Applicability: CL-600 aircraft following models and all serial numbers.

Effective date: December 3, 1998

Required as indicated in TC AD No. CF-97-16R1.

AIRWORTHINESS DIRECTIVE

THE FOLLOWING AIRWORTHINESS DIRECTIVE (AD) MAY BE APPLICABLE TO AN AIRCRAFT, WHICH OUR RECORDS INDICATE IS REGISTERED IN YOUR NAME. ADs ARE ISSUED PURSUANT TO CANADIAN AVIATION REGULATION (CAR) 593. PURSUANT TO CAR 605.84 AND THE FURTHER DETAILS OF CAR STANDARD 625, APPENDIX H, THE CONTINUING AIRWORTHINESS OF AN AIRCRAFT IS CONTINGENT UPON COMPLIANCE WITH ALL APPLICABLE ADs. FAILURE TO COMPLY WITH THE REOUIREMENTS OF AN AD MAY INVALIDATE THE FLIGHT AUTHORIZATION OF THE. AIRCRAFT. ALTERNATIVE MEANS OF COMPLIANCE SHALL BE APPLIED FOR IN ACCORDANCE WITH CAR 605.84 AND THE ABOVE-REFERENCED STANDARD.

CF-97-16R1 BOMBARDIER

Applies to the following Bombardier Inc. (formerly Canadair) CL-600 aircraft:

Compliance is required as indicated, unless already accomplished.

A check of 105 Challenger aircraft has revealed 13 aircraft with fatigue cracks in the pressure bulkhead frame at the forward end of the wing box cutout.

To preclude failure of the pressure bulkhead, accomplish the following:

l. In accordance with the following schedule:

(a) CL-600-lAll (CL-600)

(i) For aircraft with 1900 or more flight cycles, initially within 100 flight cycles after the effective date of this directive; and

(ii) For aircraft with less than 1900 flight cycles, not later than 2000 flight cycles since new.

(b) CL-600-2A12 (CL-601), CL-600-2B16 (CL-601-3A/-3R) and CL-600-2B16 (CL-604)

(i) For aircraft with 1100 or more flight cycles, initially within 100 flight cycles after the effective date of this directive; and

(ii) For aircraft with less than 1100 flight cycles, not later than 1200 flight cycles since new.

Perform a detailed visual inspection of both the fuselage frame FS409 bulkhead web (P/N 600-32014-71/-95/-105/-137, as applicable) from the corner radius at WL 49.00; LBL 6.00 and RBL 6.00, and the angles (P/Ns 600-32014-13 and -15, or -113 and -115, as applicable) between LBL 9.0 and RBL 9.0. The inspection is to be carried out in accordance with Part 2, Accomplishment Instructions, of the applicable Canadair Service Bulletin indicated in the accompanying table, or later revisions of these service bulletins approved by the Director, Aircraft Certification, Transport Canada, Ottawa.

2. Aircraft that are visually determined to be crack free are to be reinspected in accordance with the previously noted service bulletins at intervals not exceeding 600 flight cycles.

3. As a phase-in schedule for this directive, aircraft that are visually determined to have cracks that do not extend up to the angles (specified above) may only be returned to service under the following conditions:

(a) No more than one crack exists at each corner; and

(b) Angles on the aft side of the web are visually confirmed to be crack free; and

(c) No crack extends under the angles; and

(d) Aircraft shall be reinspected at intervals not exceeding 100 flight cycles; and

(e) The cracked bulkhead is to be repaired prior to the aircraft accumulating 600 flight cycles or within 12 months, whichever occurs first, after the date of initial detection of the crack.

4. Aircraft that have cracks in excess of those specified in paragraph 3 require repair prior to further flight.

5. Report findings of all cracks to Bombardier Business Aircraft Division, Customer Support, telephone (514)855-7453.

This revision supersedes Airworthiness Directive CF-97-16 which was issued 25 September 1997.

This directive retains the 15 October 1997 effective date of Airworthiness Directive CF-97-16.

For Minister of Transport

J.E. Hurley

Acting Chief, Continuing Airworthiness

For further information contact a Transport Canada Centre, or Mr. Ian McLellan, Continuing Airworthiness, Ottawa, telephone (613) 952-4362, facsimile (613) 996-9178 or e-mail mclellan@tc.gc.ca.

The purpose of this revision is to eliminate the requirement for aircraft to be repaired prior to 1 October 1998.