26 September 2007
FR Doc E7-18931
FAA

Special Conditions, Boeing B787

The special conditions are intended to address the composite structure of the wings and fuselage, and their vulnerability to penetration by tire fragments, which can aggravate the threat of a fuel fire following a crash. As the notice says, the B787 has wing fuel tanks constructed of carbon fiber composite materials for which existing airworthiness standards, based on aluminum structure, do not apply:

“The ability of aluminum wing skins, as has been conventionally used, to resist penetration by tire debris is understood from extensive experience. The ability of carbon fiber composite material to resist these hazards has not been established … Historically, accidents have resulted from uncontrolled fires caused by fuel leaks following penetration or rupture of the lower wing by fragments of tires or from uncontained engine failure.”

The special conditions require the following:

“Impacts by tire debris to any fuel tank or fuel system component located within 30 degrees to either side of wheel rotational planes may not result in penetration or otherwise induce fuel tank deformation, rupture (for example, through propagation of pressure waves), or cracking sufficient to allow a hazardous fuel leak … Fuel leaks caused by impacts from tire debris … may not result in hazardous quantities of fuel entering any of the following areas of the airplane:

• 1. Engine inlet
• 2. APU inlet
• 3. Cabin air inlet.”

Comments on the special conditions are due 26 October 2007.