Safety Innovation No. 9: System to prevent low pressure accidents

Safety Innovation No. 9: System to prevent low pressure accidents

Airbus has developed an automatic system that, if the cabin pressurization system fails, takes over from the crew and returns the plane to an altitude where it can breathe normally.

On August 14, 2005, a passenger plane experienced a pressure system failure a few minutes after takeoff from Larnaca Airport in Cyprus. This was not discovered by the crew. As the plane continued to climb to 33,000 feet (10,200 metres), oxygen became increasingly scarce. Hypoxia (decreased amount of oxygen transported by blood to tissues) caused the passengers to lose consciousness. The plane, which was en route to Prague with 121 people on board, flew under autopilot until it ran out of fuel and eventually crashed near Marathon, north of Athens in Greece. Unfortunately, similar cases have occurred on other passenger and business aircraft.

Airplanes typically fly at altitudes between 30,000 and 45,000 feet (about 9,000-13,000 meters) above sea level where the oxygen level is not sufficient for humans to breathe. That’s why planes are pressurized: to provide enough oxygen for the people on board. Normally, air pressure is maintained equivalent to an altitude of 6,000-8,000 feet (about 1,800-2,400 meters) above sea level.

In the event of a loss of pressure during a cruise, passengers and crew members should use oxygen masks immediately to prevent hypoxia. Depending on the altitude, the so-called useful awareness time is 15 seconds or less. The flight crew must then initiate an emergency landing procedure that includes immediate pilot procedures as well as contacting air traffic control and passengers in the cabin. This will enable the plane to descend to a lower altitude where the oxygen level is sufficient to breathe without an oxygen mask.

Airbus has developed the Automatic Emergency Landing (AED) function to enable the cabin crew to initiate an emergency landing by pressing a button and extending the speed brake. The aircraft will then perform the maneuver automatically while avoiding potentially high terrain such as mountain ranges. This significantly reduces the workload on the crew in this critical situation.

As an additional safety net, in the event of a drop in cabin pressure without detecting any crew reaction, the AED will automatically activate after a countdown and initiate an emergency landing.

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