AD 95-24-14

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AD Number:
95-24-14
Document Type:
AD Final Rules
Docket Number:
95-NM-219-AD
Subject Heading:
Airworthiness Directives; De Havilland Model DHC-8 Series Airplanes
Subject:
Pivot Tube in Drag Strut of NLG
Status:
Current
Citation:
Federal Register: December 1, 1995 (Volume 60, Number 231)
Citation Publish Date:
12/01/1995
Effective Date:
12/18/1995
Make:
Bombardier Inc.
Model:
DHC-8-101 | DHC-8-102 | DHC-8-103 | DHC-8-106 | DHC-8-201 | DHC-8-202 | DHC-8-301 | DHC-8-311 ...Show more
Product Type:
Aircraft
Product Subtype:
Large Airplane
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 95-24-14
CITATION:   [Federal Register: December 1, 1995 (Volume 60, Number 231)]

PAGE NUMBER:   [Page 61647]

DOCKET NUMBER:   95-NM-219-AD

AMENDMENT:   39-9444

AD NUMBER:   95-24-14

SUBJECT HEADING:   Airworthiness Directives; De Havilland Model DHC-8 Series Airplanes

ACTION:   Final rule; request for comments

SUMMARY:   This amendment adopts a new airworthiness directive (AD) that is applicable to certain de Havilland Model DHC-8 series airplanes. This action requires eddy current inspections to detect cracking of the pivot tubes in the drag strut of the nose landing gear (NLG), and repair or replacement of any cracked tube with a serviceable or new tube. This amendment is prompted by reports that the pivot tubes cracked or failed completely due to fatigue. The actions specified in this AD are intended to prevent such fatigue cracking and subsequent failure of the pivot tube, which could result in a nose gear-up landing.

DATES:   Effective December 18, 1995. The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of December 18, 1995. Comments for inclusion in the Rules Docket must be received on or before January 30, 1996.

ADDRESSES:   Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 95-NM-219-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:   Jon Hjelm, Aerospace Engineer, Airframe Branch, ANE-172, FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York 11581; telephone (516) 256-7523; fax (516) 568-2716.

SUPPLEMENTARY INFORMATION:  
Transport Canada Aviation, which is the airworthiness authority for Canada, recently notified the FAA that an unsafe condition may exist on certain de Havilland Model DHC-8 series airplanes. Transport Canada Aviation advises that it has received reports indicating that the pivot tube located in the drag strut of the nose landing gear (NLG) cracked or failed completely on several Model DHC-8 series airplanes. During one incident, the NLG failed to extend, which resulted in damage to the airplane during the subsequent landing. The cause of these pivot tube failures has been attributed to fatigue. Fatigue cracking and subsequent failure of the pivot tube in the drag strut of the NLG, if not detected and corrected in a timely manner, could result in a nose gear-up landing.

Bombardier, Inc., has issued Service Bulletin S.B. 8-32-131, dated September 8, 1995, which includes (as an attachment) Messier-Dowty Service Bulletin M-DT DHC8-32-77, dated July 5, 1995. The Messier-Dowty service bulletin describes procedures for repetitive high frequency eddy current inspections to detect cracking of the pivot tube, part number 8225-3, located in the drag strut of the NLG. The service bulletin also describes procedures for repair or replacement of any cracked pivot tube with a serviceable tube having the same part number, or with a new strengthened tube having part number 8225-5 (de Havilland Modification 8/2266). This new strengthened tube contains more material in the waisted area of the center arm. Installation of a new strengthened pivot tube would eliminate the need for inspections of the pivot tubes. Transport Canada Aviation classified the Bombardier service bulletin as mandatory and issued Canadian airworthiness directive CF-95-15, dated September 11, 1995, in order to assure the continued airworthiness of these airplanes in Canada.

This airplane model is manufactured in Canada and is type certificated for operation in the United States under 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, Transport Canada Aviation has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada Aviation, 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.

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 failure of the pivot tube in the drag strut of the NLG and a subsequent nose gear-up landing. This AD requires repetitive eddy current inspections to detect cracking of the pivot tubes in the drag strut of the NLG, and repair or replacement of any cracked tube with a serviceable tube having the same part number or with a new strengthened tube. Installation of a new strengthened pivot tube, if accomplished, constitutes terminating action for the inspection requirements of this AD. The actions are required to be accomplished in accordance with the Bombardier service bulletin described previously.

Operators should note that the service bulletin recommends accomplishing the initial eddy current inspection at the following times: Prior to the accumulation of 13,400 total landings (for drag strut assemblies with 12,650 or less total landings); within the next 750 landings (for drag strut assemblies with between 12,651 and 20,000 total landings); or within the next 500 landings (for drag strut assemblies with 20,001 or more total landings). However, the FAA has determined that these compliance times would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the recommendation specified in the service bulletin, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, the time necessary to perform the inspection (less than one hour), and the availability of replacement parts. In light of all of these factors, the FAA finds that a compliance time of prior to the accumulation of 13,400 total landings on the drag strut assembly, or within 30 days after the effective date of this AD, is appropriate for initiating the required actions in that it represents the maximum interval of time allowable for affected airplanes to continue to operate without compromising safety.

Although installation of new strengthened pivot tubes is provided as an optional terminating action, the FAA is considering further rulemaking to require the installation of those pivot tubes on all affected airplanes. Therefore, this AD is considered to be interim action.

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 be filed 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 95-NM-219-AD." The postcard will be date stamped and returned to the commenter.

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 USC 106(g), 40101, 40113, 44701.

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

REGULATORY TEXT:  
95-24-14 DE HAVILLAND, INC.: Amendment 39-9444. Docket 95-NM-219-AD.
Applicability: Model DHC-8 series airplanes, serial numbers 003 through 403 inclusive; and Model DHC-8 series airplanes on which a drag strut having serial numbers DEC 001/83 through DCL 432/94 inclusive is installed; as listed in Bombardier Service Bulletin S.B. 8-32- 131, dated September 8, 1995; 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 (d) 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 assessment of 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 failure of the pivot tube in the drag strut of the nose landing gear (NLG) and a subsequent nose gear-up landing, accomplish the following:

(a) Prior to the accumulation of 13,400 total landings on the drag strut assembly, or within 30 days after the effective date of this AD, whichever occurs later: Perform an eddy current inspection to detect cracking of the pivot tube, part number (P/N) 8225-3, located in the drag strut of the NLG, in accordance with Bombardier Service Bulletin S.B. 8-32-131, dated September 8, 1995.

NOTE 2: The Bombardier service bulletin includes (as an attachment) Messier-Dowty Service Bulletin M-DT DHC8-32-77, dated July 5, 1995. The Messier-Dowty service bulletin details the specific procedures for accomplishment of the requirements of this AD.

(1) If no cracking is found, repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 2,000 landings.

(2) If any cracking is found that can be removed completely by reworking the pivot tube in accordance with the service bulletin, prior to further flight, repair the pivot tube in accordance with the service bulletin. Thereafter, repeat the inspection required by paragraph (a) of this AD at intervals not to exceed 1,000 landings.

(3) If any cracking is found that cannot be removed completely by reworking the pivot tube in accordance with the service bulletin, prior to further flight, accomplish paragraph (a)(3)(i) or (a)(3)(ii) of this AD in accordance with the service bulletin.

(i) Replace the cracked pivot tube with a serviceable tube having P/N 8225-3. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD. Or

(ii) Replace the cracked pivot tube with a new strengthened tube having P/N 8225-5. No further action is required by this AD.

(b) Replacement of a pivot tube having P/N 8225-3 with a pivot tube having P/N 8225-5 (de Havilland Modification 8/2266), in accordance with Bombardier Service Bulletin S.B. 8-32-131, dated September 8, 1995, constitutes terminating action for the inspection requirements of this AD.

(c) As of the effective date of this AD, no person shall install a drag strut assembly having serial numbers DEC 001/83 through DCL 432/94 inclusive on any airplane unless that assembly has been inspected and found to be crack-free, or unless that assembly has been inspected and repaired, in accordance with the requirements 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, New York Aircraft Certification Office (ACO), FAA, Engine and Propeller Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

(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 Bombardier Service Bulletin S.B. 8-32-131, dated September 8, 1995. 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 Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on December 18, 1995.

FOOTER: