Leak

[Coool Hand Luke]

On all 3 pressurized planes I've flown they have all leaked like crazy on the ground while unpressurized. Have seen leaks in the cockpit windows and have had water drip out of the overhead panel. Seems like most planes dont become water tight until they get a little bit of pressure in them. Maybe the seal around one of the anttenas or beacons on the top of the fuselage is giving way and was leaking. Either way air leaks out of a lot more places in the plane than just the outflow valves.

Yea, try turning your bleed sources off at altitude and see what your cabin leak rate is. You may be suprised. I have done a number of acceptance flights and a 1500 fpm leak rate is considered really good. 2500 fpm is normal. In a Beechjet...well...don't ask.

 

[RedGuy]

I am not sure that you fully understand the concept of pressurazation then.

What you think those fuselages are air tight!:laugh: On top of the many holes that are put into an aircraft over it's life time, there are also already drain holes in the bottom of the A/C to drain water. So it's not too far out to belive that just maybe an antena or Light is leaking on the top. Are you sure you understand the concept of pressurazation?

 

[unreal]

What you think those fuselages are air tight!:laugh: On top of the many holes that are put into an aircraft over it's life time, there are also already drain holes in the bottom of the A/C to drain water. So it's not too far out to belive that just maybe an antena or Light is leaking on the top. Are you sure you understand the concept of pressurazation?

It's been my understanding that a pressurized airplane needs to be leaky just so it won't overpressurize with constant bleed air being fed in. Is that right?

 

[Coool Hand Luke]

It's been my understanding that a pressurized airplane needs to be leaky just so it won't overpressurize with constant bleed air being fed in. Is that right?

Over-pressurization protection is provided by your outflow valve(s), not by an "inherently designed" leaky pessure vessel.

 

[RedGuy]

It's been my understanding that a pressurized airplane needs to be leaky just so it won't overpressurize with constant bleed air being fed in. Is that right?

I don't think an A/C needs to be leaky, but they all are and I'm sure the engineers take that into account when they design the pressurization systems. It would be VERY difficult to make something the size of an airliner with all it's antennas, lights, doors, windows, seams, ect. air tight.

 

[great cornholio]

It's been my understanding that a pressurized airplane needs to be leaky just so it won't overpressurize with constant bleed air being fed in. Is that right?

You are right if it were totally air tight then it would pop just like when you blow a balloon up too much. To make it "leaky" they have these things called outflow valves. Outflow valves open and close to regulate the cabin PSI diff, altitude, rate of climb etc. The more the valve opens you get a higher rate of climb and a lower PSID. The more the valve closes you get a higher rate of decent and a higher PSID. When you have to dump the cabin the outflow valve goes to full open. It is usually open while on the ground so that there is not much PSID on the plane on the ground so you can open doors and windows as needed.

The other leaks come from things that pass through the pressure vessele such as wires, control cables, etc. They try to make the holes these things make as air tight as they can using rubber grommetts and what not, but they still seem to leak. Also door and window seals leak quit a bit and thats why you hear a door or window squeal sometimes.