Sunday, July 21, 2013

Can Planes Stop in Mid-Air?

When coming back from airport, I often see people staring at a 747 above us and stating "Look. That plane stopped moving. It's probably waiting to land." And when I tell them it's still flying, they say "What are you saying? You blind/crazy?"

Humans tend to believe what they see in front of their eyes, without thinking. It is because of this human tendency, sequels of movies like Paranormal Activity is being released. Believing a 747 can stop in mid-air is like Paranormal activity to me.

Anyway, Commercial aircraft cannot "stop" in mid-air. It's a fact. They are not designed to stop in mid-air. Allow me to explain this phenomena in two parts.

Part 1, Why planes cannot stop in mid-air :

The answer to this question can be explained by any average google search: "How Planes Fly?"
It's basics. It's all about four forces and an aerofoil shape.



It's old school. 

Anyway what I need you to understand from this is that, the aircraft will fall down from sky if any one of those four forces disappear ( Lift, Thrust, Weight or Drag).

Let's assume that the plane do stop in mid-air. If that is to happen, then the engines are to be switched off. Just like that of car - if the engine is stopped, the car stops. Same thing happens with aircraft. If the engine is stopped - aircraft stop producing thrust - and no lift is generated. If that happens the pilot will say nothing but " mayday mayday - Get me outta here!"

Part 2: OK,so if the plane is not moving; then why does it look like - "stopped in mid-air"?

Well actually you are staring at the aircraft for around 3 seconds max. You look once, "it ain't moving"; you look the second time within 2 seconds "nope, not moving at all" and you leave it at that. You probably must be in a vehicle when this happens.

The fact is, aircraft is moving. Since it is coming to land, the speed is considerably reduced which in turn effects its ground speed. The head wind speed is reduced from the total airspeed causing the ground speed to be less than that of the real value. It like the hour hand of a clock.


 There are plenty of literature written on this subject, feel free to read those.


Before concluding, keep in mind that there are aircraft that do stop in the air. Those are military aircraft specially designed to hover. The F-35 JSF is one of these aircraft that can hover or "stop in mid-air".


I recommend you to check Lockheed Martin YouTube channel  (http://www.youtube.com/user/LockheedMartinVideos) - they have plenty of videos on F-35s.

Live Happy - Chan

14 comments:

  1. It is possible when the wind speed is greater than aircraft stalling speed..unfortunately it happens only in paper :D

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  2. Actually i got a video about it

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    1. All that glitters is not gold Luis :).

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  3. no way not what I seen the airliner was landing just was just getting ready to line up and it stopped in midair for a minute then started again

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    1. I agree. But how do you know it stopped and then started again?

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    2. i saw that too for like minut i guess when aircraft thrust is equal to opp direction of wind flow pressure then it can stop i have saw that like 3-4 times

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  4. no way not what I seen the airliner was landing just was just getting ready to line up and it stopped in midair for a minute then started again

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    1. This is all new to me too. I was in Quinlan tx on a country road and saw a 747 type plane hovering. I had a side view of the plane, too. I figured planes must be able to do that, and so when I stepped out of my car the plane resumed flying. I don't believe in ghosts or goblins or anything that cannot be reasonably explained. What gives? What the heck did I just witness yesterday?

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    2. It's normal for anyone to have an illusion of a plane hovering if you don't have any visual reference. There is no commercial aircraft in the world now that can hover. Next time you see this, have a fixed reference point.

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    3. You're probably right, Chan. I was driving my car and that requires you to be concentrating on 10 different things at once. When I got out of my car I had a reference point, and the plane appeared to be moving, so you are probably right.

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  6. Thank you. this is very helpful to understand..

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