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 all Boeing Model 747-100, -200, -300, -SP, and -400F series airplanes was published in the Federal Register on June 15, 1998 (63 FR 32624). That action proposed to require repetitive leak tests of the lavatory drain system and repair, if necessary; installation of a cap or flush/fill line ball valve on the flush/fill line; periodic seal changes; and replacement of any "donut" type valves installed in the waste drain system. \n\n\tThe actions specified in that proposal are intended to prevent damage to airframes and property on the ground that is associated with the problems of "blue ice" that forms from leaking lavatory drain systems on transport category airplanes and subsequently dislodges from the airplane fuselage. \n\n\tInterested persons have been afforded an opportunity to participate in the making of thisamendment. Due consideration has been given to the comments received. \n\n1. Support for the Proposal \n\n\tTwo commenters support the proposed rule. \n\n2. Request to Revise the Unsafe Condition \n\n\tOne commenter, the airplane manufacturer, requests that the proposed rule be revised to remove reference to "engine damage" in the description of the unsafe condition. The airplane manufacturer bases this request on the fact that it is not aware of any in-service reports of engine damage due to "blue ice" on Model 747 series airplanes. \n\n\tThe FAA concurs. Since the FAA has not received any reports of engine damage due to "blue ice" on Model 747 series airplanes, reference to "engine damage" in the description of the unsafe condition has been removed from the AD. \n\n3. Request to Extend Leak Test Intervals for Model 747 Series Airplanes \n\n\tOne commenter requests that the leak test intervals be specified in flight cycles rather than flight hours as proposed in the Notice of Proposed Rulemaking (NPRM). The commenter also requests that, if the intervals are retained as flight hours, all of the intervals should be extended. The commenter points out that a typical "C" check on Model 747 series airplanes is between 5,000 and 6,000 flight hours, as compared to typical "C" checks of Models 727 and 737 series airplanes, which are generally between 3,000 and 4,000 flight hours. Since most of the wear and damage is caused by opening and closing the valve, which happens during a flight cycle, and is not directly related to the number of flight hours, flight cycles are more critical than flight hours with regard to the potential for leakage. Because Model 747 series airplanes have a low number of flight cycles per hour, the fleet should be allowed a greater leak test interval than the interval specified for Models 727 and 737 series airplanes. \n\n\tThe FAA does not concur that the leak test intervals should be specified in flight cycles rather than flight hours. Thecommenter did not provide any specific data that correlated the number of flight hours to the number of flight cycles for the Boeing Model 747 fleet and the Boeing 727 and 737 fleets. Additionally, existing "blue ice" Airworthiness Directives for other airplanes presently specify the leak test intervals in terms of flight hours. To change the leak test intervals from flight hours to flight cycles could result in an operator having some airplanes operating under flight hours intervals and other airplanes operating under flight cycle intervals, which may be burdensome for the operator. \n\n\tHowever, the FAA does concur that certain leak test intervals can be extended somewhat for Model 747 series airplanes for the reasons the commenter suggested. Specific extensions of leak tests for certain valves are discussed later in this disposition of comments. \n\n4. Requests to Extend PneuDraulics Leak Test Intervals \n\n\tOne commenter requests that the leak test interval for the PneuDraulicsservice panel drain valve be revised from 2,000 to 4,000 flight hours. The commenter advises that the PneuDraulics service panel drain valve specified in paragraph (a) of the proposal has had in excess of 800,000 flight hours of service history documented by operators in FAA-approved maintenance programs with only two leakage events reported. \n\n\tThe FAA concurs that, for the reasons provided by the commenter, extension of the leak test interval from 2,000 flight hours to 4,000 flight hours for those PneuDraulics valves is justified. Since that service history was obtained when the operators were using FAA-approved maintenance programs that required reporting of any leakage, the FAA has high confidence that this data is representative of the actual leakage rates. Paragraph (a)(3) of the final rule has been revised to reflect the 4,000 flight hour leak test interval. \n\n5. Request to Extend Leak Test Interval for Certain Shaw Aero Valves \n\n\tThe commenter requests that the leaktest interval for certain Shaw Aero service panel drain valves be extended from 1,000 flight hours to 2,000 flight hours. The commenter states that data submitted previously to the FAA indicates that there are nearly 8,000 Shaw Aero service panel drain valves on airplanes that have accumulated in excess of 50 million flight hours over the past 10 years. The commenter points out that, on all of the airplanes on which Shaw Aero service panel drain valves were installed during production, there were less than ten reports of leakage during that time that could have been attributed to a Shaw Aero Devices service panel drain valve. \n\n\tIn addition, the commenter states that Boeing has presented data to the FAA showing that the Shaw Aero service panel drain valve has been the baseline unit installed on Model 737 series airplanes since January 1991, and on Model 757 series airplanes since July 1992. All Boeing service data available through February 1996 indicates that all versions of theShaw service panel drain valves can be attributed to less than 0.60 percent of the reports of leakage on Model 737 and 757 series airplanes. \n\n\tThe commenter states that the data presented shows ample evidence to support a leak test interval equal to the PneuDraulics valve, which was granted a leak test interval extension based on only 412 valves installed on aircraft flown over a much shorter interval than the 10 year period cited for the Shaw valves. Additionally, the commenter points out that industry experience clearly indicates that the main problems occur after two years of residue build-up on the sealing surfaces of any valve, irrespective of the design features. The commenter points out that meaningful data must be gathered over a period of at least two years. \n\n\tAdditionally, the commenter advises that several airlines have collected, or are in the process of collecting, data in order to submit a request for extended leak test intervals for their fleets. In fact, the commenter states that it has attached a copy of one such draft request that indicates that there have been only two cases reported of any evidence of leakage on a fleet of 163 Boeing Model 727 series airplanes that have accumulated 325,678 flight hours on Shaw Aero Devices 332 series valves. \n\n\tThe FAA concurs with the commenter's request to extend certain interval times based on the general extension of intervals given to Model 747 series airplanes explained previously. Those intervals have been extended for certain Shaw Aero service panel drain valves from 1,000 to 1,500 flight hours. The leak test interval for certain other Shaw Aero service panel drain valves has been increased from 600 to 800 flight hours. The FAA has revised certain sub-paragraphs of paragraph (a) of the final rule to reflect those extensions of the leak test intervals. \n\n\tThis commenter also states that in over 50 million flight hours on 8,000 valves only four instances of leakage have been reported. However, data the FAA has received indicates that most instances of leakage are not reported. Leakage from a service panel drain valve is not a reportable event as required by Part 21.3 of the Federal Aviation Regulations (14 CFR part 21.3). The service history data was not collected as part of an FAA-approved maintenance program that requires reporting of service panel drain valve leakage. Therefore, the FAA does not have a high level of confidence that the reported leakage rates are necessarily representative of the actual leakage rate in service. As an example, a Boeing report cited by the commenter listed 157 total reports of leakage for 662 Boeing Model 747 series airplanes for the history of the fleet up until April of 1996, when the data was collected. However, the FAA recently received a copy of a report regarding ice on certain airplanes arriving at Narita Airport in Japan during a two-week period in February 1998. For 562 arrivals of Boeing Model 747 series airplanes that were inspected during the two-week period, there were 14 instances of ice found at lavatory service panels. While some of those instances were caused by leakage from the flush/fill lines instead of the waste drain valve, the fact remains that a two-week period of actual inspection at one airport revealed 14 instances of leakage compared to 157 cases of leakage reported by operators to Boeing for the entire operating history of the Model 747 fleet until 1996. Clearly, the amount of actual leakage is not reflected in the number reported by operators to Boeing. \n\n\tIn regard to the commenter's statement that several operators are in the process of gathering data regarding performing leak checks, the FAA has not received that data as of this date. Without reviewing the actual data and information, the FAA cannot provide a decision to extend the leak test interval. Therefore, no change is necessary to the final rule in this regard. \n\n6. Request to Extend the Leak Test Interval for Certain Service Panel Ball Valves \n\n\tThe same commenter requests that the leak test interval (currently 1,000 flight hours) be extended for Kaiser Electroprecision service panel ball valves, Part Number (P/N) 2651-357. The commenter contends that the Kaiser Electroprecision service panel ball valve is designed considerably different than the other valves that are subject to the proposed 1,000-flight-hour intervals for valves. The commenter notes that the Kaiser "Expander" valve, P/N 0218-0032, and Shaw Aero "Posi-Lift" valve, P/N 10101000C(), are subject to the proposed 1,000-flight-hour intervals also. The commenter points out that Kaiser P/N 2651-357 is considered a ball valve. The commenter questions that if the FAA considers similarity of valves in determining an appropriate leak test interval, Kaiser P/N 2651-357 is at least equivalent to a PneuDraulics P/N 9527 series valve. The commenter points out that P/N 9527 series valves are essentially only a half-ball valve. Since Kaiser makes the in-line ball valve, P/N 2651-278, which has a 4,500-flight-hour leak test interval, Kaiser's experience in manufacturing reliability should be considered when setting an initial leak test interval for the panel ball valve, P/N 2651-357. The commenter concludes that a new valve such as this should not receive a "generic" 1,000-flight-hour leak test, but rather should be considered for an extension of the leak test interval based on its design and similarity to other valves. \n\n\tThe FAA concurs that Kaiser Electroprecision panel ball valve, P/N 2651-357( ) series can be extended from the proposed 1,000-flight-hour interval. In fact, the FAA has recently approved the leak test interval for that panel ball valve to be extended from 1,000 to 2,000 flight hours. The FAA based this extension on similarity to the Kaiser Electroprecision in-line drain valve, the service history of over 20 panel ball valves with an average of over 2,000 flight hours per valve and with no reports of leakage, and other data and analysis. The FAA considers similarity of valves, the manufacturer's experience, and manufacturing reliability in setting the initial leak test interval for a particular valve. These factors are also considered in determining the amount of in-service monitoring by operators that is required for an extension of the leak test interval. The intent of requiring service experience in addition to similarity analysis is to make sure that there are no unforeseen design deficiencies in a valve for which similarity is claimed. Similarity can be used to reduce the amount of in-service experience needed for a particular valve to receive an extension of the leak test interval. Therefore, paragraph (a)(4) of the final rule specifies the 2,000-flight-hour interval for the Kaiser Electroprecision panel ball valve, P/N 2651-357() series. \n\n7. Request to Use Optional Method \n\n\tOne commenter requests that the proposal be revised to allow use of Monogram P/N 4803-76 or P/N 4803-96 series vacuum breaker check valve as an option to the installation of a lever lock cap on the flush/fill line or a ball valve on the flush/fill line. Another commenter requests that the proposal be revised to allow use of either a vacuum breaker check valve or an automatic shut-off valve as an option to installing a lever lock cap on the flush/fill line or a ball valve on the flush/fill line. The commenters point out that such an option to installing flush/fill line ball valves was permitted in the "blue ice" AD for McDonnell Douglas Model DC-10 series airplanes (AD 96-12-18, amendment 39-9661 (61 FR 29009, June 7, 1996)). \n\n\tThe FAA concurs with the commenter's request. Vacuum breaker check valves, Monogram P/N 4803-86, installed on McDonnell Douglas Model DC-10 series airplanes, and Monogram P/N 4803-76 and -96 installed on Boeing Model 747 series airplanes are similar to each other in design and function. The FAA has determined that those valves are adequateto install as an alternative to installing a lever lock cap of the flush/fill line or a ball valve on the flush/fill line. The FAA also has determined that installation of an automatic shut-off valve is an adequate method to prevent leakage from the flush/fill line. Certain paragraphs of this AD ((a), (b)(3), and (a)(9)(ii)) have been revised to add provisions to install vacuum breaker valves as an option to installing a lever lock cap or ball valve on the flush/fill line. Additionally, the final rule has been revised to add provisions in paragraphs (b)(3) and (a)(9)(iv) of this AD to install and test a shut-off valve per Boeing specification number 60B50341 as an option to installing a lever lock cap or flush/fill line ball valve on the flush/fill line. \n\n\tIn addition to listing optional valves for the flush/fill line, the FAA also added vacuum leak test procedures as discussed in comment 10 below, and reorganized the seal change and leak test requirements previously contained inparagraph (a)(8) of the NPRM, and moved them into paragraphs (a)(9) and (a)(10) of the final rule. \n\n8. Request to Revise Specifications of the Leak Test of the Toilet Tank Dump Valve \n\n\tThe commenter, the airplane manufacturer, points out that the proposal specifies that the toilet tank be filled with a "minimum of 10 gallons of water/rinsing fluid" prior to performing the leak test of the toilet tank dump valve. The commenter requests that the specifications for the leak test be changed to require "a minimum of 10 gallons of water/rinsing fluid for tanks with less than 30 gallons capacity, and a minimum of 20 gallons of water/rinsing fluid for tanks with more than 30 gallons capacity." The commenter states that due to the wide variation in toilet tank sizes on the Model 747 fleet, 10 gallons may not be adequate in some cases to properly conduct a leak test. \n\n\tThe FAA concurs that the amount of fluid in the tank should be sufficient to test for leakage of the toilet tank dump valve, and that the specifications for conducting the leak test should be revised. The intent of specifying that the leak test be performed with "a minimum of 10 gallons" was to indicate that sufficient fluid be used to perform a valid leak test, without having to completely fill the tank and risk a spill of fluid inside the airplane. Since some Model 747 series airplanes are equipped with toilet tanks that are considerably larger than tanks in other airplanes, an increase in the minimum amount of fluid used to perform the test is considered necessary for airplanes with the larger tanks. The FAA has revised the final rule to specify the requested revision. \n\n9. Request to Revise Table 1 of the Proposal \n\n\tThe commenter requests that Table 1 of the proposal be revised to correct the serial numbers of 10101000B-A-1 valves and to add 10101000C-R and 10101000C-G valves to Table 1. \n\n\tThe FAA concurs with the request to correct the serial numbers for 10101000B-A-1 valves and hasrevised Table 1 accordingly. However, the FAA does not concur with the commenter's request to add the two additional valves to Table 1. The FAA has determined that those valves are not used on the airplanes affected by this AD. Further, the FAA has removed certain other part numbers of valves (10101000B-A and 10101000C-A) listed in Table 1 of the proposal since they are not eligible for the 1,000-flight-hour leak test interval. Additionally, Note 2 of the AD has been revised to specify that Table 1 of the AD contains only valves that are eligible for a leak check interval of 1,500 hours. \n\n10. Request to Use Vacuum Tool \n\n\tOne commenter requests that the proposal be revised to allow testing of the inner seal of the service panel valve with a vacuum tool for a period of one minute without any fluid upstream of the valve. This same commenter states that testing with air (vacuum tool) is more stringent than testing with water. The commenter points out that when testing with air, a leak path is detected readily within one minute because the pressure gauge will move indicating a loss of vacuum. The commenter also points out that previous AD's have permitted leak testing with a vacuum tool. A second commenter states that by allowing a leak test without requiring that the inner door of the service panel be covered with fluid, the likelihood of "blue showers" (i.e., uncontrolled leakage of waste tank drain line inside the airplane) would be reduced. \n\n\tThe FAA concurs with the request to allow a vacuum leak test procedure for the reasons the commenter provided. The FAA has revised paragraphs (a), (a)(10)(ii), and Note 3 of the final rule to add provisions and instructions for the use of vacuum leak test procedures. However, the FAA does not concur with the request to establish a period of one minute for the vacuum leak test. The commenter did not provide sufficient evidence to support reducing the leak test period from five minutes to one minute. Therefore, no change is necessary to the final rule regarding the time period required for the leak test. \n\n11. Request to Revise "Dump Valve" Terminology \n\n\tOne commenter requests that paragraph (a)(5)(i) of the proposal be revised to change the current wording of "dump valve" to the correct terminology of "toilet tank dump valve." The commenter points out that changing the terminology in that particular paragraph would make the use of the term "toilet tank dump valve" consistent throughout the proposal. The FAA concurs and has revised the final rule accordingly. \n\n12. Request to Clarify Seal Replacement Interval \n\n\tOne commenter requests that the compliance time for replacement of seals be revised to clarify that the seal replacement interval would begin when the new valve is installed or a new airplane is delivered. \n\n\tThe FAA concurs. Installation of a new valve or delivery of a new airplane would also mean that a new seal is in place. Therefore, the FAA considers that a newvalve installation or delivery of a new airplane constitutes the "last documented seal change." The FAA has revised paragraphs (a)(1) and (a)(9) of the final rule to reflect this change. The FAA points out that, for the purposes of this AD, a "new" airplane is one that has accumulated less than 100 total flight hours or 30 calendar days, whichever occurs later, since the issuance of the original airworthiness certificate. \n\n13. Request to Correct a Part Number \n\n\tOne commenter requests that paragraphs (a)(8)(ii) and (b)(2) of the proposal be revised to reflect the correct part number for the flush/fill ball valve. The commenter advises that the correct part number is Kaiser Electroprecision part number series 0062-0010, not "0062-0009," as specified in the proposal. The FAA concurs with the commenter's request, and has revised paragraphs (a)(9)(iii) and (b)(2) of the final rule to reflect the correct part numbers. \n\n14. Request to Extend the Seal Change Interval \n\n\tOne commenter requests that paragraph (a)(1)(ii) of the proposal be revised to reduce the seal change interval from 6,000 to 5,000 flight hours for the PneuDraulics valve. The commenter states that the seal in a ball-valve or half-ball valve located at the service panel is subjected to a significantly greater dynamic action than that of a seal in a flapper-type valve. The distance that the ball or half-ball drags across the seal subjects the seal to considerably more wear that the wear experienced by an O-ring seal in a flapper-type valve as it moves from a sealed to an unsealed position. The plastic seals used in the ball or half-ball valves are much less forgiving and less compressible than elastomer type seals used in flapper-type valves. Therefore, the ball or half-ball valves are more susceptible to being damaged by foreign objects and consequent leakage. The potential for ice, hardened debris, and "black tar" to build up on the ball at the service panel makes the seals more susceptible to damage by service and maintenance personnel than the seals of an in-line ball valve. Additionally, the commenter contends that the performance of the seals in the in-line ball valve cannot be replicated in- service on ball or half-ball valves used at the service panel. Service panel components also experience greater temperature fluctuations (-65 degrees Fahrenheit to +130 degrees Fahrenheit) than those experienced by components upstream. \n\n\tThe FAA does not concur with the commenter's request to reduce the seal change interval for the PneuDraulics valve. The commenter did not provide any specific data to demonstrate that ball valve seals or half-ball valve seals actually do have greater failure rates than flapper type valves. The FAA established the seal change interval for the PneuDraulics valve based on data submitted by an operator and the valve manufacturer. No change is necessary to the final rule. \n\n15. Request to Standardize the Requirements for Extension ofthe Leak Test \n\n\tOne commenter, a valve manufacturer, requests that the proposal be revised to require "equivalent" criteria for extending the leak tests of all valves. The manufacturer states that certain criteria were required to obtain leak test extensions for its product, but that other valves were not subjected to the same stringent criteria. The commenter notes that valves with components prone to multiple failure and easily damaged seals will leak if exposed to the hourly usage schedules (as proposed in the NPRM). The commenter contends that a valve with exposed soft seals can leak immediately after successfully passing a test if damaged by ice, tools, or loss of the donut plug. The commenter further contends that the valves should have a primary seal and a secondary seal as required by the specifications of the airplane manufacturer for panel valves. \n\n\tThe FAA does not concur that the final rule should be revised in regard to establishing "equivalent" criteria for extending the leak test intervals. The FAA has required all operators requesting an extension to provide service history and data to support any extensions of leak test intervals. Previous service experience, similarity to existing valves, and the quality of the data are considered in determining an appropriate extension of the leak check interval for each valve. No change is necessary to the final rule. \n\n16. Request to Establish Consistent Testing Intervals for Components \n\n\tOne commenter, the airplane manufacturer, states that it is concerned that test and maintenance intervals for a particular part number component may not be consistent across all models. The commenter requests that any increased intervals for a specific component be applied to all models using that component. \n\n\tThe FAA does not concur. As explained in a previous disposition of comment (number 3), the flight cycles per flight hours are different on various airplane models. Therefore, the cyclic wear on various components differs according to the airplane model on which the component is installed. Consequently, the FAA cannot approve consistent flight hour intervals for leak checks on specific components that apply to all airplane models. \n\n\tOperators who wish to take advantage of the increase in leak test intervals may request information concerning the existence of approved alternative methods of compliance, in accordance with Note 5 of this AD. Additionally, paragraph (d) of this AD provides for any operator to request approval of an alternative method of compliance that provides an acceptable level of safety. \n\n17. Request to Provide a Maintenance Option \n\n\tOne commenter, the airplane manufacturer, requests that the FAA add a maintenance option to the AD that would permit operators to revise their FAA-approved maintenance program to include the requirements specified in the proposal. The commenter points out that such a revision would permit operators to justify extending leak test intervals to intervals that are consistent with their regularly scheduled maintenance. \n\n\tThe FAA does not concur. The FAA did not provide the maintenance option in this AD based on information it received that few operators were inclined to revise their maintenance program to incorporate the requirements of this AD. Additionally, comments submitted regarding previous "blue ice" AD's that did contain the maintenance option stated that the proposed AD's were "too long, and hard to understand." The FAA's intent by not specifying the maintenance option in this AD is to simplify and clarify the requirements of this AD. No change to the final rule is necessary in that regard. However, if an operator wishes to request approval for revision of its maintenance program, a request should be submitted to the FAA in accordance with the provisions of paragraph (d) of this AD. \n18. Request to Include Terminating Action in the AD \n\n\tOne commenter, the airplane manufacturer, requeststhat a provision for terminating action be included in the AD. The commenter agrees that incorporation of the proposed AD requirements such as "donut" lug removal, seal replacement, rinse system upgrade, and installation of improved drain valves will result in reduced incidences of "blue ice." However, if an operator incorporates the requirements of the proposed AD, and revises its maintenance program to include seal replacement and/or seal visual inspections, the commenter considers those actions to be sufficient to provide terminating action. \n\n\tThe FAA does not concur. The FAA finds that previous requests for terminating action based on the installation of certain valves have been unsuccessful. Accomplishment of the requirements of this AD will ensure that an effective and uniform program to prevent incidents of "blue ice" is in effect for the entire fleet. Therefore, no change to the final rule is necessary in that regard. \n\n19. Request to Remove the Requirement to Replace "Donut" Valves \n\n\tOne commenter, an airline operator, requests that the proposal be revised to remove the requirement "to replace 'donut' valves with another FAA-approved valves within 5,000 flight hours." The commenter points out that other AD's concerning "blue ice" have not required replacement of "donut" valves. Further, the commenter contends that the repetitive leak test intervals specified in the proposal will address the safety considerations. The commenter states that, based on financial considerations, the replacement of "donut" valves should be an option for operators. \n\n\tThe FAA does not concur with the request to remove the requirement to replace "donut valves." The FAA finds that several incidents of "blue ice" were caused by "donut" valve leakage on airplanes, despite a required leak test at intervals of 200 hours. Additionally, the largest and most potentially dangerous pieces of "blue ice" have been associated with "donut" valves. Based on the continued problems associated with the use of "donut" valves, the FAA has determined that those valves must be replaced. No change to the final rule is necessary in that regard. Regarding current AD's addressing "blue ice," continuing to require the leak test intervals for the "donut" valves may motivate operators to replace the "donut" valves. However, if the FAA finds that "donut" valves continue to be a source of "blue ice," additional rulemaking may be considered. \n\n20. Request to Call Out Part Numbers by Name \n\n\tOne commenter requests that lever/lock caps manufactured in accordance with an FAA-Parts Manufacturer Approval granted to Shaw Aero Devices be called out by part number the same way the Kaiser flush/fill ball valve part number is called out in the proposal. The commenter did not provide an explicit reason for this request. \n\n\tThe FAA does not concur. Reference to lever lock caps as "FAA-approved lever lock caps" rather than specific part numbers that are called out has been the standard practice in the development of the "blue ice" AD's. Therefore, the Shaw Aero Devices lever lock cap, part number 580-116, is encompassed in the final rule as an "FAA-approved lever lock cap." However, the Kaiser flush/fill line ball is not a lever lock cap and would not be encompassed by the phrase "FAA-approved lever lock caps." Consequently, the Kaiser valve part number is specifically called out in the final rule. No change is necessary to the final rule in that regard. \n\n21. Requests to Revise the Cost Impact Information \n\n\tOne commenter, a parts manufacturer, requests that the cost impact information, below, be revised to reflect an optional use of a hand held vacuum pump as the most cost effective method to perform the leak tests. The commenter \npoints out that a hand held vacuum pump takes less time and does not require fuel to power-up the airplane. \n\n\tThe FAA does not concur with the commenter's request. The cost impact figures provided in an AD areintended to provide an approximate cost of performing required tasks. The FAA has no way of determining the specific cost figures of each possible method of accomplishing a required task. The cost estimates, as provided, are simply estimates based on the best information the FAA has available at the time the rule is developed. No change is necessary to the final rule in that regard. \n\n\tAnother commenter states that the work hours necessary to install the flush/fill line cap is estimated in the proposal to be 1 work hour per cap. The commenter requests that the work hour estimate be revised to include heating the flush/fill line to prevent ice build-up within the line behind the cap. The commenter provided no work hour figures that would include heating of the flush/fill line. \n\n\tThe FAA does not concur. Heating for the line behind the flush/fill cap may be considered a good practice and possibly the most practical solution where flush/fill lines take a long time to drain. The FAA typically provides cost estimates only for those actions that are required to be accomplished. In this case, heating of the line behind the flush/fill cap is not necessary when operators allow the flush/fill line to drain before closing the cap. The FAA considers it to be the operator's choice to allow the flush/fill line to drain after servicing, or to install heating for the flush/fill line. Therefore, no change is necessary to the final rule. \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 711 Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 201 airplanes of U.S. registry and 89 U.S. operators will be affected by this AD\n\n\tThe waste drain system leak test and outer cap inspection will take approximately 6 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the waste drain system leak test and outer cap inspection is estimated to be $72,360, or $360 per airplane, per test/inspection. \n\n\tCertain airplanes (i.e., those that have "donut" type drain valves installed) may be required to be leak tested as many as 15 times each year. Certain other airplanes having other valve configurations will be required to be leak tested as few as 1 time each year. Based on these figures, the annual (recurring) cost impact of the required repetitive leak tests on U.S. operators is estimated to be between $360 and $5,400 per airplane, per year. \n\n\tWith regard to replacement of "donut" type drain valves, the cost of a new valve is approximately $1,200. However, thenumber of leak tests for an airplane that is flown an average of 3,000 flight hours a year is thereby reduced from 15 tests to 3 tests. The cost reduction because of the number of tests required is approximately equal to the cost of the replacement valve. Therefore, no additional cost would be incurred. \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 rate of $60 per work hour. As with leak tests, 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 annual (recurring) cost impact of the required repetitive visual inspections on U.S. operators is estimated to be between $180 and $900 per airplane, per year. \n\n\tThe installation of the flush/fill line cap will take approximately 1 work hour per cap to accomplish, at an averagelabor rate of $60 per work hour. The cost of required parts will be $275 per cap. There are an average of 4 caps per airplane. Based on these figures, the cost impact on U.S. operators of these requirements of this AD is estimated to be $269,340, or $1,340 per airplane, per replacement cycle. \n\n\tThe seal replacements of the drain valves required by paragraph (a) of this AD will require approximately 2 work hours to accomplish, at an average labor cost of $60 per hour. The cost of required parts will be $200 per each seal change. Based on these figures, the cost impact on U.S. operators of these requirements of this AD is estimated to be $64,320, or approximately $320 per airplane, per replacement. \n\n\tThe number of required work hours, as indicated above, is presented as if the accomplishment of the actions of this AD will 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 would be minimal in many instances. Additionally, any costs associated with special airplane scheduling should be minimal. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that 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 proposed 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 fullcost-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 preparedfor 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\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \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\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: