Increasing use of composites in airliners raises safety concerns

The US Government Accountability Office (GAO) has taken a close look at the process of certification of Boeing's 787 to check that repair and maintenance of major composite structures has been adequately covered.

The B787 is the first large commercial airliner built mainly of composite materials to undergo certification; and the US authoriities are concerned that traditional certification processes may not be appropriate.

In making its initial assessment the GAO reviewed certification documentation, talked to experts and interviewed FAA and Boeing people.

The GAO has concluded that the FAA followed its certification process in assessing the B787's composite fuselage and wings against applicable airworthiness standards.

The FAA applied five special conditions when it found that its airworthiness standards were not adequate to ensure that the composite structures would comply with existing safety levels. These special conditions required Boeing to take additional steps to demonstrate the 787's structures met current performance standards.

The FAA also granted Boeing an equivalent level of safety finding when the manufacturer determined it could meet the standard, but prove it differently from the method specified in that standard.

On the basis of a review of FAA’s special condition requirements, Boeing submissions, and discussions with FAA and Boeing officials, GAO found that FAA followed its process by documenting the technical issues related to the design of the composite fuselage and wings, determining the special conditions and equivalent level of safety finding, obtaining public comments on draft special conditions, and monitoring Boeing’s compliance with those conditions.

The European Aviation Safety Authority (EASA) also assessed the use of composite materials in the B787 and relied on the FAA to oversee Boeing’s compliance in some cases. EASA’s process for determining whether its existing airworthiness standards were adequate to ensure the 787’s composite fuselage and wings met current levels of safety was similar to FAA's special conditions process and resulted in some additional review items, partly because of differences in their respective standards.

On the basis of expert interviews and a review of literature, the GAO identified four key safety-related concerns with the repair and maintenance of composites in commercial airplanes:

* limited information on the behavior of airplane composite structures

* technical issues related to the unique properties of composite materials

* standardization of repair materials and techniques, and

* training and awareness.

None of the experts believed these concerns posed extraordinary safety risks or were insurmountable.

The FAA is taking action to help address these concerns identified by GAO related to the repair and maintenance of composite airplane structures.

However the GAO says that "until these composite airplanes enter service it is unclear if these actions will be sufficient".

Is that reassuring? At least the situation is being monitored.