AD 96-12-18

This amendment adopts a new airworthiness directive (AD) that is applicable to all McDonnell Douglas Model DC-10 series airplanes and Model MD-11F airplanes. Among other things, this amendment requires repetitive leak checks of the lavatory drain system and repair, if necessary; provides for the option of revising the FAA-approved maintenance program to include a schedule of leak checks; and requires the installation of a cap on the flush/fill line. This amendment is prompted by continuing reports of damage to engines and airframes, separation of engines from airplanes, and damage to property on the ground, caused by "blue ice" that forms from leaking lavatory drain systems on transport category airplanes and subsequently dislodges from the airplane fuselage. The actions specified by this AD are intended to prevent such damage associated with the problems of "blue ice."

Final rule.

96-12-18 McDONNELL DOUGLAS: Amendment 39-9661. Docket 95-NM-120-AD. \n\n\tApplicability: Model DC-10 series airplanes and Model MD-11F series airplanes; equipped with a lavatory drainage system, forward or aft; certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent engine damage, airframe damage, and/or a hazard to persons or property on the ground as a result of "blue ice" that has formed from leakage of the lavatory drain system and dislodged from the airplane, accomplish the following: \n\n\tNOTE 2: The toilet dump valve leak checks required by this AD may be performed by filling the toilet tank with water/rinsing fluid to a level such that the bowl is approximately half full (at least 2 inches above the flapper in the bowl) and checking for leakage after a period of 5 minutes. \n\n\t(a)\tExcept as provided in paragraph (b) of this AD, accomplish the applicable procedures specified in paragraphs (a)(1), (a)(2), (a)(3), (a)(4), and (a)(5) of this AD. If the individual waste drain system panel incorporates more than one type of valve, the inspection interval that applies to that panel is determined by the component with the longest inspection interval allowed. Each of thecomponents must be inspected or tested at that time at each service panel location. \n\n\t\t(1)\tWithin 1,000 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 1,000 flight hours, accomplish the applicable procedures specified in paragraphs (a)(1)(i) and (a)(1)(ii) of this AD for each lavatory drain system with a service panel drain valve installed that is listed in Table 1, below: \n\nTable 1\n Valves Requiring Leak Checks at 1,000-Flight Hour Intervals \n\n\nManufacturer\t\n\tPart Number\nSerial Number \nKaiser Electroprecision\n0218-0032 series\n\nall serial numbers \nShaw Aero Devices\t\n1010100C-N \n(or higher dash number)\n\t\nall serial numbers \nShaw Aero Devices \t\n1010100B-A-1\n0115 through 0121, \n0146 through 0164, \n0180 and higher \n\nShaw Aero Devices \t\n\n10101000BA2\t \n130 and higher\nShaw Aero Devices \t\t\n10101000BB2\n0011 and higher \nShaw Aero Devices \n\t\n331 series \t\nall serial numbers \nShaw Aero Devices \n\t\n332 series \t \nallserial numbers\nPneudraulics \t\t \n9527 series\nall serial numbers\n\n\t\t\t(i)\tConduct a leak check of the dump valve and drain valve. The service panel drain valve leak check must be performed with a minimum of 3 PSID applied across the valve. Both the inner door/closure device and the outer cap/door must be leak checked. \n\n\t\t\t(ii)\tFor service panel valves that have an inner seal: In lieu of pressure testing, the outer cap seal and seal surface may be visually inspected for damage or wear. Any damaged parts must be replaced or repaired prior to further flight, or the affected lavatory(s) must be drained and placarded inoperative until repairs can be accomplished. \n\n\t\t(2)\tWithin 600 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 600 flight hours, accomplish the applicable procedures specified in paragraphs (a)(2)(i) and (a)(2)(ii) of this AD for each lavatory drain system with a service panel drain valve installed that is listed in Table 2, below\n\nTable 2\nValves Requiring Leak Checks at 600-Flight Hour Intervals\n\n\nManufacturer\t\t\nPart Number\nSerial Number \n\nKaiser Electroprecision \t\t\n0218-0026 series\nall serial numbers \nShaw Aero Devices \n1010100C series, except as called out in Table 1, above, \n\n\nShaw Aero Devices\n1010100B series, except as called out in Table 1, above \n\n\n\t\t\t(i)\tConduct a leak check of the dump valve and the service panel drain valve. The service panel drain valve leak check must be performed with a minimum 3 PSID applied across the valve. Both the inner door/closure device and the outer cap/door must be leak checked. \n\n\t\t\t(ii)\tFor service panel valves that have an inner seal: In lieu of pressure testing, the outer cap seal and seal surface may be visually inspected for damage or wear. Any damaged parts must be replaced or repaired prior to further flight, or the affected lavatory(s) must be drained and placarded inoperative until repairs can be accomplished. \n\n\t\t(3)\tFor each lavatory drain system not addressed in paragraph (a)(1) or (a)(2) of this AD: Within 200 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 200 flight hours, accomplish the following procedures: \n\n\t\t\t(i)\tConduct a leak check of the dump valve and the service panel drain valve. The service panel drain valve leak check must be performed with a minimum 3 PSID applied across the valve. If the service panel drain valve has an inner door with a second positive seal, both the inner door and the outer cap/door must be leak checked. \n\n\t\t\t(ii)\tFor service panel valves that have an inner seal: In lieu of pressure testing, the outer cap seal and seal surface may be visually inspected for damage or wear. Any damaged parts must be replaced or repaired prior to further flight, or the affected lavatory(s) must be drained and placarded inoperative until repairs can be accomplished. \n\n\tNOTE 3: Some service panel valves have an inner seal that is closed when the outer cap is closed. For this type of valve, the fluid leakage from the outer cap can be checked only if the inner seal is removed; when the inner seal is in place, it prevents any fluid from reaching the outer cap seal. For this type of valve, the actions specified in paragraph (a)(3)(ii) are provided to allow inspection of the seal and seal surface of the outer cap seal as an alternative to leak checking the outer seal itself. \n\n\t\t(4)\tFor flush/fill lines: Within 5,000 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 5,000 flight hours, accomplish either of the procedures specified in paragraphs (a)(4)(i) or (a)(4)(ii) of this AD, as appropriate for the airplane's flush/fill line installation: \n\n\t\t\t(i)\tFor airplanes equipped with a flush/fill line cap, accomplish either paragraph (a)(4)(i)(A) or (a)(4)(i)(B) of this AD: \n\n\t\t\t\t(A)\tConduct a leak check of the flush/fill line cap. This leak check must be made with a minimum of 3 PSID applied across the cap. Or \n\n\t\t\t\t(B)\tReplace the seals on the toilet tank anti-siphon (check) valve and the flush/fill line cap. Additionally, perform a leak check of the toilet tank anti-siphon (check) valve with a minimum of 3 PSID across the valve. \n\n\tNOTE 4: The Inspection/Check procedure specified in DC-10 Maintenance Manual, chapter 38-30-00, pages 601 and 602, dated June 1, 1993, may be referred to as guidance for the procedures required by this paragraph. \n\n\t\t\t(ii)\tFor airplanes equipped with a check valve vacuum breaker, Monogram part number series 4803-86: Replace the O-rings /seals in the valve and test the check valve and vacuum breaker sections of the valve for proper operation, in accordance with the manufacturer's component maintenance/overhaul manual. \n\n\t\t(5)\tIf a leak is discovered during any leak check required by paragraph (a) of this AD, prior to further flight, accomplish either of the procedures specified in paragraph (a)(5)(i) or (a)(5)(ii) of this AD: \n\n\t\t\t(i)\tRepair the leak and retest. Or \n\n\t\t\t(ii)\tDrain the affected lavatory system and placard the lavatory inoperative until repairs can be accomplished. \n\n\t(b)\tAs an alternative to the requirements of paragraph (a) of this AD: Within 180 days after the effective date of this AD, revise the FAA-approved maintenance program to include the requirements specified in paragraphs (b)(1), (b)(2), (b)(3), (b)(4), (b)(5), and (b)(6) of this AD. \n\n\t\t(1)\tFor each lavatory drain system: Within 5,000 flight hours after revision of the maintenance program in accordance with paragraph (b) of this AD, and thereafter at intervals not to exceed 18 months, replace the valve seals. Any revision to this replacement schedule must be approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t\t(2)\tConduct periodic leak checks of the lavatory drain systems in accordance with the applicable schedule specified in paragraphs (b)(2)(i), (b)(2)(ii), and (b)(2)(iii) of this AD. If the individual waste drain system panel incorporates more than one type of valve, the inspection interval that applies to that panel is determined by the component with the longest inspection interval allowed. Each of the components must be inspected/tested at that time at each service panel location. Any revision to the leak check schedule must be approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t\t\t(i)\tWithin 1,000 flight hours after revising the maintenance program in accordance with paragraph (b) of this AD, and thereafter at intervals not to exceed 1,000 flight hours, accomplish the applicable procedures specified in paragraphs (b)(2)(i)(A) and (b)(2)(i)(B) of this AD for each lavatory drain system with a service panel drain valve installed that is listed in Table 3, below:\n \nTable 3\n Valves Requiring Leak Checks at 1,000-Flight Hour Intervals\n \n\nManufacturer\t\t\nPart Number\nSerial Number \nKaiser Electroprecision \t\t\n0218-0032 series\nall serial numbers \nKaiser Electroprecision \t\t\n0218-0026 series \nall serial numbers \nShaw Aero Devices \t\n1010100C series\t\n\nall serial numbers \nShaw Aero Devices \t\t\n1010100B series\nall serial numbers\nShaw Aero Devices \t\t\n10101000BA2\n130 and higher \nShaw Aero Devices \t\t\n10101000BB2\n0011 and higher \nShaw Aero Devices \t\n331 series \t\n\nall serial numbers \nShaw Aero Devices \t\n332 series \n\nall serial numbers \nPneudraulics \t\t\n9527 series\nall serial numbers \n\n\t\t\t\t(A)\tConduct leak checks of the dump valve and service panel drain valve. The service panel drain valve leak check must be performed with a minimum of 3 PSID applied across the valve. Only the inner door/closure device of the service panel drain valve must be leak checked. And \n\n\t\t\t\t(B)\tVisually inspect the service panel drain valve outer cap/door seal and seal mating surface for wear or damage that may cause leakage. Any worn or damaged seal must be replaced, and any damaged seal mating surface must be repaired or replaced, prior to further flight, in accordance with the valve manufacturer's maintenance manual. \n\n\t\t\t(ii)\tWithin 200 flight hours after revising the maintenance program in accordance with paragraph (b) of this AD, and thereafter at intervals not to exceed 200 flight hours, accomplish the applicable procedures in paragraph (b)(2)(ii)(A) and (b)(2)(ii)(B) of this AD for each lavatory drain system with a lavatory drain system valve that incorporates one of the valves listed in Table 4, below: \n\nTable 4\n Valves Requiring Leak Checks at 200-Flight Hour Intervals\n \n\nManufacturer\t\nPart Number\nSerial Number \nKaiser Electroprecision\n4259-20 or 4259-31\t\n"donut" assemblies \n(or substitute assemblies \nfrom another manufacturer) \n\nall serial numbers \nKaiser Roylyn\t\n2651-231\n\n\nKaiser Roylyn\t\n2651-259 \n\n\n\n\t\t\t\t(A)\tConduct leak checks of the dump valve and the service panel drain valve. The service panel drainvalve leak check must be performed with a minimum 3 PSID applied across the valve. Both the donut and the outer cap/door must be leak checked. \n\n\t\t\t\t(B)\tFor service panel valves that have an inner seal: In lieu of pressure testing, visually inspect the outer cap seal and seal surface for damage or wear. Any damaged parts must be replaced or repaired prior to further flight, or the affected lavatory(s) must be drained and placarded inoperative until repairs can be accomplished. \n\n\t\t\t(iii)\tFor each lavatory drain system that incorporates any other type of approved valves: Within 400 flight hours after revising the maintenance program in accordance with paragraph (b) of this AD, and thereafter at intervals not to exceed 400 flight hours accomplish both of the following procedures: \n\n\t\t\t\t(A)\tConduct leak checks of the dump valve and the service panel drain valve. The service panel drain valve leak check must be performed with a minimum 3 PSID applied across the valve. If the service panel drain valve has an inner door/closure device with a second positive seal, only the inner door must be leak checked. And \n\n\t\t\t\t(B)\tIf the valve has an inner door/closure device with a second positive seal: Visually inspect the service panel drain valve outer door/cap seal and seal mating surface for wear or damage that may cause leakage. Any worn or damaged seal must be replaced and any damaged seal mating surface must be repaired or replaced, prior to further flight, in accordance with the valve manufacturer's maintenance manual. \n\n\t\t(3)\tFor flush/fill lines: Within 5,000 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 5,000 flight hours, accomplish the procedure specified in either paragraph (b)(3)(i) or (b)(3)(ii) of this AD, as appropriate for the airplane's flush/fill line installation: \n\n\t\t\t(i)\tFor airplanes equipped with a flush/fill line cap, accomplish either paragraph (b)(3)(i)(A) or (b)(3)(i)(B) of this AD:(A)\tConduct a leak check of the flush/fill line cap. This leak check must be made with a minimum of 3 PSID applied across the cap. Or \n\n\t\t\t\t(B)\tReplace the seals on the toilet tank anti-siphon (check) valve and the flush/fill line cap. Additionally, perform a leak check of the toilet tank anti-siphon (check) valve with a minimum of 3 PSID across the valve. \n\n\tNOTE 5: The Inspection/Check procedure specified in DC-10 Maintenance Manual, chapter 38-30-00, pages 601 and 602, dated June 1, 1993, may be referred to as guidance for the procedures required by this paragraph. \n\n\t\t\t(ii)\tFor airplanes equipped with a check valve vacuum breaker, Monogram part number series 4803-86: Replace the O-rings/seals in the valve and test the check valve and vacuum breaker sections of the valve for proper operation, in accordance with the manufacturer's component maintenance/overhaul manual. \n\n\t\t(4)\tProvide procedures for accomplishing visual inspections to detect leakage, to be conductedby maintenance personnel at intervals not to exceed 4 calendar days or 45 flight hours, whichever occurs later. \n\n\t\t(5)\tProvide procedures for reporting leakage. These procedures shall provide that any "horizontal blue streak" findings must be reported to maintenance and that, prior to further flight, the leaking system shall either be repaired, or be drained and placarded inoperative. \n\n\t\t(6)\tProvide training programs for maintenance and servicing personnel that include information on "Blue Ice Awareness" and the hazards of "blue ice." \n\n\t(c)\tFor operators who elect to comply with paragraph (b) of this AD: Any revision to (i.e., extension of) the leak check intervals required by paragraph (b) of this AD must be approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. Requests for such revisions must be submitted to the Manager of the Los Angeles ACO through the FAA Principal Maintenance Inspector (PMI), and must include the following information:(1)\tThe operator's name; \n\n\t\t(2)\tA statement verifying that all known cases/indications of leakage or failed leak tests are included in the submitted material; \n\n\t\t(3)\tThe type of valve (make, model, manufacturer, vendor part number, and serial number); \n\n\t\t(4)\tThe period of time covered by the data; \n\n\t\t(5)\tThe current FAA leak check interval; \n\n\t\t(6)\tWhether or not seals have been replaced between the seal replacement intervals required by this AD; \n\n\t\t(7)\tWhether or not leakage has been detected between leak check intervals required by this AD, and the reason for leakage (i.e., worn seals, foreign materials on sealing surface, scratched or damaged sealing surface or valve, etc.); \n\n\t\t(8)\tWhether or not any leak check was conducted without first inspecting or cleaning the sealing surfaces, changing the seals, or repairing the valve. (If such activities have been accomplished prior to conducting the periodic leak check, that leak check shall be recorded as a "failure" for purposes of the data required for this request submission. The exception to this is the normally scheduled seal change in accordance with paragraph (b)(1) of this AD. Performing this scheduled seal change prior to a leak check will not cause that leak check to be recorded as a failure.)\n\n\tNOTE 6: Requests for approval of revised leak check intervals may be submitted in any format, provided that the data give the same level of assurance specified in paragraph (c) of this AD. \n\n\tNOTE 7: For the purposes of expediting resolution of requests for revisions to the leak check intervals, the FAA suggests that the requester summarize the raw data; group the data gathered from different airplanes (of the same model) and drain systems with the same kind of valve; and provide a recommendation from pertinent industry group(s) and/or the manufacturer specifying an appropriate revised leak check interval. \n\n\t(d)\tFor all airplanes: Within 5,000 flight hours after the effective date of this AD, accomplish the requirements of either paragraph (d)(1) or (d)(2) of this AD: \n\n\t\t(1)\tInstall a lever/lock cap on the flush/fill lines for all lavatory service panels. The cap must be either an FAA-approved lever/lock cap; or a lever/lock cap installed in accordance with McDonnell Douglas Service Bulletin 38-65 (for Model DC-10 series airplanes) or Service Bulletin 38-39 (for Model MD-11F series airplanes (freighter)), as applicable. Or \n\n\t\t(2)\tInstall a Monogram 4803-86 series check valve on the flush/fill lines for all lavatory service panels. \n\n\t(e)\tFor any affected airplane acquired after the effective date of this AD: Before any operator places into service any airplane subject to the requirements of this AD, a schedule for the accomplishment of the leak checks required by this AD shall be established in accordance with either paragraph (e)(1) or (e)(2) of this AD, as applicable. After each leak check has been performed once, each subsequent leak check must be performed in accordance with the new operator's schedule, in accordance with either paragraph (a) or (b) of this AD as applicable. \n\n\t\t(1)\tFor airplanes previously maintained in accordance with this AD, the first leak check to be performed by the new operator must be accomplished in accordance with the previous operator's schedule or with the new operator's schedule, whichever would result in the earlier accomplishment date for that leak check. \n\n\t\t(2)\tFor airplanes that have not been previously maintained in accordance with this AD, the first leak check to be performed by the new operator must be accomplished prior to further flight, or in accordance with a schedule approved by the FAA PMI, but within a period not to exceed 200 flight hours. \n\n\t(f)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA PMI, who may add comments and then send it to the Manager, Los Angeles ACO. \n\n\tNOTE 8: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO. \n\n\tNOTE 9: For any valve that is not eligible for the extended leak check intervals of this AD: To be eligible for the leak check interval specified in paragraphs (a)(1) and (b)(2)(i), the service history data of the valve must be submitted to the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate, with a request for an alternative method of compliance with this AD. The request should include an analysis of known failure modes for the valve, if it is an existing design, and known failure modes of similar valves. Additionally, the request should include an explanation of how design features will preclude these failure modes, results of qualification tests, and approximately 25,000 flight hours or 25,000 flight cycles of service history data, including a winter season, collected in accordance with the requirements of paragraph (c) of this AD or a similar program. \n\n\t(g)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(h)\tThis amendment becomes effective on July 12, 1996.

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 Model DC-10 series airplanes and MD-11F airplanes was published in the Federal Register on November 2, 1995 (60 FR 55668). That action proposed to require repetitive leak checks of the lavatory drain system and repair, if necessary; to provide for the option of revising the FAA- approved maintenance program to include a schedule of leak checks; and to require the installation of a cap on the flush/fill line. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nSupport for the Proposal \n\n\tOne commenter supports the proposal. Request to Exclude All-Cargo Configured Airplanes from Applicability \n\n\tOne commenter requests that the applicability of the proposal be revised to exclude airplanes operating in an all-cargo configuration, where lavatories and lavatory fill/drain systems have been removed. \n\n\tThe FAA concurs. This final rule requires leak checks of the lavatory/fill drain system. However, if no such system is installed on the airplane then, obviously, the requirements of the AD cannot be performed and, likewise, should not be required. Although the commenter states that, for all-cargo configurations of the affected airplanes, lavatory systems may be removed, the FAA is aware that most cases of all-cargo-configured Model DC-10's have at least one (forward) lavatory installed near the flightcrew deck. As long as there is one lavatory drainage system installed on the airplane, the requirements of this AD would still apply. To make this eminently clear to affected operators, the FAA has revised the applicability of the final rule to clarify that the AD applies to airplanes that are equipped with a lavatory drainage system. \n\nRequest to Revise Dump Valve Leak CheckProcedure \n\n\tOne commenter requests that the dump valve leak check procedures, specified throughout the proposal, be revised to permit the check to be performed using less fluid. The proposal states that the check is to be performed by filling the toilet tank with fluid to a level such that the bowl is approximately half full (at least 2 inches above the flapper in the bowl). However, this commenter states that the check can be accomplished and the same intent can be achieved with the use of less fluid. This commenter, a U.S. operator, indicates that use of less fluid would be more effective in terms of both time and cost. As an example, the commenter states that many Model DC-10 airplanes are equipped with aft waste tanks with a 90-gallon capacity; if the proposed check procedures are accomplished, over 120 gallons of fluid would be required to fill the toilet tanks to a level such that each of the four toilet bowls are half full. The commenter requests that this leak check onthese airplanes be revised to require a maximum of only 50 gallons of fluid to be used. The commenter asserts that this revision to the test procedures would still accomplish the same intent and would decrease the time required to test the system. \n\n\tThe FAA does not concur. The procedure to fill the toilet bowl to approximately 1/2 full is also meant to check the tank and the rinse line check valves. The FAA finds that performing the test using less fluid does not do as complete and adequate a job as is necessary to meet the intent of this AD. \n\nRequest to Delete the Method for Conducting Leak Checks \n\n\tOne commenter requests that the proposal be revised to delete the defined method of conducting the leak check. The commenter suggests that, in lieu of requiring the aircraft to be pressurized, the proposal should merely stipulate that operators are to "apply 3 psi (sic) across the valve" and then allow operators to determine the most economical means of verifying the integrity of the seals. The commenter contends that requiring pressurization of the airplane causes unnecessary expenses to be incurred. \n\n\tThe FAA does not consider that any revision to the final rule is necessary based on the commenter's request. The wording of the final rule (and proposal) simply states that the check must be performed with "a minimum of 3 PSID applied across the valve." To do this does not require that the airplane be pressurized. The FAA acknowledges that the NOTE contained in the proposal referred operators to the procedures specified in chapter 38-30-00 of the DC-10 Maintenance Manual procedure as one source of guidance for performing the check procedures, and those particular procedures do call for pressurizing the airplane. However, the reference to the Maintenance Manual procedure is merely informational; it is not a requirement and, likewise, pressurizing the airplane is not a requirement. The only requirement of the AD is that a minimum of 3 PSID be appliedacross the valve when the check is performed. \n\nRequest for Clarification of Check Requirements for Valves with Outer Seals and Inner Caps \n\n\tOne commenter requests that proposed paragraphs (a)(3)(i) and (a)(3)(ii) be revised to define more clearly which types of valves require the outer seal to be pressure checked for leakage. \n\n\tThe FAA agrees that some clarification is warranted. Some valves have an inner seal that is closed when the outer cap is closed. For this type of valve, leakage from the outer cap could only be checked if the inner seal were removed since, when the inner seal is correctly in place, it will prevent any fluid from reaching the outer cap seal. For this type of valve, paragraph (a)(3)(ii) of the final rule provides an alternative to allow operators to inspect the seal and seal surface of the outer cap seal in lieu of performing a leak check of the outer seal. The FAA has included a new NOTE in paragraph (a)(3) to provide this information. \n\nRequest to Increase Leak Check Interval for Certain Shaw Aero Valves \n\n\tOne commenter requests that proposed paragraph (a)(1) and (b)(2)(i) be revised to allow the following Shaw Aero valves to be leak checked at 1,000-hour intervals: \n\n\t331 series, all serial numbers; \n\n\t332 series, all serial numbers; \n\n\t10101000BA2, having serial numbers 130 and higher; and \n\n\t10101000BB2, all serial numbers. \n\nThe commenter states that these valves have been accepted previously by the FAA for a 1,000- hour leak check interval either in accordance with AD 94-23-10, amendment 39-9073 (59 FR 59124, November 16, 1994), which is applicable to Boeing Model 727 series airplanes; or a similar proposed rule applicable to Boeing Model 737 series airplanes (reference Docket No. 95-NM-111- AD; 60 FR 55673, November 2, 1995). \n\n\tThe FAA concurs in part. The FAA finds that the 1,000-hour leak check interval is acceptable for most of the valves requested by the commenter. However, based on data received, only 10101000BB2 series valves having serial number 0011 and higher are acceptable for this leak check interval. The final rule has been revised accordingly.\n\nRequest for Increase in Leak Check Interval for All Shaw Aero Valves \n\n\tThis same commenter requests that proposed paragraph (a)(1) and (b)(2)(i) be revised to permit the leak check interval of 1,000 hours for specified Shaw Aero valves to be increased to 2,000 hours upon the revision of an operator's maintenance procedures in accordance with the proposal and the submittal of data to substantiate the longer interval. \n\n\tThe FAA does not consider that any change to the rule is necessary based on this commenter's request. Paragraph (c) of the final rule provides a procedure for collecting and submitting data to substantiate an increase in the leak check interval for any valve. The procedure specified in that paragraph is the appropriate one to follow for requesting any such increase in the leak check interval. \n\nRequest to Increase Leak Check Interval for Certain Kaiser Valves \n\n\tOne commenter requests that proposed paragraphs (a)(1) and (b)(2)(i) be revised to increase the 1,000-hour leak check interval for Kaiser valves having part numbers 0218-0026 and 0218- 0032. The commenter requests that the interval be increased to 2,500 hours based on qualification and test report data submitted. \n\n\tThe FAA cannot concur with the commenter's request since insufficient data was submitted to support a longer inspection interval. \n\nRequest for Special Procedures for Systems with "Interlock" Mechanisms \n\n\tOne commenter requests that proposed paragraph (b)(2)(ii) be revised to include different requirements for systems that incorporate an "interlock" mechanism that prevents the closure of the outer cap if the "donut" is not installed. This commenter states that if the functioning of the interlock mechanism is verified, the requirement for pressure leak checks should be similar to the checks of other valves that have both an inner and an outer seal. \n\n\tThe FAA does not concur. Though the interlock mechanism ensures that the donut is installed, it does not ensure that the donut is in good condition. This type of valve, therefore, should be inspected at the same interval as other "donut valves," unless data to substantiate a longer inspection interval can be provided. For this type of valve, the inner seal (the "donut") can be leak checked and the outer cap seal and seal surface can be inspected for wear in accordance with the procedures specified in paragraph (b)(2)(ii)(B) of the final rule. \n\nRequest to Allow Installation of an Alternative Lock Cap \n\n\tOne commenter requests that proposed paragraph (d) be revised to allow the installation of a 1/4-turn ball lock cap as an alternative to the proposed lever lock cap. This commenter, a non- U.S. operator, states that its fleet is already equipped with these lock caps and the commenter considers them equivalent to the caps that would be required by the AD. \n\n\tThe FAA does not concur. Service experience has shown that, on many occasions, caps have been missing from the airplane. The lever lock cap installation required by this final rule secures the cap to the airplane better than other types of cap installations that the FAA currently knows of. However, under the provisions of paragraph (f) of this final rule, the FAA would consider approval of the use of other types of caps as an alternative method of compliance if sufficient data are presented to justify the use of a different type of cap. \n\nRequest to Address Need for Heaters on Flush/Fill Lines \n\n\tThis same commenter indicates that the proposed installation of caps on the flush/fill lines, as would be required by paragraph (d) of the proposal, also may require the installation of heaters. Without such heaters, residual water will collect at the flush/fill nipples and freeze, thus hindering maintenance. This will increase the costs associated with the proposed rule. \n\n\tThe FAA does not concur with the commenter's observation. Typically, caps already are installed on airplanes; this AD will require the installation of only a particular style of cap, and may not change the possible need for heaters on some airplanes. If the lines are allowed to drain thoroughly before the cap is closed, the need for heaters also would be minimized or eliminated. \n\nRequest for Permission to Use Alternative Check Valves on Flush/Fill Line \n\n\tSeveral commenters request that proposed paragraph (d) be revised to permit the use of Monogram 4803-86 series check valves on flush/fill lines as an alternative to the proposed lever/lock caps. These commenters point out that Monogram check valves with similar design characteristics were approved previously by the FAA as an acceptable alternative item for compliance with a similar proposed AD that is applicable to Boeing Model 737 series airplanes (reference Docket No. 95-NM-111-AD). \n\n\tThe FAA concurs with the commenters' request. Paragraph (d) of the final rule has been revised to specify that installation of Monogram 4803-86 series check valves on the flush/fill lines is an acceptable action for compliance. \n\n\tAdditionally, paragraphs (a)(4) and (b)(3) of the final rule have been revised to provide the necessary instructions for replacing the O-rings associated with the Monogram 4803-86 series check valve, and for testing the check valve for proper operation. \n\nRequest for Revision of Cost Impact Information \n\n\tOne commenter states that the cost impact information, as explained in the preamble to the proposal, indicated that required parts for installing a cap on the flush/fill line would cost $275 per airplane. The commenter states that the cost of parts is $275 per unit; based on an average of 8 units per airplane, the cost per airplane is $2,200. \n\n\tThe FAA concurs. The cost information presented in the proposal inadvertently indicated the cost per unit, rather than the total cost per airplane. The commenter's figures are correct and the cost impact discussion, below, has been revised accordingly. \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 435 Model DC-10 series airplanes and Model MD-11F airplanes of the affected design in the worldwide fleet. The FAA estimates that 285 airplanes of U.S. registry, and 18 U.S. operators, will be affected by this proposed AD. \n\n\tFor airplanes in the passenger configuration, the estimated costs associated with the requirements of this AD are as follows: \n\n\t1. Leak checks. It will take approximately 4 work hours per airplane lavatory drain toaccomplish each leak check, at an average labor cost of $60 per work hour. There normally are two drains per airplane. Depending upon the type of valve installed and the flight utilization rate of the airplane, airplanes will be required to be inspected as few as 3 times per year or as many as 15 times per year. Based on these figures, the cost impact of the proposed leak check requirement on U.S. operators is expected to be between $1,440 and $7,200 per airplane per year. \n\n\t2. Inspections. Should an operator elect to perform the inspection of the service panel drain valve cap/door seal and seal mating surface, the inspection will take approximately 2 work hours to accomplish, at an average labor cost of $60 per work hour. Depending upon the type of valves installed and the flight utilization rate of the airplane, airplanes will be required to be inspected as few as 3 times per year or as many as 15 times per year. Based on these figures, the cost impact of the inspection requirements on U.S. operators will be between $360 and $1,800 per airplane per year. \n\n\t3. Installation of cap on flush/fill line. This installation will take approximately 2 work hours to accomplish, at an average labor cost of $60 per work hour. The cost of required parts is estimated to be $2,200 per airplane. (There are 8 flush/fill lines per airplane, and parts for each line will cost approximately $275.) There currently are 175 passenger-configured airplanes of U.S. registry that will be subject to this requirement. Based on these figures, the cost impact of the installation requirement on U.S. operators is expected to be $553,000, or $3,160 per airplane. \n\n\tFor airplanes in the freighter configuration, the estimated costs associated with the requirements of this AD are as follows: \n\n\t1. Leak checks. It will take approximately 4 work hours per airplane lavatory drain to accomplish each leak check, at an average labor cost of $60 per work hour. There normally is onedrain per airplane. Depending upon the type of valve installed and the flight utilization rate of the airplane, airplanes will be required to be inspected as few as 3 times per year or as many as 15 times per year. Based on these figures, the cost impact of the leak check requirement on U.S. operators of these airplanes is expected to be between $720 and $3,600 per airplane per year. \n\n\t2. Inspections. Should an operator elect to perform the inspection of the service panel drain valve cap/door seal and seal mating surface, the inspection will take approximately 1 work hour to accomplish, at an average labor cost of $60 per work hour. Depending upon the type of valves installed and the flight utilization rate of the airplane, airplanes will be required to be inspected as few as 3 times per year or as many as 15 times per year. Based on these figures, the cost impact of the inspection requirements on U.S. operators of these airplanes will be between $180 and $900 per airplane peryear. \n\n\t3. Installation of cap on flush/fill line. This installation will take approximately 2 work hours to accomplish, at an average labor cost of $60 per work hour. The cost of required parts is estimated to be $275 per airplane. (There is 1 flush/fill line per airplane.) There currently are 110 freighter-configured airplanes of U.S. registry that will be subject to this requirement. Based on these figures, the cost impact of the installation requirement on U.S. operators of these airplanes is expected to be $43,450, or $395 per airplane. \n\n\tThe number of required work hours, as indicated above, is presented as if the accomplishment of the actions required by 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 minimalin 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 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 $60 per work hour. Based on these figures, the total cost impact of the maintenance revision requirement of this AD on the 18 affected U.S. operators is estimated to be $43,200, or $2,400 per operator. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\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 \nrelationship 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\nList 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\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: \n\nAuthority: 49 U.S.C. 106(g), 40113,44701. \n\n§ 39.13 - (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: