Is it dangerous for my ears to pop?
No, although it can be painful. Ears pop because as the plane climbs and the atmosphere outside becomes thinner, the cabin is artificially pressurised to a level that is different from the atmospheric pressure we’re accustomed to on the ground.
Under internationally agreed aviation rules, cabin air is maintained at about 75 per cent of normal atmospheric pressure — the equivalent of living in a high-altitude city such as Mexico City.
The result of this is that air trapped in our bodies at standard atmospheric pressure, such as that in the twisting Eustachian tubes that link our middle ears to our mouths and nose, starts to expand. Thus the feeling of discomfort. Swallowing, yawning or the Valsalva manoeuvre — holding your nose and gently blowing — normally equalises the pressure and eases any discomfort.
Technically, it would be possible to build planes that could allow air at standard atmospheric pressure in the cabins, but keeping them completely airtight, to stop high-pressure cabin air rushing out into the low-pressure surrounding atmosphere, would require a heavier and thus more expensive aircraft.
Why does my cup of tea taste funny?
The reason tea tastes funny on aircraft is because water boils at 90c due to the pressure - which interferes with the brewing process
Proper tea is made with water that has been heated to 100c — the temperature at which it boils on the ground. Unfortunately, in the reduced-pressure environment of an aircraft cabin, the boiling point of water is lowered to around 90c, which means that the brewing process is unsatisfactory. For the same reason, you cannot have a decent cuppa high in the mountains.
Can you really get stuck on the toilet?
No, these tales are apocryphal. Although the BBC reported in 2002 that a woman passenger had pushed the flush button before she stood up and that ‘to her horror, her body was sealed to the seat so firmly that it took airport technicians to free her’, a subsequent investigation revealed that the incident had never happened.
It is, however, true that aeroplane lavatories use vacuum flushes (which operate by connecting to a vacuum sewer system). This is because carrying enough liquid for a flight’s worth of flushes would seriously increase the plane’s weight. To avoid problems, the flush button is normally placed behind the toilet lid, making it impossible to flush without standing up.
Why do planes leave long white trails?
These are called vapour trails, or more accurately, con trails (short for condensation trails). Aviation fuel is a hydrocarbon which, when burnt, produces two compounds: carbon dioxide and water.
Vapour trail: These are caused when water is expelled as a gas from the aircraft and then turns to ice crystals at high altitude
Because of the high temperature of combustion in a jet engine — around 1,300c — water is expelled as a gas but, as it meets the very cold air of the high-altitude atmosphere, it condenses into tiny droplets or, if it’s cold enough, ice crystals.
That’s why, if you look closely, there’s always a gap between the plane and the beginning of the vapour trail — it takes a bit of time for the gas to form droplets, so they form some distance behind the plane.
What if someone tries to open a door?
Before take-off, you will hear the command ‘Doors to automatic and cross check’.
Passengers assume that the cabin crew are being told to lock the doors. In fact, the instruction is to put the inflatable evacuation slides on to automatic, so that they shoot out if the door is opened.
In practice, plane doors don’t need to be locked because once airborne it’s virtually impossible to open them. That’s partly because of the unusual way they swing — inwards first and then outwards — and the fact that cabin air pressure is so much higher than the surrounding air pressure.
As a result, as the plane climbs, the cabin air pressure pushes the door outwards, sealing it into place. The higher the plane flies, the stronger the seal becomes. So strong that it would be impossible for anyone to open it. But, please, don’t try.
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