AD 94-07-12

This amendment adopts a new airworthiness directive (AD), applicable to Jetstream Model ATP series airplanes, that requires inspections to detect fatigue-related cracking and loose rivets in the subframe yoke assemblies of the quick engine change units (QECU) on both wings; replacement of rivets; and repair or replacement of yoke assemblies, if necessary. This amendment is prompted by in-service and fatigue test reports of cracking in the yoke of a QECU subframe. The actions specified by this AD are intended to prevent loss of structural integrity of the engine mount.

Final rule

94-07-12 JETSTREAM AIRCRAFT LIMITED: Amendment 39-8870. Docket 93-NM-158-AD.
Applicability: All Model ATP airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent loss of engine mount structural integrity, accomplish the following:

(a) Within 750 hours time-in-service after the effective date of this AD, perform a detailed close visual inspection to detect cracking and loose rivets in the subframe yoke assemblies of the quick engine change units (QECU) on the left- and right-hand wings, in accordance with Jetstream (BAe) ATP Service Bulletin ATP-54-11, dated July 13, 1993; or Revision 1, dated November 9, 1993.

(1) If any loose rivet is detected: Prior to further flight, replace the existing rivet with a new or serviceable rivet in accordance with the service bulletin.

(2) If any type "A" cracking (as defined in the service bulletin) is detected having a crack length that is less than or equalto 4 rivet pitches: Repeat the inspection thereafter at intervals not to exceed 250 hours time-in-service.

(3) If any type "A" cracking (as defined in the service bulletin) is detected having a crack length that is greater than 4 rivet pitches, or that is less than or equal to 7 rivet pitches: Repeat the inspection thereafter at intervals not to exceed 35 hours time-in-service.

(4) If any type "A" cracking (as defined in the service bulletin) is detected having a crack length that is greater than 7 rivet pitches: Prior to further flight, repair in accordance with a method approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

(5) If any type "B" or "C" cracking (as defined in the service bulletin) is detected: Prior to further flight, repair in accordance with a method approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

(b) Except as provided by paragraph (c) of this AD: Prior toeach reassembly of the engine to the QECU subframe, and prior to installation of an already assembled engine and QECU subframe unit on an airplane, perform an eddy current inspection to detect cracking of the subframe yoke assembly, in accordance with Jetstream (BAe) ATP Service Bulletin ATP-54-11, dated July 13, 1993; or Revision 1, dated November 9, 1993. Prior to further flight, replace any cracked subframe yoke assembly with a new or serviceable subframe yoke assembly in accordance with the service bulletin.

(c) For QECU subframe units that have accumulated less than 500 hours time-in-service since an eddy current inspection has been conducted in accordance with paragraph (b) of this AD: Prior to reassembly of the engine to the QECU subframe, and prior to installation of an already assembled engine and QECU subframe unit on an airplane, perform a detailed close visual inspection to detect cracking of the subframe yoke assembly, in accordance with Paragraph 2.A. of the Accomplishment Instructions of Jetstream (BAe) ATP Service Bulletin ATP-54-11, Revision 1, dated November 9, 1993. Prior to further flight, replace any cracked subframe yoke assembly with a new or serviceable subframe yoke assembly in accordance with the service bulletin.

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

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

(f) The inspections and replacements shall be done in accordance with Jetstream (BAe) ATP Service Bulletin ATP-54-11, dated July 13, 1993; or Jetstream (BAe) ATP Service Bulletin ATP-54-11, Revision 1, dated November 9, 1993, which incorporates the following list of effective pages:

Page Number
Revision Level
Shown on Page
Date
Shown on Page
1, 3, 5
1
November 9, 1993
2, 4, 6-9
Original
July 13, 1993

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 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.

(g) This amendment becomes effective on May 23,1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to Jetstream Model ATP airplanes was published in the Federal Register on November 1, 1993 (58 FR 58305). That action proposed to require inspections to detect fatigue-related cracking and loose rivets in the subframe yoke assemblies of the quick engine change units (QECU) on both wings; and replacement of rivets, and repair or replacement of yoke assemblies, if 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 proposal.

Since the issuance of the proposal, Jetstream Aircraft Limited as issued Service Bulletin ATP-54-11, Revision 1, dated November 9, 1993. This revision is substantially the same as the original version. However, it contains procedures that would allow operators to perform a visual inspection, rather than an eddy current inspection, prior to reassembly of an engine to the QECU subframe, or prior to installation of an already assembled engine and QECU unit on an airplane, if the subframe unit has accumulated less than 500 hours time-in-service since the last eddy current inspection. This new provision is relieving in nature in that operators would not be required to perform an extensive and costly eddy current inspection, if one had been performed only shortly beforehand. The FAA has revised the final rule to include such a provision, and to include reference to the new revision of the service bulletin as an additional source of appropriate service information.

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, that it will take approximately 3 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $1,650, or $165 per airplane.

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.

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 evaluation has 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 14 CFR part 39 of the Federal Aviation Regulations as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: