2020-09113. Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Proposed rule; withdrawal.

SUMMARY:

The FAA is withdrawing a notice of proposed rulemaking (NPRM) that published in the Federal Register on June 22, 2018, regarding an unsafe condition with certain Bombardier, Inc. Model DHC-8-400 series airplanes. Since issuance of the NPRM, the FAA determined that additional actions are necessary to address the unsafe condition and that the applicability should be expanded to include additional airplane serial numbers. Accordingly, the NPRM is withdrawn.

DATES:

As of May 4, 2020, the proposed rule, which was published in the Federal Register on June 22, 2018 (83 FR 29059), is withdrawn.

ADDRESSES:

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2018-0548; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this AD action, the regulatory evaluation, any comments received, and other information. The street address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT:

Joseph Catanzaro, Aerospace Engineer, Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued an NPRM that proposed to amend 14 CFR part 39 by adding an AD that would have applied to the specified products. The NPRM was published in the Federal Register on June 22, 2018 (83 FR 29059). The NPRM would have required, depending on airplane configuration: Increasing the hole size in the collector tank partition wall, inspecting the motive flow line for damage, and replacing the associated grommet and motive flow line; replacing the affected single nut plate brackets and standoffs at the affected stations on the motive flow line and pressure relief line; and inspecting the motive flow line and vent line at certain wing stations, and inspecting the fuel tubes, to verify that an appropriate clearance has been maintained between the fuel tubes and their support brackets, and applicable corrective actions. The NPRM was prompted by a report of broken P-clamps on the pressure relief line and the motive flow line in the left and right fuel tanks, and fouling conditions between the motive flow line and the collector tank partition wall in both fuel tanks. The NPRM proposed to correct an unsafe condition for the specified products.

Actions Since the NPRM Was Issued

Since issuance of the NPRM, the FAA has determined that additional information was needed in the service information regarding the relocation of certain Teflon^TM sleeves and that inaccurate production and maintenance manual instructions could have caused Teflon^TM sleeves to be incorrectly installed on the vent line. The incorrect installation of Teflon^TM sleeves could lead to arcing between the vent line and airplane structure, resulting in possible fuel tank ignition, in the event of a lightning strike. In light of this information, the FAA is considering further rulemaking.

In addition, Bombardier revised Service Bulletin 84-28-19 and issued additional service information to provide instructions regarding the proper installation of Teflon^TM sleeves on the vent line by providing electrical isolation to preclude the risk of lightning strike-induced fuel tank ignition, and installation of Teflon^TM sleeves on the vent line at additional wing stations. The FAA has also determined that the applicability should be expanded to include additional airplane serial numbers. Furthermore, the FAA has determined that to adequately address the unsafe condition, the airworthiness limitations should be revised and that the use of certain maintenance procedures should be prohibited.

Withdrawal of the NPRM constitutes only such action and does not preclude the FAA from further rulemaking on this issue, nor does it commit the FAA to any course of action in the future.

Explanation of Change to Manufacturer's Name Specified in the NPRM

The FAA has revised references to the manufacturer's name specified in the NPRM to identify the manufacturer name as published in the most recent type certificate data sheet for the affected models.

FAA's Conclusion

Upon further consideration, the FAA has determined that the NPRM does not adequately address the identified unsafe condition. Accordingly, the NPRM is withdrawn.

Regulatory Findings

Since this action only withdraws an NPRM, it is neither a proposed nor a final rule. This action therefore is not covered under Executive Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

The Withdrawal

Accordingly, the notice of proposed rulemaking, Docket No. FAA-2018-0548, which was published in the Federal Register on June 22, 2018 (83 FR 29059), is withdrawn.

Issued on April 23, 2020.

Lance T. Gant,

Director, Compliance & Airworthiness Division, Aircraft Certification Service.