AD 2020-19-08

This AD is effective October 21, 2020.

For service information identified in this final rule, contact Bell Textron Inc., P.O. Box 482, Fort Worth, TX 76101; telephone 817-280-3391; fax 817-280-6466; or at https://www.bellcustomer.com. You may view the referenced service information at the FAA, Office of the Regional Counsel, Southwest Region, 10101 Hillwood Pkwy, Room 6N-321, Fort Worth, TX 76177.

Kuethe Harmon, Safety Management Program Manager, DSCO Branch, FAA, 10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817-222-5198; email kuethe.harmon@faa.gov.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Bell Model 204B, 205A-1, and 212 helicopters with TT strap assembly part number (P/N) 204-012-112-005 installed. The NPRM published in the Federal Register on June 9, 2020 (85 FR 35227). The NPRM was prompted by three incidents of fatigue cracking in TT strap assembly P/N 206-010-105-3 installed on Model 206 helicopters. These TT strap assemblies have stainless steel filament windings (wires) encased in a urethane cover, which was manufactured using Caytur 21 (also known as Cature 21) as the urethane-curing accelerator. Caytur 21 contains chlorides, which are retained in the urethane cover after curing and result in premature failure of the urethane cover and subsequent corrosion and failure of the encased wires of the TT strap assemblies. As a result, Bell changed the curing accelerator in the manufacturing process.

Due to manufacturing process similarities of the urethane cover, TT strap assembly P/N 204-012-112-005, which is installed on Model 204B, 205A-1, and 212 helicopters, is affected by the same unsafe condition.

Accordingly, the NPRM proposed to require reducing the life limit of the TT strap assembly from 2,400 total hours time-in-service (TIS) to 1,200 total hours TIS or 18 months since initial installation on any helicopter, whichever occurs first, and creating a component history card or equivalent record. The NPRM also proposed to prohibit installing the affected TT strap assembly on any helicopter.

The actions of this AD are intended to prevent the TT strap assembly from remaining in service beyond its fatigue life. This condition, if not addressed, could result in failure of a TT strap, loss of a main rotor blade, and subsequent loss of control of the helicopter.

The FAA gave the public the opportunity to participate in developing this final rule. The FAA received one comment in support of the NPRM.

The FAA has reviewed the relevant information and determined that an unsafe condition exists and is likely to exist or develop on other helicopters of these same type designs and that air safety and the public interest require adopting the AD requirements as proposed.

The service information specifies replacing TT strap assemblies with less than 1,200 hours TIS no later than January 1, 1979, and replacing TT strap assemblies with more than 1,200 hours TIS no later than September 1, 1978. This AD requires reducing the life limit of the TT strap assembly to 1,200 total hours TIS or 18 months since initial installation on any helicopter, whichever occurs first, instead. This AD also prohibits installing the TT strap assembly on any helicopter after the effective date of this AD.

The FAA reviewed Bell Helicopter Textron Alert Service Bulletin (ASB) No. 204-78-3 for Model 204B helicopters, ASB No. 205-78-2 for Model 205A-1 helicopters, and ASB No. 212-78-4 for Model 212 helicopters, all dated April 19, 1978. This service information specifies replacing TT strap assembly P/N 204-012-112-005 at 1,200 hours TIS but no later than January 1, 1979. For any TT strap assembly P/N 204-012-112-005 that already has accumulated 1,200 hours TIS, this service information specifies replacing it no later than September 1, 1978.

The FAA estimates that this AD affects 143 helicopters of U.S. registry. The FAA estimates that operators may incur the following costs in order to comply with this AD. Labor costs are estimated at $85 per work-hour.

Determining the total hours TIS and the total months since initial installation of each TT strap assembly takes about.5 work-hours for an estimated cost of $43 per helicopter.

Replacing each TT strap assembly takes about 10 work-hours and parts cost about $9,000, for an estimated cost of $9,850 per TT strap assembly.

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

This AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Will not affect intrastate aviation in Alaska, and

(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):