AD 97-07-11

This amendment supersedes Airworthiness Directive (AD) 81-20-01, which currently requires repetitively inspecting the nose landing gear (NLG) actuator support structure and the front pressure bulkhead for cracks on Jetstream Aircraft Limited (JAL) HP137 Mk1 and Jetstream series 200 airplanes, and replacing any cracked part. This AD retains the repetitive inspections required by AD 81-20-01; requires repetitively inspecting the NLG retraction jack upper mounting fitting and attachment hardware for security bolt failure and for bolts with improper torque levels on the HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplanes, and requires replacing any failed security bolts and adjusting any bolt with an improper torque level; and requires modifying the NLG retraction jack on all affected airplanes, as terminating action for the repetitive inspections. This AD results from reports of NLG jack mounting fitting failures on several of the affected airplanes, and the Federal Aviation Administration's policy on aging commuter-class aircraft. The actions specified by this AD are intended to prevent failure of the NLG caused by a cracked NLG actuator support structure or cracked front pressure bulkhead, which, if not detected and corrected, could lead to nose gear collapse and damage to the airplane.

Final rule

97-07-11 JETSTREAM AIRCRAFT LIMITED: Amendment 39-9985; Docket No. 95-CE- 10-AD. Supersedes AD 81-20-01, Amendment 39-4223.
Applicability: The following airplanes, certificated in any category, that do not have an improved design attachment bracket for the nose landing gear (NLG) retraction jack (Modification JM 5285) installed in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Jetstream Service Bulletin (SB) 53-JM 5285:

- HP137 Mk1 airplanes, all serial numbers;
- Jetstream Series 200 airplanes, all serial numbers;
- Jetstream Model 3101 airplanes, all serial numbers; and
- Jetstream Model 3201 airplanes, serial numbers 601 through 840.

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 (e) 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 body of this AD, unless already accomplished.

To prevent failure of the NLG caused by a cracked NLG actuator support structure or cracked front pressure bulkhead, which could lead to nose gear collapse and damage to the airplane, accomplish the following:

NOTE 2: The paragraph structure of this AD is as follows:

Level 1: (a), (b), (c), etc.
Level 2: (1), (2), (3), etc.
Level 3: (i), (ii), (iii), etc.
Level 2 and Level 3 structures are designations of the Level 1 paragraph they immediately follow.

(a)For HP137 Mk1 and Jetstream series 200 airplanes that do not have the front pressure bulkhead strengthened in the area of the NLG jack attachment fitting (Modification 5127), upon accumulating 1,600 landings or within the next 200 landings after the effective date of this AD, whichever occurs later, and thereafter at intervals not to exceed 200 landings until the modification required by paragraph (c) of this AD is incorporated, inspect (using dye penetrant methods) the nose landing gear actuator support structure, part number (P/N) 137139C-13 and P/N 137139C-25 (or FAA-approved equivalents), and the membrane of the front pressure bulkhead for cracks. Accomplish the inspection in accordance with British Aerospace (BAe) SB No. 6/5, dated September 4, 1978.

(1) Prior to further flight after any of the inspections required by paragraph (a) of this AD, replace any cracked P/N 137139C-13 (or FAA-approved equivalent) NLG actuator support structure. This replacement does not eliminate the repetitive inspection requirement of this AD.

(2) Prior to further flight after any of the inspections required by paragraph (a) of this AD, repair any cracked P/N 137139C-25 (or FAA-approved equivalent) NLG actuator support structure in accordance with the applicable maintenance manual. This repair does not eliminate the repetitive inspection requirement of this AD.

(3) Prior to further flight after any of the inspections required by paragraph (a) of this AD, repair any cracked front pressure bulkhead membrane in accordance with the applicable maintenance manual. This repair does not eliminate the repetitive inspection requirement of this AD.

(b) For all HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplanes, upon accumulating 3,500 landings or within the next 200 landings after the effective date of this AD, whichever occurs later, accomplish the following:

(1) Inspect the NLG retraction jack upper mounting fitting and attaching hardware for correct installation, security bolt failure, and bolts with improper torque levels in accordance with Part A and B of the ACCOMPLISHMENT INSTRUCTIONS section of Jetstream SB 53-A-JA870510, which incorporates the following pages and revision levels:

Pages
Revision Level
Date
3, 5, 6, 8, 9,
and 10
Original Issue
May 26, 1987
1, 2, 4 and 7
Revision 1
November 10, 1987

Prior to further flight, replace any failed security bolt and adjust any bolt with an improper torque level in accordance with Jetstream SB 53-A-JA870510.

(2) Reinspect the NLG retraction jack upper mounting fitting and attaching hardware for security bolt failure and bolts with improper torque levels in accordance with Part A of the ACCOMPLISHMENT INSTRUCTIONS section of Jetstream SB 53-A-JA870510 at intervals not to exceed 1,600 landings until the modification required by paragraph (c) of this AD is incorporated. Prior to further flight, replace any failed security bolt and adjust any boltwith an improper torque level in accordance with Jetstream SB 53-A-JA870510.

(3) Reinspect the NLG retraction jack upper mounting fitting security nuts for correct installation in accordance with Part B of the ACCOMPLISHMENT INSTRUCTIONS section of Jetstream SB 53-A-JA870510 at intervals not to exceed 200 landings until the modification required by paragraph (c) of this AD is incorporated. If correct installation is not evident, prior to further flight, accomplish the reinspection specified in paragraph (b)(2) of this AD.

(c) For all applicable HP137 Mk1, Jetstream series 200, and Jetstream Models 3101 and 3201 airplanes, upon accumulating 25,000 landings or within the next 2,000 landings after the effective date of this AD, whichever occurs later, install an improved design attachment bracket for the NLG retraction jack (Modification JM 5285) in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Jetstream SB 53-JM 5285, which incorporates the following pages and revision levels:

Pages
Revision Level
Date
1 and 4
Revision 2
November 12, 1992
2,3, and
5 through 26
Revision 1
May 18, 1992

(1) Incorporating Modification JM 5285 on Jetstream HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplanes terminates the repetitive inspection requirement of this AD.

(2) Incorporating Modification JM 5285 on Jetstream Model 3201 airplanes eliminates the need for the repetitive inspections specified in the applicable maintenance manual.

(3) Modification JM 5285 may be accomplished at any time prior to accumulating 25,000 landings or within the next 2,000 landings after the effective date of this AD, whichever occurs later, at which time it must be incorporated.

(d) 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.

(e)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, Brussels Aircraft Certification Division, Europe, Africa, Middle East office, FAA, c/o American Embassy, 1000 Brussels, Belgium. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Brussels Aircraft Certification Division. Alternative methods of compliance approved in accordance with AD 81-20-01 (superseded by this action) are not considered 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 Brussels Aircraft Certification Division.

(f) The NLG actuator support structure inspections required by this AD shall be done in accordance with British Aerospace (BAe) Service Bulletin No. 6/5, dated September 4, 1978. The inspection of the NLG retraction jack upper mounting fitting and attaching hardware required by this AD shall be done in accordance with Jetstream Service Bulletin 53-A-JA870510, which incorporates the following pages and revision levels:

Pages
Revision Level
Date
3, 5, 6, 8, 9,
and 10
Original Issue
May 26, 1987
1, 2, 4 and 7
Revision 1
November 10, 1987

The installation required by this AD shall be accomplished in accordance with Jetstream SB 53- JM 5285, which incorporates the following pages and revision levels:

Pages
Revision Level
Date
1 and 4
Revision 2
November 12, 1992
2, 3, and
5 through 26
Revision 1
May 18, 1992

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 Limited, Manager Product Support, Prestwick Airport, Ayrshire, KA9 2RW Scotland; or Jetstream Aircraft Inc., Librarian, P.O. Box 16029, Dulles International Airport, Washington, DC, 20041-6029. Copies may be inspected at the FAA, Central Region, Office of the Assistant Chief 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.

(g) This amendment becomes effective on May 23, 1997.

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 JAL HP137 Mk1, Jetstream series 200, and Jetstream Models 3101 and 3201 airplanes that do not have an improved design attachment bracket (Modification JM 5285) installed for the nose landing gear (NLG) retraction jack was published in the Federal Register as a notice of proposed rulemaking (NPRM) on September 19, 1995 (60 FR 48429). The NPRM proposed to supersede AD 81-20-01 with a new AD that would:

- retain the requirement contained in AD 81-20-01 of repetitively inspecting (using dye penetrant methods) the NLG actuator support structure and the front pressure bulkhead for cracks on JAL HP137 Mk1 and Jetstream series 200 airplanes that do not have the front pressure bulkhead strengthened in the area of the NLG jack attachment fitting (Modification No. 5127), and replacing or repairing any cracked NLG actuator support structure or cracked front pressure bulkhead. Accomplishment of the proposed inspections as specified in the NPRM would be in accordance with Jetstream Service Bulletin (SB) No. 6/5, dated September 4, 1978.

- require repetitively inspecting the NLG retraction jack upper mounting fitting and attachment hardware for security bolt failure and bolts with improper torque levels on the HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplanes, and replacing any failed security bolts and adjusting any bolt with an improper torque level. Accomplishment of the proposed inspections as specified in the NPRM would be in accordance with Jetstream SB 53-A-JA870510, which consists of the following pages and revision levels:

Pages
Revision Level
Date
3, 5, 6, 8, 9,
and 10
Original Issue
May 26, 1987
1, 2, 4 and 7
Revision 1
November 10, 1987

- require modifying the NLG retraction jack on the HP137 Mk1, Jetstream series 200, and Jetstream Models 3101 and 3201 airplanes, as terminating action for all the repetitive inspections, including the inspections referenced in the Model 3201 maintenance manual. Accomplishment of the proposed modification as specified in the NPRM would be in accordance with Jetstream SB 53-JM 5285, which consists of the following pages and revision levels:

Pages
Revision Level
Date
1 and 4
Revision 2
November 12, 1992
2, 3, and
5 through 26
Revision 1
May 18, 1992

Interested persons have been afforded an opportunity to participate in the making of this amendment. One comment was received regarding the NPRM. An analysis of the comment follows:

The commenter provides information on the company's fleet size and the estimated projection on when the proposed replacement would be mandatory on the affected airplanes in the company's fleet, as well as the number of repetitive inspections that would be required during that time. The commenter states that it ismore economical for the company to incorporate the modification on its entire fleet immediately rather than continuing to repetitively inspect. The commenter also mentions that parts to modify the NLG retraction jack cost $1,800 instead of $1,600. The FAA concurs with the correction to the cost and has incorporated this change.

As written, the original NPRM would have allowed continued flight if cracks are found in the front pressure bulkhead membrane or actuator support structure when the cracks do not exceed certain limits. Since issuing that NPRM, the FAA established a policy to disallow airplane operation when known cracks exist in primary structure, unless the ability to sustain ultimate load with these cracks is proven. The front pressure bulkhead and actuator support structure are considered primary structure, and the FAA has not received any analysis to prove that ultimate load can be sustained with cracks in this area.

For this reason, the FAA has determined that the crack limits contained in the NPRM should be eliminated and that AD action should be taken to require immediate replacement of any cracked front pressure bulkhead membrane or actuator support structure. Since revising the proposed AD to require immediate replacement of any cracked part went beyond the scope of what was presented in the original NPRM, the FAA published a supplemental NPRM in the Federal Register on October 21, 1996 (61 FR 54582), in order to give the public an opportunity to comment on the proposal.

Interested persons were again afforded an opportunity to participate in the making of this amendment. No comments were received regarding the substance of the supplemental NPRM 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 AD 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.

The FAA's Aging Commuter Aircraft Policy
The actions required by this AD are consistent with the FAA's aging commuter aircraft policy, which briefly states that, when a modification exists that could eliminate or reduce the number of required critical inspections, the modification should be incorporated. This policy is based on the FAA's determination that reliance on critical repetitive inspections on airplanes utilized in commuter service carries an unnecessary safety risk when a design change exists that could eliminate or, in certain instances, reduce the number of those critical inspections. In determining what inspections are critical, the FAA considers (1) the safety consequences of the airplane if the known problem is not detected by the inspection; (2) the reliability of the inspection such as the probability of not detecting the known problem; (3) whether the inspection area is difficult to access; and (4) the possibility of damage to an adjacent structure as a result of the problem.

Cost Impact
The FAA estimates that 170 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 41 workhours per airplane to accomplish the proposed modification, and that the average labor rate is approximately $60 an hour. Parts cost approximately $1,800 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $724,200 or $4,260 per airplane. This figure only takes into account the cost of the inspection-terminating modification and does not take into account the cost of the repetitive inspections. The FAA has no way of determining the number of repetitive inspections each HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplane owner/operator will incur over the life of the airplane.

This figure is also based on the presumption that no affected airplane owner/operator has accomplished the required modification. This AD eliminates the need for the repetitive inspections required by AD 81-20-01. The FAA has no way of determining the operational levels of each individual operator of the affected airplanes, and subsequently cannot determine the repetitive inspection costs that will be eliminated by this AD. The FAA estimates these costs to be substantial over the long term.

In addition, JAL has informed the FAA that parts have been distributed to owners/operators to equip approximately 39 of the affected airplanes. Presuming that each set of parts has been installed on an affected airplane, the cost impact of the required modification upon the public is reduced $166,140 from $724,200 to $558,060.

The intent of the FAA's aging commuter airplane program is to ensure safe operation of airplanes that are in commercial service without adverselyimpacting private operators. Of the approximately 170 airplanes in the U.S. registry that will be affected by this AD, the FAA has determined that approximately 95 percent are operated in scheduled passenger service by 10 different operators.

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 USC 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by removing Airworthiness Directive (AD) 81-20-01, Amendment 39-4223, and by adding a new AD to read as follows: