Aircraft without wings! (NASA M2-F1)

Wingless Aircraft NASA M2-F1

Image from: - Wikimedia

The wing is most important part of the aircraft. From my post, How Aircraft Fly, we know that Wing gives a lift to the Aircraft. To know about how Aircraft wing produces a lift, look at my this post. But in 1963 NASA developed an aircraft which had no wings. The Aircraft was NASA M2-F1.  Here M stands for Manned & F stands for flight. (So Manned 2 Flight 1).

M2-F1 was developed by NASA engineers at the Ames Research Center. It was developed as an alternative to a capsule spacecraft. So it can re-enter in earth's atmosphere.

Image from: - Wikimedia

The M2-F1 was made of wood, had an internal framework of steel tubes, looked like a bathtub sitting on a tricycle. M2-F2 didn't use wings to produce lift. Aircraft was designed in such way that it used air flowing over its body to produce lift. This design allowed it to re-enter in earth's atmosphere and land on a runway like a conventional airplane. 

The wingless, M2-F1 aircraft design was initially conceived as a means of landing a spacecraft horizontally after atmospheric reentry. The absence of wings would make the extreme heat of reentry less damaging to the vehicle. M2-F1 took its first flight on 16 August 1963. But this design was rejected & retired on 16 August 1966.

General characteristics (From Wikipedia)

Crew: one
Length: 20 ft (6.1 m)
Wingspan: 14 ft 2 in (4.32 m)
Height: 9 ft 6 in (2.89 m)
Wing area: 139 ft² (12.9 m²)
Empty weight: 1,000 lb (454 kg)
Loaded weight: 1,182 lb (536 kg)
Max. takeoff weight: 1,250 lb (567 kg)
Powerplant: 1 × Solid fuel rocket, 250 lbf (~1.1 kN)

Performance (From Wikipedia)

Maximum speed: 150 mph (240 km/h)
Range: 10 mi (16 km)
Wing loading: 9 lb/ft² (44 kg/m²)

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Russian Plane Tupolev Tu-154 Crashed in Black Sea!

Tupolev Tu-154 Crash

Image From: - Wikimedia

A Russian military plane Tupolev Tu-154 has crashed in the Black Sea near Sochi. There are apparently no survivors, according to the Russian Defense Ministry. A Tupolev Tu-154 plane was carrying 92 people, including 84 passengers and 8 crew members. Tu 154 was an old model, no longer flown by airlines in Russia but still used by the military. It was 33 years old.

The plane took off from Moscow and was headed to the Russian Hmeymim airbase in Latakia, Syria. Coming from Moscow, the plane had landed in Sochi for refueling. It disappeared from radar 2 minutes after taking off from Adler airport, Sochi at 05:25 AM (Local Time) on Sunday. The flight data recorder has been recovered and brought to Moscow. Flight Data recorder was found by a Seaeye Falcon underwater remotely operated vehicle at a depth of 17m & 1,600m from the shore. The recorder was in a satisfactory condition. Investigators are searching for second black box & it is believed that it could be recovered shortly. According to BBC news reports, A plane was unable to gain height and for some reason - possibly overloading or a technical fault. According to the reports, the plane had made a U-turn back towards the coastline shortly after take-off, before disappearing off the radar. But in an audio recording of a final conversation between air traffic controllers and the plane, there was no sign of any difficulties. Voices were normal until plane disappear.

The cause of the disaster is still being investigated but there is no suggestion of a terror attack.

Information Courtesy: - BBC News, CCN News

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Why Do Air Traffic Control (ATC) Towers Have Slanted Windows?

Air Traffic Controller slanted windows

Image from: - Wikimedia

While waiting for a flight at the airport you must have seen a tall tower at every airport. That tall tower is called as Air Traffic Controller. Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground.

Each airport has its own ATC Tower. Even if different airports have different ATC towers you will see one thing common in all which is their slanted windows. Slant angles vary but most of the time slant angle is 15°.  But why are ATC towers windows are slanted?

There are various reasons one of which is, Many people assume that they are designed that way to prevent the sun's reflection or glare from disturbing incoming pilots. But its not valid explanation. Because not all the windows surrounding ATC tower have slanted windows, so if that's the reason then even buildings surrounding ATC tower which are having flat windows can disturb pilot!

Here are some of the valid reasons,

Slanted windows collect much less rainwater & wind-blown dust that sticks to drops of water as compared to flat windows. So this provides a much better look through windows. So person inside ATC tower can get good vision through such windows. 

we see reflections in a glass all the time, for example from computer monitors or car windows. But air traffic controllers must not have any distracting reflections as they monitor flights. By slanting windows, any other light from inside the tower such as Computer screens, etc. is reflected up onto the ceiling, which is painted black.

So these are some valid reasons for slanted ATC tower windows.

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shortest International Flight in the world

The World's shortest International Flight!

Image from:- wikimedia

In my Previous post, I mentioned about world's shortest flight. It is shortest domestic flight. This flight is between two islands in Scotland. But today I am going to tell you guys about world's shortest international flight.

Austrian Airline People's Viennaline provides world's shortest international flight. This flight is just eight minutes long. Just think about it, you will be in the another country just after flight of 8 minutes. This flight connects St. Gallen-Altenrhein in Switzerland to Friedrichshafen in Germany. Vienna Airline operates Embraer E170 for this shortest flight. The flight distance is just 20 km. Passengers can book this shortest journey between the two countries for around 40 euros.

(Route between two airports if traveling by car)
Courtesy: - Google maps

So, you can travel from Switzerland to Germany either by this flight in 8 minutes or by taking a train ride for two hours. If going by car it takes an hour to travel this distance of 63 km between two airports.

(Route between two Airports if travelling via train)
Courtesy: - Google maps

Previously, the world’s shortest international flight was a ten-minute journey between the Austrian capital Vienna and the Slovakian capital Bratislava.

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Shortest flight in the world

World's Shortest flight

Courtesy: - Google Maps

The world’s shortest commercial flight is between the two Orkney Islands, Westray and Papa Westray. These islands are just at north of Scotland. These two islands are separated by a distance of only 1.7 miles. This shortest flight is operated by Loganair Scotland's Airline.
Loganair operates this flight with one of its two Pilatus Britten-Norman BN2B-26 Islander aircraft.

Courtesy:- Wikimedia

The flight duration is officially two minutes, but under ideal wind condition can be completed in only 47 seconds. Pilot Stuart Linklater flew the short hop a record more than 12,000 times, more than any other pilot, before he retired in 2013. Linklater set the record for the fastest flight between the islands at 53 seconds

Courtesy: - Wikimedia

Tickets are priced at about $30 per passenger with no in-flight service.
It’s used by teachers, doctors, policemen and school pupils, helping them to go about their daily routines with ease and simplicity.

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What if aircraft door opened in mid flight?

What if aircraft door opened in mid flight?

Image from:- Wikimedia

Just think about it? what if aircraft door opened in mid flight?

First of all it is not Possible!
As we know air pressure decreases as we go higher. Air pressure inside aircraft cabin is maintained so that passengers won't face any kind of problems due to low pressure. There is a huge pressure difference inside and outside of the cabin. Aircraft doors are fixed from the inside. Air inside aircraft cabin applies internal pressure force on the door. And that's really a very massive force. And its not possible to open aircraft door.

Now consider hypothetical situation, some miracle happened & aircraft door opened in mid flight.

Due to high air pressure difference between aircraft cabin & atmosphere, everything near Aircraft door will suck out until pressure inside cabin becomes equal to atmospheric pressure.

Image from:- Wikimedia

Something like this happened in 1988, an Aloha Airlines flight Boeing 737 with 90 people on board was on route to Honolulu, cruising at an altitude of 24,000 feet, when a small section of the roof ruptured. Rapid decompression caused large section of roof tore off & flight attendant Clarabelle Lansing was sucked out of it. But all passengers were safe.

10 June 1990 British Airways Flight 5390,
Pilot Tim Lancaster was sucked out of aircraft as windshield of the aircraft broke. Check out the video for full story.

Also if aircraft door opened in mid flight temperature inside aircraft cabin will drop at massive rate. Amount of oxygen in aircraft cabin will drop.

But don't worry as I said earlier it is not possible that aircraft door will open in mid flight!

Thanks for reading!

What happens when Lightning strikes an aircraft?

Lightning strike on Aircraft

Aircraft lightning strike
Aircraft Lighting strike: - Wikimedia

Imagine you are in flight. And suddenly weather turns stormy. A lightning bolt struck on your aircraft. What will happen? Will you aircraft blast and crash?

Lightning is just electric current with a massive amount of energy. Lightning can be 5 times hotter than the surface of the sun. Lightning contains 5 billion joules of energy. And such massive energy containing bolt of lightning struck on your aircraft. But no need to fear. Today's aircraft can survive a lightning strike. Every aircraft experiences lightning strike at least once a year. Things which you will experience is just bright light and loud noise.

Pan Am flight 214 Boeing 707
Pan Am flight 214 - Wikimedia
But on 8th December 1963, Lightning struck on Pan Am flight 214(Shown in the picture above). And this flight with 81 on board crashed near Elkton, Maryland. This crash killed all 81. Actually what happened was lightning stricken on the fuel tank of the aircraft, causing burning of the fuel and wing broken. Aircraft lost its control. So after that incident aircraft, fuel tanks are protected by thick layer so lightning cannot damage it.

(Pan Am flight 214 Crash)
Pan Am flight 214 Boeing 707 crash
Pan Am flight 214 crash - Wikimedia
There are many modifications in today's aircraft. Today aircraft are manufactured in such a way that they can survive a lightning strike. Do you know even Aircraft itself produces lightning when it travels through clouds?

Static electrical buildup due to the friction between air and surface of the aircraft. The air friction separate electrons from atoms. It is same as rubbing balloon produces a static charge. Hence, the static wicks are used which provides pointed structure where air flow leaves aircraft surface. And additional charge flows away from the aircraft into the air.

Aircraft static wicks
Aircraft Static wicks - Wikimedia
Aircraft are mostly made up of Aluminum & its alloy. Aluminum & its alloys are a good conductor of electricity. Lightning usually strikes on the extremity of aircraft such as nose & wing tips.  So when Lightning strikes on aircraft it travels through conducting a body of aircraft. And continues to air.

Modern aircraft are made up of non-conducting material Carbon Fibre. So when Lightning strikes on such material this material resist current from flowing through it. And such massive electrical energy of lightning gets converted into heat energy & material burns. Hence such material is embedded with conducting material such as Aluminum. So when Lightning strikes, it flows through this material & protects aircraft from burning. This principle is same as that of Faraday's cage.

To protect aircraft electrical circuits from lightning, Aircraft circuits are grounded. Also, surge suppression device is used for protection.

So don't worry about a lightning strike on Aircraft while traveling in stormy weather.

Check out: - How are Airbus planes named?

Source: - Boeing

How does stealth technology work? (Stealth Technology behind B2 Spirit)

Stealth technology

Image from: - Wikimedia

RADARs are used to detect aircraft. But there are some aircraft which are designed in such a way that they get ignored by RADAR. Those aircraft are known as stealth aircraft. Those aircraft are not actually invisible but they are somewhat ignored by RADAR.

But how stealth aircraft get ignored by RADAR?

In my previous post, I told about how RADAR works? 
RADAR uses reflection & Doppler effect (Doppler shift) property of Radio waves to detect aircraft. Radio waves after reflection from aircraft go back to the RADAR receiver. If we modified our aircraft in such a way that after reflection, Radio waves won't reach back to Radio receiver of RADAR Then our aircraft will remain undetected.
Stealth aircraft do something like this only to remain undetected!

Let's talk about world's most expensive stealth bomber aircraft B2 Spirit & stealth technology behind it.
B2 spirit is most expensive stealth aircraft in the world. The production cost of 1 unit of B2 spirit including its designing, engineering, etc. is $2.1 billion.

Check out Cool B2 Spirit model kit on Amazon!

B2 Spirit Model kit - Amazon

Stealth technology behind B2 Spirit

B2 Spirit - Wikimedia

All the parts of B2 spirit are blended. So that this aircraft reflects the very little amount of Radio waves.
For maneuverability, this aircraft has two pair ailerons. One for normal flying & other for stealth flying. So that in a case of stealth flying reflection due to ailerons will be less.
Wings of the B2 Spirit are designed in such a way that whatever Radio waves aircraft will reflect back they will go away from Radio receiver of RADAR. Wings are angled backward.
The surface of B2 Spirit was coated with an alternate high-frequency material (AHFM). This material absorbs some amount of radio waves striking on aircraft.
The combination of these all features B2 spirit is low observable. B2 spirit is not 100% ignored by RADAR. But a number of Radio waves reflection is very low. Hence less observable.

Check out Cool B2 Spirit model kit on Amazon!

B2 Spirit Model Kit - Amazon

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How RADARs are used to detect an aircraft?

How RADARs work?

Image from:- wikimedia

RADARs are used to track an aircraft. RADAR stands for RAdio Detection And Ranging. Radio waves are used in RADAR for detection purpose. Radio waves are electromagnetic waves. Mainly two properties of radio waves are used for detection purpose. One is reflection property and other is doppler effect.
Let's discuss about these two properties of Radio waves!

Radio waves reflect back when they come in contact with any obstacle. It is same as reflection of sound waves. Echo is the best example for reflection of sound waves. Sound waves produced by sound source will reflect back when they collapse on obstacle kept in front of them. In this case we will hear an echo. Sound waves & Radio waves are completely different wave forms. But property of reflection is same in both the cases. Of course you cannot hear Radio waves. Then how can we find that radio waves are reflected back?
Transmitter of RADAR will transmit Radio waves. And receiver of RADAR will detect the reflected Radio waves.
In such a way Aircraft can be detected by using reflection property of Radio wave. Radio waves will reflect back from aircraft. Reflected waves are detected by Radio receiver. According to amount of radio waves received & time taken for reflection even type of aircraft can be detected.

Now we have detected that aircraft is flying! What about its speed? How can we obtain its speed?
For that second property of Radio waves i.e. Doppler effect(doppler shift) is used.

Doppler Effect
Speed of aircraft can be obtained by this property of radio waves. When radio waves collapse on fixed obstacle (obstacle which is not moving) radio waves will simply reflect back without any change. But when radio waves collapse on moving object, the frequency of radio waves will change according to motion of an object. If object is moving towards the RADAR, Frequency of Radio waves reflected back will increase. On the other hand if object is moving away from RADAR frequency of  Radio waves reflected back will reduce.
So based on change in frequency of radio waves computer automatically detects the speed of an Aircraft.

In such a way using two properties of Radio wave Aircraft can be detected.

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Aircraft into Space?

Aircraft into Space?

Aircraft into Space?

In my previous post, I mentioned that escape velocity is the maximum velocity of aircraft within earth's atmosphere. Escape velocity is minimum velocity required for any object to leave planet's atmosphere. On our earth 11.2 Kmps or 32 mach is escape velocity for any object.

When aircraft flies, its the earth's gravitational pull which keeps aircraft in earth's atmosphere. So aircraft can't go straight into space. Earth's gravity will pull aircraft into circular path as aircraft don't have much energy to escape from gravitational pull. So if we provide our aircraft energy to escape from earth's gravity our aircraft will leave earth's atmosphere. So we provide aircraft this energy in terms of kinetic energy.

Kinetic Energy= 1/2(mv^2)
M= mass of aircraft
V= Velocity of aircraft

Gravitational potential energy to leave earth's gravity= (Gm)/R - 0
G= Universal gravitational Constant
m= mass of earth
R= distance of aircraft from earth's centre.

(Gm/R is gravitational potential energy on earth's surface, 0 is gravitational potential energy at infinity (here, at infinity R becomes infinity so (Gm)/R becomes zero)

So, we will provide same energy to our aircraft which any object will have at infinite distance from earth.


1/2(mv^2) = (Gm)/R

So, velocity becomes

V= sqrt[(2Gm)/r]

So here, V is known as escape velocity which any object should have to  leave earth's atmosphere.
For earth it is 11.2Kmps or 32 Mach.

At such a high speed it is not possible to keep aircraft in earth's atmosphere. So what if we tried to keep aircraft in earth's atmosphere by turning aircraft nose down?

At present we use elevator to turn aircraft nose up & down.  if we use  elevator to turn aircraft nose down air impact will produce massive force of more than 11200N on elevator which will probably break elevator. Suppose if we make very strong elevator which can withstand such a massive force then is it possible to stay in earth's atmosphere at speed of escape velocity?
My answer is No!!
Because suppose aircraft is flying with speed exactly equal to speed of escape velocity & if we turn down aircraft nose using  elevator it will produce resistance to airflow & reduce speed of aircraft less than escape velocity.
If speed of  aircraft is little bit equal to or greater than escape velocity then aircraft will leave earth's atmosphere!!

Conclusion:- Escape velocity is maximum velocity of aircraft on earth!!!

How fast can an Aircraft fly on the Earth?

Maximum Aircraft speed on the Earth

Image from:- Wikimedia

The invention of Aircraft speeded up human life. First successful aircraft Wright flyer developed by Wright brothers had a speed of approx. 28.9 Mph (48 Km/h). Then in world war I & world war II there was a revolutionary development in the field of aviation.

Image from:- Wikimedia

In 1947 Chuck Yeager was first human to break the sound barrier with Bell X 1. That is Bell X 1 was the first aircraft to travel faster than the speed of sound [ Speed of sound is  767.2 Mph (1234.8 Km/h) ]. The speed of Bell X 1 was approx. 957.5 Mph (1,541 Km/h).

Image from:- Wikimedia

In 1969 passenger Supersonic Aircraft Concorde took its first flight. The top speed of Concorde was 1354.58 Mph (2180 Km/h). It was twice the speed of sound. Tupolev TU-144 was also the supersonic passenger Aircraft.

Image from:- Wikimedia

At present time Lockheed SR-71 Blackbird holds a record of world's fastest flown aircraft.  Top speed of Lockheed SR-71  Blackbird is approx. 2200 Mph (3540 Km/h). It is approx. 3 times the speed of sound.

Image from:- Wikimedia

North Americal X-15 is research aircraft with speed of 4,520Mph (7,274 Km/h). William J. Pete Knight flew it with top speed. It was approx. 7 times the speed of sound (6.7 Mach).

Image from:- Wikimedia

Engineers keep on trying to increase the speed of aircraft. So what is the maximum speed which aircraft can achieve on earth?

As we know from my previous post how lift is produced by the aircraft wing. And also how drag is induced to the aircraft due to lift. Check out this post (Check out lift induced drag).

As we keep on increasing the speed of aircraft first problem we faced is when aircraft reaches near the speed of sound. As Aircraft reaches near the speed of sound aircraft Shockwaves starts forming over a wing of aircraft. And when aircraft crosses sound barrier drag produced due to shock waves will make it difficult for a pilot to control aircraft.
But this problem has been solved by making some modifications in aerodynamic shape of the aircraft wing. Aerofoil used for supersonic aircraft are a diamond shaped.

Another problem due to supersonic flight is a Sonic boom. As Aircraft crosses sonic barrier sonic boom forms which have an ability to break glasses on the ground also it can create hearing problems to humans on the ground.The sonic boom is one of the reasons for why at present there are no any functioning supersonic passenger aircraft.  Aircraft industries are trying to solve this problem. NASA was successful in reducing sonic boom up to certain extent using spike cone to F15 Aircraft.

Image from:- Wikimedia

After this problem is solved we will be able to see supersonic passenger aircraft. So at present speed of sound i.e. 1 mach(767.2 Mph (1234.8 Km/h)) is a limit for the speed of  passenger aircraft. But not for combat aircraft. There are lots of combat aircraft with their top speed greater than a speed of sound.

Let's assume that we solved all the problems due to a high speed of aircraft. Then what will be the maximum speed of aircraft?

If we keep on increasing the speed of aircraft using rocket engines(Rocket propellant) at speed of 24987.26 Mph (11.1705 Km/s) Aircraft will leave earth's atmosphere at a height of 12 km from the surface of the earth.This velocity [24987.26 Mph (11.1705 Km/s)] is known as Escape velocity. Wanna know how? Check out now

But remember that as the height from the surface of the earth increases the density of air keeps on decreasing. so at that height aircraft won't get much lift on the wing. So maneuverability methods of aircraft won't be much effective which we use in a normal air(Ailerons & Rudders). But maneuverability is possible by thrusters. once aircraft is out of the atmosphere there won't be much air resistance, so no need of much power for thrust. This is also a reason for why we use space shuttles for space missions & not aircraft. Space shuttles have wings for re-entry purpose so it can glide & land successfully.

Image from:- Wikimedia

And again even if increase the speed of aircraft hypothetical there is nothing which can travel faster than speed of light!!!

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Why are Aircraft wings angled backwards?

Swept Wings

Image from:-

Nowadays almost all Aircraft wings are angled backward. Such wings are known as swept wings. So why we use swept wings in modern aircraft?

Speed of world's first heavier than air aircraft wright flyer was 48kmph. But now speed of modern aircraft is upto 800kmph to 900kmph.

Image from:-

As we know lift to the aircraft is due to pressure difference above & below the aircraft wing. Speed of airflow above the wing is higher than the speed of airflow under the wing. Even if an aircraft is moving with subsonic (less than the speed of sound) speed, the speed of the airflow above aircraft wing can be supersonic (greater than the speed of sound). This supersonic speed causes production of shock waves above aircraft wing. Shockwaves breaks the airflow above aircraft wing. So instead of moving in direction of shape of wing airflow goes straight causing production of drag. This flow causes drag to the horizontal stabilizer behind the aircraft. This creates difficulties to pilot to control aircraft.

So to overcome this problem, engineers placed horizontal stabilizer above its original position (as in bell X-1). So that straight airflow above aircraft wing won't cause any problem to the horizontal stabilizer. But it wasn't so effective.

Image from:-

So Engineers found another way to overcome this problem. They made aircraft wings swept.

Swept wings reduce the speed of the airflow above it. Speed of airflow gets divided into two components. One component parallel to chord line & other along the leading edge of the wing. This reduces the speed of airflow above the wing. So Shockwave is not produced.

But As we know the pressure difference above & below the wing produce lift. And this pressure difference is due to speed difference above & below the wing. As we are reducing the speed of airflow above the wing, keeping, speed of airflow below wing same this reduces lift to the aircraft. In a case of the high speed its not problem because lift produced is enough for aircraft. But in a case of low speed this is a problem. The Lift produced in a case of low speed is not enough. So some of the aircraft are having movable wings, which gets swept back in a case of high speed & stays normal in a case of normal speed.

Do you know?
Sweep angle of the Airbus A380 is 33.5°

Image from:-

Thanks for reading!

How winglets work?

How do winglets work?

Image from:-

If you look at the wing of the aircraft, you will see the bent wing tip. So what is the reason for such bent wing tips? 

Those bent wing tips of the aircraft are known as winglets. Winglets in aircraft are used for the very important purpose. Winglets of aircraft reduce the induced drag produced due to the air above & below the aircraft. If you have read our previous post related to how aircraft fly, then you know that how lift is produced. Air flowing above the wing has more velocity that air flowing below the wing. So, according to Bernoulli's principle higher the velocity lesser the pressure. So Aircraft wing has lesser pressure above the wing & higher pressure below the wing. This pressure difference causes lift.


But due to this velocity difference phenomena, air with the higher velocity above the wing pushes air with lesser velocity below the wing causing the production of vortices(Image is shown above). These vortices are like small tornadoes. These vortices produce drag & reduce lift to the aircraft. As these vortices produce disturbance to the flow of air. 

Image from:-

Richard T. Whitcomb(Image is shown above) concluded that Winglets can be used to reduce drag of the aircraft. By reducing drag aircraft can be made more fuel efficient. The idea about the winglets came from birds. Birds bent their wings while flying to reduce drag.

So aircraft wing tips were bent so that vortices produced due to air velocity difference will be small. So less drag will produce. As bent wing will force vortices to form on the side so that vortices won't disturb airflow.

Using winglets made the aircraft more fuel efficient as the drag of the aircraft was reduced.

Thanks for reading!

Aircraft Lighting: What do they mean?

Aircraft Lighting

Image credits: -

As aircraft nerds, we keep watching in the sky for aircraft.
If you look at the Aircraft at night you will see different colorful lights. What is the purpose of these lights? Are those lights installed just to make the aircraft look good?

Let's take a look at various aircraft lighting & know about their purpose.

Aircraft Lighting

Navigation Lights:-

Image from: - Wikimedia

Navigation lights are located at leading edge each wing tip. Navigation lights include two steadies(No flashing) colored lights. One is Green colored & other is Red colored. Greenlight is located at the leading edge of the Right wing tip, whereas the Red light is located at the leading edge of the Left wing tip. These lights help pilots of other aircraft to know the direction of motion of the aircraft.

Position Lights:-

Position lights could be located at trailing edge of each wing tip, at the end of the fuselage, trailing edge of the horizontal tail. They are white colored steady(No flashing) Lights. As these lights are located at the back of the aircraft it helps pilots of other aircraft to determine the direction of motion of the aircraft. The purpose of these lights is also to make aircraft visible at night to pilots of other aircraft.

Strobe Lights(Anti-Collision lights):-

Strobe lights are placed behind Red & Green Navigation lights. In some aircraft, these are also placed at trailing edge of the wing. These are high intensity flashing white lights. These lights flash at the rate of once per second. These are very bright lights. The purpose of these lights is to attract the attention of other pilots during flight.

Wing Lights:-

Image from: - Wikimedia

These lights are located at wing root of leading edge(Generally white in color). The main purpose of these lights is to make wings visible. These lights make aircraft visible while take-off & landing. Also, these lights help the pilot to inspect frozen ice on wings & damages on wings if any.

Taxi Lights:-

Image from: - Wikimedia

Taxi lights are located just in front of nose landing gear of the aircraft(Generally white in color). The purpose of these lights is to make runway visible while taxi, take-off or landing.These lights are generally used for aircraft ground operation purpose.

Anti-Collision Beacon lights:-

Image from: - Wikimedia

These are Red flashing lights(These lights rotate to produce the flash effect) located at top of fuselage & bottom of the fuselage. These lights flash at the slow rate. These are light which we watch from the ground, which flashes(Red flashing light). These lights are turned on when the pilot starts an aircraft engine. And remain on until the engines are turned on. When all engines are turned off these lights stops flashing. The purpose of these lights is to warn the ground person that engines are working.

Logo Light:-

Image from: - Wikimedia

Logo light is not compulsory light (Generally white in color). But these lights are used to show Company logo printed on the tail of the aircraft. Also, these lights could be used for advertisement purpose. These are located on the horizontal tail of the aircraft. 

Landing lights:-

Landing lights are used in aircraft to make runway visible while landing at night time or in low visibility region or foggy time. These lights could be located in front of the fuselage, at bottom of the fuselage, at the root of the leading edge of each wing tip.

Runway turnoff lights:-

Runway turnoff lights are located on leading edge of the wing tip. These are white colored lights. It provides front & side visibility of runways while taxiing, & turning on the runway.

Thanks for reading!

Aircraft Cockpit Sounds

Aircraft Cockpit Sounds

The aircraft sound warning system is an integral part of the cockpit.T his warning system plays a significant role when aircraft instruments or system faces some technical difficulty or problem.

This warning system in the form of sound or light tells pilot about the problem.

Warning sounds are made when aircraft is descending faster than the normal rate, low Terrain warning when aircraft is cruising at low altitude(where it may collide with any obstacles) , autopilot disconnect, etc..

Check out some of the warning sounds given below!!!

1.Autopilot Disconnect Sound

2.Incorrect Take-off configuration

3. Selected Altitude reached

4. Exited Selected Altitude

5. Windshear Warning

6.Excess Rate of Descend

Thanks for reading!

Hole in aircraft window- Breather Hole

Breather Hole

Window seat of the aircraft is the favourite seat of almost all of us aircraft nerds. Ordinary peoples will just see scenery from aircraft window. But we aircraft nerds observe various things of aircraft such as movement of various elements of aircraft wings such as slits, flaps, ailerons, aircraft engine, etc.

Have you ever taken a look on the small hole at the bottom of aircraft window? If not, then next time whenever you will travel by plane just take a look at that small hole at the bottom of aircraft window.

This small hole is known as breather hole or bleed hole. There are mainly two purposes of this hole
  • Controlling moisture
  • Equalizing pressure difference

The small air gap is present between outer & middle pane.
This tiny hole lets moisture escape from air gap & prevent aircraft window by fogging up or by frosting. And let passengers enjoy the outer scenery.

As stated breather hole also helps to equalizing pressure difference. As aircraft ascends atmospheric pressure decreases & cabin pressure is maintained by the cabin pressure stabilizer system as outer atmospheric low pressure is not good for human health. This causes a pressure difference between cabin & atmosphere. Which produces lots of physical stress on aircrafts window which can damage aircraft windows. So to prevent this damage breather hole is used. Breather hole equalizes the pressure difference between inner & outer aircraft window pane by releasing some amount of pressure in the air gap. So outer pane takes lots of pressure & middle pane acts as a fail safe. If the outer pane got damaged due to some reason air get leaked from breather hole & prevent middle pane by damaging.

This is why breather hole is used!!

Hope you guys understand the importance of that tiny hole.

Thanks for reading!

How do wings generate lift?

Lift theory

Aerofoil lift theory - NASA
Aerofoil lift theory - NASA
Lift on an aerofoil is due to the presence of pressure difference between above and below the aerofoil. According to Bernoulli's principle, this pressure difference is a result of the difference in the velocity of airflow above & below the aerofoil. But most of the people are having a misconception about what is a cause of velocity differences above and below the aerofoil.

Incorrect Lift Theory: - Aerofoils are shaped in a such a way that upper surface is more curved than the lower surface. So that air flowing above the aerofoil has to travel a longer distance than air flowing below the aerofoil. And both airflow has to meet at the same point at the end of an aerofoil. This is a reason why air flowing above aerofoil has the higher velocity than air flowing below aerofoil.

But this theory mentioned above is wrong.

There are many of issues in this theory. According to this theory, aerofoil is designed in such a way that air flows longer distance above the aerofoil than air flowing below the aerofoil. But in a case of a symmetrical aerofoil, air flow above & below the aerofoil travels same distance even though symmetrical aerofoil provides sufficient amount of lift at some angle of attack. Airflow above & below the aerofoil does not meet at a single point of the trailing edge of an aerofoil. According to NASA air flowing above aerofoil is so fast that it passes the end of aerofoil before air flow below aerofoil.

So what is the reason of velocity difference above & below aerofoil

Venturi - Wikimedia

There are mainly two types of pressure, one is static pressure and other is dynamic pressure. Dynamic pressure will be the pressure on the flat plate held in front of the flow. While static pressure is a pressure on the walls of the tube. While talking about Bernoulli's principle, we are talking about static pressure. It means pressure acting on the walls of the tube through which fluid is flowing.

Bernoulli's principle states that larger the cross section area, lower the velocity of flow. And hence high pressure at the larger section.

Physical meaning of Bernoulli's principle

As the area of cross section is reduced, the velocity of flow at that cross section will increase. This is due to conservation of mass. Consider a flow in a tube with the varying cross section area. The mass flow rate through a bigger cross section will be equal to the mass flow rate through a smaller cross section area. So to conserve mass flow rate, the velocity of flow increases while flowing from bigger cross section area to smaller cross section area. This condition can be given in terms of continuity equation for constant density,

A1 * V1=A2 * V2

A1, V1 = Area, Velocity at bigger cross section
A2, V2 = Area, Velocity at smaller cross section

 Now, this was about the increase in velocity with reducing cross section. Now about pressure, This can be explained simply by conservation of energy. When cross section area of the tube is reduced, the velocity at that cross section will increase, it means kinetic energy at that section will increase. So to conserve total energy, pressure energy at that section will reduce. And hence, static pressure at that cross section will reduce.

Application on an aerofoil

Now Consider any unsymmetrical aerofoil. If you consider an aerofoil in XY plane, you will notice that upper curve of the aerofoil will be increased in Y axis initially with respect to the X axis from the leading edge. And the then same upper curve will meet X axis at the trailing edge. And lower curve will be a straight line. If you take a look at the upper curve of the aerofoil, it forms semi venturi shape with the far away undisturbed air flow which is just above the upper curve. And now applying Bernoulli's principle on this semi venturi. The region where the upper curve of the aerofoil is at the highest point in the x axis will form an area of the lower cross section (and hence higher velocity) with the far away undisturbed flow which is present just above the upper curve of an aerofoil. And thus the speed of the airflow is higher above the aerofoil as compared to the speed of the airflow below the aerofoil. Which results in pressure difference above and below the aerofoil. This unbalanced pressure force results in the production of the lift.

Lift explanation based on Newton's third law

Again, Consider any unsymmetrical aerofoil, assume that air flowing above aerofoil is going straight without any deflection with respect to aerofoil curve. But as the upper surface of the aerofoil is curved, the low-pressure region will be created in between aerofoil and airflow. This low-pressure region will suck the airflow and airflow will follow the curve of an aerofoil. This effect in which airflow attaches to the nearest surface is known as Coanda effect. Now according to Newton's third law, every action has an equal and opposite reaction. So, reaction to the force which bends the air flow is the lift force. So, this was an explanation for the production of lift based on Newton's third law.

That's why lift is known as reaction force!!!!

Now you know the correct concept of lift.  Ask your teachers or friends about the lift to the aerofoil, if they are giving the same wrong explanation then clear their doubt & become hero!!!

Thanks for reading!

Aircraft Brake systems:- Disk Brake

Aircraft Brake systems:- Disk Brake

Have you ever think about how aircraft with high speeds stops after landing? So here's the explanation to your questions about aircraft brake systems.

In aircraft there are three brake systems are used
  • Disk brake
  • Thrust reversal
  • Spoilers

Explanation about Disk brake is given below

Disk brake:-

Image from:

Disk brake in aircraft is same as disk brake used in our cars. So how this disk brake works? Wheel of aircraft or car is connected to disk. So as wheel rotates disk rotates with wheel. So by stopping rotation of disk, wheel can be stopped. Pilot applies disk brake after landing by rotating fpot pedal. Foot pedal can be used for two purposes. One for rudder & other for disk brake. If pedal is pushed rudder (Rudder is used for yawing motion of aircraft) can be moved & if pedal is rotated by applying force on upper part of pedal, disk brake comes into action. Disk brake works on principle of pascal's law. As pilot applies pressure on foot pedal piston comes in contact with disk & due to friction velocity of the disk reduced. So that velocity of wheel is reduced.
When disk brake is applied due to friction disk gets heated upto high temperature. Some times it causes wheels on fire.

This is all about Disk brake explained in simple language. If any queries related to this topic 

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Why food taste changes in flight?

Food tastes worst in flight


Have you ever tried a food in flight? I think you surely did. Sometimes you will taste that food worst in flight. And we blame the airline for that thing. But truth is the airline is not responsible for that thing. 

Food tastes worst because you lost your one thing as you go higher in aircraft.
The thing that we lost as we go high in the air is some part of our sense of taste & smell. In aircraft's fuselage temperature is usually low & as we go higher air becomes thinner & atmospheric pressure reduces. Also, as we go higher humidity in the air reduces. It is even less than 15%. It dries out the air. This causes we lost some part of our sense of smell & taste. It is as same as we are having cold, in cold we lost our some part of the sense of smell. That is, we lost 30% of our sense smell & taste according to a 2010 study conducted by Germany's Fraunhofer Institute for Building Physics, commissioned by German airline Lufthansa.

It is surprising to know that we lost our only sense of sweet & salty tastes. Other tastes such as sour, bitter, almost remain unaffected.

Other reasons responsible for changing food taste are engine noise. The study suggests that in loud noise food tastes less salty & less sweet. But in flight this effect of reducing taste is much lower. But food seems more crunchier.

Also one of the reasons is reheating the food in flight. As it is not allowed to use flames or microwave in flight so it is not possible to prepare food in aircraft. So food is prepared on the ground & then stored in the aircraft. Food is served hours later of its preparation. So it is reheated causes lost in some part of taste.

But one thing is good in all this,
Tomato juice or soup tastes better in flight than on the ground. Hence lots of passengers in flight ask for tomato juice or soup in flight.

So next time you go by flight, try tomato soup or tomato juice and experience its taste.

Thanks for reading!