Airplane pressure question...

Paul11

Paul11

Paul11

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i was wondering, if airplanes are pressurised and once inside we are kept at a constant pressure, different from the outside pressure.

how come our ears pop?

if it were constant pressure inside, our ears would not pop as pressure changed outsite.??
 
we have to be kept at constant pressure inside the cabin otherwise our heads would pop I think.
Pressure is proportional to product of fluid density (air 1000 kg/m^3 ), accelleration to due mavity (9.81 m/s^2) and the height above the datum, which would be sea level.

I don't know why the ears pop.
 
They *try* to keep it at constant pressure, but it's a complicated process and it isn't always constant.
 
The Pressure changes in the cabin to about 7000ft so basically the cabin pressure is the same as if you were at the top of a 7000ft mountain.

The outside pressure is much lower but if the cabin pressure wasnt decreased to ~7000 the fuselage takes a beating.
 
The pressure at ground level is not the same as the pressure on 30,000 ft. So it's not constant. If you've ever had a soda can on board you'll see the top buldge out more than usual because the aircraft is at a lower pressure than ground level.
 
Paulus said:
ihow come our ears pop?
Click to expand...

Rapid changes in air pressure cause the air pocket inside the ear to expand during takeoff and contract during descent, stretching the eardrum. To equalize pressure, air must enter or escape through the Eustachian tube hence the pop.
 
i get why it is pressurised, and i get why our ears pop when the pressure changes.

the question is , if it is pressurised at a constant pressure, we would not be effected by outside pressure changes.

but we are.. why
 
Well because the pressure inside the cabin is not the same as the pressure outside at ground level. As was said before, the pressure in the cabin is the same as at 7000ft as if the pressure was the same as below that (once you got to 30,000ft) as was said before, there'd be too much pressure on the fuselage.

Once you descend below 7000ft the pressure inside and outside the cabin equalises and increases in pressure until ground level, and the increasing pressure as you descend is why your ears pop.

Well I think that's it anyway as it explains it but someone (scuzi?) correct me if I'm wrong.
 
Longbow said:
The pressure at ground level is not the same as the pressure on 30,000 ft. So it's not constant. If you've ever had a soda can on board you'll see the top buldge out more than usual because the aircraft is at a lower pressure than ground level.
Click to expand...
There's a much more effective way of demontrating this tbh - get a bottle of water (other drinks in soft plastic bottles also work, but avoid 'sports' caps, and get it after security, obviously :p) take onboard and drink contents. Before the plane starts to descend for landing, seal the bottle tightly. See what shape the bottle is in when you land. :)
 
Berserker said:
There's a much more effective way of demontrating this tbh - get a bottle of water (other drinks in soft plastic bottles also work, but avoid 'sports' caps, and get it after security, obviously :p) take onboard and drink contents. Before the plane starts to descend for landing, seal the bottle tightly. See what shape the bottle is in when you land. :)
Click to expand...

OOH..I KNOW, I KNOW!

Hexagonal.
 
They are not pressurised to the same pressure at sea level, but to the same pressure at around 3000m, which is less than that at sea level, but high enough to prevent altitude sickness, but also high enough to cause your ears to pop.
 
all i know is whilst playing mario kart battlemode (ds) on the plane last week, the balloons would automatically charge :D.

usually you blow into the mic to "charge" these balloons.
 
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