AD 99-16-11

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-600, -700, and -800 series airplanes. This action requires a test of the squib circuit ground studs of the engine fire extinguisher bottles to measure the resistance, and repair or replacement of the ground stud with a new ground stud, if necessary. This amendment is prompted by reports of improper grounding of the squib circuit. Such a condition would prevent the engine fire extinguisher bottle from discharging when commanded, which could result in the inability to extinguish an engine fire.

Final rule; request for comments

99-16-11 BOEING: Amendment 39-11246. Docket 99-NM-188-AD. \n\n\tApplicability: Model 737-600, -700, and -800 series airplanes; line numbers 1 through 110 inclusive, 112 through 183 inclusive, 185, 186, 188, 189, 191, 193, and 195; 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 (c) 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 addressit. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo detect and correct improper grounding of the squib circuit, which would prevent the engine fire extinguisher bottle from discharging when commanded and could result in inability to extinguish an engine fire, accomplish the following: \n\nTest \n\n\t(a)\tWithin 90 days after the effective date of this AD, perform a test of the squib circuit ground studs of the engine fire extinguisher bottles to measure the resistance, in accordance with Boeing Telex M-7200-99-01098, dated February 5, 1999. \n\nRepair/Replacement \n\n\t(b)\tIf the resistance is greater than 0.5 milliohms, prior to further flight, repair in accordance with Boeing Telex M-7200-99-01098, dated February 5, 1999; or replace the ground stud with a new ground stud, in accordance with either paragraph (b)(1) or (b)(2) of this AD. \n\n\t\t(1)\tInstall a ground stud having Boeing part number BACS53B, in accordance with Boeing Telex M-7200-99-01098, dated February 5, 1999; or \n\n\t\t(2)\tInstall a standard built-up ground stud (nut and bolt type), in accordance with Subject 20-20-00 of Boeing Document No. D6-54446, "Standard Wiring Practices Manual." \n\nAlternative Methods of Compliance \n\n\t(c)\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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \n\n\t(d)\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\nIncorporation by Reference \n\n\t(e)\tExcept as provided by paragraph (b)(2) of this AD, the actions shall be done in accordance with Boeing Telex M-7200-99-01098, dated February 5, 1999. 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(f)\tThis amendment becomes effective on August 24, 1999.

The FAA has received a report indicating that the flight crew of a Boeing Model 737-800 series airplane pulled the engine fire handle in response to an elevated exhaust gas temperature indication on the right engine. Maintenance personnel found the fire handle turned to the right, indicating that the flight crew had attempted to discharge the right engine fire extinguisher bottle. Flight crew reports state that the pilot did not intend to discharge the bottle. It is not known if the fire handle was held in position long enough to discharge the bottle; however, ground resistance measurements revealed an open circuit from the right bottle squib and the ground stud to structure. Subsequent investigation determined that the open circuit was caused by an improperly installed ground stud during production. The engine fire extinguisher bottle installations on certain Model 737-600 and -700 series airplanes are identical to those installed on the affected Model 737-800 series airplanes. Since the initial event, the FAA has received reports indicating that approximately 25 percent of the squib ground studs installed on these Model 737-600, -700, and -800 series airplanes have improper grounding of the squib circuit. Such a condition would prevent the engine fire extinguisher bottle from discharging when commanded, which could result in the inability to extinguish an engine fire. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed Boeing Telex M-7200-99-01098, dated February 5, 1999, which describes procedures for a test of the squib circuit ground studs of the engine fire extinguisher bottles to measure the resistance, and repair or replacement of the ground stud with a new ground stud, if necessary. Accomplishment of the actions specified in the telex is intended to adequately address the identified unsafe condition. \n\nExplanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to detect and correct improper grounding of the squib circuit. Such a condition would prevent the engine fire extinguisher bottle from discharging when commanded, which could result in inability to extinguish an engine fire. This AD requires accomplishment of the actions specified in the telex described previously, except as discussed below. \n\nDifferences Between This AD and the Telex \n\n\tThe telex recommends accomplishing the test at the earliest opportunity where manpower and facilities are available, not to exceed two weeks from February 5, 1999, and specifies that operators should report the findings of the test to the airplane manufacturer. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the extent of the problem in the fleet based on findings from operators' reports, and the time necessary to perform the test (less than one hour). In light of all of these factors, the FAA finds a 90-day compliance time for initiating the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety. Operators should also note that this AD does not require reporting of test findings. \n\n\tOperators should note that, although the telex only describes procedures for replacement of the squib circuit ground stud with a new squib circuit ground stud, the airplane manufacturer has advised the FAA that replacement with a standard built-up ground stud (nut and bolt type) is an acceptable alternative to replacement with a squib circuit ground stud. Therefore, the FAA has included the option of replacing the squib circuit ground stud with a standard built-up ground stud as an acceptable method of compliance with the requirements of this AD. \n\nDetermination of Rule's Effective Date \n\n\tSince 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\n\tAlthough 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\n\tComments 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\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 99-NM-188-AD." The postcard will be date stamped and returned to the commenter. \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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it 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 final regulatory 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\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:\n\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. 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: