A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737, 757, 767, and 777 series airplanes was published in the Federal Register on November 22, 1999 (64 FR 63762). That action proposed to require a one-time general visual inspection to determine the vendor and manufacturing date of all oxygen masks in the passenger cabin; and corrective action, if necessary. \n\nComments\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nSupport for the Proposed AD\nTwo commenters support the proposed AD.\n\nRequest to Extend Compliance Time\n\tTwo commenters request that the FAA extend the compliance time for the actions proposed in paragraph (a) from four years to five years. One commenter states that, to comply with the proposed AD, the oxygenmasks would have to be accessed twice: once to determine which masks are affected, so that an adequate number of replacement lanyards can be ordered, and a second time, to install the replacement lanyards. The other commenter states that, due to the amount of time needed to access and repack the oxygen marks, the inspection should be accomplished during a major maintenance visit. Thus, the commenters are requesting that the compliance time be extended to ensure that the inspection can be accomplished on all airplanes during a major maintenance visit.The FAA concurs with the commenters' request to extend the compliance time for the actions required by paragraph (a) from four years to five years. The FAA concurs that additional maintenance planning and work hours may be necessary to accomplish the inspection. The FAA finds that such an extension of the compliance time will not have an adverse impact on safety. Paragraph (a) has been revised accordingly.\n\nRequest to Increase Estimate ofCost Impact\n\tThe commenters that request an extension of the compliance time also request that the FAA revise the cost impact information in the proposal to reflect higher work hour estimates. One commenter requests that the work hour estimate be doubled because operators may need to access the oxygen masks twice (as described above). The other commenter states that the estimates in the service bulletin and the proposed rule do not account for the time needed to repack the oxygen masks. The commenter asserts that the masks are generally packed such that the tubing obscures the manufacturer's identification. Thus, it may be necessary to unwrap the tubing to accomplish the inspection, and, following the inspection, the masks would have to be carefully repacked. The commenter estimates that the inspection may actually take 1 to 2 work hours per oxygen mask.\n\n\tThe FAA partially concurs with the commenters' request to increase the cost impact estimate. The FAA does not concur with the commenters' estimates of the number of necessary work hours. The commenter's estimates may include extra time for "incidental" costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. The FAA recognizes that, in accomplishing the requirements of any AD, operators may incur incidental costs in addition to the "direct" costs. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate.\n\n\tHowever, as stated previously, the FAA acknowledges that the actions required by this AD may take longer than estimated in the proposed rule. The estimated number of work hours stated in the proposed rule was based on a figure of 0.16 work hour per mask. That figure included the 0.15 work hour needed to accomplish the applicable Boeing service bulletin, plus 0.01 work hour to accomplish the Puritan-Bennett service bulletin referenced in the Boeing service bulletins. In consideration of the fact that additional work hours may be necessary to accomplish certain actions required by this AD (e.g., to identify the manufacturer of the masks), the FAA has revised the cost impact information in this final rule to reflect an estimate of 0.25 work hour per mask, rather than the 0.16 work hour per mask estimated in the proposal.\n\nRequest to Remove Requirement for Certain Oxygen Masks\n\n\tOne commenter requests that the FAA revise paragraph (a) of the proposed rule to eliminate the requirement to determine the manufacturing date for oxygen masks not manufactured by Puritan-Bennett. The proposed paragraph (a) specifies a general visual inspection to determine both the manufacturer and the manufacturing date of each oxygen mask. The commenter points out that it is only relevant to determine the manufacturing date for masks manufactured by Puritan-Bennett. The commenter states that if the visual inspection establishes that the mask was not manufactured by Puritan-Bennett, no further inspection should be required. The FAA concurs with the commenter's request, and paragraph \n(a) has been revised accordingly, and new paragraphs (a)(1) and (a)(2) have been added to this AD. However, the FAA notes that, if the manufacturing date of the mask cannot be determined, or if the manufacturing date is between May 1986 and July 1998 inclusive but the manufacturer of the mask cannot be determined, the lanyard must be replaced. Thus, paragraph (b) of this AD has been revised to provide for such instances.\n\nRequest to Allow Replacement of Mask in Lieu of Replacement of Lanyard\n\n\tOne commenter requests that the FAA revise paragraph (b) of the proposed rule to allow replacement of the entire mask with a new mask manufactured by another vendor or manufactured outside the subject timeframe, in lieu of replacement of the lanyard only, if a mask is determined to be manufactured by Puritan-Bennett between May 1986 and July 1998.\n\n\tThe FAA partially concurs with the commenter's request. Replacement of an existing oxygen mask with a new mask manufactured by Puritan-Bennett before May 1986 or after July 1998, or manufactured by another vendor, would be acceptable alternatives to replacement of the lanyard, provided that the replacement mask has the same Boeing part number, or provided that the FAA has approved the replacement mask for installation as a replacement. Paragraph (b) of this AD has been revised to provide such replacement as another option for compliance.\n\nRequest to Clarify Justification of Proposed Compliance Time\n\n\tOne commenter, the airplane manufacturer, requests that the FAA revise the proposed rule to clarify that the compliance time recommended by the manufacturer is shorter than the compliance time the FAA proposed. The commenter notes that the section, "Differences Between Proposed Rule and Service Bulletin" in the preamble of the proposed rule implies that the FAA proposed a compliance time of four years because the manufacturer's recommendation would not ensure that operators would comply in a timely manner. The commenter points out that the manufacturer's recommendation that the service bulletin be incorporated at the next "2C" check would, for most operators, result in accomplishment of the service bulletin earlier than the proposed four-year compliance time.\n\n\tThe FAA acknowledges that the language in the "Differences Between Proposed Rule and Service Bulletin" section of the preamble of the proposed rule may have been misleading. However, this section is not restated in this final rule, so no change to this AD is necessary in this regard. The compliance time recommended by the manufacturer in its service bulletin is indeed more conservative than the compliance time specified in this AD. The FAA finds a five-year compliance time for completing the required actions is warranted, in that it represents anappropriate interval of time allowable for affected airplanes to continue to operate without compromising safety. As stated previously, this compliance time will also allow most operators to accomplish this AD during a major maintenance visit. As explained previously, the compliance time for the requirements of paragraph (a) of this AD has been revised from four years, as proposed, to five years. No other change to the final rule has been made in this regard.\n\nRequest to Withdraw Proposed Rule\n\n\tOne commenter requests that the FAA withdraw the proposed rule. The commenter asserts that the proposed AD is not warranted. The commenter points out that tests conducted by the airplane manufacturer show that few lanyards actually failed to hold a ten-pound test load, and those that failed had been subjected to relatively harsh environments where heat and humidity or use of insecticides or ammonia-based cleaning products had been a factor. The commenter states that the inspection and replacement of oxygen masks recommended in the service bulletin is adequate.\n\n\tThe FAA does not concur with the commenter's assertion that this AD is not warranted. This action is based on an in-flight decompression of a Boeing Model 767 series airplane during which about 30 percent of the lanyards failed when passengers attempted to use the oxygen masks. Investigation revealed that the design of the crimped copper alloy ferrules on the lanyards is susceptible to stress corrosion cracking. Though environmental factors can accelerate the rate of cracking, the FAA finds that such cracking would eventually occur on most masks. The FAA acknowledges that many airplanes do not operate in the most severe environments; for this reason, a relatively long compliance time has been set to allow operators to comply with the requirements of this AD during scheduled maintenance. No change to the final rule is necessary in this regard.\n\nRequest to Remove Certain Airplanes from Applicability StatementOne commenter requests that the FAA remove Boeing 737-600, -700, and -800 series airplanes from the "Applicability" statement of the proposed rule. The commenter provides no justification for its request. The FAA does not concur with the commenter's request. The subject oxygen masks could have been installed on these airplanes either during production or as spares. No change to the final rule is necessary in this regard.\n\nConclusion\n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.\n\nCost Impact\n\n\tThere are approximately 4,547 Model 737, 757, 767, and 777 series airplanes of the affected design in the worldwide fleet. The FAA estimates 2,206 airplanes of U.S. registry will be affected by this AD.\n\n\tFor Model 737 series airplanes (approximately 1,334 U.S.-registered airplanes), it will take approximately 40 work hours per airplane to accomplish the required actions, at the average labor rate of $60 per work hour. Required parts will cost approximately $576 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $3,969,984, or $2,976 per airplane. \n\n\tFor Model 757 series airplanes (approximately 558 U.S.-registered airplanes), it will take approximately 59 work hours per airplane to accomplish the required actions, at the average labor rate of $60 per work hour. Required parts will cost approximately $846 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $2,447,388, or $4,386 per airplane. \n\n\tFor Model 767 series airplanes (approximately 280 U.S.-registered airplanes), it will take approximately 69 work hours per airplane to accomplish the required actions, at the average labor rate of $60 per work hour. Required parts will cost approximately $990 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $1,436,400, or $5,130 per airplane. \n\n\tFor Model 777 series airplanes (approximately 34 U.S.-registered airplanes), it will take approximately 82 work hours per airplane to accomplish the required actions, at the average labor rate of $60 per work hour. Required parts will cost approximately $1,170 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $207,060, or $6,090 per airplane. \n\n\tThe cost impact figures discussed above are 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. \n\nRegulatory Impact\n\n\tThe regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.\n\n\tFor 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."\n\nList of Subjects in 14 CFR Part 39\n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference,Safety.\n\nAdoption of the Amendment \n\nAccordingly, 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: \n\nPART 39 - AIRWORTHINESS DIRECTIVES\n1. The authority citation for part 39 continues to read as follows:\nAuthority: 49 U.S.C. 106(g), 40113, 44701. \n§ 39.13 (Amended)\n2. Section 39.13 is amended by adding the following new airworthiness directive: