Examining the Docket
You may examine the airworthiness directive (AD) docket on the Internet at http://dms.dot.gov or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone (800) 647-5527) is located on the ground floor of the West Building at the street address stated in the ADDRESSES section.
Discussion
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to all Bombardier Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes. That NPRM was published in the Federal Register on September 11, 2006 (71 FR 53345). That NPRM proposed to require revising the Certification Maintenance Requirements and the Maintenance Review Board (MRB) Report sections of the Canadair Regional Jet Maintenance Requirements Manual (MRM) to include changes and additions to checks of the aileron power control units (PCUs) and a change to the interval of the backlash check of the aileron control system.
Comments
We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.
Request To Provide Additional Information on Selection of Check Interval
The National Transportation Safety Board (NTSB) requests that we provide additional information in the final rule indicating how the repeat interval for the aileron backlash check was selected and why the interval will prevent flight with aileron freeplay greater than the maximum limit. The NTSB notes that the Discussion section of the proposed AD does not explain how the 2,000-flight-hour interval was selected or why it would prevent flight with aileron freeplay greater than the maximum limit.
We agree to provide additional information. The repeat interval was selected after consideration of several factors related to known service experience, guidance fromflutter analysis reference materials, and detailed flutter analysis. With respect to service experience, the absence of reports of buzzing or flutter events, known values of backlash freeplay, and the existing inspection interval were evaluated. Known backlash freeplay values were assessed against those recommended in flutter reference materials. A review of a recent flutter analysis conducted by Bombardier was also included in our consideration of an appropriate interval.
Also, Bombardier, with the agreement of the airworthiness authorities (Transport Canada Civil Aviation (TCCA) and the FAA), has started monthly monitoring of the Model CRJ200 fleet since the inspection interval was lowered from 4,000 to 2,000 flight hours. After collecting sufficient data on the backlash freeplay that develops during the 2,000-flight-hour interval, further evaluation of the interval may be conducted.
Therefore, we consider the proposed interval to be appropriate at this time. No change to the AD is necessary in this regard.
Request To Collect Aileron Freeplay Data
The NTSB also requests that the FAA revise the AD to include a method for operators to record, retain, and report aileron freeplay check data. The NTSB is concerned that the FAA, TCCA, and Bombardier might fail to monitor the effects of the reduced interval appropriately by not collecting and analyzing aileron freeplay check data.
We do not agree to revise the AD to add a requirement to collect and report data. While we have not mandated reporting of the aileron freeplay check measurements to the manufacturer, Task Card 000-27-900- 015 specifies recording and retaining this measurement. Bombardier is soliciting the measurement results from operators during the bi-monthly Technical Steering Committee meetings. As of January 2007, Bombardier has received feedback on over 70 airplanes and is confident that sufficient data will be available at the end of the 2-year term to provide validation of the check interval. TCCA requires Bombardier to provide the data results within 2 years after issuing Temporary Revision 1-2-33 to the MRM. Bombardier will tabulate the results based on the current methods and provide a matrix along with a recommendation to TCCA in mid-2008. There is no need to mandate a method for collecting the data, as there is a process in place. No change to the AD is necessary in this regard.
Request To Use Data in Monitoring Reclassification of Aileron Freeplay Check
The NTSB suggests that aileron freeplay data provided by the operators also be used to assist the FAA, TCCA, and Bombardier in monitoring the reclassification of the bearing backlash test portion of the aileron freeplay check. The NTSB states that the NPRM proposes to reclassify the bearing backlash test portion of the aileron freeplay check from a certification maintenance requirement (CMR) task to an MRB task. The aileron freeplay backlash check would be replaced with an aileron PCU internal leakage test and would remain a CMR task.
We agree that the aileron free play data could be useful. We will consider the NTSB's suggestion to use aileron freeplay data to monitor reclassification of the bearing backlash test once the service data are collected and we have reviewed the data. No change to the AD is necessary in this regard.
Clarification of Alternative Method of Compliance (AMOC) Paragraph
We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.
Conclusion
We have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the change described previously. We have determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.
Costs of Compliance
This AD affects about 742 airplanes of U.S. registry. The required actions take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the AD for U.S. operators is $59,360, or $80 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 anunsafe condition that is likely to exist or develop on products identified in this rulemaking action.
Regulatory Findings
We have 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 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); 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. See the ADDRESSES section for a location to examine the regulatory evaluation.
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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):