A proposal to amend part 39 of the Federal Aviation Regulations to add an airworthiness directive (AD), applicable to Boeing Model 727 series airplanes, was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on March 18, 1994 (59 FR 12865). That supplemental NPRM proposed to supersede AD 86-05-07, amendment 39-5250 (51 FR 7767, March 6, 1986). That AD currently requires periodic leak checks of the forward lavatory drain system and provides for the installation of a new drain valve as terminating action. \n\n\tAmong other things, the supplemental NPRM proposed to: \n\n\t1.\tdelete the existing provision for terminating action; \n\t2.\trequire repetitive leak checks of both the forward and the aft lavatory drain \t\tsystems; \n\t3.\tprovide an optional procedure for complying with the rule, which would entail revising the FAA-approved maintenance program to incorporate a schedule and procedure to conduct leak checks of the lavatory drain systems; and \n\t4.\trequire the installation of a lever lock cap on flush/fill lines, and periodic leak check of the flush/fill line. \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\nPersonal Injury Risk Of Blue Ice \n\n\tSeveral commenters request that all actions applicable to the aft lavatory drainage systems be deleted from the proposed rule, since the risk of injury caused by "blue ice" forming at an aft lavatory, dislodging from an airplane, and striking a person on the ground is extremely remote. As justification for their request, these commenters cite an analysis that was performed in 1990 to determine the probability of personal injury. This analysis concludes that such probability is on the order of 1 x 10-9 per flight. \n\n\tThe FAA does not concur with these commenters' request. The criteria of a probability of injury being on the order of 1x 10-9 per flight hour is relevant when an aircraft system is originally certified. However, once an unsafe condition becomes known to the FAA, an analysis is not necessarily sufficient to refute the unsafe condition. The FAA considers that the numerous reported cases of "blue ice" striking and damaging houses, cars, and populated areas is sufficient to support the conclusion that "blue ice" falling from aft lavatory drain system presents an unsafe condition. \n\n\tMoreover, the FAA does not find the analysis submitted by the commenters to be conclusive. That particular analysis was based on several assumptions whose adequacy the FAA questions. Among them are: \n\n\t1.\tThe analysis assumed that a piece of "blue ice" falls to the ground once every two weeks in the United States. These figures were based upon language that appeared in a newspaper article and are apparently anecdotal data. The FAA points out that the cases addressed in the newspaper article (and, therefore, in the analysis) may be only the "reported" cases; however, the vast majority of cases go unreported, and are likely to be on the order of many magnitudes greater than the number reported. \n\n\t2.\tAdditionally, the crux of the analysis is based on assumptions that the size of a shadow of a person on the ground is two square feet. This appears to assume that the person is standing up, the ice comes straight down, the ice falls as a single projectile, and the ice does not break into smaller pieces as it comes through a roof and ceiling. None of these assumptions are proven or representative of a typical scenario. \n\n\tFurther, the FAA points out that demographic studies have shown that population density has increased around airports, and probably will continue to increase. These are populations that are at greatest risk of damage and injury due to "blue ice" dislodging from an airplane during descent. Without actions to ensure that leaks from the aft lavatory drain systems are detected and corrected in a timely manner, "blue ice" incidents would go unchecked and eventually someone would be struck, perhaps fatally, by falling "blue ice." To discount the unsafe condition to persons on the ground presented by falling "blue ice" would be a gross breach of the FAA's safety obligations and commitment to the public.\n\n Reliability Targets for Leak Check Intervals \n\n\tOne commenter requests that the FAA provide reliability targets so that operators would know what data were necessary to obtain FAA approval of any request for an extension of a leak check interval. The FAA cannot concur with the commenter's request. The FAA has not provided such a "reliability target" because of the difficulty involved in specifying a target that would be applicable to and appropriate for all or most operators. While the FAA recognizes that larger operators are more likely to be able to provide a statistically significant data package, it considers that the approach to the development of "reliability targets" must also allow smaller operators to participate. For these reasons, and until a universal reliability target program can be developed, the FAA will review individual requests on a case-by-case basis. Paragraph (c) of the final rule provides for the submission of data to be considered for the approval of extensions to leak check intervals; these data can be summarized and accompanied by recommendations from industry groups. \n\nData From Boeing Model 737's \n\n\tOne commenter requests that the FAA consider data from Boeing Model 737 airplanes, in conjunction with data from Boeing Model 727 airplanes, when reviewing requests to extend the leak check interval. The FAA points out that, even though the design of the Model 727 and Model 737 are not similar in many aspects, the functioning of the lavatory drain systems on both models may be similar due to the similarity of the hardware used. Therefore, the FAA will consider data from similar drain systems of different airplane models when reviewing requests received to extend leak check intervals; however, in accordance with the data gathering requirements of paragraph (c) of this final rule, any data submitted must reflect which airplanes and which drain valves the data represent. \n\nBoeing Specifications vs. Brand Name Valves \n\n\tSeveral commenters request that the proposed rule be revised so that affected hardware is identified by Boeing Specification number, rather than by vendor part numbers. These commenters are concerned that certain parts may not qualify for longer inspection intervals because they have dash numbers not called out specifically in the proposed rule. They consider that this is not only confusing, but inequitable, since many later hardware configurations will fall into the "any other type valve" category that provides for a leak check interval of only 400 flight hours. The commenters consider that requesting "alternative methods of compliance" will become the norm, unless the rule is revised to refer to hardware specification numbers. One commenter, a manufacturer of valves, is concerned that it will be unable to market its equipment because the proposed rule provides no performance standards under which its valves can qualify. \n\n\tOn the other hand one commenter objects to the FAA's statement in the preamble to the supplemental NPRM that indicated, "One of the factors that the FAA will consider in approving alternative valve designs is whether the valve meets Boeing Specification S417T105 or 10-62213." This commenter interprets the phrase to be a requirement for Boeing approval of any alternative valve only to the Boeing specifications. \n\n\tThe FAA does not concur with the commenters' requests to call out valves by Boeing specification only. Boeing specifications were not referenced in this final rule because the FAA does not consider it appropriate for Boeing to screen and potentially disapprove, for purposes of this AD, alternative valves that may notqualify to Boeing's specifications. This would have the effect of delegating to Boeing, through its specification qualification procedure, the authority to approve or disapprove alternative methods of compliance with this AD. Approval under a Boeing specification is not a requirement for a valve design under this rule; it is only a factor to be considered. Other factors may be taken into account as well, such as having extensive service history data. Review and approval of alternative valve designs is a function of the FAA through the "alternative methods of compliance" procedures provided by paragraph (f) of the final rule. The wording of the NOTE 7 following paragraph (f) of the final rule has been revised to clarify this point.\n\n Qualifying For 1,000 Flight Hour Leak Check Interval \n\n\tSeveral operators request that the proposed rule be revised to include a provision that would allow any service panel drain valve, manufactured by any manufacturer, to become qualified for the 1,000-flight hour leak check interval. These commenters state that, by restricting the 1,000-flight hour interval to only certain brand name valves, the FAA restricts competition that could lead eventually to the development of better valves. \n\n\tThe FAA does not agree that the 1,000 flight hour leak check interval should be allowed unequivocally for all service panel drain valves. Current service history data indicate that some valves are more reliable than others; those valves that have demonstrated such reliability in service so far are the valves identified (by brand name) in this rule. The FAA does not consider that a design review and qualification test are sufficient to determine how well a valve will perform in actual service. This has been clearly demonstrated by the history of this specific AD action: the installation of any of several valves was designated previously as terminating action for the required leak check, but those valves were later found to be subject toleakage. However, the FAA does agree that requirements for service history data should not be so rigid as to preclude competition by valve manufacturers with new designs. Therefore, the FAA will consider requests for inclusion in the 1,000-flight hour leak check category any valve for which the design, qualification test, and service history data are provided. The request should include an analysis of known failure modes for the valve and failure modes of similar valves; an explanation should be included as to how the design features of the valve will preclude these failure modes. Also included should be the results of qualification tests, and service history data covering approximately 25,000 flight hours or 25,000 flight cycles (including a winter season), collected in accordance with the requirements of paragraph (c) of the final rule, or a similar program. The final rule has been revised to include a new NOTE 7 to specify the request for this information. \n\n\tFurther, the FAA notes that one operator and a manufacturer, Pneudraulics, already have provided these data to the FAA, and the final rule has been revised to add certain Pneudraulics valves to the category of valves subject to a 1,000-flight hour leak check interval. (Without the submission and approval of this data, these valves would have been required to be leak checked at the 200-flight hour interval.)\n\n Differences Between Paragraphs (a) and (b) of the Rule \n\n\tOne commenter maintains that the FAA's safety objective in addressing the "blue ice" issue should be to ensure that each and every operator has a comprehensive lavatory drain service program in place. The commenter points out that the FAA attempted this approach under the provisions of proposed paragraph (b), but made the conditions of compliance more stringent than those of proposed paragraph (a), such that no operator would elect to comply with paragraph (b). The commenter considers this unfortunate since it will result in a lesseffective "blue ice" prevention program fleetwide. \n\n\tThe FAA acknowledges that a difference exists between the provisions of paragraphs (a) and (b), both in the supplemental NPRM and in this final rule. However, as explained elsewhere in this preamble, the FAA has revised several requirements of paragraph (b) of the final rule to make it more "attractive" to operators. Certain of these revised requirements include extended leak check intervals for some valves. The FAA does consider that revising the maintenance program to include the procedures specified in paragraph (b) will be more effective overall in addressing "blue ice" as an on-going issue. The provisions of paragraph (b) are more comprehensive in approach: they include requirements not only for leak checks of the valves, but replacement of valve seals, repetitive visual inspections for leakage, procedures for reporting leakage, and training programs to inform pertinent personnel on "blue ice" awareness. \n\n\tThe FAA considers that it is appropriate to maintain the provisions of paragraph (a) as an option, so that operators without an FAA-approved maintenance program will have some means to comply with the rule. \n\n\tAlong this same line, another commenter points out other differences between the provisions of paragraphs (a) and (b). The commenter indicates that any valve service history data that is gathered by an operator complying with paragraph (a) may not be as valuable as data gathered by an operator complying with paragraph (b). Unless there is a specific, scheduled maintenance program, there is no way to determine if a valve may have begun leaking before a leak check was conducted and was subsequently repaired; therefore, merely passing a leak check successfully, as under the provisions of paragraph (a), does not verify the valve's reliability. The FAA acknowledges this commenter's observations. However, the FAA expects that some operators will choose to comply with the provisions of paragraph (b) and will provide the FAA with valve service history data. These data may indicate that the current leak check intervals are acceptable for operators operating under a maintenance program, but should be shortened for operators without a maintenance program. If, as the commenter suggests, leak tests alone prove to be inadequate to prevent "blue ice" formation, the FAA may consider revising this rule at a later time to modify or delete paragraph (a).\n\n Alternative Recordkeeping \n\n\tSeveral commenters request that a revision be made to proposed paragraph (b) that would allow for the use of an alternative method of recordkeeping to that otherwise required by Federal Aviation Regulations section 121.380 (14 CFR 121.380), "Maintenance recording requirements". The commenters' main concern is that it should be clear to the cognizant Principal Maintenance Inspectors (PMI), and other FAA officials in the years ahead, that once the maintenance program revision is made and approved, the AD is "signed off as complete." No other special records should be required to track the various tasks specified in proposed paragraph (b) (such as valve seal replacement, training, reporting procedures, visual checks, etc.), which are in addition to the recordkeeping requirements that now exist within each of the affected operator's maintenance program. \n\n\tThe FAA does not concur with the commenters' request for many of the same reasons it did not concur with a similar request made in response to the previous supplemental NPRM. The FAA considers that, even though this AD would affect the maintenance program, it is of such importance that it warrants other than "normal" procedures to be followed in certain aspects. Some method of recordkeeping must be maintained to ensure that the required valve seal changes and periodic leak checks continue, and to ensure that the procedures required by this AD are not eventually dropped from any operator's maintenance program.\n\n Principal Maintenance Inspector Involvement \n\n\tThese same commenters request that a statement be added to proposed paragraph (b) to indicate that the "AD is no longer applicable once a revision to the FAA-approved maintenance program is implemented." These commenters indicate that it would be less cumbersome to operators to accomplish all of the AD-required tasks within the parameters of their FAA-approved maintenance program, where the cognizant PMI would be the FAA official permitted to approve any further changes to the program. These commenters contend that it is much more appropriate for the PMI, rather than the Seattle Aircraft Certification Office (ACO) engineering staff, to approve subsequent changes to the program once the program has been approved. The commenters consider that the PMI is more qualified than the ACO staff to approve tasks on training, reporting, and adjustments to the leak check intervals based upon reliability program recommendations. The commenters point out thatthe subject matter of the rule is clearly maintenance-related, and the ACO staff is not equipped to effectively respond to requests for maintenance interval changes that may occur. \n\n\tThe FAA does not concur with this request for the same reasons it did not concur with a similar request made by these commenters to the previous supplemental NPRM. While the FAA agrees that the PMI may be permitted certain oversight of the proposed alternative maintenance program provision of the rule (specifically with regard to recordkeeping), the FAA does not agree that the PMI should be tasked with approving certain adjustments of the program. As was explained in detail in the preamble to the supplemental NPRM, failure threshold criteria and definitive leak/failure rate data do not exist for the majority of the subject valves; therefore, a PMI would have no data on which to base the approval of an extension of a leak check interval for many valves with the assurance that the valve would not fail within the adjusted interval. In light of this, it is essential that the FAA, at the ACO level, have feedback as to the leak and failure rates experienced in the field. Although the PMI's serve as the FAA's critical link with the operators (and the PMI's oversight responsibilities will not be minimized by this AD action), it is the staff of the ACO that provides the engineering support necessary to evaluate whether increases in leak check intervals will maintain an acceptable level of safety. \n\n\tFurther, the FAA considers it essential that any adjustment of the required leak check intervals, seal change intervals, and data reporting procedures should be approved in a uniform manner in order to ensure that the program is administered uniformly (and appropriately) fleetwide. The staff of the Seattle ACO is in the best position to ensure that this is accomplished. Additionally, given that possible new relevant issues might be revealed during the approval process, it is imperative thatthe engineering staff at the ACO have such feedback. In any case, the ACO staff will work closely with the cognizant PMI to ensure that any approved revisions to this aspect of the maintenance program are appropriate and workable for the applicable airline.\n \nSpecific Leak Check Instructions \n\n\tOne commenter requests that the proposed rule be revised to include a procedure for performing the leak checks. The commenter suggests that the instructions contained in Boeing Service Letter 737-SL-38-3-A (which applies to Model 737 series airplanes) be referenced in order to ensure that all affected operators perform the same leak check. The FAA does not concur totally. The instructions contained in Boeing Service Letter 737-SL-38-3-A address only the forward lavatory service panel (not the aft or executive panels), and do not correlate with the requirement to perform a leak check of the outer cap on certain valves. The instructions do contain procedures for performing a leak test ofthe toilet tank anti-siphon (check) valve, which are appropriate for performing that leak check in accordance with the requirements of this AD; therefore, the FAA has added a Note to paragraphs (a)(5) and (b)(3) to indicate that operators may consider the leak check procedures relative to the toilet tank anti-siphon (check) valve in accordance with the service letter as an acceptable means of compliance with those paragraphs. The FAA does agree that a standard leak check procedure would be beneficial, and will consider revision of this final rule to include one if an acceptable procedure becomes available in the future. \n\n\tAnother commenter requests that the proposed rule be revised to include specific procedures for conducting the leak check of the dump valve. This commenter suggests that this leak check should be performed by filling the toilet tank with water or rinsing fluid to a level such that the bowl is approximately half full (at least 2 inches above the flapper in the bowl) and waiting at least 5 minutes to determine if leakage is present. The FAA concurs and has revised the rule to include a new NOTE 1, which indicates that operators may conduct this particular leak check in accordance with the procedures suggested by this commenter.\n \nService Panel Waste Drain Cap Leak Check \n\n\tSeveral commenters request that paragraphs (a)(1)(i) and (b)(2)(i) of the proposed rule be revised to delete the requirement to perform a leak check of service panel waste drain cap that does not have an inner door with a second positive seal. These commenters state that, to perform this leak check, approximately 20 gallons of contaminated waste water are required to be dumped on the ramp; such dumping violates various environmental regulations. \n\n\tThe FAA does not agree that conducting this leak check will necessarily require spilling a vast amount of waste water on the ramp. Compliance with FAA rules is not a license to violate environmental regulations. Operatorscould devise a means to catch or handle the waste water to ensure that they will be in compliance with applicable state or Federal environmental regulations. \n\n\tHowever, the FAA has reconsidered this requirement for leak checks of the service panel waste drain cap in waste drain systems incorporating in-line drain (ball) valves. The FAA has determined that, for these configurations, the valve reliability is sufficient to obviate the need for additional assurance provided by performing a leak check of the cap, as long as a leak check of the dump valve is accomplished. A leak check of the dump valve (in-tank valve that is spring loaded closed and operable by a T-handle at the service panel) can be accomplished easily and does not entail spillage of waste on the ramp. Therefore, the FAA has revised paragraph (b)(2)(i) of the final rule to require operators to perform a leak check of the dump valve, in lieu of performing a leak check of the cap valve. Operators would still be required to perform a leak check of the in-line drain (ball) valve. The leak checks must be accompanied by visual inspections of the service panel drain valve outer cap/door seal, the inner seal (if the valve has an inner door/closure device with a second positive seal), and seal mating surface for wear or damage that may cause leakage. \n\n\tThis revision to the requirements of the final rule does not entail any additional burden on operators. As previously proposed, operators would have been required to perform leak checks of both the inner and outer doors of the cap valve and of the in-line drain valve, and a visual inspection of the service panel drain valve outer cap/door seal. As now required by the final rule, operators will be required to perform fewer leak checks of valves, and one additional visual inspection of the (inner) door seals. Since visual inspections are less labor-intensive and less costly than leak checks, the FAA considers that the revised requirements will significantly reduce the economic burden on affected operators. \n\n\tSimilarly, the FAA has revised the requirements of paragraphs (b)(2)(ii) and (b)(2)(iv), which require leak checks of the dump valve and service panel valve. The final rule now specifies that the leak check of the service panel drain valve need only entail a leak check of the inner door/closure device (rather than leak checks of both the inner and outer door, as was previously proposed), provided that a visual inspection is made of the outer cap/door seal and seal mating surface for wear or damage. \n\n\tThe FAA has not revised the similar requirements of paragraph (b)(2)(iii), which pertains to drain systems incorporating "donut" valves. As explained later in this preamble, the reliability of this type of valve is such that a leak test of the downstream cap is considered necessary; therefore, paragraph (b)(2)(iii) retains the requirement for leak checking the cap in drain system configurations where "donut" valves are installed. \n\nWaste Drain System Leak Check Procedure \n\n\tOne commenter requests that proposed paragraphs (a) and (b)(2) be clarified to specify that, for drain systems that may contain more than one kind of valve, only one of the waste drain system leak check procedures needs to be conducted at each service panel location. The procedure conducted should be the one that applies to the equipment with the longest leak check interval. The FAA concurs with the commenter's request, since this was the intent of this requirement. The final rule has been revised to clarify this point. \n\nKaiser Valve Part Numbers \n\n\tOne commenter requests that the part number for the Kaiser Electroprecision in-line drain valve, specified in the proposal as "part number 2651-329-5 (or higher dash number)," be revised to include the entire part number 2651-329 series. The valves in this series are all virtually identical in design and, therefore, would have the same reliability. The FAA concurs and has revised the final rule to call out these valves as "Kaiser Electroprecision part number series 2651-329." \n\n\tAdditionally, this same commenter requests that the proposed rule be revised to include Kaiser Electroprecision in-line drain valves, having part number series 2651-334 and 2651-278, in all requirements that apply to part number series 2651-329 valves. Although these valves differ slightly in their inlet/outlet configurations, actuating handle sizes and shapes, and actuating handle orientation and movement, they are identical in their main sealing components, design standards, and principle of operation; therefore, their reliability can be assumed to be equivalent. The FAA concurs and has revised the final rule accordingly. Operators should note that a review of available data indicates that the latter valve series are not currently installed on Boeing 727 airplanes, however.\n\n Leak Check Interval for Kaiser Valves \n\n\tOther commenters request that the proposed rule be revisedto permit the Kaiser Electroprecision part number series 0218-0026 valves (Expander Valves) to be leak checked at the same interval as the valves listed in the supplemental NPRM for 1,000-flight hour leak checks. This valve series was qualified to and meets the design/performance criteria of Boeing Specification 10- 62213 (Revision A). The commenter indicates that a large number of these valves have been installed in various transport category aircraft, and a tracking of the service history of the installed valves reveals that over one million flight hours have been accumulated without any reported leakage. \n\n\tThe FAA partially concurs with the commenter's request to provide an extended leak check interval for this specific valve series. The FAA considers that the presence of a forced-opening, or "icebreaker," feature in a valve reduces the likelihood that service abuse will occur that would create a leaking valve. Unlike other valves eligible for inspections at 1,000-flight hourintervals in this rule, the Kaiser Electroprecision part number series 0218-0026 valves do not have such an "icebreaker" feature. In light of this, as well as the service history data provided, the FAA has revised the final rule to add a new paragraph (a)(3) to address these Kaiser Electroprecision valves and to provide for a repetitive 600-flight hour leak check of them for those operators electing to comply with paragraph (a) of the final rule. The FAA has also revised paragraph (b)(2)(ii) of the final rule to include these Kaiser Electroprecision valves in the requirements for leak checks at 1,000 flight hour intervals. The FAA has determined that the difference in this leak check interval between paragraph (a) and (b) is appropriate, since the repetitive visual inspections, seal replacement requirements, and other comprehensive aspects of paragraph (b) will ensure that any leakage will be detected that may be caused by service damage inflicted on the valve (due to lack of an icebreaker feature on the valve). \n\n\tAdditionally, the FAA has revised the repetitive leak check interval for the Kaiser Electroprecision valves subject to the requirements of paragraph (b)(2)(i). That paragraph has been revised to provide for conducting the applicable repetitive leak checks at intervals of "5,000 flight hours or 24 months, whichever occurs later." (The supplemental NPRM proposed a repetitive leak check interval of 5,000 flight hours only.) This provision has been made in acknowledgment of those operators who may have related maintenance procedures that are conducted on a schedule based on calendar time rather than on flight hours. \n\nKaiser Expander Valve \n\n\tOne commenter has concerns about the requirements of proposed paragraph (b)(2)(i) of the supplemental NPRM, which is applicable to forward lavatory drain systems modified in accordance with Boeing Service Bulletin 727-38-0021. This commenter indicates that the proposed paragraph does not require that a Kaiser Electroprecision Expander Valve or a lever-lock cap be installed in accordance with that Boeing service bulletin, even though the service bulletin does refer to such installations in certain of its modification procedures. This commenter questions whether those installations are required to be installed and, if so, suggests that the FAA re-issue this AD action as a proposal to clearly indicate the intent of that paragraph. \n\n\tThe FAA acknowledges this commenter's concerns and agrees that different interpretations are possible from the wording of paragraph (b)(2)(i) as it appeared in the supplemental NPRM. The FAA has revised the final rule to delete reference to Boeing Service Bulletin 727-38-0021, and to merely call out the applicable Kaiser Electroprecision part number series valves. This revision should make clear that there is no requirement for installation of a Kaiser Electroprecision Expander Valve to qualify for the repetitive 5,000 flight hour leak checks. The requirement for installing a lever lock cap is contained paragraph (d) of the supplemental NPRM and this final rule. \n\nKaiser Expander Valve/ In-Line Drain Valve Combination \n\n\tOne commenter requests that the proposed rule be revised to establish a 6,000-flight hour leak check interval for installations of an in-line drain valve in combination with a Kaiser Electroprecision Expander Valve. As proposed, the leak check interval for this combination of valves is 5,000 flight hours. The commenter provided no justification for this request, however. \n\n\tThe FAA does not concur with the commenter's request. Available data have demonstrated that the seal life and reliability of the Expander Valve are significantly less than that of the in-line drain valve. In light of this, an extension of the 5,000-flight hour interval to a 6,000-flight hour interval is not justified for the in-line drain valve in combination with the Expander Valve. However, under the provisions of paragraph (b)(5)(i)(B)of the final rule, if an in-line drain valve is found to have abnormal operation of the handle, the system may continue in operation, provided a service panel drain valve that is in the 1,000-flight hour leak check interval category is installed in the system and has passed a leak check within the preceding 1,000 flight hours.\n\n Shaw Aero Valves Part Numbers \n\n\tSeveral commenters request that the proposed rule be revised to include Shaw Aero Devices valves in the part number 1010100B and 1010100C series in the requirements for 1,000-flight hour leak check intervals. One of these commenters indicates that these part-numbered valves are merely later generations of the Shaw Aero Devices part number 1010100C-N (or higher dash number) valve, which was called out in the supplemental NPRM and for which a 1,000-flight hour leak check interval was proposed. \n\n\tThe FAA agrees that these Shaw Aero Devices valves should be addressed in the AD, and that some increase in the leak check interval, above the basic 200-flight hour interval, is justified for these valves. However, the FAA does not concur with the commenters' request to provide for a 1,000-flight hour leak check interval for them in all circumstances. The FAA has obtained data on certain design improvements, such as an "ice breaker" feature, that have been made to certain Shaw Aero Devices valves to correct previously identified deficiencies. Evidence indicates that Shaw Aero Devices valves having part number 1010100B-A-1, and having serial numbers 0115 through 0121 (inclusive), 0146 through 0164 (inclusive), and 0180 and higher, incorporate these design improvements. Therefore, the FAA has revised paragraph (a)(2) of the final rule to include these specific valves in the requirements for the 1,000-flight hour leak check interval. \n\n\tThese data also indicate that, while some Shaw Aero Devices valves in the part number series 1010100C incorporate the "ice breaker" feature and have a configuration that corrects known design deficiencies, other valves in this same series do not incorporate these features. Therefore, not all Shaw Aero Devices part number series 1010100C are included in the 1,000-flight hour interval leak check category. Accordingly, the FAA has revised the final rule to include a new paragraph (a)(3), applicable to certain part number series 1010100C valves (those without the ice breaker feature and other improvements), which provides for a 600-flight hour leak check interval for them. Paragraph (b)(2)(ii) of the final rule has been revised to address these valves and provides for a 1,000-flight hour leak check interval for them. (As explained previously, justification for the extended interval under paragraph (b) is that the maintenance program provisions of paragraph (b) should detect any leakage caused by service damage inflicted due to lack of an icebreaker feature or other improvement on the valve.) This is considered interim action, however. The FAA plans further review of the valves in this part number series to determine if these leak check intervals are appropriate, or whether they should be extended or shortened. \n\n\tFor these same reasons, the FAA also is reviewing the valves included in the part number 1010100C-N (and higher dash number) group, which was called out in paragraphs (a)(2) and (b)(2)(ii) of the supplemental NPRM. Currently, this final rule provides for a 1,000-fight hour leak check interval for these valves. However, as more data become available, the FAA may consider further rulemaking to address the leak check interval for this particular valve group. \n\n"Donut" Valves \n\n\tOne commenter contends that "donut" valves, which are addressed in proposed paragraph (b)(2)(iii), are unsafe and should be banned immediately. This commenter states that these valves are of design that has resulted in significant leakage and "blue ice" incidents. In discussions with airline personnel, this commenter has found that it is commonplace to find these valves leaking, or to find that the "donuts" are missing when an aircraft reaches its destination. It is common to have the "donut" installed at the start of the day and find it to be missing only one to two flights into the day. This is clearly a dangerous situation. \n\n\tThe FAA acknowledges this commenter's remarks. During the past year the FAA has received two additional reports of engine damage caused by "blue ice" formation from lavatory drain systems using "donut" valves. The FAA is continuing to review this service history of these valves and may consider further rulemaking to require their removal from service. \n\n\tAdditionally, the FAA has revised paragraph (b)(2)(iii) of the final rule to specify certain Kaiser Roylyn part-numbered valves as ones that incorporate the "donut" configuration and are, therefore, subject to the requirements of that paragraph.\n\n "Taco" Valves \n\n\tOne commenter requests that the Kaiser Electroprecision "taco" valve be deleted from proposed paragraph (b)(2)(iii), which would require that it be leak checked at intervals of 200 flight hours. The commenter suggests that it be included in paragraph (b)(2)(iv), instead, since that paragraph addresses similar double-door types of valves and requires their inspection at intervals of 400 flight hours. \n\n\tThe FAA concurs with this request and has revised the final rule accordingly. This change leaves only the "donut" valve in the category of valves (addressed by paragraph (b)(2)(iii)) requiring leak checks at the 200-flight hour interval. The FAA considers this appropriate, since the "donut" valve clearly has the been the valve associated with the greatest number of problems relative to "blue ice." \n\nVisual Inspections to Detect Leakage \n\n\tSeveral commenters request that paragraph (b)(4) be revised to allow flight crew to perform the visual inspections to detect leakage. These commenters state that, since this inspection involves only a visual examination, trained maintenance personnel should not be made to accomplish it. \n\n\tThe FAA does not concur with the commenters' request. While flight crews are authorized to perform walk-around inspections of the airplane, in accordance with FAR 91.7(b) (14 CFR 91.7(b)), "Civil aircraft airworthiness," there is no requirement for the flight crew to record the results of that inspection. The FAA considers that certified maintenance personnel are best suited to perform this inspection due to their specific skills, training, and experience with reporting procedures. \n\nFlush/Fill Line Cap Installation \n\n\tSeveral commenters request that the proposed rule be revised to delete paragraph (d), which would require the installation of a cap on the flush/fill lines for forward, aft, and executive lavatories. One commenter states that the caps on the service panel are a secondary sealing system, and that the toilet check valve is the primary seal preventing fluid from flowing back down this line.Other commenters also request that the requirements for periodic leak testing of the cap be deleted. Additionally, one commenter believes that installation of a cap on the flush/fill line will cause problems because, in their experience, if the caps are installed, the residual flush/fill fluid trapped inside the line will freeze by the time it reaches the next destination; the frozen line and installed cap must be thawed out prior to servicing of the lavatory, which can create a delay in normal operations. This commenter and others suggest that, as an alternative to the installation of a cap and a leak test, the proposed rule should be revised to require periodic replacement of the seal in the toilet tank anti-siphon (check) valve. The commenters point out that this valve, when maintained, effectively prevents the toilet fluid from being siphoned out through the flush/fill line, thereby making the cap unnecessary. \n\n\tThe FAA does not concur with the requests to delete the requirement for installation of a cap on the flush/fill line, but does concur that certain alternative procedures may be provided. The FAA has received a report of a Boeing Model 727 series airplane that experienced an in-flight shutdown of the number 3 engine due to the ingestion of "blue ice" caused by leakage from the flush/fill line. Investigation revealed that approximately one in four of the toilet tank anti-siphon (check) valves in the affected operator's fleet was found to leak within a three-month period. The FAA has concluded that the anti-siphon (check) valve alone does not appear to have sufficient integrity and reliability to prevent leakage from the flush/fill line. However, the FAA does acknowledge that, because the flush/fill line does not normally have water in it and a leak test of the flush/fill line cap is impractical in many circumstances, it is sufficient to replace the seals in the toilet tank anti-siphon valve and the cap, and perform a leak check of the toilet tankanti- siphon (check) valve. Paragraphs (a)(5) and (b)(3) of the final rule have been revised to provide for this alternative procedure. \n\n\tSeveral commenters request that proposed paragraph (d) be revised to delete the requirement that installation of the cap must be accomplished only in accordance with Boeing Service Bulletin 727-38-0021, dated July 30, 1992. That service bulletin specifies the installation of a particular lever-lock cap; however, the commenters request that other FAA-approved lever-lock caps also be permitted to be used. (In their comments, certain commenters provided design and service history data on another such lever-lock cap.) The FAA agrees that other FAA-approved lever-lock caps are acceptable in this installation, and has revised the final rule to specify this. \n\n\tOne commenter requests that any FAA approved cap, as opposed to only lever/lock caps, be considered sufficient for the installation required by proposed paragraph (d). The FAA does not concur, since the commenter provided no design or service history data for any other particular cap. However, under the provisions of paragraph (f) of the final rule, this commenter may elect to provide such data in a request for an alternative method of compliance with the rule. \n\n\tOne commenter considers that installation of a cap without a provision for a heating element will cause ice to form in the line at the cap. This commenter has experienced this problem on airplanes in its fleet that are equipped with a lever-lock cap. This freezing problem has been further exacerbated when service personnel have damaged the caps or flush/fill line by trying to remove the ice with a tool (such as a screw driver). The commenter suggests that the rule should require installation of a heating element to prevent freezing in or on the flush/fill line, and points out that Boeing Service Bulletin 727-38-0021, which is referenced in proposed paragraph (d) for the cap installation procedures, doesnot call for installation of any heating element. \n\n\tThe FAA agrees that one way to prevent freezing in the subject area may be to install an FAA- approved heating element. It is also possible to avoid the freezing problem by allowing the fluid to drain out of the flush/fill line after servicing the tank. Since frozen flush/fill lines are avoidable without a heating element, provided proper servicing is done, the FAA does not consider a specific requirement to install a heating element to be warranted. \n\nTerminating Action \n\n\tOne commenter requests that installation of an in-line drain valve per Boeing Specification S417T105 be considered terminating action for the required leak checks. As justification for this request, the commenter provided data indicating that, out of several million flight hours of airplanes equipped with this particular valve, there have been very few incidents of leakage. \n\n\tThe FAA does not concur with the commenter's request. Based on the availabledata to date relative to all valves, the FAA has determined that periodic leak testing of valves, as well as the replacement of valve seals, is warranted in order to ensure that the valves do not start to leak. Because of this, the FAA does not consider that there is currently a "terminating action" for these necessary requirements. \n\nTerminology Changes \n\n\tOne commenter requests that the wording of the proposed rule be revised by changing the term "operating torque" to "operation" in all procedures relative to inspections of the valve handle for the in-line drain valves. This commenter points out that the actuation of neither the in-line drain valve nor the service panel drain valve is a rotational movement at the service panel. The FAA concurs and has revised the terminology of the final rule accordingly. \n\n\tThis same commenter requests that proposed paragraph (b)(5) be revised by changing the phrase "blue streak findings" to "horizontal blue streak findings" when specifyingwhich findings must be reported to maintenance. The commenter states that this change is necessary in order to differentiate between indications of leakage that has resulted from spills that occurred during servicing and indications of leakage that occurred during flight. Leakage that has occurred during flight would be indicated by horizontal blue streaks. The FAA concurs and has revised the terminology in the final rule accordingly. \n\n\tThis commenter also requests that the proposed rule be revised by deleting the terms "forward and aft" when referring to "each lavatory having an in-line drain valve installed." This commenter states that some Model 727 aircraft have been built with an executive mid-cabin lavatory with an in-line drain valve. The FAA concurs and has revised the rule accordingly. The intent of the rule is clear that the related procedures are to be performed on "each" lavatory having the subject drain valve, regardless of where the lavatory is located on the airplane. \n\n\tThis commenter further points out that the terms "service panel drain valve," "cap valve," and "drain valve at the service panel" are used in various places throughout the proposed rule to describe the same valve. The commenter suggests that, in order to be consistent, the rule be revised to call this valve "the service panel drain valve" in all pertinent references. The FAA concurs and has revised the final rule accordingly. For similar reasons, the final rule has been revised by changing the term "ball valve" to "in-line drain valve" in several places.\n\n Estimated Cost Figures \n\n\tSeveral operators state that the estimated cost impact of the rule, as presented in the preamble to the supplemental NPRM, is too low and should be revised to reflect estimates of the costs as submitted by these individual operators. The FAA does not concur that the estimated cost impact figure need to be revised. While it is reasonable to assume that the costs to some operators may behigher than those presented in this preamble, it is also reasonable to assume that the costs to other operators may be considerably lower. Therefore, the estimated cost impact represents an average for the U.S. fleet, based on the best data available to date. The FAA considers the cost impact estimate, as presented, to be sufficiently accurate for the purposes of this rulemaking action. \n\nCost Impact \n\n\tThere are approximately 1,752 Boeing Model 727 series airplanes of the affected design in the worldwide fleet, operated by 153 operators. It is estimated that 1,277 airplanes of U.S. registry and 54 U.S. operators will be affected by this AD. \n\n\tThe FAA estimates that it will take approximately 4 work hours per airplane lavatory drain (normally, there are 2 drains per airplane) to accomplish a leak check, at an average labor cost of $55 per work hour. \n\n\tCertain airplanes (i.e., those that have "donut" type of drain valve installed ) may be required to be leak checked as manyas 15 times each year. Certain other airplanes having other valve configurations will be required to be leak checked as few as 3 times each year. Some airplanes that have various combinations drain valves installed will require approximately 2 leak checks of one drain valve and 3 leak checks of the other drain valve each year. Based on these figures, the total annual (recurring) cost impact of the required repetitive leak checks on U.S. operators is estimated to be between $6,600 and $1,320 per airplane per year. \n\n\tThe FAA estimates that it will take approximately 1 work hour per airplane lavatory drain to accomplish a visual inspection of the service panel drain valve cap/door seal and seal mating surfaces, at an average labor cost of $55 per work hour. \n\n\tAs with leak checks, certain airplanes will be required to be visually inspected as many as 15 times or as few as 3 times each year. Based on these figures, the total annual (recurring) cost impact of the required repetitive visual inspections on U.S. operators is estimated to be between $825 and $165 per airplane per year. \n\n\tThe 1,277 affected airplanes of U.S. registry have, on an average, 3 flush/fill lines per airplane. The FAA estimates that the installation of a level lock cap assembly will require approximately 2 work hours to accomplish, at an average labor cost of $55 per work hour. Required parts are estimated to be $275 per drain installation. Based on these figures, the total cost impact of the requirement to install a cap on the flush/fill lines is estimated to be $1,474,935, or an average of $1,155 per airplane. \n\n\tThe number of required work hours, as indicated above, is presented as if the accomplishment of the actions proposed in this AD were to be conducted as "stand alone" actions. However, in actual practice, these actions could be accomplished coincidentally or in combination with normally scheduled airplane inspections and other maintenance program tasks. Therefore, the actual number of necessary "additional" work hours will be minimal in many instances. Additionally, any costs associated with special airplane scheduling should be minimal. \n\n\tIn addition to the costs discussed above, for those operators who elect to comply with proposed paragraph (b) of this AD action, the FAA estimates that it will take approximately 40 work hours per operator to incorporate the lavatory drain system leak check procedures into the maintenance programs, at an average labor cost of $55 per work hour. Based on these figures, the total cost impact of the proposed maintenance revision requirement of this AD action on the 54 U.S. operators is estimated to be $118,800, or $2,200 per operator. \n\n\tThe "total cost impact" figures described above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe FAA recognizes that the obligation to maintain aircraft in an airworthy condition is vital, but sometimes expensive. Because AD's require specific actions to address specific unsafe conditions, they appear to impose costs that would not otherwise be borne by operators. However, because of the general obligation of operators to maintain aircraft in an airworthy condition, this appearance is deceptive. Attributing those costs solely to the issuance of this AD is unrealistic because, in the interest of maintaining safe aircraft, prudent operators would accomplish the required actions even if they were not required to do so by the AD. \n\n\tA full cost-benefit analysis has not been accomplished for this AD. As a matter of law, in order to be airworthy, an aircraft must conform to its type design and be in a condition for safe operation. The type design is approved only after the FAA makes a determination that it complies with all applicable airworthiness requirements. In adopting and maintaining those requirements, the FAA has already made the determination that they establish a level of safety that is cost- beneficial. When the FAA, as in this AD, makes a finding of an unsafe condition, this means that the original cost-beneficial level of safety is no longer being achieved and that the required actions are necessary to restore that level of safety. Because this level of safety has already been determined to be cost-beneficial, a full cost-benefit analysis for this AD would be redundant and unnecessary. \n\nRegulatory Impact \n\n\tThe 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. \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\n List of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation forpart 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by removing amendment 39-5250 (51 FR 7767, March 6, 1986), and by adding a new airworthiness directive (AD), amendment 39-9073, to read as follows: