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Flying Trivia – your questions answered

Flying Trivia - your questions answered

Despite the best efforts of the airlines, long-haul flying can be a rather boring business and, if you are anything like me, this provides the opportunity for deep contemplation.

The first thing I generally consider is how on earth something weighing several hundred tons can remain airborne. Having little scientific understanding, this question troubles me immensely so I swiftly move on having failed to come up with any explanation other than some kind of magic. Further questions raise themselves as I stare around the cabin and again I am unable to come up with answers to these either.

This page is designed for those of you with similar questions. Wherever possible, “expert” sites have been consulted to find the answers. So, the big one first:

Why do planes fly?

You may have noticed that aeroplane wings are shaped so that the upper surface is curved. This is known as an aerofoil. When the wing moves through the air, some air passes below and some passes over the top. Since the air moving over the top of the wing has further to travel, it speeds up and is "stretched" thinner and this decreases the pressure above the wing. The air underneath the wing is relatively unimpeded so its speed and pressure stay the same.

High pressure air always moves towards low pressure air and therefore the air underneath tries to rise to the air above the wing. The wing clearly provides resistance to this and this is what creates lift. The quicker a wing moves through the air, the greater the force of lift and when this force exceeds that of gravity, a plane will take off.

How does a jet engine work?

A jet engine (which is also known as a gas turbine) sucks in air at the front and then compresses it, thus raising the air pressure. This pressurised air is then mixed with fuel and this explosive mix is then ignited by a spark. The mixture expands as it burns and the burning gases blast out of the back of the engine. As these jets of gas shoot backwards so the aircraft is pushed forwards.

What is turbulence?

This is one of the more unpleasant aspects of flying though in practical terms it represents very little danger to your safety. It can be caused by any number of factors – changes in atmospheric pressure, thunderstorms, jet streams (high-altitude air currents) or mountain waves.

The only cause for concern for the passenger is clear air turbulence (CAT) which is impossible to see or predict and as such can come as a surprise to pilots as well as passengers. When air is disrupted around the jet stream, variations can occur in the amount of lift that the wing generates. If a plane hits one of these "air-pockets" then the plane can lose height very rapidly and anything, or indeed anyone, that is not secured will get thrown about. Wearing your seat-belt at all times when sitting down will stop this happening – the getting thrown about bit, not the turbulence.

Why do my ears pop on take off and landing?

Your middle ear is the problem here. This is an air pocket inside your head that is sensitive to changes in air pressure. When you swallow, air moves from the back of your throat or nose through your Eustachian tube and keeps the pressure on both sides of your ear-drum equal. If the pressure changes, a vacuum is created which will stretch the ear-drum meaning sounds will be muffled and it can also cause pain. Your ears will "pop" when the pressure is restored either through swallowing or by pinching your nose and blowing gently against the resistance. Yawning whilst listening to your boring neighbour will help too.

How many bits and pieces make up a jumbo jet?

Around six million.

Why is air travel so tiring?

After take-off, there is a quite a sizeable change of pressure in the cabin. As such, there is less oxygen available than you are used to breathing usually. Your cardio-vascular system has to work just a little harder than normal to get the oxygen it needs so your heart-beat and pulse speed up slightly. If you are in a plane for ten hours then this is naturally going to make you feel fatigued by the end of the flight.

What is the pressure of the air in a cabin?

Airline cabins are generally pressurised to a level that is equivalent to being at about 2400 metres (8000 ft) above sea level.

What does a jumbo jet cost?

The Boeing website lists prices for its planes and the current price of a Boeing 747-400 is between $228 – $260 million depending on fitting and specifications.

How much fuel does a jumbo jet use?

According to Boeing, a 747 uses 5 gallons (19 litres) of fuel every mile.

What would happen if someone fired a bullet through a plane window?

Apparently not too much. If the hole was fairly small, then the air would certainly whistle out but it would have little effect on a large airliner. In 1988 a Boeing 737 had half of its roof come away at 24,000ft due to metal fatigue which naturally caused a very rapid depressurisation. Despite this, the plane still landed safely and only one person was killed. Feel free NOT to test out the veracity of this answer.

How fast am I going at take off and landing?

A 747 takes off at around 180 mph (290 km/h and lands at 160 mph (260 km/h).

Why do I get so dehydrated on long-haul flights?

The air that we breathe on a daily basis has a surprising amount of moisture in it. In an aeroplane, it is not uncommon to get humidity levels of less than 25% in the cabin since the air being used to supply you from outside, contains very little moisture. Alcohol and caffeine also contribute to the problem so drink plenty of water and you will be fine.

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