Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to the specified products. That NPRM was published in the Federal Register on April 26, 2007 (72 FR 20780). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:
It was detected by the STC holder that in earlier installations of the ACASII system there were no isolation diodes installed in the Heading and Attitude Valid lines. The absence of an isolation diode in the valid lines can prevent the valid flag to come up even if a gyro fault exists. The problem has only been detected for Heading Valid lines but could equally affect the Attitude Valid lines.
With installation of the ACASII, the heading and attitude valid lines have to be connected to the TPU67A. On valid state, the signals are +28VDC. On invalid, the signals are open. This condition of direct connection (without an isolation diode installed) of the valid lines to the TPU67A, if not corrected, could cause the TPU67A to feed current into the open stated valid lines. This prevents the flag to appear even if the gyro is invalid, providing the flight crew with erroneous navigation information.
For the reasons stated above, this Airworthiness Directive (AD) requires the installation of isolation diodes into the signal lines to the TPU67A to prevent reverse feed of the valid lines.
Comments
We gave the public the opportunity to participate in developing this AD. We received no comments on the NPRM or on the determination of the cost to the public.
Conclusion
We reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed.
Differences Between This AD and the MCAI or Service Information
We have reviewed the MCAI and related service information and, in general, agree with their substance. But we might have found it necessaryto use different words from those in the MCAI to ensure the AD is clear for U.S. operators and is enforceable. In making these changes, we do not intend to differ substantively from the information provided in the MCAI and related service information.
We might also have required different actions in this AD from those in the MCAI in order to follow FAA policies. Any such differences are highlighted in a Note within the AD.
Costs of Compliance
The FAA is not aware of any airplanes on the U.S. Registry that have the affected equipment installed. All airplanes with this equipment included in the applicability of this rule currently are operated by non-U.S. operators under foreign registry; therefore, they are not directly affected by this AD action at this time. However, the FAA considers this rule necessary to ensure that the unsafe condition is addressed in the event that any of these subject airplanes are imported and placed on the U.S. Registry.
Should an affected airplane be imported and placed on the U.S. Registry, accomplishment of the required action will take approximately 8 work-hours at an average labor rate of $80 per work-hour. Required parts will cost about $50 per product. Where the service information lists required parts costs that are covered under warranty, we have assumed that there will be no charge for these costs. As we do not control warranty coverage for affected parties, some parties may incur costs higher than estimated here.
Based on these figures, the total cost impact of this AD will be $690 per airplane.
Authority for This Rulemaking
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.
Regulatory Findings
We determined that 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 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); 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.
We prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD Docket.
Examining the AD Docket
You may examine the AD docket on the Internet at http://dms.dot.gov ; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains the NPRM, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone (800) 647-5527) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new AD: