Simulated safety

Simulation software developed at Greenwich University has shown that a concept aircraft can satisfy emergency evacuation certification criteria — even in the event of a cabin fire.

Prof Ed Galea and colleagues from the university's fire safety engineering group (FSEG) have used their airEXODUS software to show that a blended wing body (BWB) aircraft can be evacuated in less than 90 seconds.

Running the simulation with FSEG's SMARTFIRE CFD software further validated BWB's design in the event of flashover, where flames flash over and through vapours produced by combustible items in the cabin.

The BWB is one concept under investigation in the €30m (£24m) new aircraft concepts research (NACRE) programme led by Airbus and part-funded by the EC.

NACRE aims to evaluate novel aircraft design concepts to provide the aerospace industry with improvements in efficiency, environmental performance, comfort and economics.

Delta-winged BWB designs being considered in the project are claimed to be capable of carrying over 1,000 passengers on a single deck with 20 exits and eight aisles running the length of the cabin.

For the concept to get off the ground it would have to pass a series of emergency evacuation certification tests. One requires manufacturers to demonstrate that a full complement of passengers and crew can be evacuated within the 90 seconds before flashover can occur.

The BWB's cabin layout is complicated by the fact that passengers may not necessarily be able to see an exit.

Galea told The Engineer that airExodus was first developed after studying accidents and interviewing survivors.

This led to the development of simulation software that takes into account human factors in aircraft evacuation — something not considered in certification drills.

To demonstrate a 'real-world' evacuation situation, a cabin mock-up was built at Cranfield University where four trials were conducted over two days with 733 people aged between 20 and fifty.

The experiment showed that the exit usage distribution predicted by airEXODUS was reflected in the trial results.

The Greenwich team then applied SMARTFIRE to the simulation to assess flashover, taking into consideration materials proposed in the cabin design. It found that in a BWB it would not occur in the first 400 seconds after impact, so the 90-second rule would be easily met.