AIRWORTHINESS DIRECTIVE

CAA-AD-071/2001

Date of issue: August 10, 2001

AIRCRAFT - MAIN DECK FLOOR BEAMS - INSPECTION

Applicability: Model 737-100 and -200 series airplanes as listed in Boeing Service Bulletin 737-57-1210, dated April 4, 1991, certificated in any category.

Effective date: October 04, 2001

Compliance: Required as indicated in FAA AD 2001-14-20.

Remarks: The compliance of this AD must be recorded in Aircraft Logbook, where applicable the requirements of this AD must be integrated into Aircraft Technical Documentation. Address inquiries concerning this AD to: Civil Aviation Authority, Airworthiness Division, Ruzyne Airport, 160 08 Prague 6, Czech Republic, tel: 420 2 33320922, fax: 420 2 20562270.

Ing. Pavel MATOUŠEK

Director of Airworthiness Division

CAA CZ

2001-14-20 Boeing: Amendment 39-12331. Docket 2000-NM-327-AD.

Applicability: Model 737-100 and -200 series airplanes as listed in Boeing Service Bulletin 737-57-1210, dated April 4, 1991, certificated in any category.

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d)(1) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the main deck floor beams at certain body stations (BS) due to fatigue cracking, which could result in rapid decompression and consequent reduced controllability of the airplane, do the following:

Inspections

(a) Before the accumulation of 20,000 total flight cycles, or within 6,000 flight cycles or 15 months after the effective date of this AD, whichever occurs later: Do a detailed visual inspection to find cracking of the main deck floor beams (body buttock line 0.07) located between BS 650 and BS 730, per the Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, dated April 4, 1991. If no cracking is found, do the requirements in paragraph (a)(1) or (a)(2) of this AD at the applicable times specified.

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 find 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.''

(1) If no cracking is found around BS 710 (Figure 1) or BS 727 (Figure 2), do the requirements in either paragraph (a)(1)(i) or (a)(1)(ii) of this AD.

(i) Repeat the detailed visual inspection at intervals not to exceed 6,000 flight cycles until accomplishment of the change specified in paragraph (c) of this AD. Or

(ii) Before further flight, do a one-time eddy current inspection for cracking of the fastener holes. If no cracking is found, before further flight, install the change at BS 710 (Figure 6) or BS 727 (Figure 7), as applicable, per the Accomplishment Instructions of the service bulletin. Doing the change ends the repetitive inspections for that area.

(2) If no cracking is found at BS 650 through BS 675 (Figure 8), do the requirements in either paragraph (a)(2)(i) or (a)(2)(ii) of this AD.

(i) Repeat the detailed visual inspection at intervals not to exceed 6,000 flight cycles until accomplishment of the change specified in paragraph (c) of this AD. Or

(ii) Before further flight, do a one-time eddy current inspection for cracking of the fastener holes. If no cracking is found, before further flight, install the change at BS 663 (Figure 9) per the Accomplishment Instructions of the service bulletin. Doing the change ends the repetitive inspections for that area.

Repair

(b) If any cracking is found during any inspection required by paragraph (a) of this AD, before further flight, either do the repair per the Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, dated April 4, 1991, or do the change specified in paragraph (c) of this AD. Where the service bulletin specifies to contact Boeing for repair instructions: Before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.

Optional Terminating Action

(c) Accomplishment of the main deck floor beam change in the applicable areas (BS 710 (Figure 6), BS 727 (Figure 7), or BS 650 through 675 (Figure 9)), as specified in the Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, dated April 4, 1991; or repair of the applicable area per the service bulletin; ends the repetitive inspections for that area.

Alternative Methods of Compliance

(d) (1) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

(2) Alternative methods of compliance, approved previously in accordance with AD 90-06-02, amendment 39-6489 (55 FR 8372, March 7, 1990), and AD 93-08-04, amendment 39-8551 (58 FR 25546, April 27, 1993), are approved as alternative methods of compliance with this AD.

Note 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Incorporation by Reference

(f) Except as provided by paragraph (b) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 737-57-1210, dated April 4, 1991. 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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Effective Date

(g) This amendment becomes effective on August 28, 2001.

Issued in Renton, Washington, on July 12, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 01-18017 Filed 7-23-01; 8:45 am]

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