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Safety Recommendation Details

Safety Recommendation A-00-106
Details
Synopsis: On 7/17/96, about 2031 eastern daylight time, Trans World Airlines, Inc. (TWA) Flight 800, a Boeing 747-131, N93119, crashed into the Atlantic Ocean near East Moriches, New York. TWA Flight 800 was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 121 as a scheduled international passenger flight from John F. Kennedy International Airport (JFK), New York, NY, to Charles de Gaulle International Airport, Paris, France. The flight departed JFK about 2019, with 2 pilots, 2 flight engineers, 14 flight attendants, and 212 passengers on board. All 230 people on board were killed, and the airplane was destroyed. Visual meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Review the design specifications for aircraft wiring systems of all U.S. -certified aircraft and (1) identify which systems are critical to safety and (2) require revisions, as necessary, to ensure that adequate separation is provided for the wiring related to those critical systems.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: EAST MORICHES, NY, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA96MA070
Accident Reports: In-flight Breakup Over the Atlantic Ocean Trans World Airlines Flight 800, Boeing 747-141, N93119
Report #: AAR-00-03
Accident Date: 7/17/1996
Issue Date: 9/19/2000
Date Closed: 1/13/2011
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s): Regulation, Wiring

Safety Recommendation History
From: NTSB
To: FAA
Date: 1/13/2011
Response: The NTSB reviewed the list of completed actions that the FAA described, including issuance of the Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety final rule, which was published on November 8, 2007; requirements implemented regarding wiring maintenance for newly type certificated and existing airplanes; and a variety of ACs concerning training for personnel who maintain electrical and wiring systems on airplanes. Although the NTSB believes that the FAA should continue to fund research into ongoing wire problems and potential technical means to address wire-related problems, the actions described meet the intent of Safety Recommendations A-00-106 and A-00-108, which are classified CLOSED -- ACCEPTABLE ACTION.

From: FAA
To: NTSB
Date: 7/27/2010
Response: Letter Mail Controlled 8/9/2010 11:09:24 AM MC# 2100271 - From J. Randolph Babbitt, Administrator: The FAA completed the following actions to ensure the safety of wiring systems and to reduce the chance of an in-flight fuel-tank explosion on transport category airplanes: On October 22, 2007 we issued a final rulemaking package entitled the Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS). The rule was published in the Federal Register on November 8, 2007 and became effective on December 10, 2007. This final rule introduced new maintenance, inspection, and design criteria for airplane wiring to address conditions that put transport airplanes at risk of wire failures, smoke, and fire. (enclosure 8) We added requirements for DAHs to develop maintenance and inspection requirements for the airplane wiring system. The DAH analyzes the zones of their airplanes for the presence of wire and for the likely accumulation of contaminant materials. The requirements are contained in section (25.1729) applicable to new type certificate and supplemental type certificate applicants, and in a new 14 CFR part 26, applicable to existing transport category airplanes. These rules require applicants to develop maintenance and inspection tasks to identify, correct, and prevent wiring conditions that introduce risk to continued safe flight. These tasks are required to be included in new lCAs for wiring and be compatible with ICAs for fuel tank systems. We also amended 14 CFR parts 91, 121, 125, and 129 operating rules to require operators to incorporate maintenance and inspection tasks for wiring into their regular maintenance programs and clarified existing requirements for fuel tanks. We updated 14 CFR part 25, subpart H to contain the majority of the certification requirements for airplane wiring systems, including new rules to improve safety in manufacture and modification. Many of the rules contained in subpart H are previously existing requirements moved from different parts of the regulations. Some areas were reworded to make it clear as it applies to wiring systems. Several of the rules in subpart H are recent. The rules in subpart H are meant to improve the safety of transport airplane wiring by ensuring a safe design. We issued guidance materials in the form of ACs that present one way, but not the only way, to comply with specific parts of these regulations. AC 120-94 presents a suggested curriculum for EWIS training. Existing § 121.375 required that certificate holders or anyone performing maintenance have a training program. This requirement ensures that anyone determining the adequacy of maintenance work (including inspectors) is fully informed about the procedures and techniques involved and is competent to perform them. AC 120-94 provides guidance for complying with § 121.375 as it applies to EWIS maintenance and inspection. In AC 120-94, we provide a suggested training program to address people who come in contact with airplane EWIS, and encouraged operators to include this training voluntarily. There are eleven other ACs associated with the EAPAS/FTS rule as guidance on different requirements contained in the rulemaking package. In all, the EAPAS/FTS rulemaking package contains over 70 new, revised, or renumbered regulations in 14 CFR parts 1,21,25,26,91, 121, 125, and 129. This comprehensive set of design, maintenance, and inspection requirements works in harmony to ensure the safety of transport category airplanes wiring systems, both in the existing and future fleets. I believe that the FAA has effectively addressed these safety recommendations, and I consider our actions complete.

From: NTSB
To: FAA
Date: 12/10/2003
Response: The Safety Board notes and commends the FAA for the wide variety of activities it has initiated in response to these recommendations, many of which have been included in the work of ATSRAC and activities related to the Enhanced Airworthiness Program for Airplane Systems (EAPAS). Safety Board staff attend ATSRAC meetings to discuss progress with FAA staff and regularly review ATSRAC products. However, although the FAA has initiated numerous actions, most of the efforts to date provide only guidance, rather than the needed changes to FAA requirements. The Safety Board is also concerned that some of the FAA's proposed regulatory revisions are inadequate. For example, the Board has learned that the proposed aircraft wiring systems inspection requirements will only mandate a visual inspection, despite FAA-sponsored studies that have shown that visual inspections may miss half (or more) of wiring defects. Visual inspections are inappropriate where access is not possible, and they may not detect stiffened insulation that is easily cracked or other changes in material properties. In addition, visual inspections cannot detect corroded pins in wire connectors, or systems in which the electrical resistance is increasing to unacceptable levels. With regard to the need for improved documentation and reporting of potentially unsafe electrical wiring conditions, the Board notes that the Air Transport Association (ATA) has established a new Subchapter 97 for wiring, and the FAA proposed that the code in Subchapter 97 be used as the second two digits included in the four-digit ATA code in service difficulty reports (SDR) whenever the problem identified relates to wiring. The FAA is developing guidance to identify the use of Subchapter 97 in its SDR system and is also developing an automated tool for the SDR system that will support trend analysis. The Safety Board believes these are positive steps in response to Safety Recommendation A-00-108 but notes that (1) the FAA's SDR system has not yet been rebuilt and (2) although the Subpart 97 code may be in the SDR system, the rest of the SDR system remains difficult to use to monitor electrical wiring system problems. Without accurate and usable data, underreporting of defects will hamper any cost-benefit analysis used to evaluate regulatory changes being considered as a result of these recommendations. With regard to the need to incorporate the use of new technology, such as arc-fault circuit breakers (AFCB) and automated wire test equipment, the Safety Board is disappointed that the productive research efforts in these areas will not result in new requirements to more broadly incorporate this technology into new and existing airplanes. For example, although the FAA cites the implementation of AFCB technology, this implementation will be limited. The Board also notes that 5 1/2 years after the FAA identified aging mechanical systems as an issue in the ATNSSP, the FAA has not yet completed research, let alone translated that research into changes in maintenance. The Board understands that by December 2003, the FAA plans to issue a notice of proposed rulemaking (NPRM) for all EAPAS regulatory revisions. When it is published, the Board will review the NPRM and provide comments. The Board's review of the NPRM and the final regulatory changes following the NPRM's issuance will provide the basis for the Board's determination of whether the FAA's action is responsive to the recommendations. In the interim, Safety Recommendations A-00-106 and -108 remain classified OPEN -- ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 4/8/2003
Response: Letter Mail Controlled 4/21/2003 4:53:44 PM MC# 2030213 - From Marion C. Blakey, Administrator: The Federal Aviation Administration (FAA) is continuing to address all elements of wire system concerns through the Enhanced Airworthiness Program for Airplane Systems (EAPAS). The following improvements are in process or have been completed: · In a proactive approach to increase awareness of wire installation and separation requirements and to deal with general issues of wiring maintenance practices, the FAA produced two training aids. An 8-hour interactive video training course, entitled "Aircraft Wiring Practices," was developed for FAA engineers, designated engineering representatives, aviation safety inspectors, and principal inspectors. The FAA also produced an Internet-based job aid entitled, "Aircraft Wiring Practices (Job Aid)," which is available to everyone dealing with wire installation issues. The job aid can be found at httn://www.academv.iccbi.gov/AIRDL/wiringcourse. · The FAA developed an interactive video training course entitled "Aircraft Wiring Practices" for airworthiness safety inspectors.. · The FAA published a policy statement (ANM-01-04 dated July 2, 2001) entitled "System Wiring Policy for Certification." The policy statement addresses wire installation drawings, safety analyses of wiring and wire bundles, and continued airworthiness considerations for wiring. In the policy statement, the FAA outlined requirements for improving installation drawings so that installers obtain a clear definition of airplane wiring configurations. Modifiers to the original airplane manufacturer's wiring system should demonstrate that installation specifications and routing practices for the wiring used is either the same as, or compatible with, originally approved standards. Specifically, wiring separation, wire types, wire bundle sizes, brackets, and clamping should be consistent with the original manufacturer's approved standards. · In addition to the tasks for enhancements to the current rules for design, operation, maintenance, and training requirements, the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) working groups are also working on the following tasks to develop and propose improvements as related to electrical wiring separation: - Determine if a comprehensive wire separation regulation, in addition to the existing requirements of 14 CFR 25.1353, should be included in the new wire system rule. The recommendations obtained from this task should include general requirements for all wire systems regarding wire separation. - Review 14 CFR 25.1309 and associated advisory circular, corresponding JAR-25 material, and related Aviation Rulemaking Advisory Committee recommendations. Submit a recommendation on whether or not particular methods of compliance with 14 CFR 25.1309 should be mandated in the new wire systems rule. The methods include, but are not limited to: § common mode analysis; § safety zonal analysis; and § particular risk analysis. - Provide recommendations on the need for the special identification of wire and/or wire bundles based on the airplane-level effect of failures of systems contained in a given wire bundle. - Provide comments and recommendations for inclusion of the following items in Appendix H to 14 CFR Part 25, Instructions for Continued Airworthiness: § Wire Separation Design Guidelines; § Special Identification Requirements; § Electrical Load Analysis; and § Enhanced Zonal Analysis Procedure..3 - Develop guidance for enhanced maintenance criteria for systems. - Assist in developing a Special Federal Aviation Regulation to address aircraft wiring maintenance problems. The ATSRAC working group report on "Enhanced Maintenance Criteria for Systems" was completed on July 15,2002, and the report on "Enhanced Training Program For Wire Systems" was completed on August 2, 2002. The reports on "Wire System Certification Requirements" and "Electrical Standard Wire Practices Manual" were completed in November 2002. These reports can be found at http://www.mitrecaasd.orp/atsrac. The FAA organized an internal rulemaking team to develop a notice of proposed rulemaking (NPRM) for all EAPAS regulatory enhancements when the ATSRAC recommendations are received and reviewed by the FAA. The FAA plans to publish the EAPAS NPRM by December 2003. The FAA regularly provides the EAPAS program updates to the ATSRAC public meetings. The Board's staff participates in these meetings and is aware of FAA's progress. I will keep the Board informed of the FAA's progress on this safety recommendation.

From: NTSB
To: FAA
Date: 5/17/2002
Response: In response to the FAA's first request, the Safety Board is concerned with any failure mode that could allow short circuiting as a result of inadequate wire separation. Such failure modes could result from normal aging, wear, and usage. The Board notes that, for example, Boeing specifications for protected systems require wire separation distances of 1/4- to 1/2-inch, depending on whether wires are installed in pressurized or unpressurized areas. However, inspections of in-service airplanes have found wire bundles that sagged greater than these required separation distances; therefore, any wires in such bundles that were subject to 1/4- or 1/2-inch separation criteria might not be in compliance with those criteria. Further, both direct and indirect effects of short circuits must be taken into account. For example, the Board found that arcing wire bundles damaged other wire bundles located more than 1 1/2 inches away from the arc. These examples are discussed in the Safety Board's accident report of the in-flight breakup of TWA flight 800 (NTSB/AAR-00/03). In response to the FAA's second question, the Safety Board believes that a critical system is any in which the inadvertent application or loss of power or signal to any wire associated with that system might result directly or indirectly in the loss of an airplane under any failure condition or combination of failure conditions. This definition of a critical system is consistent with 14 CFR 25.1309 and AC 25.1309, which specify that the occurrence of any failure condition that would prevent continued safe flight and landing be extremely improbable. However, the Safety Board notes that manufacturers vary in their definitions of which systems are critical, and the FAA should reduce these variations. For example, in contrast to Boeing's 1/4- or 1/2-inch separation criteria for certain systems, the Douglas Aircraft Company classified four systems (some of which are not protected under Boeing's criteria) as critical systems and specified at least 3 inches of separation from other wiring: · Fuel quantity indicating system (FQIS) and other fuel system wiring, · Fire warning systems, · Generator feeder cables, and · Electro-explosive devices. The Safety Board noted in the TWA flight 800 accident report that "there is no FAA regulation that specifies wire separation criteria or identifies which circuits must be protected." The Board is encouraged that the FAA is evaluating clearance criteria and other potential changes to emphasize that certain wiring may affect airplane safety (Enhanced Airworthiness Program for Airplane Systems [EAPAS] Item R.10). The Board found during the TWA flight 800 accident investigation that criteria considered acceptable by one manufacturer would not meet the minimum safety requirements of another manufacturer. Further, through the rulemaking action of April 19, 2001, the FAA is taking steps to protect the FQIS, which is one of the systems that the TWA flight 800 investigation found to be vulnerable. The Safety Board encourages the FAA to quickly complete action on this recommendation by identifying which other systems are critical to safety and requiring revisions to ensure that adequate separation is provided for the wiring related to those critical systems. Pending completion of the recommended actions, Safety Recommendation A-00-106 remains classified OPEN -- ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 5/24/2001
Response: Letter Mail Controlled 05/31/2001 9:08:49 PM MC# 2010450: - From Jane F. Garvey, Administrator: On October 17, 2000, the FAA's staff met with the Board's staff to discuss this safety recommendation, along with previously issued safety recommendations that resulted from this accident. During the meeting, the Board's staff clarified that this safety recommendation is a followup recommendation from the review of separation from the fuel quantity indication system (FQIS). The Board's staff indicated that there might be differences between major manufacturers of transport airplanes as to the assignment of criticality to systems such as FQIS. On January 4, 2001, the FAA's staff met with the Board's staff to provide an update of efforts to address all safety recommendations in an V'open" status that were issued as a result of this accident. The following information was related to the Board's staff: ??Safety Recommendation A-00-106 is closely related to Safety Recommendations A-98-l and -2, which address adequate clearance around electrical wiring (separation from flight control cables, hydraulic lines, oxygen lines, and fuel lines). The FAA is currently evaluating these issues and will use the results from its evaluation to develop a response to Safety Recommendation A-00-106. ??Enhancements to wire separation and identification for critical systems will be addressed in future rule changes to the 14 CFR Part 25 and in developing AC's, policy guidance, and training. During the meeting on January 4, 2001, the FAA asked that the Board provide the following information to address the issues raised in Safety Recommendation A-00-106 more effectively: ??Information regarding the type of failure modes that the Board is concerned with and used to support the issuance of Safety Recommendation A-00-106. ??Information regarding the Board's definition of "critical systems" to make sure that it matches the FAA's definition of "critical systems." I would appreciate receiving this information quickly so that we can address this safety recommendation more completely. I will keep the Board informed of the FAA's progress on this safety recommendation

From: FAA
To: NTSB
Date: 12/20/2000
Response: Letter Mail Controlled 12/26/2000 12:43:34 PM MC# 2001813 - From J. Randolph Babbitt, Administrator: The FAA will address the critical system wire separation and the results of that review in response to Safety Recommendation A-00-106, which was issued on September 19, 2000, as a result of the TWA 800 accident. Safety Recommendation A-00-106 asks that the FAA review the design specifications for aircraft wiring systems of all U.S.- certified aircraft and identify which systems are critical to safety and require revisions, as necessary, to ensure that adequate separation is provided for the wiring related to those critical systems. I will inform the Board of the results of the Learjet and Raytheon audits as soon as they are completed.

From: NTSB
To: FAA
Date: 12/5/2000
Response: FAA and Safety Board staff met on 10/17/00, to discuss these recommendations. The meeting initiated a dialogue that will lead to mutually agreeable actions for each of these recommendations. The FAA anticipates providing the Board with a complete response to these recommendations by 1/31/01. Pending submission of that complete response, A-00-105 through -108 are classified OPEN – ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 10/12/2000
Response: Letter Mail Controlled 10/16/2000 3:58:40 PM MC# 2001542 - From Jane F. Garvey, Administrator: Your staff has agreed to meet with FAA technical specialists on 10/17/00, to discuss these recommendations. This meeting will offer an opportunity to begin a dialogue between our agencies that can lead to mutually agreeable actions for each of these recommendations. After this meeting, the FAA will have a better understanding of the intent of these recommendations and be in a better position to provide detailed response to these recommendations. We anticipate providing the Board with a complete response to these recommendations by 1/31/01.