ctempleton3
Topic Author
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Cabin Pressure On Taxi

Mon Mar 21, 2011 4:54 pm

I my last flight I noticed that my ear's start to pop on taxi before takeoff. What would cause this? Is the pressure in the cabin decressed or increased before takeoff in any way?

Thanks,
Charles
 
Fly2HMO
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RE: Cabin Pressure On Taxi

Mon Mar 21, 2011 5:03 pm

Quoting ctempleton3 (Thread starter):
What would cause this? Is the pressure in the cabin decressed or increased before takeoff in any way?

On some planes the cabin is pressurized slightly to put some pressure against door seals. Also if the pilot is moving the throttles briskly often the cabin outflow valves may take a bit to adjust or "catch up" to the changes in bleed air being fed into the cabin.
 
WNCrew
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RE: Cabin Pressure On Taxi

Mon Mar 21, 2011 6:08 pm

As a side-note when working AFT Cabin, I can tell when the FWD door has been closed because I can feel the slight pressure change in my ears. I too notice this on taxi-out occasionally.
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113312
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RE: Cabin Pressure On Taxi

Tue Mar 22, 2011 1:18 am

Most Boeing aircraft are designed to have about .125 psid prior to takeoff and landing to minimize pressure bump. However, any more differential than that would make it nearly impossible to open emergency exits and that is why such a small amount of pressurization is permitted on the ground.
 
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HAWK21M
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RE: Cabin Pressure On Taxi

Tue Mar 22, 2011 10:32 am

On Ground Pre pressurization to adjust the TO pressure bump.
Normally by a toggle switch on the B737/757.
regds
MEL.
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kingairta
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RE: Cabin Pressure On Taxi

Tue Mar 22, 2011 12:00 pm

Could also be a test of the pressurization system prior to take off. Prior to every flight we test the system to ensure the cabin will pressurize. Each bleed air source is tested. This could also be the pressure you feel.
 
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HAWK21M
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RE: Cabin Pressure On Taxi

Tue Mar 22, 2011 3:35 pm

Quoting KingairTA (Reply 5):

Could also be a test of the pressurization system prior to take off. Prior to every flight we test the system to ensure the cabin will pressurize. Each bleed air source is tested. This could also be the pressure you feel.

What type are you referring to......On most larger commercial Aircraft the tests are carried out automatically with power up & vide Air Ground sense or vide the CPCs.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
kingairta
Posts: 454
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RE: Cabin Pressure On Taxi

Tue Mar 22, 2011 3:41 pm

We do it on the Kingair and the C-130.

Just throwing that out as a possibility is all.
 
XFSUgimpLB41X
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RE: Cabin Pressure On Taxi

Thu Mar 24, 2011 2:51 am

While that is a procedure on the king air, it is not a procedure on any boeing, airbus, or douglas plane (or the canadair regional jet). Pressurization is fully automatic, and the cabin is slightly pressurized on takeoff partly for door seals, party for the pressure bump, and also the structural integrity of the plane in the event of an excursion.
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