Cabin Altitude Pressure Warning Switch

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5 months 1 week ago #1306 by dynamics
Do oxygen masks drop if cabin altitude warning switch is tested at altitude of 10000 ft by  a test set?

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5 months 1 week ago #1307 by Mark
I'm going to need a copy of the schematic for the mask system to give you a correct answer.

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5 months 1 week ago #1308 by dynamics
I emailed the schematic

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5 months 1 week ago - 5 months 1 week ago #1309 by Mark
It's 14,000 feet to set off masks automatically.
I don't know what your paperwork reads, but if I wanted to test the altitude switch..... I'd pull relay R322 and look for a ground to show up on "X2".
  
  
 
  

  
If you test with everything hooked up, the masks will drop. "Pass Oxy Left" and "Pass Oxy Right" breakers could be pulled to test the system without actually dropping the masks.
  
  
 
  
 
Last edit: 5 months 1 week ago by Mark.

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5 months 1 week ago - 5 months 1 week ago #1310 by dynamics
Given the altitude pressure switch makes warning at 10000ft however masks drop at 14000ft, does it mean that there are two contact in the switch?
ref:FAA AD2022-24-09
Last edit: 5 months 1 week ago by dynamics.

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5 months 1 week ago #1311 by Mark
Two different systems. The warning at 10K should alert the crew of a problem. If the problem has not been corrected..... the masks will drop at 14K.

They can manually drop them at any time.

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5 months 1 week ago - 5 months 1 week ago #1312 by dynamics
Regarding two pages of the diagram I sent an email attached with, there are two different altitude pressure switches at different locations, one of them underneath the flight deck floor that operates at 10000ft for warning system, and another in E&E shelf that operates at 14000ft for automatic deployment of masks.am I correct?
Last edit: 5 months 1 week ago by dynamics.

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5 months 1 week ago #1314 by Mark
You are correct.

The 10K can be tested "on aircraft" for aural and visual warning.
The 14K can also be tested on the aircraft if the mask breakers are pulled.
I did an cabin altitude switch for a King Air with a chamber....  rotate.aero/forum/ata-35-oxygen/292-ata-...-altitude-switch#507

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