AD 2000-01-12

Required as indicated, unless accomplished previously.

To detect and correct fatigue cracking in the underfloor pressure bulkhead of the fuselage, which could result in uncontrolled depressurization of the airplane and/or reduced structural integrity of the fuselage, accomplish the following:

Detailed Visual Inspections

(a) Perform a detailed visual inspection to detect cracks at FS409+128 of the bulkhead web drawing number 601R32208-123 of the fuselage, in accordance withCanadair Regional Jet Alert Service Bulletin A601R-53-045, Revision `D,' includingAppendix 1, dated December 22, 1997, at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable, until accomplishment of paragraph

(b) or (c) of this AD, as applicable.

(1) For airplanes that have accomplished a detailed visual inspection in accordance with AD 97-14-11 prior to the effective date of this AD: Perform a subsequent detailed visual inspection prior to the accumulation of 1,000 total flight hours, or within 100 flight hours after the immediately preceding inspection accomplished in accordance with AD 97-14-11, whichever occurs later. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours.

(2) For airplanes that have not accomplished a detailed visual inspection in accordance with AD 97-14-11 prior to the effective date of this AD: Perform a detailed visual inspection within 20 flight hours after the effective date of this AD. Perform a subsequent detailed visual inspection prior to the accumulation of 1,000 total flight hours, or within 100 flight hours after accomplishment of the immediately preceding inspection, whichever occurs later. Thereafter, repeat the inspection at intervals not to exceed 100 flight hours.

Note 2: For the purposes of this AD, a detailed visual inspection is defined as: ``An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required.''

Note 3: Accomplishment of the inspection required by paragraph

(a) of thisAD, prior to the effective date of this AD in accordance with Canadair Regional Jet AlertService Bulletin A601R-53-045, dated June 25, 1997; Revision `A,' includingAppendix 1, dated June 26, 1997; Revision `B,' including Appendix 1, dated June 27,1997; or Revision `C,' including Appendix 1, dated July 2, 1997; is considered acceptable for compliance with the applicable action specified by this AD.

Modification

(b) For any airplane on which no cracking has been detected during any inspection required by paragraph (a) of this AD: Within 9 months after the effective date of this AD, modify FS409+128 of the bulkhead web drawing number 601R32208-123 of the fuselage in accordance with Canadair Regional Jet Service Bulletin 601R-53-047, Revision `D,' including Appendix 1 and Appendix 2, dated December 22, 1997. Accomplishment of this modification terminates the requirements of this AD.

Note 4: Any modification accomplished prior to the effective date of this AD in accordance with Canadair Regional Jet Service Bulletin 601R-53-047, including Appendix 1 and Appendix 2, dated July 18, 1997; Revision `A,' including Appendix 1 and Appendix 2, dated July 31, 1997; Revision `B,' including Appendix 1 and Appendix 2, dated August 22, 1997; or Revision `C,' including Appendix 1 and Appendix 2, dated October 7, 1997; is considered acceptable for compliance with the applicable actions required by this AD.

Repair

(c) For any airplane on which any cracking is detected during any inspection required by paragraph (a) of this AD: Prior to further flight, determine the extent of the cracking as specified in Part A of paragraph 2.B. of the Accomplishment Instructions of Canadair Regional Jet Alert Service Bulletin A601R-53-045, Revision `D,' including Appendix 1, dated December 22, 1997, and accomplish the requirements of paragraph (c)(1) or (c)(2), as applicable.

(1) If the cracking is within the limits specified by Part A of paragraph 2.B. of the Accomplishment Instructions of the alert service bulletin, accomplish the requirements of paragraphs (c)(1)(i) and (c)(1)(ii) of this AD at the time specified in those paragraphs.

(i) Repeat the detailed visual inspection required by paragraph

(a) of this AD thereafter at intervals not to exceed 100 flight hours; and

(ii) Within 6 months after the effective date of this AD, or within 3 months after the initial date the crack was detected, whichever occurs later: Repair the affected area in accordance with Canadair Regional Jet Service Bulletin 601R-53-046, Revision `B,' dated December 22, 1997. Accomplishment of this repair terminates the requirements of this AD.

Note 5: Any repair accomplished prior to the effective date of this AD in accordance with Canadair Regional Jet Service Bulletin 601R-53-046, dated June 27, 1997, or Revision `A,' dated July 2, 1997, is considered acceptable for compliance with the applicable actions specified by this AD.

(2) If the cracking is outside the limits specified by Part A of the Accomplishment Instructions of the alert service bulletin, prior to further flight, perform a high frequency eddy current (HFEC) inspection to detect cracks of the forward side of the web of fuselage FS409+128 bulkhead web drawing number 601R32208-123, along the upper edge of the horizontal angle part number 601R32208-73, in accordance with Part B of paragraph 2.B. of the Accomplishment Instructions of the alert service bulletin.

(i) If, during any HFEC inspection required by paragraph (c)(2) of this AD, any cracking is detected that is within the limits specified by Part B of paragraph 2.B. of the Accomplishment Instructions of the alert service bulletin, accomplish the requirements of paragraphs (c)(2)(i)(A) and (c)(2)(i)(B) of this AD at the times specified in those paragraphs.

(A) Repeat the HFEC inspection required by paragraph (c)(2) of this AD thereafter at intervals not to exceed 50 flight hours, and repeat the detailed visual inspection required by paragraph (a) of this AD thereafter at interval not to exceed 100 flight hours; and

(B) Within 6 months after the effective date of this AD, or within 3 months after the initial date the crack was detected, whichever occurs later: Repair the affected area in accordance with Canadair Regional Jet Service Bulletin 601R-53-046, Revision `B,' dated December 22, 1997. Accomplishment of this repair terminates the requirements of this AD.

(ii) If, during any HFEC inspection required by paragraph (c)(2) of this AD, any cracking is detected that is outside the limits specified by Part B of paragraph 2.B. of the Accomplishment Instructions of the alert service bulletin, prior to further flight, determine the extent of the cracking as specified in paragraph 1.D. (``Compliance'') of Canadair Regional Jet Service Bulletin 601R-53-046, Revision `B,' dated December 22, 1997, and accomplish the requirements of paragraph (c)(2)(ii)(A) or (c)(2)(ii)(B) of this AD, as applicable.

(A) If the cracking is within the limits specified by paragraph 1.D. (``Compliance'') of the service bulletin, prior to further flight, repair in accordance with the service bulletin. Accomplishment of this repair terminates the requirements of this AD.

(B) If the cracking is outside the limits specified by paragraph 1.D. (``Compliance'') of the service bulletin, prior to further flight, repair in accordance with a method approved by the Manager, New York Aircraft Certification Office (ACO).