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Topic: Cabin Pressure On Taxi
Username: ctempleton3
Posted 2011-03-21 09:54:02 and read 5025 times.

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

Topic: RE: Cabin Pressure On Taxi
Username: Fly2HMO
Posted 2011-03-21 10:03:05 and read 5020 times.

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.

Topic: RE: Cabin Pressure On Taxi
Username: wncrew
Posted 2011-03-21 11:08:44 and read 4966 times.

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.

Topic: RE: Cabin Pressure On Taxi
Username: 113312
Posted 2011-03-21 18:18:42 and read 4849 times.

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.

Topic: RE: Cabin Pressure On Taxi
Username: HAWK21M
Posted 2011-03-22 03:32:09 and read 4732 times.

On Ground Pre pressurization to adjust the TO pressure bump.
Normally by a toggle switch on the B737/757.
regds
MEL.

Topic: RE: Cabin Pressure On Taxi
Username: KingairTA
Posted 2011-03-22 05:00:42 and read 4711 times.

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.

Topic: RE: Cabin Pressure On Taxi
Username: HAWK21M
Posted 2011-03-22 08:35:47 and read 4650 times.

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.

Topic: RE: Cabin Pressure On Taxi
Username: KingairTA
Posted 2011-03-22 08:41:17 and read 4647 times.

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

Just throwing that out as a possibility is all.

Topic: RE: Cabin Pressure On Taxi
Username: XFSUgimpLB41X
Posted 2011-03-23 19:51:00 and read 4346 times.

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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