Fuel Tank Safety (FTS) / Airworthiness Limitation (AWL) / Critical Design Configuration Control Limitation (CDCCL) AIRWORTHINESS MANAGEMENT - AVIONICS BACKGROUND TWA B747-131 Fligth-800 accident, involving Centre Wing Tank (CWT) explosions Investigations revealed penetration of 115 Vac electrical energy into the center fuel tank due to chaffed Fuel Quantity Indicating System (FQIS) wiring Together, with the inadequate electrical bonding of fuel system Components, separation of fuel system wiring, and fuel vapors, resulted in loss of the passenger lives and the airplane. Fuel tank explosions can only occur when an ignition source is in contact with flammable fuel vapor. 12/1/2013 2 AIRWORTHINESS MANAGEMENT - AVIONICS 12/1/2013 3 AIRWORTHINESS MANAGEMENT - AVIONICS FUEL TANK EXPOLSION INCIDENT March 2001, Thai Airways 737 CWT fuel pumps left running on when dry. Electrical ARC / fault resulted in Centre Tank explosion airplane was being prepared for a departure to Chiang Mai 149 passengers were waiting to board The fire erupted into the cabin, killing one cabin crew member and injuring 6 others The fire was put out in 60 minutes The airplane was destroyed 12/1/2013 4 AVIONICS 12/1/2013 5 .AIRWORTHINESS MANAGEMENT . AIRWORTHINESS MANAGEMENT .AVIONICS FUEL TANK EXPOLSION INCIDENTS China Air 737-800 While retracting slats during taxi. 12/1/2013 6 . one loosened slat fairing bolt penetrated into the CWT resulting CWT explosion. AIRWORTHINESS MANAGEMENT .AVIONICS FUEL TANK EXPOLSION INCIDENTS Philippines Airlines B737 1990 CWT explosion during push back 12/1/2013 7 . approx. 120 degree Jet-A1 fuel.B-747.B-737-300 Manila.AVIONICS COMMON FEATURES OF SIGNIFICANT ACCIDENTS/INCIDENT 1990 . Thailand 10 year old airplane Air Conditioning Packs running during Ground Operations Empty CWT explosion minutes after refueling CWT pumps operating at time of explosion 1 fatality Air Conditioning Packs running Air Conditioning Packs running during Ground Operations during Ground Operations Empty CWT explosion during pushback from gate CWT pumps operating at time Of Explosion 8 fatalities Empty CWT explosion During climb CWT pumps operating at time of Explosion 230 fatalities Jet-A fuel. 97 degree F ambient temp. approx.B-737-400 Bangkok.AIRWORTHINESS MANAGEMENT .(35’C) F tank temp. approx. Philippines Almost new airplane 1996 .(36’C) NO IGNITION SOURCE NO IGNITION SOURCE NO IGNITION SOURCE IDENTIFIED IDENTIFIED IDENTIFIED 12/1/2013 8 . JFK. TWA 800.USA 25 year old airplane 2001 .(49’C) ambient temp. 95 degree F Jet-A fuel. A fire hazard can be minimized by eliminating any one side of the fire triangle 12/1/2013 9 . The process in a fire is called oxidation. HEAT and FUEL Without one of these elements.AIRWORTHINESS MANAGEMENT .AVIONICS THE “FIRE” TRIANGLE Fire is a chemical process requires three things: OXYGEN. a fire cannot start or continue. AIRWORTHINESS MANAGEMENT . JAR 25. advising airplane manufacturers to carry out a design review of fuel tank system to avoid entry of any ignition source into the fuel tanks in compliance of FAR 25-901 & 25. National Aviation Authorities (NAA) using NT/POL/25/12.981 (a) and (b).901 / 25.1309 & Technical Guidance Leaflet (TGL) 47. 12/1/2013 10 .AVIONICS REGULATORY ACTION/ REQUIREMENTS Special Federal Aviation Regulation 88 (SFAR 88). and the airplane has either a maximum type certificated passenger capacity of 30 or more. or a maximum type certificated payload capacity of 7. 12/1/2013 11 . This SFAR also applies to applicants for type certificates. the effective date of this SFAR. amendments to a type certificate. and supplemental type certificates affecting the fuel tank systems for those airplanes identified above.500 pounds or more. 2001. and supplemental type certificates that may affect the airplane fuel tank system. and the certificate was not issued before June 6.AVIONICS SFAR No.AIRWORTHINESS MANAGEMENT . 88--Fuel Tank System Fault Tolerance Evaluation Requirements Applicability the holders of type certificates. if the application was filed before June 6. for turbine-powered transport category airplanes. 1958. provided the type certificate was issued after January 1. 2001. (b) Develop all maintenance and inspection instructions (c) Submit a report for approval to the FAA Airplane Certification Office (ACO) 12 12/1/2013 .901 and 25.AVIONICS SFAR No.AIRWORTHINESS MANAGEMENT . 88--Fuel Tank System Fault Tolerance Evaluation Requirements Compliance (a) Conduct a safety review of the airplane fuel tank system to determine that the design meets the requirements of §§ 25.981(a) and (b). c.” Critical Design Configuration Control Limitations (CDCCL).981 Fuel tank ignition prevention a. b. to prevent development of ignition sources within the fuel tank system and must be included in the Airworthiness Limitations section of the Instructions for Continued Airworthiness. inspections. The fuel tank installation must include either: (1) Means to minimize the development of flammable vapors in the fuel tanks (in the context of this rule. “No ignition source may be present at each point in the fuel tank or fuel tank system where catastrophic failure could occur due to ignition of fuel or vapors. or other procedures must be established.AVIONICS FAR §25.AIRWORTHINESS MANAGEMENT .” 12/1/2013 13 . as necessary. or (2) Means to mitigate the effects of an ignition of fuel vapors within fuel tanks such that no damage caused by an ignition will prevent continued safe flight and landing. “minimize'' means to incorporate practicable design methods to reduce the likelihood of flammable vapors). Fuel vapors become flammable when they are mixed in certain proportions with oxygen. and are under specific temperature and pressure conditions. some fuel tanks have a significantly higher exposure to flammable vapors than other tanks.AIRWORTHINESS MANAGEMENT .AVIONICS THE CONCEPT OF IGNITION SOURCE PREVENTION Fuel tank explosions can only occur when an ignition source is in contact with flammable fuel vapor. 12/1/2013 14 . Airplane manufacturer’s reviewed the airplane fuel system designs to meet the above requirements.AVIONICS THE CONCEPT OF IGNITION SOURCE PREVENTION First Line of Defense to prevent recurrence of such events. a number of service Bulletins (SBs) /Production Modifications (Production Revision Record: PRR) have been introduced for incorporation on Production and In-Service airplanes. or an Ignition Mitigation Means (IMM). trying to build the airplane fuel system design immune to such occurrences. 12/1/2013 15 . which exceed the average flammability exposure level (> 7%). FAA legislation requires that airplane types that have fuel tanks.AIRWORTHINESS MANAGEMENT . specified in the rule shall be fitted with either a Flammability Reduction System (FRS). service airplane retrofit. 12/1/2013 16 .AVIONICS THE CONCEPT OF IGNITION SOURCE PREVENTION EASA has issued a Safety Information Bulletin (SIB 2010-10) which mandates the installation of a FRS on production airplane subject to high flammability exposure and manufactured after 31st December 2011. EASA will publish a Notice of Proposed Amendment (NPA) by mid 2011 to address the in.AIRWORTHINESS MANAGEMENT . AIRWORTHINESS MANAGEMENT . fifty percent (50%) of each operator's fleet of airplane are to be completed within 4 years of release of the Service Bulletins i.5 percent is considered Oxygen deficient. by 2014.5 percent. Monitoring these figures is critical to the safety of the maintenance crew. Oxygen concentrations should be between 19.e.5 and 23.AVIONICS THE CONCEPT OF IGNITION SOURCE PREVENTION Compliance Target In relation to the affected airplane. while levels above 23. One hundred percent (100%) of each operator's fleet of airplane are to be completed within 7 years after the release of the Service Bulletins i. by 2017.e. Level below 19. 12/1/2013 17 . NOTE: Portable gas detectors are used to monitor Oxygen and flammable vapor concentrations within the fuel tanks.5 percent will significantly increase the risk of fire and/or explosion. AVIONICS A Flammability Reduction System (FRS) FRS is a system that is designed to prevent fuel vapors from being in a flammable condition A practical Flammability Reduction System (FRS) will reduce fuel tank oxygen content to below the level that will support combustion (approach being adopted by Airbus). 12/1/2013 18 . Boeing has developed Nitrogen Generation System (NGS) to satisfy FRS requirement.AIRWORTHINESS MANAGEMENT . Such a technology is used on small military airplane but is not considered sufficiently robust for use in large commercial airplane and as such is not being pursued by Airbus or Boeing.AIRWORTHINESS MANAGEMENT .AVIONICS An Ignition Mitigation Means (IMM) IMM is a system that detects an ignition source and releases a fire suppressant to prevent the development of a fire. 12/1/2013 19 . This requirement ensures proper documentation of any maintenance action performed on the airplane and / or its components for safety.AIRWORTHINESS MANAGEMENT . reliability and maintainability.AVIONICS CHANGES TO “INSTRUCTIONS FOR CONTINUING AIRWORTHINESS” (ICA) Second Line of Defense of the FTS regulations account for this situation and requires updating of Instructions for Continued Airworthiness (ICA) / Airplane Maintenance Program for all the type certificated airplane to avoid any likelihood of compromise / violation of the fuel system design criteria during any scheduled and / or unscheduled maintenance. AWL / CDCCL tasks were introduced by airplane manufacturers in Maintenance Planning Documents AND have already been incorporated into the PIA’s fleet maintenance program. 12/1/2013 20 . AIRWORTHINESS MANAGEMENT . structural Airworthiness Limitation Items (ALI) and systems Certification Maintenance Requirements (CMR) comprise the Airworthiness Limitation Section which satisfies the regulatory requirements. 12/1/2013 21 . These requirements.AVIONICS CHANGES TO “INSTRUCTIONS FOR CONTINUING AIRWORTHINESS” (ICA) Boeing MPD section-9 is related to Airworthiness Limitations (AWL) which describes the Fuel Airworthiness Limitation Items (ALIs) and the associated CDCCL tasks. together with the Life Limits / Monitored Parts. Airbus / ATR publishes “Airworthiness Limitations” (ALS) section -5 which is related to Fuel Airworthiness Limitations (FAL). 12/1/2013 22 .AIRWORTHINESS MANAGEMENT . techniques and practices as prescribed is required to ensure the ALI is complied with. Any use of methods. Strict adherence to methods. techniques or practices not contained in these ALIs must be approved by the applicable regulatory agency.AVIONICS Airworthiness Limitation Items (ALIs) ALIs identify inspection tasks related to fuel tank ignition source prevention which must be done to maintain the design level of safety for the operational life of the airplane. These ALIs are mandatory and cannot be changed or deleted without the approval of applicable regulatory agency. could interact with the fuel system in such a way that an unsafe condition would develop without this limitation.AVIONICS Critical Design Configuration Control Limitations (CDCCLs) CDCCLs are a means of identifying certain design configuration features intended to preclude a fuel tank ignition source for the operational life of the airplane.” 12/1/2013 23 .AIRWORTHINESS MANAGEMENT . if a failure condition were to develop. CDCCLs are mandatory and cannot be changed or deleted without the approval of the applicable regulatory agency. “A critical fuel tank ignition source prevention feature may exist in the fuel system and its related installation or in systems that. Any use of parts. techniques.methods. and practices as prescribed is required to ensure compliance with the CDCCL. techniques or practices not contained in the applicable CDCCL must be approved by the FAA office that is responsible for the airplane model Type Certificate.AIRWORTHINESS MANAGEMENT .AVIONICS Critical Design Configuration Control Limitations (CDCCLs) Strict adherence to configuration. 12/1/2013 24 . . methods. or applicable regulatory agency. AVIONICS Certification Maintenance Requirements (CMRs) A CMR is a required periodic task.AIRWORTHINESS MANAGEMENT . numerical analysis conducted to show compliance with catastrophic and hazardous failure conditions. 12/1/2013 25 . CMRs usually result from a formal. established during the design certification of the airplane as an operating limitation of the type certificate. AIRWORTHINESS MANAGEMENT .AVIONICS Sample of AWL / FAL for B777 12/1/2013 26 . Reference AMM 28-42-31 pb 401 28-42-32 pb 401 28-42-33 pb 401 Applicability ALL ALL ALL Air gap between a fuel quantity indicating probes and the airplane structure.AIRWORTHINESS MANAGEMENT . 2 Separation of fuel quantity and level indicating system wiring from other wiring. To prevent cross coupling of high voltage transients and thereby keep unsafe ignition energies from inside the tank it is required that operators obey the wire routing and separation standards given in the Electrical Standard Practices Manual (ESPM).AVIONICS Sample of AWL / FAL for A310 CDCCL 1 Requirement Critical to prevent spark generation during lightning strike conditions and must not be compromised The gap stated in the relevant maintenance procedure in the AMM must be achieved during installation of a fuel quantity probe. ESPM 20-10-00 20-33-20 20-33-21 20-33-22 ALL ALL ALL ALL 12/1/2013 27 . AIRWORTHINESS MANAGEMENT .AVIONICS Sample of AWL / FAL for A310 CDCCL 3 Direct bonding on items of equipment inside a fuel tank. Reference AMM 28-00-00 pb 401 28-11-21 pb 401 28-11-22 pb 401 28-11-24 pb 401 28-11-32 pb 401 28-12-21 pb 401 28-12-33 pb 401 28-12-34 pb 401 28-21-13 pb 401 28-21-21 pb 401 28-24-31 pb 401 28-25-15 pb 401 28-27-12 pb 401 28-43-21 pb 401 28-46-21 pb 401 Applicability ALL ALL ALL ALL A310-300 ALL A310-300 A310-300 ALL ALL ALL ALL A310-300 ALL ALL 12/1/2013 28 . Requirement Direct bonding is critical to prevent spark generation during component failure and lightning strike conditions and must not be compromised Direct bonding in fuel tanks must be carried out during component installation to the appropriate bonding method and standard stated within the installation procedure in the AMM. Repair and overhaul of fuel pumps must be carried out in accordance with the equipment manufacturer’s maintenance instructions or other maintenance instructions acceptable to the certifying authority. CMM 28 09 01 28 24 11 ALL ALL 12/1/2013 29 . friction etc.AIRWORTHINESS MANAGEMENT .AVIONICS Sample of AWL / FAL for A310 CDCCL Requirement Reference Applicability 4 Safety critical features of fuel pumps These features must be maintained throughout the full life of the fuel pump to avoid the possibility of generation of an ignition source by overheating or sparks caused by arcing. 12/1/2013 30 .AVIONICS MANAGEMENT / CONTROL OF CDCCL Refer Doc ref # PIA/CDCCL/SFAR88 for detailed procedure for the Management & Control of CDCCL in PIA.AIRWORTHINESS MANAGEMENT . or overheating of the CWT fuel pumps. It is the responsibility of certifying staff / maintenance personnel to ensure that the above stated CDCCL configurations are maintained to reduce the risk of any ignition source penetration into the fuel tank (s). If any of these CDCCL is compromised. This in turn may result in fuel tank explosion. this may lead to wire chaffing. fault current (short circuit). This requirement has been addressed both by Airbus & Boeing by introduction of new logic circuitry to avoid dry running on CWT fuel pumps.AIRWORTHINESS MANAGEMENT . Introduction of Ground Fault Interrupter (GFI) relays also ensures NO overheating / fault current in the fuel pump circuitry. 12/1/2013 31 .AVIONICS MANAGEMENT / CONTROL OF CDCCL Dry running of the fuel pumps should not be allowed as it has already resulted in catastrophic incidents. AIRWORTHINESS MANAGEMENT .AVIONICS MANAGEMENT / CONTROL OF CDCCL 12/1/2013 32 . materials. repair or overhauling of a fuel system component should be used accordingly. jigs. Tools. 12/1/2013 33 . test equipment required for servicing.AVIONICS OVERHAUL SHOP CONTROL FOR CDCCL Fuel pumps CMM have also been revised in compliance of CDCCL requirements and provides specific instructions / procedures.AIRWORTHINESS MANAGEMENT . kits. AIRWORTHINESS MANAGEMENT .AVIONICS 12/1/2013 34 . work instructions provided by the AD / SB or task card should be revised / corrected in coordination with Airworthiness Management Division to preclude any chance of CDCCL violation. SBs. and ECO which have an effect on any of the CDCCL requirements. and if.AIRWORTHINESS MANAGEMENT .AVIONICS AD/ SB Control for CDCCL AD/SB evaluation check list was updated to include a clause to check whether the literature under evaluation affects CDCCL or not. A data base will be updated to have a record of all the ADs. 12/1/2013 35 . it is confirmed that a CDCCL / AWL is directly or indirectly affected. Certifying staff / maintenance personnel should assess the affect of the current activity on any of the AWL/CDCCL. FQI Tank unit. harnesses.AVIONICS AD/ SB Control for CDCCL Scheduled / unscheduled repair schemes control Any scheduled /un-scheduled locally prepared repair scheme should be examined for effect on any of the CDCCL item(s). Same level of understanding is required by shop personnel involved in the servicing / repair / overhaul of Fuel pumps. Fuel Quantity Indicating Computer (FQIC).AIRWORTHINESS MANAGEMENT . Fuel Quantity Processor Unit (FQPU). 12/1/2013 36 . AVIONICS AD/ SB Control for CDCCL Maintenance Program Control for CDCCL Inspections/ tasks introduced through Locally generated task cards as per requirements of an AD.AIRWORTHINESS MANAGEMENT . This exercise should be continued in future as well. 12/1/2013 37 . to sort out the newly introduced tasks for having an impact on the CDCCL. inspection SB. PIA fleet Maintenance program should be scrutinized on a regular basis upon receipt of MPD revision. or any other local operational /maintenance requirement also requires assessment whether it affects the CDCCL or not. CDCCL warning notes have also been introduced in AMM and Components Maintenance Manuals (CMM). All certifying staff / maintenance personnel are required to consult concerned AMM /CMM (as applicable). 12/1/2013 38 .AIRWORTHINESS MANAGEMENT .AVIONICS MAINTENANCE DATA .MANUAL CONSULTATION Use of updated / latest maintenance data is of utmost importance for maintaining FTS design criteria / CDCCL. Air Transport Association of America (ATA) Chapter 47 has been assigned for FRS / NGS in concerned airplanes Airplane Maintenance Manuals (AMM). AIRWORTHINESS MANAGEMENT .AVIONICS 12/1/2013 39 . AVIONICS 12/1/2013 40 .AIRWORTHINESS MANAGEMENT . AIRWORTHINESS MANAGEMENT .AVIONICS 12/1/2013 41 .