16 May 2013

A350 XWB equipped with a new oxygen system, which delivers oxygen based on a person’s breathing cycle. Risky?

Oxygen cylinders are vulnerable to explosion if exposed to fire or impact damage. Oxygen facilitates the spread of fire or increases its intensity. The vulnerability of onboard bulk oxygen to post crash or in-flight fire is dependant upon its location within the aircraft. The risk of a major explosion is dependant on the quantity stored and whether it is stored in one place or distributed around the aircraft. 

Airbus A350XWB is to be equipped with a new type of oxygen  system,  the  BE Aerospace Pulse® system,  which  delivers  oxygen  based  on  a  person’s breathing cycle and has oxygen stored in small vessels, one at each PSU. This type of system may be  relatively well protected from  crash  impact  damage  compared  with much  larger  bulk  oxygen cylinders that are often located beneath  the cabin  floor, but might pose a greater overall  risk  in a cabin fire, albeit with a smaller explosion.

The Pulse passenger oxygen system weight can be reduced by up to 450 pounds. Pulse also requires less maintenance while supporting various aircraft mission profiles and seating reconfigurations. It eliminates the need for rigid pipe, providing mission flexibility. To conserve energy, the Pulse System is not powered during typical flights and activates immediately if required. In addition, its built-in microprocessors are designed to improve reliability with minimal preventative maintenance required.

EASA recommends a  research  to be  carried  out  to  establish  the  explosion risks presented by different passenger emergency oxygen storage systems when subjected  to cabin fire or post crash impact.

However, it is likely that this method of oxygen storage would present a greater risk of explosion in a fire than chemical oxygen systems. 787 has the same new type of oxygen system.

Small oxygen storage vessels  located at each PSU in the A350 XWB and in the B787 present a greater risk than large (centralised) storage vessels?

Based on the “STUDY ON CS-25 CABIN SAFETY REQUIREMENTS i.6” published by the European Aviation Safety Agency

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