US FAA officials intend to issue a “special condition” providing clarification of the lightning protection requirements that must be complied with before Boeing’s 787 can be certified.
The airframer is fully confident, however, that its proprietary lightning protection design will meet FAA requirements.
Special conditions are issued when an aircraft is to have novel or unusual design features compared to the state of technology envisioned in the airworthiness standards for transport category airplanes.
“There has been good communication between Boeing and the FAA as the special condition has been developed and they are not a surprise to us,” Boeing tells ATI.
“They are not a result of any specific 787 design concern or feature. It will be the FAA’s responsibility to make the finding of compliance for the 787. Our job is to define the design in a manner that we are confident will meet these requirements. We do not know when the special condition will become final.”
Boeing’s overall lightning protection scheme entails a wire mesh embedded in the 787’s composite fuselage to conduct lighting away from the twinjet. An airliner’s fuselage is the most frequently damaged part of aircraft due to lightning.
Boeing says its system “is primarily there for economic reasons to reduce the effects of lightning damage on the fuselage to minimize the impacts to customer airlines”.
It notes that the extremities of the aircraft, such as wing tips, engine nacelles, horizontal stabilizer and tail are other areas where lightning is expected to attach “but they utilize other methods of protection based upon the expected lightning threats in those areas”.
“These areas primarily use metal foils similar to past models as the major protection method rather than the wire mesh. The design focus for the wings is not as much on structural damage but on protecting the fuel tanks and the wire mesh provides less benefit there.”
Earlier this year, Boeing said it had found a path forward with the FAA to resolve lightning protection issues.
“The lightning protection discussions have related to the application of new regulations to the 787 and obtaining guidance from the FAA in how to demonstrate we have adequately met the intent of them,” says the company. “We are applying this guidance in developing our certification data package.”
Boeing adds that it understands “the requirements that the design must meet for certification”.
Source: flightglobal.com's sister premium news site Air Transport Intelligence news