AD 98-16-15

This amendment adopts a new airworthiness directive (AD) that applies to certain British Aerospace Model B.121 Series 1, 2, and 3 airplanes. This AD requires installing an inspection opening in the area of the main spar web, repetitively inspecting the area at the main spar web for cracks, and repairing or replacing any cracked part. This AD also requires installing nuts of improved design at the wing to fuselage main-spar attachment fittings. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom. The actions specified by this AD are intended to prevent structural failure of the main spar web area caused by fatigue cracking or separation of the wing caused by loose nuts at the wing to fuselage main-spar attachment fittings, which could result in loss of control of the airplane.

Final rule.

98-16-15 BRITISH AEROSPACE (OPERATIONS) LIMITED: Amendment 39-10691; Docket No. 98-CE-03-AD.

Applicability: Model B.121 Series 1, 2, and 3 airplanes, all serial numbers, 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 (f) 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 in the bodyof this AD, unless already accomplished.

To prevent structural failure of the main spar web area caused by fatigue cracking or separation of the wing caused by loose nuts at the wing to fuselage main-spar attachment fittings, which could result in loss of control of the airplane, accomplish the following:

(a) Within the next 100 hours time-in-service (TIS) after the effective date of this AD, replace the nuts (with improved design nuts) at the wing to fuselage main-spar attachment fittings in accordance with British Aerospace PUP Mandatory Service Bulletin No. B121/106, dated January 12, 1998.

(b) Upon accumulating 2,000 hours TIS on the main spar or within the next 50 hours TIS after the effective date of this AD, whichever occurs later, install an inspection opening and inspect, using eddy current methods, the area at the main spar web for cracks in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of British Aerospace PUP Mandatory Service Bulletin No. B121/105, dated January 12, 1998.

NOTE 2: Accomplishing the installation inspection opening and initial eddy current inspection required by this AD in accordance with British Aerospace PUP Mandatory Service Bulletin No. B121/102, Revision No. 1, Issued April 16, 1997, is considered "already accomplished" for the requirements of paragraph (b) of this AD.

(c) Within 800 hours TIS after the initial inspection required by paragraph (b) of this AD, and thereafter at intervals not to exceed 800 hours TIS, reinspect the area of the main spar web as specified in paragraph (b) of this AD.

(d) If any cracks are found during any inspection required by this AD, prior to further flight, accomplish the following:

(1) Obtain a repair or replacement scheme from the manufacturer through the FAA, Small Airplane Directorate, at the address specified in paragraph (f) of this AD; and

(2) Incorporate this scheme and continue to repetitively inspect as required by paragraph (c) of this AD, unless specified differently in the instructions to the repair or replacement scheme.

(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.

(f) An alternative method of compliance or adjustment of the initial or repetitive compliance times that provides an equivalent level of safety may be approved by the Manager, Small Airplane Directorate, Aircraft Certification Service, 1201 Walnut, suite 900, Kansas City, Missouri 64106. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Small Airplane Directorate.

(g) Questions or technical information related to British Aerospace PUP Mandatory Service Bulletin No. B121/106, dated January 12, 1998, and British Aerospace PUP Mandatory Service Bulletin No. B121/105, dated January 12, 1998, should be directed to British Aerospace (Operations) Limited, British Aerospace Regional Aircraft, Prestwick International Airport, Ayrshire, KA9 2RW, Scotland; telephone: (01292) 479888; facsimile: (01292) 479703. This service information may be examined at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri.

(h) The replacements, installation, and inspections required by this AD shall be done in accordance with British Aerospace PUP Mandatory Service Bulletin No. B121/106, dated January 12, 1998, and British Aerospace PUP Mandatory Service Bulletin No. B121/105, dated January 12, 1998. 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 British Aerospace (Operations) Limited, British Aerospace Regional Aircraft, Prestwick International Airport, Ayrshire, KA9 2RW, Scotland. Copies may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

NOTE 4: The subject of this AD is addressed in British AD 005-01-98, not dated.

(i) This amendment becomes effective on September 21, 1998.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain British Aerospace Model B.121 Series 1, 2, and 3 airplanes was published in the Federal Register as a notice of proposed rulemaking (NPRM) on March 16, 1998 (63 FR 12708). The NPRM proposed to require installing an inspection opening in the area of the main spar web, repetitively inspecting the area at the main spar web for cracks and the area of the wing to fuselage attach bolt holes for corrosion, and repairing or replacing any cracked or corroded part. Accomplishment of the proposed inspections as specified in the NPRM would be required in accordance with British Aerospace PUP Mandatory Service Bulletin No. B121/102, Revision No. 1, Issued April 16, 1997. If necessary, the proposed repair or replacement would be required in accordance with a scheme obtained from the manufacturer through the FAA, Small Airplane Directorate.

The NPRM was the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom.

After issuance of the NPRM, British Aerospace developed additional service information to that referenced in the previous proposal to include the installation of nuts of improved design at the wing to fuselage main-spar attachment fittings and the deletion of the inspection at the area of the wing to fuselage attach bolt holes for corrosion. The improved design nuts provide better torque retention than the ones originally installed.

In addition, British Aerospace re-examined the service history and evaluated reports from the field and changed the compliance time (that is referenced in the service information) for the inspection opening installation and the initial eddy current inspection to upon the accumulation of 2,000 flying hours.

To incorporate the above changes, British Aerospace issued the following service bulletins, which supersede British Aerospace PUP Mandatory Service Bulletin No. B121/102, Revision No. 1, Issued April 16, 1997:

- British Aerospace PUP Mandatory Service Bulletin No. B121/106, dated January 12, 1998, which specifies procedures for replacing the nuts (with improved design nuts) at the wing to fuselage main-spar attachment fittings; and

- British Aerospace PUP Mandatory Service Bulletin No. B121/105, dated January 12, 1998, which specifies procedures for installing an inspection opening in the area of the main spar web, and inspecting the area at the main spar web for cracks. These procedures are basically the same as contained in British Aerospace PUP Mandatory Service Bulletin No. B121/102, Revision No. 1, Issued April 16, 1997.

This prompted the FAA to issue a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain British Aerospace Model B.121 Series 1, 2, and 3airplanes. This proposal was published in the Federal Register as a supplemental NPRM on May 29, 1998 (63 FR 29362). The supplemental NPRM proposed to also require installing nuts of improved design at the wing to fuselage main-spar attachment fittings and deleting the inspection at the area of the wing to fuselage attach bolt holes for corrosion. Accomplishment of the proposed action as specified in the supplemental NPRM would be in accordance with the service information previously referenced.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

The FAA's Determination
After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Cost Impact
The FAA estimates that 2 airplanes in the U.S. registry will be affected by this AD; that it will take approximately 37 workhours per airplane to accomplish the initial inspection, inspection opening installation, and improved design nut installations; that the average labor rate is approximately $60 an hour. There is no cost for the parts to accomplish the replacements. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $4,440, or $2,220 per airplane. These figures only take into account the cost of the initial inspections, inspection opening installation, and improved design nut installations; and do not take into account the cost of repetitive inspections. The FAA has no way of determining the number of repetitive inspections each owner/operator of the affected airplaneswill incur.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption "ADDRESSES".

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: