AD 98-21-11

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-700 and -800 series airplanes. This action requires a one-time inspection to determine the serial numbers of the fire detector assemblies and elements for the auxiliary power unit (APU) and engines, and replacement of the assemblies or elements with new or serviceable parts, if necessary. This amendment is prompted by a report indicating that certain fire detector elements were not checked for leaks during manufacturing and, therefore, may not have the correct set points for the fire warning system. The actions specified in this AD are intended to prevent failure of the APU or engine fire detection systems to detect a fire in a timely manner, which could result in egress of an APU or engine compartment fire to other parts of the airplane.

Final rule; request for comments

98-21-11 BOEING: Amendment 39-10819. Docket 98-NM-272-AD. \n\n\tApplicability: Model 737-700 and -800 series airplanes; line positions 1 through 81 inclusive, except line positions 73 and 80; 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 address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent failure of the auxiliary power unit (APU) or engine fire detection system to detect a fire in a timely manner, which could result in egress of an APU or engine compartment fire to other parts of the airplane, accomplish the following: \n\n\t(a)\tWithin 21 days after the effective date of this AD, perform a one-time inspection of the APU and engine fire detector assemblies to determine the serial number of the assemblies and the elements. Replace any fire detector assembly or element as required by paragraph (a)(1), (a)(2), or (a)(3) of this AD in accordance with procedures specified in Chapters 26-11-01-401 and 26-15-01-401 of the Boeing 737 Aircraft Maintenance Manual, as applicable. \n\n\tNOTE 2: The serial number of the fire detector assembly is stamped on the support tube. \n\n\t\t(1)\tIf any assembly having a serial number 100 through 999 inclusive is installed, prior to further flight, replace it with a new or serviceable assemblyhaving a serial number 1000 or higher.\n\n\t\t(2)\tIf any element of the APU fire detectors having a serial number 1 through 1999 inclusive is installed, prior to further flight, replace it with a new or serviceable element having a serial number 2000 or higher. \n\n\t\t(3)\tIf any element of the engine fire detectors having a serial number 1 through 4999 inclusive is installed, prior to further flight, replace it with a new or serviceable element having a serial number 5000 or higher. \n\n\t(b)\tAs of the effective date of this AD, no person shall install on any airplane an APU or engine fire detector assembly or element having a serial number listed in paragraph (b)(1), (b)(2), or (b)(3) of this AD. \n\n\t\t(1)\tFor the APU or engine fire detector assembly: Boeing part numbers S332T100-27, -28, -29, -30, -31, -38, -42, -43, and -44; Whittaker part numbers 902013, 902014, 902015-01, 902016-01, 902017-01, 902018-01, 902020, 902862, and 902864; serial numbers 100 through 999 inclusive. \n\n\t\t(2)For APU fire detector elements: Whittaker part numbers 8880-01, -02, and -03; serial numbers 1 through 1999 inclusive. \n\n\t\t(3)\tFor engine fire detector elements: Whittaker part numbers 8870-01, -02, -03, and -04; serial numbers 1 through 4999 inclusive. \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 3: 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(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 theairplane to a location where the requirements of this AD can be accomplished. \n\n\t(e)\tThis amendment becomes effective on October 21, 1998.

The FAA has received a report from the manufacturer of the auxiliary power unit (APU) and engine fire detectors installed on Boeing Model 737-700 and -800 series airplanes indicating that certain fire detector elements were not checked for leaks during manufacturing and may be leaking helium gas. Any leaking would cause the set point for the fire warning system to rise, which may lead to an undetected fire and delayed flight crew response. Failure of the APU or engine fire detection system to detect a fire in a timely manner, if not corrected, could result in egress of an APU or engine compartment fire to other parts of the airplane. \n\nFAA's Determination \n\n\tIn order to ensure that APU and engine fire detection assemblies and elements that were not checked for leaks during manufacturing are not installed on the affected airplanes, the FAA has determined that verification of the serial numbers of these components, and replacement of parts having certain serial numbers, is necessary. Accomplishment of these actions will adequately address failure of the APU or engine fire detection system. \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 Boeing Model 737-700 and -800 series airplanes of the same type design, this AD is being issued to prevent failure of the APU or engine fire detection system to detect a fire in a timely manner, which could result in egress of an APU or engine compartment fire to other parts of the airplane. This AD requires a one-time inspection to determine the serial numbers of the fire detector assemblies and elements for the APU and engines, and replacement of the assemblies or elements with new or serviceable parts, if necessary. The actions are required to be accomplished in accordance with the Boeing 737 Aircraft Maintenance Manual. \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 evaluatingthe 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 98-NM-272-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 betweenthe 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, 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: