155 - ATPL - An aircraft with a pressurized cabin is settled at its cruise level. During the flight, a malfunction of the pressure controller is detected by the crew and the cabin altitude rate indicator reads -200ft/min. Given that: DELTA P: Differential pressure Zc: Cabin altitude

Question 155 - Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

A descent must be initiated to prevent the oxygen masks dropping when Zc reaches 14000 ft.

The aircraft has to climb to a higher flight level in order to reduce Zc to its initial value.

DELTA P will rise up to its maximum value, thus causing the safety relief valves to open.

The crew has to intermittently cut off the incoming air flow in order to maintain a zero Zc.