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 February 12, 2010 (75 FR 6862). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:
Seven cases of on-ground hydraulic accumulator screw cap or end cap failure have been experienced on CL-600-2B19 (CRJ) aircraft, resulting in loss of the associated hydraulic system and high-energy impact damage to adjacent systems and structure. The lowest number of flight cycles accumulated at the time of failure, to date, has been 6991 flight cycles.
Although there have been no failures to date on any CL-600-1A11, CL-600-2A12 or CL-600-2B16 aircraft, the same accumulators as those installed on the CL-600-2B19, Part Numbers (P/N) 08-60163-001, 08- 60163-002, 08-60164-001 and 08-60164-002, are installed on some of the aircraft listed in the Applicability section of this directive.
Notes:
1. Earlier accumulators, P/Ns 2770571-102, 2770571-103, 2770571- 104 and 2770571-105, were installed in production on the following aircraft: CL-600-1A11 [all Serial Numbers (S/Ns)], CL-600-2A12 (all S/Ns) and CL-600-2B16 (S/Ns 5001 through 5194 and 5301 through 5524 only). These accumulators do not require inspection or replacement. However, if any of the accumulators with the above P/Ns have been replaced in-service by P/Ns 08-60163-001, 08-60163-002, 08-60164-001 and 08-60164-002, these latter accumulators require replacement.
2. The only accumulators ever installed on CL-600-2B16 aircraft, S/Ns 5525 through 5665 and 5701 and subsequent, are P/Ns 08-60163- 001, 08-60163-002, 08-60164-001 and 08-60164-002; these accumulators require replacement.
A detailed analysis of the systems and structure in the potential line of trajectory of a failed screw cap/end cap for each accumulator, P/Ns 08-60163-001, 08-60163-002, 08-60164-001 and 08- 60164-002, has been conducted. It has been identified that the worst case scenario would be failure of one of the brake accumulator screw caps/end caps, resulting in impact damage causing loss of both hydraulic systems No. 2 and No. 3, with consequent loss of both braking and nose wheel steering and the potential for a runway excursion [resulting in damage to the airplane and hazards to persons or property on the ground].
This directive gives instructions to perform identification and records checks, where applicable, and replace accumulators, P/Ns 08- 60163-001, 08-60163-002, 08-60164-001 and 08-60164-002, within the time compliance specified.
You may obtain further information by examining the MCAI in the AD docket.
Comments
We gave the public the opportunity to participate in developing this AD. We considered the comments received.
Request to Revise the AD to Allow Replacement of Accumulators With an Overhauled or Refurbished UnitBombardier Aerospace requests that we revise the NPRM to allow replacement of the accumulator with either a new accumulator with the same part number, or an overhauled accumulator with the same part number containing a T-suffix, in accordance with a future revision of the applicable service bulletin listed in the following table "Service Bulletins." Bombardier states that Transport Canada Civil Aviation (TCCA) has been notified of this upcoming change, and a similar request will be made to revise Canadian Airworthiness Directive CF-2009-39, dated October 27, 2009.
Service Bulletins
Service BulletinsBombardier Service Bulletin
Revision
Dated
600-0742
01
July 6, 2009
601-0597
01
July 6, 2009
604-29-008
01
July 6, 2009
605-29-001
01
July 6, 2009
We agree with the request to revise the AD. Since the NPRM was issued, Bombardier has issued Revision 02 of the service bulletins, as specified in Table 1 of this AD. These revised service bulletins allow for the replacement of the accumulators with an overhauled or refurbished unit identified by a "T" or "TNA" suffix. Paragraph (g) of this AD has been changed accordingly.
Request for Confirmation of Compliance Time
Pittco, Inc., requests confirmation that a calendar or schedule requirement for the replacement of the system accumulators will not be added. The commenter states that according to the compliance time in the proposed AD, airplanes with low flight cycles could take many years to reach the threshold to replace the accumulator. The commenter wants to confirm that this compliance time is acceptable and will not be changed to a calendar or schedule requirement.
We confirm that accumulator failures are based on flight cycles and not calendar schedule. The compliance times for this AD are based on a parameter related to failure of a particular component. In this case the failure of an accumulator screw cap or end cap is related to the number of flight cycles. Therefore, thisAD includes no calendar or schedule requirement. No change has been made to the AD in this regard.
Request for Clarification of Compliance Time
Pittco, Inc., requests clarification regarding the manufacturer's compliance time for replacing the accumulator. The commenter states that the service bulletin recommends not replacing the accumulator earlier than at the due cycles.
We agree that clarification is necessary. The manufacturer's recommendation was based on the availability of parts. According to the MCAI and this AD, replacement of the accumulators is required "within" the applicable number of flight cycles, rather than the service bulletin's compliance time of replacing the accumulators "at" 3,750 landings. Operators are permitted to accomplish the requirements of this AD before the specified compliance time. No change has been made to the AD in this regard.
Request for Clarification of Inspections in the Original and Revision 01 of Bombardier Service Bulletin 601-0597
Pittco, Inc., requests a change of wording to state that Bombardier Service Bulletin 601-0597, dated November 10, 2008, specifies an inspection; and that Bombardier Service Bulletin 601-0597, Revision 01, dated July 6, 2009, does not specify an inspection, but merely provides data for replacement of the accumulators. The commenter requests that stronger language be incorporated to clarify the difference.
We find that clarification is necessary. The actions required by paragraph (g) of the AD include an inspection, which is not specified in Revision 01 of the applicable service bulletin specified in Table 2 of this AD, to determine if the airplane has an affected accumulator. If the airplane has an affected accumulator, it must be replaced within the specified number of flight cycles. Credit for the previous accomplishment of the original version of the applicable service bulletin specified in Table 2 of this AD as noted in paragraph (g)(4) of the AD, is for the replacement of an accumulator with a new accumulator having the same part number, which is also acceptable for compliance with the requirements of paragraph (g)(2) of the AD. An ultrasonic inspection for cracking, which was specified in the original version of the applicable service bulletins specified in Table 2 of this AD, was removed from Revision 01 of these service bulletins, and is no longer required. No change has been made to the AD in this regard.
Request for Addition of Equivalent Part Numbers to AD
Pittco, Inc., requests the addition of equivalent part numbers to the proposed AD. The commenter states that Bombardier and its vendors use the terms "specification numbers" and "part numbers" synonymously, which is not consistent with the service bulletins listed in Table 1 of the NPRM. The commenter states that there are other identification numbers that are likely to be found during a review of the maintenance records. The commenter states that the service bulletins listed in Table 1 of the NPRM have tables that specify equivalent Bombardier part numbers. The commenter requests that the equivalent part numbers be added to the AD.
We agree. This AD requires an inspection to determine the part numbers of the system accumulators that are installed on the airplane. This AD also states that a review of airplane maintenance records is acceptable in lieu of this inspection if the part number of the accumulator can be conclusively determined from that review. The service bulletins listed in Table 1 of this AD list the equivalent Bombardier accumulator part numbers to identify the suspect system accumulators; therefore, we have added those equivalent part numbers in parentheses in paragraphs (g)(2)(i), (g)(2)(ii), (g)(2)(iii), and (g)(3) of this AD.
Conclusion
We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We determined that these changes will not increase the economic burden on any operator or increase the scope of the AD.
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 necessary to 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 our FAA policies. Any such differences are highlighted in a NOTE within the AD.
Costs of Compliance
We estimate that this AD will affect 340 products of U.S. registry. We also estimate that it will take about 20 work-hours per product to comply with the basic requirements of this AD. The average labor rate is $85 perwork-hour. Required parts will cost about $7,717 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 parts. As we do not control warranty coverage for affected parties, some parties may incur costs higher than estimated here. Based on these figures, we estimate the cost of this AD to the U.S. operators to be $3,201,780, or $9,417 per product.
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 aircommerce 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 the 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://www.regulations.gov; or in person at the Docket Operations office 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 Operations 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:
PART39--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: