AD 2004-03-08 Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 36, and 36A Airplanes

The following airplanes, certificated in any category, as applicable: Table 1.—Applicability Model— As Listed in Bombardier Service Bulletin— 31 and 31A Airplanes 31-51-2, dated February 1, 2001; and 31-51-3, Revision 1, dated August 2, 2001. 35, 35A (C-21A), 36 and 36A Airplanes 35/36-51-3, dated February 1, 2001; and 35/36-51-4, Revision 1, dated August 2, 2001.

Required as indicated, unless accomplished previously. To prevent significant structural damage to the engine pylons, possible separation of the engines from the fuselage, and consequent reduced controllability of the airplane, accomplish the following: Inspections (a) At the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD: Do a detailed inspection (using a probe) and a general visual inspection of the shear webs of the forward engine beams (including modification of the drag angles) for cracking in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 31-51-2 (for Model 31 airplanes) or 35/36-51-3 (for Model 35 and 36 airplanes), both dated February 1, 2001; as applicable. (1) Prior to the accumulation of 3,000 total flight hours; or (2) Within 1,200 flight hours or 1 year after the effective date of this AD, whichever occurs first. Note 1: For the purposes of this AD, a general visual inspection is defined as: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to enhance visual access to all exposed surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.” Note 2: For the purposes of this AD, a detailed 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.” Detailed Probe Inspection Follow-On Actions (b) Following the detailed probe inspection required by paragraph (a) of this AD, do the follow-on actions specified in paragraphs (b)(1), (b)(2), or (b)(3) of this AD, as applicable, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 31-51-2 or 35/36-51-3, both dated February 1, 2001; as applicable. (1) If the resistance measured during the inspection is less than 0.110 milliohm: Repeat the inspections required by paragraph (a) of this AD thereafter at intervals not to exceed 1,200 flight hours. (2) If the resistance measured during the inspection is 0.110 milliohm or more, but less than 0.150 milliohm: Within the next 1,200 flight hours, repair and modify the forward engine beam shear web in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 31-51-3, Revision 1 (for Model 31 airplanes) or 35/36-51-4, Revision 1 (for Model 35 and 36 airplanes), both dated August 2, 2001; as applicable. (3) If the resistance measured during the inspection is 0.150 milliohm or more: Before further flight, repair and modify the forward engine beam shear web in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 31-51-3, Revision 1, or 35/36-51-4, Revision 1; as applicable. General Visual Inspection Follow-On Actions (c) Following the general visual inspection required by paragraph (a) of this AD, do all of the applicable follow-on actions at the times specified in the Accomplishment Instructions of Bombardier Service Bulletin 31-51-2 or 35/36-51-3, both dated February 1, 2001; as applicable; except as specified in paragraph (d) of this AD. (d) If any crack opening is found that is more than 0.03 inch during the general visual inspection required by paragraph (a) of this AD: Before further flight, do the actions specified in paragraphs 2.C.(16)(a) and 2.C.(16)(b) of Bombardier Service Bulletin 31-51-2 or 35/36-51-3, both dated February 1, 2001; as applicable; repair per a method approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA; and do the terminating action specified in paragraph (e) of this AD. Terminating Action (e) Modification of the shear webs by accomplishing all of the actions specified in the Accomplishment Instructions of Bombardier Service Bulletin 31-51-3, Revision 1, or 35/36-51-4, Revision 1, both dated August 2, 2001; as applicable; terminates the initial inspections required by paragraph (a) and the repetitive inspections required by paragraph (b)(1) of this AD. Repair Approval (f) Where any service bulletin identified in this AD specifies that the manufacturer may be contacted for disposition of certain repair conditions, repair per a method approved by the Manager, Wichita ACO, FAA. Submission of Inspection Results Not Required (g) Although the service bulletins identified in this AD specify to submit information to the manufacturer, this AD does not include such a requirement. Alternative Methods of Compliance (h) In accordance with 14 CFR 39.19, the Manager, Wichita ACO, is authorized to approve alternative methods of compliance for this AD. Incorporation by Reference (i) Unless otherwise specified in this AD, the actions shall be done in accordance with Bombardier Service Bulletin 31-51-2, dated February 1, 2001, and Bombardier Service Bulletin 31-51-3, Revision 1, dated August 2, 2001; or Bombardier Service Bulletin 35/36-51-3, dated February 1, 2001, and Bombardier Service Bulletin 35/36-51-4, Revision 1, dated August 2, 2001; as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. Effective Date (j) This amendment becomes effective on March 15, 2004. Issued in Renton, Washington, on January 29, 2004. Kalene C. Yanamura, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 04-2585 Filed 2-6-04; 8:45 am] BILLING CODE 4910-13-P