Thursday, May 13, 2021
Home Variety Can you tell if this aeroplane is landing or taking off? Here are the...

Can you tell if this aeroplane is landing or taking off? Here are the hints in the picture

Take off or landing?

Though most people who responded, got the answer correct, many of them didn’t know why it was a ‘landing’ photograph and not ‘take off’ photograph. Those who knew got some basic terms wrong. Taking a cue, I decided to write a full explainer for this. Here is a brief answer to the above question

But before I can begin to explain you the above terms, I have to explain, very briefly, the fundamentals of aerodynamics at play for an aircraft to fly.

Aerodynamics acting on an aircraft

There are 4 fundamental forces acting on an aircraft while it’s airborne. Drag pulls it back due to air resistance as it moves through the air while thrust helps it move forward. The weight of the aircraft pulls it down due to gravity and lift keeps it flying. For an aircraft to fly, thrust has to be greater than drag and lift higher than weight. How the lift is generated at the wings, is beyond the scope of this article. However, for the sake of clarity, a brief explainer would be in order. 

Thrust – The engine, which is a set of turbine fans rotating at high speed, sucks in air, compresses it, mixes it with fuel and burns it. The hot gas then exhausts through the rear of the engine generating thrust which propels the aircraft forward.

Turbojet engine. Image courtesy – https://commons.wikimedia.org/w/index.php?curid=460106

Lift – As the aircraft moves forward it travels through the air. The unique aerofoil shape of the wing makes it possible for the air over the wing to move faster than the air below it. This creates a pressure difference and the air below the wing travels upward to equalise the pressure difference. This creates the lift. 

Now, this is important to understand.

More the air velocity, more the pressure difference, more the lift. So, lift is a direct coefficient of velocity. The faster you travel, the higher you will fly.” 

Now, let’s come back to the answer and explain it point by point.

Spoilers – Here is how spoilers look like while deployed. 

Spoilers Deployed

Spoilers serve 2 purposes. They aid in aerodynamic braking. They also help by killing the lift to prevent the aircraft from leaving the ground, once it touches down. Perform this simple experiment with a paper plane at home. Fly the plane in the first pic, observe the smooth flight. Deploy the spoilers as shown in the 2nd pic and see how the plane falls down. That’s because it obstructs the air flying over the wing of the aeroplane hence killing the lift.

Paper plane with spoilers

Thrust Reverser – As I said at the beginning of this article, thrust is used to move the plane forward. Now imagine, if I guide the turbine output in the reverse direction. Instead of speeding up the plane, it will actually slow down, isn’t it? How do we achieve this? By opening the reverse door as shown in the pic.

Thrust reverser. Image courtesy: YouTube

These are guiding vents in the midsection of the bypass channel of the turbine. They guide the accelerated air from the turbine fans into the opposite direction i.e. same direction as the plane is moving. This also means the more engine power we apply at reverse thrust, it will further slow down the plane. As weird as it may sound, but this is how it is. At snow or wet condition, pilots are advised to apply full reverse thrust that is, engine power is increased upto 70% to achieve higher reverse thrust and slow down the plane. On a normal day, what we see is called “Idle reverse thrust”, engines outputting power at idle RPM. The small switches below thrust levels deploy reverse thruster doors.

Thrust Reverse levers. Image courtesy: aviationpanel.com

Flaps – Now, this is interesting. Remember what I said in the beginning, “more speed, more lift and higher you fly”. But what if the air traffic control tower tells you to slow down because you are about to land but don’t descend because you may hit the ground early. So, basically, you have to maintain your flight level while decreasing speed. Now a decrease in speed will automatically decrease altitude. To compensate this, what we need is more lift in less speed. How do we achieve that? How about increasing the surface area of the wings? That’s exactly what flaps do. When they come out of the wings, they increase the surface area giving more lift at the same speed because more amount of air is now acting beneath the wings.

Flaps extended

So why not deploy it during the full duration of the flight and achieve more lift by burning less fuel? Because this also increases the total area of the aircraft increasing the drag significantly. It further slows down the plane (aids in landing), hence can’t be deployed for full duration but only when we need more lift. Flaps are deployed during at landing and take off. However, during takeoff, we can’t afford to increase drag and hence slow down. Therefore, flaps are deployed at 1 or 2 depending on aircraft load and weather conditions. During landing, they are deployed at full. Here is the flap lever.

Flap levers. Image courtesy: Here

I hope that is a good explainer for the average layman. So next time you fly out, grab a window seat and watch these amazing aerodynamics at play while a 70-tonne metal bird sores into the sky and touches the tarmac exactly at the spot where we want it to.

  Support Us  

Whether NDTV or 'The Wire', they never have to worry about funds. In name of saving democracy, they get money from various sources. We need your support to fight them. Please contribute whatever you can afford

Related Articles

Trending now

‘Just order Shaheen to attack’: Pakistanis want Imran Khan to use missiles and show off their nuclear power against Israel

"Do we have these atom bombs and missiles to use as decoration at weddings?" an irked Pakistani asked Imran Khan

Amidst COVID-19 crisis, Maharashtra govt spends Rs 6 cr in hiring agency to handle Ajit Pawar’s SM accounts, says DGIPR ‘lacks expertise’

Maharashtra government has earmarked nearly Rs 6 crore for the handling of the social media accounts of Deputy Chief Minister Ajit Pawar

French President Macron’s party bans hijab wearing candidate to contest election, says hijab on election poster goes against secularism

Macron's La Republique en Marche (LREM) clarified that in secular France, there should be no place for the overt display of religious symbols like the Hijab on electoral campaign documents

Watch: Israel Defence Forces destroy 14-floor terrorist hideout inside Gaza in a precision airstrike

"Terror organisations have been hit hard and will continue to be hit because of their decision to hit Israel. We'll return peace and quiet for the long term," Israeli Defence Minister Benny Gantz said.

Israeli actress Gal Gadot, who once hailed ‘Shaheen Bagh dadi’, wishes for safety for Israel, gets hate from Islamists and ‘liberals’ in return

Gal Gadot's prayer for peace in her home country Israel irks up 'liberals' who even accused her of being a genocide enabler.

Shekhar Gupta’s ThePrint indulges in tragedy porn while emotionally manipulating a grieving family of RSS worker

Instead of giving a distressed family some space and letting them grieve the loss of a loved one, Gupta sends his vultures to settle political scores.

Recently Popular

Israel spy agency Mossad’s parody account pokes fun at Bollywood entertainer Swara Bhasker over her ‘#FreePalestine’ campaign

Swara Bhasker had posted a tweet calling Israel apartheid and terrorist state following the clashes at the Al Aqsa Mosque in Jerusalem

Watch: Israel’s Iron Dome intercepts hundreds of rockets launched by the Palestinian terror group Hamas

The high-tech 'Iron Dome' is a short-range air-defence system designed to intercept rockets, artillery, and mortars. The surface-to-air missile system has been deployed by Israel Defence Forces since 2011 and has helped reduce casualties from rocket attacks against Israeli cities.

NCP supremo Sharad Pawar believes he committed a big mistake by making Uddhav Thackeray the CM of Maharashtra: Report

A report published in Marathi daily Tarun Bharat said that Sharad Pawar conveyed to Sanjay Raut that he made a big mistake by making Uddhav Thackeray the chief minister of Maharashtra.

Pakistani actress Veena Malik’s justifies genocide of Jews as Israel-Palestine conflict escalates

Veena Malik's Twitter account has been withheld in India owing to a legal demand.

Israel’s ‘Iron Dome’ Air Defence System: What is it and how does it work

To counter the low-cost warfare initiated by Hamas, the Israel Defence Forces has activated its state-of-art air defence system - 'Iron Dome' to protect its civilian population from the barrage of rockets.

Israeli actress Gal Gadot, who once hailed ‘Shaheen Bagh dadi’, wishes for safety for Israel, gets hate from Islamists and ‘liberals’ in return

Gal Gadot's prayer for peace in her home country Israel irks up 'liberals' who even accused her of being a genocide enabler.
- Advertisement -

 

Connect with us

254,930FansLike
542,729FollowersFollow
24,300SubscribersSubscribe