AD 2022-17-04 Prompted By Reports Of Broken P-Clamps On The Pressure Relief Line

The FAA is adopting a new airworthiness directive (AD) for certain De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes.

This AD was prompted by reports of broken P-clamps on the pressure relief line and the motive flow line in the fuel tanks, and a subsequent determination that certain service information lacked instructions for maintaining appropriate clearance between certain fuel tubes and their support brackets, and may also have led to incorrect installation of certain TeflonTM sleeves. This AD was also prompted by a determination that new or more restrictive airworthiness limitations are necessary. This AD requires inspecting the motive flow line, vent line, and related parts, and adding support or additional clearance if necessary. This AD also requires inspection, and replacement or relocation if necessary, of affected TeflonTM sleeves on the vent line, and installation of TeflonTM sleeves on the vent line at additional wing stations. This AD also requires revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective November 1, 2022.

Supplementary Information: Transport Canada Civil Aviation (TCCA), which is the aviation authority for Canada, has issued TCCA AD CF-2017-05R2, dated September 20, 2019 (CF-2017-05R2) (also referred to after this as the Mandatory Continuing Airworthiness Information, or the MCAI), to correct an unsafe condition for certain De Havilland Aircraft of Canada Limited Model DHC-8-400, -401, and -402 airplanes. You may examine the MCAI in the AD docket at www.regulations.gov by searching for and locating Docket No. FAA-2022-0287.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes. The NPRM published in the Federal Register on March 24, 2022 (87 FR 16661). The NPRM was prompted by reports of broken P-clamps on the pressure relief line and the motive flow line in the fuel tanks, and a subsequent determination that certain service information lacked instructions for maintaining appropriate clearance between fuel tubes and their support brackets at wing stations -371.019 and -209.109 in the left-hand fuel tank and wing stations 371.019 and 209.019 in the right-hand fuel tank. This may also have led to incorrect installation of certain TeflonTM sleeves. The NPRM was also prompted by a determination that new or more restrictive airworthiness limitations are necessary. The NPRM proposed to require inspecting the motive flow line, vent line, and related parts, and adding support or additional clearance if necessary. The NPRM also proposed to require inspection, and replacement or relocation if necessary, of affected TeflonTM sleeves on the vent line, and installation of TeflonTM sleeves on the vent line at additional wing stations. The NPRM further proposed to require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitation. The FAA is issuing this AD to address adverse impacts on the integrity of the electrical bonding paths throughout the fuel line, which could lead to arcing between the vent line and airplane structure, and could result in possible fuel tank ignition in the event of a lightning strike. See the MCAI for additional background information.

FMI: www.regulations.gov