AD 2013-20-16

This AD is effective December 5, 2013.

For service information identified in this AD, contact MDHI, Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615, Mesa, AZ 85215-9734, telephone (800) 388-3378, fax (480) 346-6813, or at http://www.mdhelicopters.com. You may review a copy of the referenced service information at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

Roger Durbin, Aerospace Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, ANM-120L, 3960 Paramount Blvd., Lakewood, CA 90712, telephone (562) 627-5233, fax (562) 627-5210, email roger.durbin@faa.gov.

On June 14, 2013, at 78 FR 35773, the Federal Register published our notice of proposed rulemaking (NPRM), which proposed to amend 14 CFR part 39 to add an AD that would apply to MDHI Model MD900 helicopters with certain bolts installed. The NPRM proposed to require a daily check of the position of each bolt, a daily check and a repetitive inspection for a gap in each bolt, and, if necessary, removing and inspecting the bolt for a crack and replacing any cracked bolt with an airworthy bolt. The NPRM was prompted by multiple reports of in-service bolt failures. The proposed requirements were intended to prevent failure of a bolt, which could lead to loss of MRB structural integrity and subsequent loss of control of the helicopter.

We gave the public the opportunity to participate in developing this AD, but we did not receive any comments on the NPRM (78 FR 35773, June 14, 2013).

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

MDHI issued Alert Service Bulletin SB900-116R1, dated April 9, 2010 (ASB SB900-116R1), which supersedes ASB SB900-116, dated February 24, 2010 (ASB SB900-116).

ASB SB900-116 specifies a repetitive check of the blade retention bolts, part number (P/N) 900R3100001-103 and 900R3100001-105, for a gap and, depending on the outcome of the inspection, removing and inspecting the bolt for damage. The ASB also specifies a repetitive force check of each bolt, P/N 900R3100001-103, and a torque check of each bolt, P/N 900R3100001-105. Lastly, the ASB specifies a daily preflight check of each bolt to examine the position of the bolt and for a gap, and, if any bolt has moved up or down or if there was no gap, removing and inspecting the bolt.

Superseding ASB SB900-116R1 retains the same specifications as ASB SB90016, except that it revises the interval for the bolt force and torque checks from 4-6 flight-hours to 8-10 flight-hours. ASB SB90016R1 also revises the change of force or torque from not more than 10 percent to not more than ±10 percent.

This AD uses the term “inspect” when describing the action of inspecting a bolt for a crack and inspecting for a gap between the thrust washer and the retainer. The ASB uses the term “check.”

We estimate that this AD will affect 29 helicopters in the U.S. registry. We estimate that operators may incur the following costs to comply with this AD: The average labor rate is $85 per work hour. It will take about.5 work hour to do a gap inspection of each bolt. It will take about 1 work hour to replace a cracked bolt and the required parts will cost $800 at a total cost per helicopter of $928.

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.

We are 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) Is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

(3) Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction; and

(4) 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.

We prepared an economic evaluation of the estimated costs to comply with this AD and placed it in the AD docket.

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):