AD 95-19-06

This amendment supersedes an existing airworthiness directive (AD), applicable to all British Aerospace Model ATP series airplanes, that currently requires inspections to detect cracking of the aft end of the wing rib boom angles on the left and right engine, and repair or replacement of the wing rib boom angle assemblies, if necessary. That AD was prompted by the detection of cracks in the engine outboard rib boom angles at the main landing gear (MLG) actuator attachment point. The actions specified by that AD are intended to prevent structural failure of the actuator attachment point, which could lead to collapse of the MLG. This amendment limits the applicability of the rule to only a certain number of airplanes; revises the initial inspection threshold, depending on whether or not certain modifications have been accomplished on the boom angles; and requires that modified boom angles be installed whenever replacement is necessary.

Final rule

95-19-06 JETSTREAM AIRCRAFT LIMITED (Formerly British Aerospace Commercial Aircraft Limited): Amendment 39-9368. Docket 94-NM-107-AD. Supersedes AD 93-14-08, Amendment 39-8632.
Applicability: Model ATP series airplanes; serial numbers 2002 through 2063, inclusive; 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 use the authority provided in paragraph (j) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessmentof the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent structural failure of the actuator attachment point, which could lead to collapse of the main landing gear (MLG), accomplish the following:

(a) Conduct a detailed visual inspection to detect cracking of the aft end of the engine outboard rib boom angles under the wing rib outboard of the left and right engine, in accordance with British Aerospace Service Bulletin ATP-57-13, Revision 1, dated January 15, 1993; or Jetstream Service Bulletin ATP-57-13, Revision 5, dated June 3, 1994; at the applicable time indicated below.

(1) For airplanes on which Modification 10313A (reference British Aerospace Service Bulletin ATP-56-16-1013A, Revision 1, dated July 2, 1994) has not been accomplished: Conduct the initial inspection within 400 hours time-in-service after September 8, 1993 (the effective date of AD 93-14-08, amendment 39-8632), or within 12 months since airplane manufacture, whichever occurs later.

(2) For airplanes on which Modification 10313A has been accomplished (modified inboard and outboard boom angles on both the left wing and right wing): Conduct the initial inspection prior to the accumulation of 30,000 landings on the boom angle assembly or within 12 months after the effective date of this AD, whichever occurs later.

(b) For the purposes of compliance with this AD, the following apply:

(1) Repair of cracked rib boom angles shall be accomplished in accordance with a method approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

(2) Replacement of cracked rib boom angle assemblies with modified assemblies shall be accomplished in accordance with Jetstream Service Bulletin ATP-57-16-10313A, Revision 1, dated July 2, 1994 (as corrected by Erratum 2, dated August 30, 1994). Prior to the accumulation of 30,000 landings on the replaced (modified) boom angle assembly, repeat the inspection in accordance with paragraph (a) of this AD.

(c) If no crack is detected: Repeat the detailed visual inspection at intervals not to exceed 3,000 landings or 12 months, whichever occurs first.

(d) If any crack is detected on only one rib boom angle, and that crack does not extend beyond bolt hole X: Repeat the detailed visual inspection of the rib boom angle for additional crack propagation at intervals not to exceed 300 hours time-in-service.

(1) If no additional crack propagation is detected during any of the repetitive inspections: Within 6 months after discovery of the crack, either repair the rib boom angle or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(2) If any of the repetitive inspections reveal that crack propagation has reached or extends beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angle or replace the rib boom assembly in accordance with paragraph (b) of this AD.

(e) If any crack is detected on only one rib boom angle, and that crack extends beyond bolt hole X, but not beyond bolt hole Y or down towards bolt hole A: Repeat the detailed visual inspection of the rib boom angle for additional crack propagation at intervals not to exceed 100 hours time-in-service.

(1) If no additional crack propagation is detected during any of the repetitive inspections: Within 3 months after discovery of the crack, either repair the rib boom angle or replace the rib boom angle assembly in accordance paragraph (b) of this AD.

(2) If any of the repetitive inspections reveal that crack propagation has reached or extends beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angle or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(f) If any crack is detected on only one rib boom angle, and that crack extends beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angle or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(g) If any crack is detected on both rib boom angles, and cracks do not extend beyond bolt hole X: Repeat the detailed visual inspection of the rib boom angles for additional crack propagation at intervals not to exceed 100 hours time-in-service.

(1) If no additional crack propagation is detected during any of the repetitive inspections: Within 3 months after discovery of the cracks, either repair the rib boom angles or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(2) If any of the repetitive inspections reveal that crack propagation has reached or extends beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angles or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(h) If any crack is detected on both rib boom angles, and cracks extend beyond bolt hole X, but not beyond bolt hole Y or down towards bolt hole A: Repeat the detailed visual inspection of the rib boom angles for additional crack propagation at intervals not to exceed 50 hours time-in-service.

(1) If no additional crack propagation is detected during any of the repetitive inspections: Within 1 month after discovery of the cracks, either repair the rib boom angles or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(2) If any of the repetitive inspections reveal that crack propagation has reached or extends beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angles or replace the rib boom angle assembly in accordance with paragraph (b) of this AD.

(i) If any crack is detected on both rib boom angles, and cracks extend beyond bolt hole Y or into bolt hole A: Prior to further flight, either repair the rib boom angles or replace the rib boom angle assembly in accordance with paragraph (b) of this AD

(j) 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, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

NOTE 3: Alternative methods of compliance previously granted for amendment 39-8632, AD 93-14-08, continue to be considered as acceptable alternative methods of compliance with this amendment.

(k) 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.

(l) The inspections shall be done in accordance with Jetstream Service Bulletin ATP-57-13, Revision 5, dated June 3, 1994. Revision 5 of Jetstream Service Bulletin ATP-57-13 contains the following list of effective pages:

Page Number
Revision Level
Shown on Page
Date
Shown on Page

1-3, 5
5
June 3, 1994

4, 6
4
May 31, 1994

7-12
3
March 23, 1994

The replacement shall be done in accordance with British Aerospace Service Bulletin ATP-57-13, Revision 1, dated January 15, 1993, or Jetstream Service Bulletin ATP-57-16-10313A, Revision 1, dated July 2, 1994 (as corrected by Erratum 2, dated August 30, 1994). The incorporation by reference of British Aerospace Service Bulletin ATP-57-13, Revision 1, dated January 15, 1993, was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of September 8, 1993 (58 FR 42194, August 9, 1993). The incorporation by reference of the remainder of the service documents listed above is 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 Jetstream Aircraft, Inc., P.O. Box 16029, Dulles International Airport, Washington, DC 20041-6029. 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.

(m) This amendment becomes effective on November 1, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 93-14-08, amendment 39-8632 (58 FR 42194, August 9, 1993), which is applicable to all British Aerospace Model ATP series airplanes, was published as a supplemental notice of proposed rulemaking in the Federal Register on May 9, 1995 (60 FR 24589). The action proposed to continue to require repetitive detailed visual inspections to detect cracking of the aft end of the wing rib boom angles on the wing rib outboard of the left and right engine, and repair or replacement of cracked rib boom angle assemblies. It also proposed to limit the applicability of the rule, revise the initial inspection threshold, and require that modified boom angles be installed whenever replacement of the boom angles is necessary.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received.

The commenter supports the proposed rule.

The FAA has revised the final rule to reflect the corporate name change of British Aerospace to Jetstream Aircraft Limited.

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

The FAA estimates that 10 airplanes of U.S. registry will be affected by this AD. The inspections that are currently required by AD 93-14-08 take approximately 2 work hours per airplane to accomplish. The average labor rate is $60 per work hour. Based on these figures, the total cost impact of the current inspection requirements AD on U.S. operators is estimated to be $1,200, or $120 per airplane, per inspection cycle.

The total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. However, since AD 93-14-08 became effective on September 3, 1993, the FAA assumes that at least the initial inspection already has been performed on several of the affected airplanes. Thus, the total cost impact of this AD may be reduced by the amount of the costs associated with those inspections that have already been accomplished.

Additionally, since this AD will extend the compliance time for the initial inspection of some airplanes, it has the effect of reducing the economic burden for operators of those airplanes, since it will preclude scheduling an airplane for inspections at a time earlier than is necessary.

Should replacement of the boom angles with modified boom angles be necessary, it will require approximately 150 work hours to accomplish,at an average labor charge of $60 per work hour. Required parts will cost approximately $3,800 per airplane.

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 final evaluationhas been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from 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 USC 106(g), 40101, 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by removing amendment 39-8632 (58 FR 42194, August 9, 1993), and by adding a new airworthiness directive (AD), amendment 39-9368, to read as follows: