The emergency descent should only be initiated on positive confirmation that cabin altitude and rate of climb are excessive and uncontrollable. However, the flight crew must rely on the - CAB PR EXCESS CAB ALT warning, even if not confirmed on the CAB PRESS SD page. The CAB PR EXCESS CAB ALT warning can be triggered by a cabin pressure sensor, different from the one used to control the pressure and display the cabin altitude on the SD.
The flight crew should perform the actions of the EMER DESCENT in two steps:
- Apply the memory items
- Perform the read-&-do procedure (ECAM or QRH)
To initiate the emergency descent, the use of autopilot (AP) and autothrust (AT) is highly recommended. At high flight levels, the flight crew should extend the speed brakes while monitoring the VLS. This is in order to avoid the activation of the angle of attack protection which may result in the retraction of the speed brakes and in AP disconnection.
Note: When in IDLE thrust, high speed and with speed brake extended, the rate of descent is approximately 7000 ft/min. To descend from FL 390 to FL 100, it takes approximately 4 min and 40 NM.
The flight crew should be aware that the MORA displayed on ND is the highest MORA value within a radius of 40 NM around the aircraft. The flight crew should suspect structural damage in case of a loud bang or high cabin vertical speed. If the flight crew suspects structural damage, apply both of the following:
- Set the SPEED/MACH pb to SPEED, to prevent an increase in the IAS, or to reduce the speed. This action minimizes the stress on aircraft structure
- Carefully use the speed brakes, to avoid additional stress on aircraft structure.
If the cabin altitude goes above 14 000 ft, the flight crew must press the
MASK MAN ON pb. When it is obvious that the cabin altitude will exceed 14 000ft, the flight crew could press the
MASK MAN ON pb, before the cabin altitude reaches 14 000 ft.
Emergency Descent Checklist
|Crew Oxygen Mask|
|If A/THR not active|
When descent established
|Engine Mode Selector|
|Emergency Descent PA|
|If CAB Alt > 14000 ft|
Only for Flight Simulation!