AD 94-03-07

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 767 series airplanes. This action requires inspections of the brake rod inner cylinder bolts on the main landing gear (MLG) wheels and brakes; inspections of certain MLG bushings; installation of retainer plates at each MLG brake disconnect; inspection and modification of the brake rod pin assembly at each MLG wheel; repair or replacement of discrepant parts; and revision of the Airplane Flight Manual (AFM), as necessary. This amendment is prompted by numerous reports of brake failure during landing and during a low energy rejected takeoff. The actions specified in this AD are intended to prevent failure of two or more MLG brakes, which could adversely affect the stopping performance of the airplane.

Final rule; request for comments.

94-03-07 BOEING: Amendment 39-8814. Docket 93-NM-209-AD. \nApplicability: Model 767 series airplanes equipped with carbon brakes, certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent failure of two or more MLG brakes, which could adversely affect the stopping performance of the airplane, accomplish the following: \n\n\t(a)\tExcept as provided in paragraph (f) of this AD, within 60 days after the effective date of this AD, accomplish paragraphs (a)(1) and (a)(2) of this AD in accordance with Boeing Service Bulletin 767-32A0116, Revision 1, dated January 13, 1994: \n\n\t\t(1)\tPerform a surface temper etch inspection and a fluorescent magnetic particle inspection to detect cracks or thermal damage of the brake rod inner cylinder bolts on the main landing gear (MLG) wheels and brakes in accordance with the service bulletin. As a result of these inspections, accomplish either paragraph (a)(1)(i) or (a)(1)(ii) of this AD, as applicable: \n\n\t(i)\tIf cracking or thermal damage is found on any bolt: Prior to further flight, replace the existing bolt with a new or serviceable bolt in accordance with the service bulletin. Repeat the inspections thereafter at intervals not to exceed 800 flight cycles. \n\n\t\t(ii)\tIf cracking or thermal damage is not found on any bolt: Apply finish and reinstall the bolt in accordance with the service bulletin. Repeat the inspections thereafter at intervals not to exceed 800 flight cycles. \n\n\t\t(2)\tPerform a visual inspection to detect cracking of the inner cylinder fork lug bushings and the brake rod bushings at the inner cylinder fork lug end in accordance with the service bulletin. Repeat that inspection thereafter at intervals not to exceed 800 flight cycles. \n\n\t(b)\tFor airplanes having line positions 132 through 518, inclusive: Except as provided in paragraph (f) of this AD, within 60 days after the effective date of this AD, accomplish paragraphs (b)(1), (b)(2), and (b)(3), as follows: \n\n\t\t(1)\tInstall the retainer plates at each MLG brake disconnect; and adjust the torque of the "B"-nut on the hydraulic line connection to the disconnect fitting; in accordance with Boeing Alert Service Bulletin 767-32A0125, dated November 11, 1993. \n\n\t\t(2)\tRemove the cross bolt from the brake housing and brake rod pin assembly at each MLG wheel; remove the brake rod pin assembly; perform a visual inspection of the brake rod pin assembly to detect cracks, bronze transfer, corrosion, chrome discoloration, and areas of missing chrome plate; prior to further flight, replace any damaged brake rod pin assembly with a new or serviceable assembly; modify the brake rod pin assembly; install the modified brake rod pin into the brake housing and brake rod; and install a new brake attach pin retainer configuration; in accordance with Boeing Service Bulletin 767-32A0126, Revision 1, dated January 13, 1994. \n\n\t\t(3)\tPerform a one-time visual inspection to detect cracking,deformation, and/or a missing piece in the bushings in the brake housing, and the bushings in the end of the brake rod, in accordance with Boeing Service Bulletin 767-32A0126, Revision 1, dated January 13, 1994. \n\n\t(c)\tFor any bushing that is found broken and/or any bushing that is found having a piece missing during the inspection(s) required by paragraphs (a)(2) and/or (b)(3) of this AD, accomplish the requirements of either paragraph (c)(1) or (c)(2), as follows: \n\n\t\t(1)\tWithin 10 flight cycles after detection, repair or replace the bushing in accordance with the appropriate service bulletin. No performance decrements are required within the first 10 flight cycles since detection. Or \n\n\t\t(2)\tIf the affected bushing has not been replaced within 10 flight cycles after detection, observe one-brake-deactivated performance decrements in accordance with the FAA-approved Airplane Flight Manual (AFM) until replacement of the affected bushing is accomplished. Operation must be performed with all brakes and the antiskid system fully functional, while operating with one-brake-deactivated performance decrements for broken bushings and/or a bushing with a missing piece. \n\n\t(d)\tFor any bushing that is found to be cracked or deformed during the inspection(s) required by paragraphs (a)(2) and/or (b)(3) of this AD, accomplish the requirements of either paragraph (d)(1) or (d)(2), as follows: \n\n\t\t(1)\tWithin 100 flight cycles since detection, repair or replace the bushing in accordance with the appropriate service bulletin. No performance decrements are required within the first 100 flight cycles since detection. Or \n\n\t\t(2)\tIf the affected bushing(s) has not been replaced within 100 flight cycles since detection, observe one-brake-deactivated performance decrements in accordance with the FAA-approved AFM until replacement of the affected bushing is accomplished. Operation must be performed with all brakes and the antiskid system fully functional, while operatingwith one-brake-deactivated performance decrements for cracked bushings. \n\n\t(e)\tOperators may operate beyond 60 days after the effective date of this AD with one-brake-deactivated performance decrements for cracked or broken bushings, provided that the actions required by paragraphs (a) through (b)(3) of this AD have been accomplished. \n\n\t(f)\tRevise the Limitations and Flight Performance sections of the FAA-approved AFM (or computer generated takeoff weight tables) to include the following information. (This may be accomplished by inserting a copy of this AD in the AFM.) If the actions required by paragraphs (a) through (b)(3) of this AD have not been accomplished within 60 days after the effective date of this AD, the following two-brake-deactivated performance decrements must be observed until the actions required by paragraphs (a) through (b)(3) of this AD have been accomplished. The following adjustments reflect takeoff and landing performance, assuming failure of two brakes.Operation must be performed with all brakes operative and the anti-skid system operative. \n\n"OPTION 1: \n\t(1)\tSubtract 70,000 LB ( 31,750 KG) from the takeoff limited weight (the most \t\tlimiting \t(lowest) of maximum certified, obstacle clearance, tire speed, brake \t\tenergy, climb, or field length limited weight). No adjustment to the takeoff \t\t\tspeeds for the resulting weight is required. \n\n\t(2)\tLanding Field Length - Section 4.13 of the Airplane Flight Manual: Multiply 'all \n\t\tbrakes operative' FAR landing field length by a factor of 1.20. \n\n\t(3)\tMaximum Quick Turnaround Weight - Section 4.13 of the Airplane Flight \t\t\tManual: No change from the 'all brakes operative' value. \n\nOPTION 2: \n\t(1)\tField Length Limited Weight - Section 4.4 of the Airplane Flight Manual: \t\t\tReduce the 'all brakes operative' field length limited weight by 10,500 LB \t\t\t(4,750 KG). The maximum allowable takeoff weight is the most limiting \t\t\t(lowest) of maximum certified, climb, obstacle clearance, tire speed, or this \t\tadjusted field length limited weight. \n\n\t(2)\tReference V1(mcg) Limited Accelerate-Stop Distance - Section 4.8 of the \n\t\tAirplane Flight Manual: Increase the reference V1(mcg) limited \t\t\t\taccelerate-stop distance by 1000 FT. \n\n\t(3)\tTakeoff Decision Speed, V1 - Section 4.7 of the Airplane Flight Manual: \t\t\tReduce V1 by the following: \n\n\t\t\tWeights below 330,000 LB (150,000 KG): \n\t\t\t\t Subtract 4 knots \n\t\t\tWeights at or above 330,000 LB (150,000 KG): \n\t\t\t\t Subtract 3 knots\n\n\t If the resulting V1 is less than V1(mcg), takeoff is permitted with V1 set equal to V1(mcg) provided the corrected accelerate-stop distance available exceeds the adjusted reference V1(mcg) limited accelerate-stop distance from Step 2. \n\n\t(4)\tBrake Energy Limits - Section 4.7 of the Airplane Flight Manual: Reduce the \n\t\tmaximum brake energy speed allowed with all brakes operative by 30 knots. \n\t\tVerify the scheduled V1 is less than the reduced VMBE. If not, then takeoffweight must be reduced. \n\n\t(5)\tLanding Field Length - Section 4.13 of the Airplane Flight Manual: Multiply 'all \n\t\tbrakes operative' FAR landing field length by a factor of 1.20. \n\n\t(6)\tMaximum Quick Turnaround Weight - Section 4.13 of the Airplane Flight \t\t\tManual: No change from the 'all brakes operative' value. \n\nOPTION 3: \n\n\tOnce the following adjustments to corrected accelerate-stop distance and VMBE are determined, the takeoff weights should be calculated in the normal fashion (using these adjusted data) to determine the maximum allowable takeoff weight. \n\n\t(1)\tCorrected Accelerate Stop Distance - Section 4.3 of the Airplane Flight \t\t\tManual: Use the following table to adjust the corrected accelerate-stop \t\t\tdistance. \n\n\nCorrected Accel-Stop Distance \n(feet)\nAdjusted Corrected Accel-Stop Distance \n(feet)\nCorrected Accel-Stop Distance\n(feet)\nAdjusted Corrected Accel-Stop Distance\n(feet)\n4,000\n3,420\n13,000\n11,552 \n5,000\n4,312\n14,000\n12,470 \n6,000\n5,206\n15,000\n13,391\n7,000\n6,104\n16,000\n14,315\n8,000\n7,005\n17,000\n15,241\n9,000\n7,908\n18,000\n16,171\n10,000\n8,815\n19,000\n17,104\n11,000\n9,724\n20,000\n18,039\n12,000\n10,637\n\n\n\nLinearly interpolate for accelerate-stop distance values between those shown. \n\n\n\t(2)\tReference V1(mcg) Limited Accelerate-Stop Distance - Section 4.8 of the \n\t\tAirplane Flight Manual: Increase the reference V1(mcg) limited \t\t\t\taccelerate-stop distance by 500 FT. If V1 is less than V1(mcg), takeoff is \t\t\tpermitted with V1 set equal to V1(mcg) provided the corrected \t\t\t\taccelerate-stop distance available exceeds this adjusted reference V1(mcg) \t\tlimited accelerate-stop distance. \n\n\t(3)\tBrake Energy Limits - Section 4.7 of the Airplane Flight Manual: Use the \n\t\tfollowing table to adjust the maximum brake energy speed allowed with all \n\t\tbrakes operative after correcting for runway slope and wind. \n\t\n\nAll Brake Op\nVMBE - KIAS \nAdjusted\nVMBE - KIAS \nAll Brake Op\nVMBE - KIAS \nAdjusted \nVMBE - KIAS \n100\n84.2\n170\n141.4 \n110\n92.4\n180\n149.6 \n120\n100.6\n190\n157.8 \n130\n108.7\n200\n166.0 \n140\n116.9\n210\n174.2 \n150\n125.1\n220\n182.3 \n160\n133.3\n\n\n\nLinearly interpolate for VMBE values between those shown. \n\n\t(4)\tLanding Field Length - Section 4.13 of the Airplane Flight Manual: Multiply 'all \n\t\tbrakes operative' FAR landing field length by a factor of 1.20. \n\n\t(5)\tMaximum Quick Turnaround Weight - Section 4.13 of the Airplane Flight \t\t\tManual: No change from the 'all brakes operative' value." \n\n\t(g)\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, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(h)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(i)\tThe actions shall be done in accordance with Boeing Service Bulletin 767-32A0116, Revision 1, dated January 13, 1994; Boeing Alert Service Bulletin 767-32A0125, dated November 11, 1993; and Boeing Service Bulletin 767-32A0126, Revision 1, dated January 13, 1994. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(j)\tThis amendment becomes effective on February 18, 1994.

The FAA has received reports from Boeing that certain Model 767 series airplanes, equipped with carbon brakes, have experienced vibratory conditions, which resulted in damage or failure of the brake torque rod cross bolts and pins. Recently, one operator experienced a two-brake failure on a low energy rejected takeoff, whereas previously, there had been reports of two-brake failures occurring only during landings. To date, there have been 13 reported incidents of one-brake failure and 5 incidents of a two-brake failure, all due to the vibratory phenomenon. This type of failure could result in the loss of one or two brakes (out of eight total brakes), depending upon the location of the failure. The possibility exists that more than one brake-couple pair could experience simultaneous failure of the cross bolts or pins, which could result in the loss of more than two brakes. \n\nBoeing has advised the FAA that heat damage resulting from high vibrational loads could lead to fracture of the brake rod inner cylinder bolts. If this should occur, the adjacent brake rods would disconnect from the inner cylinder, causing the brakes not to operate at two MLG wheels. As a result, secondary damage to the hydraulic lines and damage to wiring and the airframe could occur. \n\nBoeing has also advised the FAA that vibrations during braking can lead to separation of the brake disconnect. Separation of brake hoses from the brakes would increase braking distances, which is of greatest concern if this should happen during a rejected takeoff. \n\nAdditionally, Boeing has advised the FAA that the development of a fracture in a cross bolt in the brake rod pin assembly could cause the brake not to operate at that MLG wheel. The brake rod could separate from the brake housing, permitting the brake housing to turn on the axle. Under such conditions, while the wheel turns and brake pressure is applied, rotation of the brake housing would cut the hydraulic line and electrical wires attached to the brake. \n\nThese conditions, if not corrected, could adversely affect the stopping performance of the airplane. \n\nThe FAA has reviewed and approved Boeing Service Bulletin 767-32A0116, Revision 1, dated January 13, 1994, that describes procedures for repetitive surface temper etch inspections and fluorescent magnetic particle inspections to detect cracks or thermal damage of the existing brake rod inner cylinder bolts on the MLG wheels and brakes, and replacement of cracked or damaged bolts with new or serviceable bolts. The service bulletin also describes procedures for performing repetitive visual inspections to detect cracking of the inner cylinder fork lug bushings, and the brake rod bushings at the inner cylinder fork lug end, and repair of cracked bushings. Accomplishment of the repetitive inspections, and replacement or repair as necessary, will help prevent the possibility of a fracture developing in the brake rod inner cylinder bolts. (The service bulletin limits the effectivity to Model 767 series airplanes equipped with carbon brakes.) \n\nThe FAA has also reviewed and approved Boeing Alert Service Bulletin 767-32A0125, dated November 11, 1993, that describes procedures for installation of retainer plates at each MLG brake disconnect. The alert service bulletin also describes procedures for adjustment of the torque of the "B"-nut on the hydraulic line connection to the disconnect fitting. Accomplishment of the installation of retainer plates at each MLG brake disconnect will provide an improved installation of the brake disconnect, which keeps the brake hose connected to the brake. (The alert service bulletin limits the effectivity to Model 767 series airplanes equipped with carbon brakes, line positions 132 through 518, inclusive.) \n\nThe FAA has also reviewed and approved Boeing Service Bulletin 767-32A0126, Revision 1, dated January 13, 1994, that describes procedures for performing a visual inspection of the brake rod pin assembly at each MLG wheel to detect cracks, bronze transfer, corrosion, chrome discoloration, and areas of missing chrome plate; replacement of any damaged brake rod pin assembly; modification of the brake rod pin assembly; installation of the modified brake rod pin into the brake housing and brake rod; and installation of a new brake attach pin retainer configuration. The service bulletin also describes a visual inspection to detect cracking, deformation, and/or missing pieces of material in the bushings in the brake housing, and the bushings in the end of the brake rod; and repair or replacement as necessary. Accomplishment of this inspection and modification of the brake rod pin assembly at each MLG wheel, inspection of certain MLG bushings, and replacement or repair as necessary, will help prevent the possibility of a fracture developing in a cross bolt. The manufacturer has installed this modification on airplanes (equipped with carbon brakes) in production, starting at line number 519 and subsequent. (The service bulletin limits the effectivity to Model 767 series airplanes equipped with carbon brakes, line positions 132 through 518, inclusive.) \n\nSince an unsafe condition has been identified that is likely to exist or develop on other Model 767 series airplanes of the same type design, this AD is being issued to prevent failure of two or more MLG brakes, which could adversely affect the stopping performance of the airplane. This AD requires the following actions: \n\n1.\trepetitive surface temper etch inspections and fluorescent magnetic particle inspections to detect cracks or thermal damage of the existing brake rod inner cylinder bolts on the MLG wheels and brakes, and replacement of cracked or damaged bolts with new or serviceable bolts; \n\n2.\trepetitive visual inspections to detect cracking of the inner cylinder fork lug bushings and the brake rod bushings at the inner cylinder fork lug end; \n\n3.\tinstallation of retainer plates at each MLG brake disconnect and adjustment of the torque of the "B"-nut on the hydraulic line connection to the disconnect fitting; \n\n4.\ta one-time visual inspection of the brake rod pin assembly at each MLG wheel to detect cracks, bronze transfer, corrosion, chrome discoloration, and areas of missing chrome plate; replacement of any damaged brake rod pin assembly with a new or serviceable assembly; modification of the brake rod pin assembly; installation of the modified brake rod pin into the brake housing and brake rod; and installation of a new brake attach pin retainer configuration; \n\n5.\ta one-time visual inspection to detect cracking, deformation, and/or missing pieces in the bushings in the brake housing, and the bushings in the end of the brake rod; and \n\n6.\tsubsequent repair or replacement of any cracked and/or deformed bushings, and/or any bushings having missing pieces of material. \n\nThe actions are required to be accomplished in accordance with the service bulletins described previously. \n\nThis AD allows operation with one-brake-deactivated performance decrements for cracked or broken bushings, for operators who comply with the requirements of paragraphs (a) through (b)(3) of this AD within the acceptable compliance timeframe. \n\nThis AD allows operation with two-brake-deactivated performance decrements, for operators who have not accomplished the requirements of paragraphs (a) through (b)(3) of this AD within the acceptable compliance timeframe. For those operators, this AD requires revising the Limitations and Flight Performance Sections of the Airplane Flight Manual (AFM) to include two-brake-deactivated performance decrements. Three options are provided: the first and second options are simple, conservative corrections; the third option, while more complicated, can provide a less penalizing correction, depending upon the conditions. The effect of this AD is to ensure that flight crews are advised of the potential hazard and of theprocedures to address it. \n\nThe applicability of this AD is limited to only Model 767 series airplanes equipped with carbon brakes. \n\nSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \n\nAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\nComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\nCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 93-NM-209-AD." The postcard will be date stamped and returned to the commenter. \n\nThe 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\nThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a finalregulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n1.\tThe authority citation for part 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. \n\n§ 39.13 - (Amended) \n2.\tSection 39.13 is amended by adding the following new airworthiness directive: