ATA 35

Passenger Oxygen Mask Check
When our customers are bringing their aircraft in for an 800-hour “C” inspection, we encourage them to deploy the passenger oxygen masks, simulating an actual cabin de-pressurization. This familiarizes the pilots with what goes on during a mask drop-out. Our procedure is as follows:
• Level the aircraft at 16,000 ft.
• Slowly open the manual dump valve (red knob). Watch for ”10,000 ft. cabin” light on annunciator panel to illuminate at 10,000 ft. cabin altitude. The cabin should level off at 13,000 ft.
• Select Ram. The cabin will climb and you should get the red “Pass Oxygen On” light on the passenger oxygen control panel on the copilot’s side console and a simultaneous drop of the passenger masks.
If any of these events do not occur, you might have a problem with the system, and corrective maintenance should be accomplished.