Aircraft

'Special condition' expected over twinjet's crashworthiness before flight tests begin

Boeing expects the US Federal Aviation Administration to propose a "special condition" to prove the crashworthiness of the 787, 50% of which will be made up of composite materials by weight.

Special conditions for certification are being issued for the twinjet by the FAA as the applicable airworthiness regulations "do not contain adequate or appropriate safety standards for the 787 because of novel or unusual design features".

Although all the special conditions issued to date have been seen before by Boeing over the certification of the 777, the anticipated crashworthiness condition is new because of the composite construction used for the primary structure of the 787.

In particular, the special condition is expected to address compliance on regulations concerning fire-blocking properties, toxic fumes and impact strength.

Boeing, which has been working closely with the FAA on the certification requirements of the 787 since applying for type certification in 2003, has already been working on "burn through" tests of composites that take substantially longer to penetrate than aluminium, as well as tests of the material's strength and toxicity.

"One of the things we tried to do differently with the FAA this time was trying to understand the certification basis - special conditions included - earlier than ever before," says Boeing 787 director of government, environment and certification Jeff Hawk.

"We wanted to understand everything that could potentially affect the systems and the design. We had the [Airbus] A380, which had special conditions issued well after it was flying. If you get surprised when you get into flight tests it can be quite burdensome."