Why are airliners pressurized to 8000 feet instead of ground level air pressure? Is there something special?

Answer 1

Most pressurized aircraft are designed for a differential pressure of between 8.0 and 8.5 PSI.
Sea level pressure is 14.7 PSI
at 8000 ft it is 10.9 PSI, still enough to breath normally.
At 35000 ft it is 3.5 PSI, Time of useful conscienceness is less than one minute.
10.9 -3.5= 7.4PSI differential pressure.
Most likely at this altitude, cabin pressure would be less than 7000', to maintain max diff pressure and passenger comfort.

Answer 2

Air Pressure At 10000 Feet

Answer 3

The pressure gradient of our atmosphere is greatest closer to the ground. Sea level pressure is about 14 psi The difference between sea level and 17000 feet is about 7 psi the difference between the next 17000 feet is about 3.5 psi. Since planes fly well above 30000 feet where the pressure is way lower it is easier to maintain the pressure difference of the flight level and 8000 ft for instance than it would be to maintain a differential of the flight level and sea level.
Planes are not designed to withstand the higher pressure differentials. If they were, the aircraft fuselage would have to be much heavier and therefore less efficient.

Answer 4

If they were pressurized to ground level then the aircraft structure would have to be much stronger to withstand the higher differential pressure between the inside of the cabin and the outside. This would have made the airplanes much heavier and less fuel efficient. Since people can tolerant 8000 foot alitude quite easily, at least while sitting still, this altiude was picked to minimize weight.

Answer 5

My guess would be that ground level air pressure would be too much pressure for the plane to handle and will reduce it lifetime by causing fatigue in the metal. Also, if a plane depressurized while flying, people would probably die because of the difference in air pressures. 8000 air pressure would be less of a difference so people can actually survive and not get sucked out of the plane. Just my opinion though.

Answer 6

there is a trade off between the strength of the fuselage and hypoxia. fuselage wise, it's best to have the cabin pressure as high as possible so that the pressure differential between outside and inside is small (called 'delta p') this will allow the manufacturer to build a lighter fuselage cos it doesn't have to contain all that pressure. however humans go crazy if the pressure is above 10,000 ft so they compromise and made it 8000ft.

Answer 7

There is no practical need to pressurize to a lower (cabin) altitude. Hypoxia usually isn't a factor in a sedentary subject until around 12000 feet. Higher pressures would mean heavier airframes, lower payloads, shorter range, longer takeoff and landing rolls, wasted fuel.

Answer 8

I spend my summers at 8000 feet. No big deal.

Riding a bicycle up there, that is a different story. Phew!