Thursday, November 23, 2006

Of Wings and Things

In answer to a question posted by the TCA.

When the air flows over a wing it doesn't flow in a straight line but because of the (3-D) shape of the wing it tends to move towards the outboard end, as displayed in the picture below:

See how the air 'slips' sideways over the wing? This is okay for lift but towards the end of the wing, where the control surfaces are (on the wing this is the aileron) a lot of the air is lost off the end of the wing. (The little rectangle to the bottom right is the aileron, used to roll the aircraft)
By curling the end of the wing up the air is forced to travel over the control surface which gives the design greater control - or more efficient control - over the roll manoeuvre.

My sources tell me that sometimes this is accomplished by simply attaching very small barriers to the end of the wing, only a couple of inches high. Some planes, like the mighty Orion, are cool enough and their pilots are talented enough that such measures are not required.


simon said...

Geez! is that why jumbos have upturned wings?

I read that the fighter planes of today require the computers to steer them as they cannot fly by pilot alone! is this true?

Anonymous said...

Our Number 1 low cost airline (Ryanair) mainly uses the Boeing 737 300 series, and I've noticed only in about the last year have they introduced the turned up wing-tip device. I wondered weather it might also be something to do with fuel efficiency too, as this is such a hot topic these days.

Ju's little sister said...

Yes, that's why some jumbos have upturned wings.

The modern method of controlling the flight surfaces of planes is called fly-by-wire. In older planes like the mighty Orion a system of control rods, cables and hydraulics are used to move the control surfaces (ailerons, elevators and rudder). Modern planes turn the movements on the control column or joystick into electrical signals - I guess this could be analageous (sp?) to the difference between normal and power steering in a motorcar.

I'm not sure if it is true that modern fighter aircraft cannot be flown by human alone, but it doesn't surprise me - the planes may be capable of manoeuvres which induce G-Forces beyond the pilot's ability to move against effectively. Also, whilst New Zealand deliberately maintains systems which require the pilot to be able to fly alone, it seems to me that America doesn't have the same concern that in the event of a system failure the pilot is no longer in a position to recover the aircraft
On the other hand, the US of A can afford to spend lots of money on something and have the pilot eject and lose the plane when things go wrong.

Ju's little sister said...

I would also like to point out that these are my own personal views and NOT the views or policies of the New Zealand Defence Force AT ALL.

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