Airworthiness directives: Boeing,
[Federal Register: September 15, 1999 (Volume 64, Number 178)]
[Proposed Rules]
[Page 50016-50017]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr15se99-29]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-124-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 757-200 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 757-200 series airplanes. This proposal would require repetitive clearing of the drain passage at the aft end of the main landing gear truck beam to ensure moisture and contaminants within the truck beam can properly drain. This proposal is prompted by reports of fracture of main landing gear truck beams. The actions specified by the proposed AD are intended to prevent stress corrosion cracking, leading to fracture of a main landing gear truck beam during ground operations, which could result in either reduced controllability of the airplane or a fire.
DATES: Comments must be received by November 1, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-124-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.
The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.
FOR FURTHER INFORMATION CONTACT: Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filedin the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 99-NM-124-AD.'' The postcard will be date stamped and returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-124-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
Discussion
The FAA has received reports indicating that the main landing gear truck beam on Boeing Model 757-200 series airplanes has fractured due to stress corrosion cracking originating at corrosion pits on the surface of the inside diameter of the truck beam. The inner surface of the truck beam is protected from corrosion by several methods, including coatings over the metal surface and a gravity drain hole in the aft end of the truck beam inner surface that allows any moisture that enters the area to drain out. The drain holes on the fractured truck beams were found to be plugged with coating material, preventing moisture from draining out of the inside of the truck beam, which may result in increased corrosion on the inner surface of the truck beam. The primary cause of the condition may be inadequate adhesion of the coating to the inner surface of the truck beam during manufacture. This condition, if not corrected, could result in stress corrosion cracking, leading to fracture of a main landing gear truck beam during ground operations, which could result in either reduced controllability of the airplane or a fire.
Explanation of Relevant Service Information
The FAA has reviewed Boeing Service Letter 757-SL-32-060, dated March 31, 1999, which describes procedures for repetitive clearing of the drain passage at the aft end of the main landing gear truck beam to ensure moisture and contaminants within the truck beam can properly drain. Accomplishment of the actions specified in the service letter is intended to adequately address the identified unsafe condition.
Explanation of Requirements of Proposed Rule
Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service letter described previously, except as discussed below.
[[Page 50017]]
Differences Between Proposed Rule and Service Letter
Operators should note that, although the service letter recommends accomplishing the clearing procedure at the next convenient maintenance opportunity, and at planned maintenance intervals thereafter (such as ``C'' checks), the FAA has determined that the next convenient maintenance opportunity and at ``C'' checks thereafter 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 manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the inspection (less than one hour). In light of all of these factors, the FAA finds a compliance time of 4 years since the last overhaul of the main landing gear or since the date of manufacture of the main landing gear (for main landing gear that has not been overhauled), or within 90 days after the effective date of this AD, whichever occurs latest, for initiating the required actions to be warranted. For the repetitive clearing procedures, the FAA finds an interval of 6 months, if the drain was previously found to be clogged, or 18 months, if the drain was previously found to be unclogged, to be warranted. The FAA finds that these intervals are warranted in that they represent appropriate intervals of time allowable for affected airplanes to continue to operate without compromising safety.
Cost Impact
There are approximately 750 airplanes of the affected design in the worldwide fleet. The FAA estimates that 300 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $18,000, or $60 per airplane, per inspection cycle.
The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.
Regulatory Impact
The regulations proposed herein would 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed regulation (1) is not a ``significant regulatory action'' under Executive Order 12866; (2) is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 draft regulatory 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, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
-
Section 39.13 is amended by adding the following new airworthiness directive:
Boeing: Docket 99-NM-124-AD.
Applicability: All Model 757-200 series airplanes, 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 (b) 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, unless accomplished previously.
To prevent stress corrosion cracking, leading to fracture of a main landing gear truck beam during ground operations, which could result in either reduced controllability of the airplane or a fire, accomplish the following:
Inspection
(a) Within 4 years since the last overhaul of the main landing gear or since the date of manufacture of the main landing gear (for main landing gear which have not been overhauled), or within 90 days after the effective date of this AD, whichever occurs latest: Insert a wooden probe, or similar non-metallic object, into the aft drain hole of the main landing gear truck beam, to clear the drain passage and ensure it can properly drain, in accordance with Boeing Service Letter 757-SL-32-060, dated March 31, 1999.
(1) If the aft drain hole is found unclogged, repeat the clearing procedure thereafter at intervals not to exceed 18 months.
(2) If the aft drain hole is found clogged, repeat the clearing procedure thereafter at intervals not to exceed 6 months.
Alternative Methods of Compliance
(b) 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, Seattle Aircraft Certification Office (ACO), 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, Seattle ACO.
Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
Special Flight Permits
(c) 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.
Issued in Renton, Washington, on September 8, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-23997Filed9-14-99; 8:45 am]
BILLING CODE 4910-13-P
