Comair, Inc.

These comments are being submitted on the behalf of Comair, Inc. The first comment is to withdraw this NPRM. The minor editorial correction to the ‘Applicability’ section should not warrant a revised or new directive. Reissuing this AD will not increase the airworthiness of any airplane. To address the following statement in the “Discussion” section of the NPRM: “Service Bulletins affect only airplanes in service, not airplanes “in production”. A review of any CL-600-2B19, CL-600-2C10 or CL-600-2D24 Aircraft Technical Log – Section 3 will indicate that service bulletins are complied with by Bombardier, on a limited bases, prior to delivery to a customer. The determination would need to be made for what terminology should be used for “post-production” but “pre-in service” compliance of these service bulletins. Additional comments in case this NPRM is not withdrawn: Applicability Paragraph (c): Service Bulletin 670BA-29-008 is currently at Revision B, dated Aug 28/2007. Applicability Paragraph (c), Table 1 – limit serial number range. Comments were submitted to the NPRM which would become AD 2005-13-02 to limit the serial number range for which the AD should apply. In the preamble section of that AD, in addressing that comment, the FAA agreed with that comment. However, Table 1 was published listing Applicability for the CL-600- 2C10 from serial numbers 10003 – 10999 and for the CL-600-2D24 serial numbers 15001 – 15990. The following is a restatement of that comment as it appears in the preamble of AD: One commenter requests that certain airplane serial numbers be excluded from the applicability specified in paragraph (c) of the proposed AD. The commenter states that the inspection of the hydraulic tube adapters specified in Bombardier CRJ 700/900 Series Temporary Revision (TR) MRM2-129, dated June 1, 2004 (referenced in the proposed AD as the appropriate source of service information), should be applicable to Bombardier Model CL-600-2C10 (Regional Jet Series 700 & 701) series airplanes having serial numbers 10003 through 10099 inclusive, since Modification Summary 670T11944 was introduced in production at serial number 10100. The commenter also states the two remaining inspections of the bulkhead assembly and pylon pressure pan specified in TR MRM2-129 should be applicable to only airplanes having serial numbers 10003 through 10156 inclusive, since Modification Summary 670T11508 was incorporated in production at serial number 10157. For the above stated reason, Table 1 of the final rule should be limited to Serial numbers 10003 – 10156 inclusive for the CL-600-2C10. Although not addressed in the comment for AD 2005-13-02, for the same reason, Table 1 of the final rule should be limited to Serial numbers 15001 – 15026 inclusive for the CL-600-2D24. This information can be readily found in the Effectivity section of SB 670BA-29-008 Revision B. It does not make sense to issue an AD against airplane serial numbers for which there is no action required. TR MRM2-129 quantifies in the ‘Service Restriction’ column which airplanes requires these additional supplementary requirements. From the time of delivery, airplanes serial number 10157 and subsequent and 15027 and subsequent do not require the inspections introduced by this TR and should not be included in Table 1. Under the Cost of Compliance section of the NPRM it states that about 116 airplanes of U.S. registry would be affected. This is the same number provided in AD 2005-13-02. At the time of release of this NPRM, there are approximately 255, CL-600-2C10 and -2D24 of U.S. registry. Either the Cost of Compliance takes into account that only airplanes with serial numbers below 10157 and 15027 are affected by this AD or the number needs to be adjusted to today’s U.S. registry level. Additionally, although not able to determine the compliance status of all U.S. Operators, a conversation with a Bombardier Field Service Representative indicates that perhaps all affected serial numbers have complied with the Modification Summaries and / or Service Bulletin combination listed in Paragraph (c) making the existing AD and this proposed AD not applicable to any U.S registered airplanes.