• Question: How come a heavy airplane can fly high up in the sky?

    Asked by Maya to Camilla, Katie, Mike, Rhys on 24 Jun 2015. This question was also asked by Tess.
    • Photo: Katie Sparks

      Katie Sparks answered on 24 Jun 2015:

      Aeroplanes are made as a light as possible – but you’re right, that is still heavy!
      To fly, they need to have power to overcome the gravity of Earth – but that doesn’t need to be as much power as a rocket – a rocket wants to escape completely, an aeroplanes wants to get around and come back down.
      Aeroplanes are also shaped to be able to use the wind to help lift them up (like a kite) – they need to get going first though and they still need to keep those engines running if they want to stay up.
      Have a look at gliders – they are dragged up into the air, then they slowly drift to the ground.

    • Photo: Camilla Weiss

      Camilla Weiss answered on 24 Jun 2015:

      I want to say magic because even though I know how they stay up in the air whenever I’m in one you can’t actually see how it stays up which is strange for me! You need two things to keep an aeroplane moving through the air: lift and thrust. Lift is what gets the plane up, fighting against gravity, and thrust is what keeps the plane moving forward, fighting against drag from the air. Thrust is easier to understand because it comes from engines that you can see and understand. Lift is trickier – you have to shape the wings in a certain way so that air passing over the top of the wing is moving fast than air underneath. Fast air has a lower pressure so the air above is lower pressure than the air below the wing which is what gives it its lift. As long as you’re moving fast enough to begin with on the runway you get a really heavy plane off the ground. Rockets don’t need to worry about lift, they’re pure muscle and use thrust all the way!

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