Ask Norbert Lohl, director of certification at the European Aviation Safety Agency, about the prospects of simulated evacuation technologies being used as part of the certification process, and he will insist that in principle there are no regulatory barriers to the use of computer modelling.

Today, the relevant regulation for large aircraft - CS25.803(c) - allows for the use of "a combination of analysis and testing", allowing simulation technologies to feature within any analysis. "The regulatory authorities have followed the development of evacuation modelling and there appears to be much promise in the technique," says Lohl.

And yet, while there may be a bright future for computer modelling in terms of employing it as a basis for future certification, a detailed protocol for the accepted use of computer simulations for certification purposes has still to be developed - something that rulemakers insist requires collaboration on the part of aircraft manufactures.

"Within the constraints [the safety and practical issues associated with full-scale demonstrations] and should aircraft manufacturers wish it, there is every reason to suppose that evacuation simulation software tools can play a significant role in future certifications," Lohl insists.

Ali Bahrami, US Federal Aviation Administration manager within the regulator's Air Transport Directorate, also notes that there should be an underlying commercial imperative in support of simulation, something that regulators want in principle to support: "A manufacturer's time available for certification is getting shorter and shorter because of market drivers and any testing can be very time consuming.

"As regulators we realise that, and the fact that the industry needs to move therefore towards a more analytical system of modelling, but we would first want to make sure that it is a fully validated system and builds on the safety levels we already have."

The FAA, like EASA, has accepted an element of analysis since 1978 in an effort to determine the number and type of exits, their distribution, access to exits and performance of evacuation devices with partial testing conducted before a full-scale evacuation trial. Bahrami say the current requirements for that analysis are quite prescriptive and represent a virtual sea change since before full-scale evacuations became a regulatory requirement for type certification in 1967.


All eyes are now on Boeing's 787 evacuation methodology. What element of computer modelling will be used in support of the evacuation certification? And will the US airframer apply for "grandfathering" for the new aircraft?

As Lohl says, the decision whether to require a full-scale evacuation test is affected by several factors. "Generally, a new aircraft type will require such a test. However, this is not always the case. A new aircraft type might be similar in general configuration, internal layout and evacuation equipment to an earlier type from the same manufacturer."

If so, it is possible that data from full-scale tests on the earlier type could be sufficient to be combined with new smaller-scale test data and analysis techniques to cover the new type's evacuation certification. This "grandfathering" has applied several times in the past.

Jeff Gardlin, aerospace engineer from the FAA's Transport Standards Staff, says that while from an evacuation point of view, Boeing's first-step approach will be to draw from its experience of the long and successful service histories of the 767/777, the airframer will still be required to generate test data for many of the aircraft systems on the 787.

"Boeing is likely to come with a proposal supported with some analysis in the shape of modelling, although this will not be the first time that has been done," he says. So what if anything will spur the use of computer modelling in the field evacuation certification?

Bahrami foresees a halfway house: "One of the main advantages of analytical modelling is the fact that you can simulate multiple scenarios, change exits and seating arrangement at the design stage so its application at this stage could also help support regulatory validation."

Even that, however, remains a matter for aircraft manufacturers to pursue. "The manufacturing community needs to present to the regulatory authorities a proposal as to how they want to move forward and that could easily be more reliance on analysis," Bahrami says.


Gardlin agrees. He says regulators are very close to agreeing what would constitute an acceptable certification approach that combines simulation and live evacuation. "We are not saying what the tool should look like, but we will tell the manufacturer what it should do," he says.

"We are in the position of having completed 37 full-scale tests that have generated sufficient data for the manufacturing community to start looking at modelling and get those models to a level of maturity so a regulator could form a proposal. We think we could do that but, to maximise effectiveness, that would probably require manufacturers sharing data. If the goal is to have this type of capability, sharing data would go a long way," he says.

Source: Flight International