AD 97-18-08 ACTIVE

This amendment adopts a new airworthiness directive (AD) that is applicable to certain British Aerospace (Jetstream) Model 4101 airplanes. This action requires a visual inspection to detect wear damage of the drag brace of the main landing gear (MLG), and replacement of any worn parts with new or serviceable parts. This action also requires an inspection to determine whether there is movement in the spherical bearing of the lower link of the drag brace, certain measurements of the drag brace, and repetitive inspections, if necessary. This amendment is prompted by reports of loose spherical bearings in the links of the drag brace of the MLG. The actions specified in this AD are intended to prevent reduced structural integrity and potential collapse of the MLG due to loose spherical bearings and subsequent wear damage of the links of the drag brace.

Final rule; request for comments

97-18-08 BRITISH AEROSPACE REGIONAL AIRCRAFT [Formerly Jetstream Aircraft Limited, British Aerospace (Commercial Aircraft) Limited]: Amendment 39-10118. Docket 97-NM-181-AD.
Applicability: Jetstream Model 4101 airplanes, constructors numbers 41004 through 41100 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 request approval for an alternative method of compliance in accordance with paragraph (d) 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 shouldinclude specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent reduced structural integrity and potential collapse of the main landing gear (MLG) due to loose spherical bearings of the drag brace, accomplish the following:

(a) For all airplanes: Within 30 days after the effective date of this AD, perform a visual inspection to detect wear damage of the drag brace of the left- and right-hand MLG, in accordance with Jetstream Alert Service Bulletin J41-A32-061, dated July 11, 1997.

(1) For airplanes on which no wear damage has been detected and that have accumulated 8,000 or more total landings as of the effective date of this AD or on which APPH Service Bulletin AIR84352-32-05 has been accomplished: Prior to further flight, perform an inspection to detect movement of the spherical bearing of the drag brace and measure the area between the lower link and the strut, in accordance with the Jetstream alert service bulletin.

(i) If no movement of the spherical bearing is detected and the measurement of the area between the lower link and the strut is within the limits specified by the service bulletin, no further action is required by this AD.

NOTE 2: For the purposes of this AD, "flight day" is defined as any day on which the airplane is flown.

(ii) If any movement is detected or the measurement of the area between the lower link and the strut is beyond the limits specified by the service bulletin, repeat the inspections required by paragraph (a) of this AD prior to the first flight of the day for the next 100 flight days of the airplane.

(2) For all other airplanes on which no wear damage has been detected: Prior to further flight, perform an inspection to detect movement of the spherical bearing of the drag brace and measure the area between the lower link and the strut, in accordance with the service bulletin.

(i) If no movement of the spherical bearing is detected, and the measurement of the area between the lower link and the strut is within the limits specified by the service bulletin, repeat the inspections required by paragraph (a) of this AD at the time specified in paragraph (a)(2)(i)(A) or (a)(2)(i)(B) of this AD, as applicable.

(A) For drag braces that have accumulated less than 501 total landings: Repeat the inspections at intervals not to exceed 100 flights until the drag brace has accumulated 500 total landings.

(B) For drag braces that have accumulated more than 500 total landings, but less than 8,000 total landings: Repeat the inspections at intervals not to exceed 1,000 flights.

(ii) If any movement is detected or the measurement of the area between the lower link and the strut is beyond the limits specified by the service bulletin, repeat the inspections required by paragraph (a) of this AD prior to the first flight of the day for the next 100 flight days of the airplane.(b) For all airplanes: If any wear damage of the drag brace is detected during any inspections required by this AD, prior to further flight, remove the wear damaged part(s) and replace with a new or serviceable part, in accordance with Jetstream Alert Service Bulletin J41-A32-061, dated July 11, 1997. Within 30 days after the replacement of a wear damaged part with a new or serviceable part, perform the requirements of paragraph (a) of this AD.

(c) Accomplishment of APPH Service Bulletin AIR84352-32-05, dated June 1997, constitutes terminating action for the repetitive inspection requirements of paragraph (a)(2) of this AD.

(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. 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 3: 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 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) The actions shall be done in accordance with Jetstream Alert Service Bulletin J41-A32-061, dated July 11, 1997. 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 AI(R) American Support, Inc., 13850 McLearen Road, Herndon, Virginia 20171. 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 September 17, 1997.

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, recently notified the FAA that an unsafe condition may exist on British Aerospace (Jetstream) Model 4101 airplanes. The CAA advises that it has received reports of loose spherical bearings in the lower link of the drag brace of the main landing gear (MLG). The loosened spherical bearings have been attributed to improper swaging on some landing gear units. Such loosened spherical bearings and subsequent wear damage of the links of the drag brace, if not detected and corrected, could result in reduced structural integrity and potential collapse of the MLG.

Explanation of Relevant Service Information
British Aerospace has issued Jetstream Alert Service Bulletin J41-A32-061, dated July 11, 1997, which describes procedures for performing a visual inspection to detect wear damage of the drag brace of the left- and right-hand MLG, and replacement of any worn part with a new or serviceable part. The alert service bulletin also describes procedures to detect any movement of the spherical bearing and to measure the lower link to the upper link and the lower link to the strut attachment of the drag brace, and repetitive inspections, if necessary.

Additionally APPH Ltd. has issued APPH Service Bulletin AIR84352-32-05, dated June 1997, which describes procedures for an inspection to detect movement of the spherical bearings installed in the lower links of the drag braces of the MLG, and rework, if necessary. The CAA has approved APPH Service Bulletin AIR84352-32-05, and has classified Jetstream Alert Service Bulletin J41-A32-061 as mandatory, and issued British airworthiness directive 003-07-97, dated July 25, 1997, in order to assure the continued airworthiness of these airplanes in the United Kingdom.

FAA's Conclusions
This airplane model is manufactured in the United Kingdom and is type certificated for operation in the United Statesunder the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent reduced structural integrity and potential collapse of the MLG due to loose spherical bearings in the links of the drag brace, which could result in wear damage to the drag brace of the MLG. This AD requires a visual inspection to detect wear damage of the drag brace of the MLG, and replacement of any worn parts with new or serviceable parts. This AD also requires an inspection to determine whether there is movement in the spherical bearing of the lower link of the drag brace, certain measurements of the drag brace, and repetitive inspections, if necessary. The actions are required to be accomplished in accordance with the Jetstream alert service bulletin described previously.

Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will befiled in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-181-AD." The postcard will be date stamped and returned to the commenter.

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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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 U.S.C. 106(g), 40113, 44701.

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

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 97-NM-181-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from AI(R) American Support, Inc., 13850 McLearen Road, Herndon, Virginia 20171. This information may be examined 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.

Mark Quam, Aerospace Engineer, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2145; fax (425) 227-1149.