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Automatic Emergency Descent System

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Category: Flight Technical Flight Technical
Content source: SKYbrary About SKYbrary


A system which automatically performs an emergency descent to an altitude which does not necessitate supplementary oxygen when the crew does not respond to warnings concerning cabin altitude.

Such systems are under development by major manufacturers.


Some modern aircraft are being equipped with an Automatic Emergency Descent System.

The system monitors cabin pressure altitude and if the cabin altitude exceeds a pre-set value, the emergency descent system may direct the autopilot to descend the airplane to minimum safe altitude. The emergency descent system may also communicate with ground facilities informing them of the descent.

The system will only initiate the descent if the pilots fail to respond to a cautionary alert - potentially indicating that the crew is incapacitated through the effects of Hypoxia.

Should the aircraft's monitoring system detect an unsafe cabin pressure, it will warn the crew via the primary flight display and begin a countdown. If the crew do not act to cancel the warning or take positive control of the aircraft, the aircraft will perform a side-step manoeuvre, taking it to the right of the designated airway to avoid conflict. This sidestep would automatically account for any existing lateral offset selected by the crew. The aircraft will also be put into a rapid descent at maximum operating speed towards FL 100 - the target altitude for depressurisation incidents, at which oxygen masks are no longer necessary - although the system would adjust for minimum altitude and terrain-clearance requirements.

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