speed & higher angle of attack, aircraft will have more lift. But as the angle of attack increases, the air pushes the aircraft in the backward direction. This backward push is the induced drag. Technically speaking change in a vector direction of lift of the aircraft results in the formation of this type of drag.

Other types of induced drag are due to a mixture of airflow above and below the wing. The air flow mixes at the tips of the aircraft. We know that speed of airflow above the wing is higher than the speed of an airflow below the wing. Want to know the reason? Check here!

At the wing tips, these two air flows with variable speed, get mixed with each other which produces vortices at wing tips. The Reason for production of vortices is that high-pressure airflow gets pulled toward low-pressure airflow. 

How is lift induced drag reduced?
                                                                          
Using winglet or shark-lets at wing tips.

Winglets
Winglets - Wikimedia

8.Wave drag

Wave drag is generally produced at transonic speed (speed almost equals to speed of sound) & Supersonic speed (speed greater than speed of sound). Due to high speed of airflow, shock waves are produced. Shockwaves are nothing but the disturbance in the air. This disturbance increases drag of the aircraft known as wave drag.

How wave drag is reduced?
NASA F-15 - Wikimedia
Shock wave drag is one of the reason that at present time there are no supersonic passenger aircraft. Hence scientists are looking for the way to reduce shock wave drag. NASA is trying to reduce the shock wave drag by making aircraft noses sharp.  NASA's quite spike  F-15 is aircraft somewhat reduced the shockwave drag.

Drag Curve
Drag Curve - Wikimedia
This drag curve shows the variation of different types of drag with respect to airspeed.


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How do airplanes fly?

How do airplanes fly?

How Airplanes fly
How do airplanes fly

Airplanes have made human life faster. We know that when a small stone is thrown up it will come back to the earth due to its gravitational force. On the other hand an airplane, with hundreds of passengers, flies thousands of kilometers. So how do airplanes fly? We will unveil this mystery today.

So basically, there are four forces acting on the airplane which makes them fly and keeps it in the air.
Aerodynamic forces acting on the aircraft
Aerodynamic forces: - Wikimedia

How do airplanes fly?

Four forces which help an airplane fly are

1. Weight
2. Lift
3. Thrust
4. Drag

1. Weight

The weight of an airplane is due to the gravitational pull of the earth. The direction of this force is towards the center of the earth. The magnitude of this force equals to 'mg'. Where 'm' is the mass of an airplane & 'g' is acceleration due to gravity. The point at which this force acts is known as the centre of gravity of the aircraft. The location of the center of gravity of the aircraft is very important. Stability of the aircraft depends on the location of its center of gravity. Center of gravity of the aircraft is positioned in such a way that if any, external disturbance, such as wind, disturbs flight of the aircraft, it should return to its original position on its own. The Airbus A380 is world's biggest passenger aircraft. The maximum takeoff weight of the Airbus A380 is 560,000kg (1,234,600lb).

2. Lift

The lift force on an aircraft is equal to the weight force of an aircraft while in cruise. The lift force acts normal to the direction of oncoming airflow towards the airplane. This force keeps the aircraft in the air. An aircraft gets lift from its wings. Lift to the aircraft wings is produced due to their aerofoil shape (cross section shape of the wing). Lift is produced due to the presence of the pressure difference above and below the wing. There are two main explanations for the production of lift. One is Bernoulli's principle and other is Newton's third law.  Click here for more details on the lift.

3. Thrust

Aircraft engine - propulsion device
Aircraft Engine - Wikimedia

Thrust is a force which pushes an aircraft forward. Thrust is provided to the aircraft with the help of engines. There are various types of engines used. In early aircraft, piston engine was used. Various arrangements of piston engine such as V-shaped, linear & circular arrangements were used for various purposes. Nowadays turboprop engine, turbojet engine, turbofan engines are used. The afterburner is used to increase the thrust of the aircraft for some time. For supersonic aircraft Ramjet & Scramjet engines are used. Conservation of momentum is the principle for working of engines. In an aircraft engine, Enthalpy (heat energy) of air is increased by increasing its pressure by compressing it in the compressor and increasing its temperature in the Combustion Chamber. Then this energy is converted into kinetic energy. Which results in a change in momentum and production of thrust.

4. Drag

The drag force is a restrictive force to the motion of the aircraft. The drag force is equal and opposite in magnitude to the thrust force in a steady condition (cruise) of the aircraft (When an aircraft travels at constant speed). There are various types of drag. Mainly Parasite drag, Lift induced drag, Wave drag, Skin friction drag, Form drag, Interference drag. To know more about drag check out this article.


Thanks for reading!

Also Read: Different type of drag