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Old 01-22-2016, 08:17 PM
  #20  
threeighteen
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Joined APC: Dec 2010
Posts: 3,090
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Originally Posted by JohnBurke View Post
What is the cabin air frefresh or replacement rate in most modern large airplanes? Do you know?

Approximately every 2-3 minutes the cabin air is completely replaced, in that it takes approximately that period of time to flow an entire cabin's volume through the packs and out the outflow valves. What's coming in is very dry air. The relative humidity at altitude is considerably less at lower altitudes.

Your ridiculous comparisons to a home air compressor on the ground, and cabin air obtained from a dry source in a low pressure cabin holds no water.

Ever wonder why one tends to dehydrate on long flights at altitude, and should keep drinking, or why skin tends to dry out on long flights? It's not a humid place at altitude, especially given the fact that large volumes of very dry air are being pumped into the cabin.

Nearly all condensation takes place at lower elevations on descent, and it's not a result of pressurization, but of condensation due to a cold fuselage descending into warmer, humid air.

As for maintenance experience with composites, you clearly wouldn't know, but we've been working composites for many decades now. You're not familiar with fiberglass work, honeycomb structures, bonding, vacuum bagging, or other common maintenance facets of constructing and repairing composite structures, but most mechanics are. Go figure.
The experience of dealing with composites is not equivalent to experience with complete carbon fiber fuselage/pressure vessel capable of lower altitudes of pressurization. The material is the same, the application of the material and the subsequent environment that it creates is drastically different.

I must regretfully step out of this debate. You call my comparisons ridiculous and then proceed to illogically compare and link unrelated items such as the average elevation of a country to the elevation at which the majority of its population lives... You also did not read anything I linked because even BOEING and AIRBUS are actively trying to find ways to reduce condensation building up in long-haul aircraft because of the humidity created inside. The pressure vessel itself in the aircraft is cold. The air inside is warmer than the physical pressure vessel. This causes condensation to build inside the pressure vessel as the flight progresses, even if the air is constantly being replaced. Just like condensation would build on a cold glass of lemonade in a room at room temperature. I've had plastic cups of iced soda collect condensation on the outside of the cup while in cruise.
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