I hope that you've been getting rid of those myths of flying and mis-understandings that you used to have about flying.
You'll perhaps remember from the last letter that I said planes don't defy gravity. One of the questions that I'm always asked is how does a plane as big as a jumbo fly? My answer is that it has to. It has no choice because when it's going fast enough the wings have such a large upward force that the plane has to fly, and the way it's designed means that it will stay steady quite naturally.
The reason that the wings have so much upward force on them is because of their shape. The wind passing over them causes suction on the top and generates a thick cushion of air† underneath.
Remember it must be something to do with the shape because there are all sorts of things that are lighter than a plane but don't fly very well...a dining room table for instance.
It's all to do with the shape. There are all sorts of things you can try to demonstrate the principles of lift ...like holding a piece of A4 paper lengthwise and at two adjacent corners†and blowing over it...watch as the paper stops drooping because of its weight and starts rising .
Or there's the spoon in water demonstration.If you don't know this one you'll either have to buy the CD set or come on our course.
Just because you can't see what's holding a plane up, it doesn't mean that there isn't anything holding it up. If the air was made of† coloured jelly you'd see quite easily what keeps a plane up but as air is invisible you'll just have to believe the science!
I hope you'll have noticed that I made the statement why planes fly rather than the usual How do planes fly? Because from my point of view as pilot, planes fly and the reasons are simple....the question how (on earth) do planes fly ...seems to start with the idea that they shouldn't!
Most people seem to be able to accept that once planes are 'up there' then they'll probably stay there but how do they get up in the first place? That's quite simple too.
When a plane starts its takes off, there's no air blowing over the wings.
Then as the engines push the plane forward more and more air passes over the wings until at take off speed there's enough suction upwards on the wing to support the weight. (The airflow isn't complicated, it's just like when you ride your bicycle...the faster you ride the more 'airflow' you get blowing against you)††
As the plane gets faster there's an increasing airflow and therefore increasing lift until...the plane climbs. Simple as that.
We usually take off into the wind to get extra airflow...††
Captain Keith www.flyingwithoutfear.com