FUEL TANK SAFETY / EWIS CONTINUATION TRAINING

Transcription

1 FUEL TANK SAFETY / EWIS CONTINUATION TRAINING Q3 & Q Page 1 of 15

2 CONTENTS: 1 Introduction 2 Fuel Tank Safety 3 Part 145 & Fuel tank safety 4 EWIS 5 Related Airworthiness Directives 6 Air Trans Flight Down to the wire Page 2 of 15

3 1. Introduction The purpose of this module is to refresh SFAR 88 & EWIS knowledge, other aircraft specific related information can be found in the relevant aircraft modules of this CBT package. This module also reminds us of the importance of CDCCL s and ALI s under SFAR Fuel Tank Safety With the introduction of the Fuel Tank Safety requirements Part 145 organizations are to provide Fuel Tank Safety training for their personnel Initially a Phase 1 training is required for all Part 145 related staff such as management, QA, maintenance staff, planners, engineering and stores Secondly a more detailed and specific phase 2 training is provided to maintenance staff, engineering and production planning. Engineers are reminded that they should have received training in both phase 1 and phase 2 FTS. This is detailed in PART 145:- Phase 1 + Phase 2 + Continuation training: Personnel of the Part-145 approved maintenance organisation required to plan, perform, supervise, inspect and certify the maintenance of aircraft and fuel system components specified in paragraph A). If you have not received phase 1 training previously Altitude Global Engineering Bulletin 26-Gen-028 covers the phase 1 FTS Awareness syllabus and can be provided with a read and sign record. Please contact the Compliance Department for details. Note: Phase 1 and Phase 2 equate to the same when detailed as level 1 and level 2. Since 1959 there have been 17 fuel tank ignition events, resulting in: 542 fatalities 11 hull losses 3 others with substantial damage. Page 3 of 15

4 Thai Airways Boeing 737 On March 2001, a B737, operated by Thai Airways, was destroyed by an explosion and fire at Bangkok International Airport, Thailand. After investigation, the NTSB has determined that the centre fuel tank exploded, shortly after the main fuel tanks were refuelled. The cause of the explosion was the ignition of the flammable fuel/air mixture in the centre fuel tank. The source of the ignition energy for the explosion could not be determined with certainty, but the most likely source was an explosion originating at the centre tank fuel pumps. NOTE: The pumps were operating dry (no fuel passing through them) at the time of the explosion! TWA Flight 800 Twenty minutes after taking off from New York's JFK International Airport on July 17, 1996, Paris-bound TWA Flight 800 exploded. All 230 passengers were most likely killed from what medical examiners described as "phenomenal whiplash". It is widely accepted that an explosion in the central fuel tank of the aircraft caused its destruction. However, it is unclear exactly what caused this explosion. The two key factors that contributed to the dangerous environment for the 25 year-old Boeing model were the condition of the aircraft s electrical hardware and the presence of a highly explosive fuel-air ratio in the central fuel tank. In each case, an ignition source occurred that has not been positively identified. Page 4 of 15

5 Electrical Arcing In search of answers to the question of ignition, the NTSB conducted an investigation into the state of electrical wiring in operational Boeing 747s and similar models from other manufacturers to see if a spark could occur in the central fuel tank. The findings from this investigation were discouraging. Between May of 1997 and July of 1998, the NTSB examined a number of existing jets, of which many were old, reaching ages up to 27 1 /2 years old. Findings include sharp metal shavings both on and between wire bundles, and three-quarter inch coatings of lint on wires, what NTSB investigators describe as syrup: a sticky combination of spilled beverages, leaking water and lavatory fluids, dust and other materials that build up over years of service. The presence of sharp metal shavings, which can be attributed to drilling, can strip insulation away from wires. As a result, the core conducting wires become exposed and enhance the likelihood of a spark. Exposed wires that are coated with "syrup" or metallic drill shavings can be dangerous because either substance can act as a conductor. Consequently, substances such as these could function as a base point for an electric arc, which could ignite the contents of a fuel tank. Auto ignition Another possible source of ignition is from the terminals of the FOIS wires in the central fuel tank on which copper sulphide can build up. This phenomenon has been observed in aging electrical systems, and is a result of the natural deterioration of wiring. The build-ups can become sources of localized heat. This can cause a threat because of auto ignition. If the localized heat source is hot enough, the fuel around it may reach a temperature at which it will automatically ignite. Another theory of how auto ignition could have occurred within the central fuel tank of TWA Flight 800 involves the scavenger pump and faulty check valves. Page 5 of 15

6 The scavenger pump is a possible source of ignition because it resides within the central fuel tank. NTSB officials believe that fuel was being transferred between tanks when the explosion occurred; suggesting that the scavenger pump in the central fuel tank was operating. If the scavenger pump was operating and its check valve was too tight, it may have allowed only fuel, and not vapour to pass through it, resulting in a concentration of vapour around the check valve of the scavenger pump.. The vapours have a lower auto ignition temperature than the liquid and the pump is a significant source of energy that could become hot enough to cause auto ignition of fuel vapour. Fuel Airworthiness Limitations Fuel Airworthiness Limitations are items arising from a systems safety analysis that have been shown to have failure mode(s) associated with an "unsafe condition" as defined in FAA's memo "SFAR 88 Mandatory Action Decision Criteria These AWL's are divided into two categories: CDCCL (Critical Design Configuration Control Limitations): These are critical fuel system design features which must be maintained in order to minimize the reaction of a fuel tank ignition source. CDCCLs are identified in the AMMs, CMMs. Some examples of CDCCLs are the bonding and grounding of fuel system components, and the routing of fuel system wiring. ALI s (Airworthiness Limitation Inspections): These are repetitive inspections/tasks which are required to help ensure that components/systems which are subject to degradation or damage do not deteriorate to the point where they may fail and create an ignition source in the fuel tanks. Some examples of ALI s are verification of fault current bonds, and inspection of wiring insulation and clamping. These tasks must be included in an operator's approved maintenance program schedule. The task interval may be quoted in any usage parameter (FH, FC or Calendar Time) depending on the cause of potential degradation that, if not detected and addressed, could lead to an unacceptable risk. Operators should pay particular attention to AWLs during modifications, as SFAR 88 imposes a more significant regulatory approval burden on ALI/CDCCL changes than many other maintenance program changes. Page 6 of 15

7 All changes to a CDCCL or ALI or a procedure involving a CDCCL or ALI must be approved by the appropriate regulatory office. 3. PART 145 and Fuel tank Safety Fuel tank safety is integral to Part It ensures that engineering staff are correctly trained not only in Human factors but also Fuel tank safety. AMC 3 to Part 145. A. 30(e). Additional training in fuel tank safety as well as associated inspection standards and maintenance procedures should be required for maintenance organisations technical personnel, especially technical personnel involved in the compliance of CDCCL tasks. AMC 145.A.42 (b): includes the requirement to verify CDCCL requirements when receiving and accepting components. The EASA Form 1 or equivalent identifies the status of an aircraft component. Block 12 Remarks on the EASA Form 1 in some cases contains vital airworthiness related information which may need appropriate and necessary actions. The receiving organisation should be satisfied that the component in question is in satisfactory condition and has been appropriately released to service. In addition, the organisation should ensure that the component meets the approved data/standard, such as the required design and modification standard. This may be accomplished by reference to the manufacturer s parts catalogue or other approved data (i.e. Service Bulletin). Care should also be taken in ensuring compliance with applicable airworthiness directives, the status of any life-limited parts fitted to the aircraft component as well as Critical Design Configuration Control Limitations. AMC 145.A.45(d): provides a note that when modifying maintenance procedures regarding CDCCL s this is considered a modification and requires Part 21 approval: For the use of alternative tools / equipment Important Note: Critical Design Configuration Control Limitations (CDCCL) are airworthiness limitations. Any modification of the maintenance instructions linked to CDCCL constitutes an aircraft modification that should be approved in accordance with Part 21. AMC 145. A 45(e) The maintenance organisation should: --- transcribe accurately the maintenance data onto such work cards or worksheets, or make precise reference to the particular maintenance task(s) contained in such maintenance data, which already identifies the task as a CDCCL where applicable. Page 7 of 15

8 4. EWIS AMC 145.A.45(g): special attention to be given for control of approved data regarding airworthiness limitations, etc: To keep data up-to-date, a procedure should be set up to monitor the amendment status of all data and maintain a check that all amendments are being received by being a subscriber to any document amendment scheme. Special attention should be given to TC related data such as certification life-limited parts, airworthiness limitations and Airworthiness Limitation Items (ALI), etc. AMC to Part-145: Appendix IV to AMC to 145.A.30 (e) and 145.B.10 (3) Fuel Tank Safety training: Provides instructions and information regarding the contents of Fuel Tank Safety training. It explains why we provide this training Phase 1 only: The group of persons representing the maintenance management structure of the organisation, the quality manager and the staff required to quality monitor the organisation. Personnel of the competent authorities responsible as per 145.B.30 for the oversight of Part-145 approved maintenance organizations specified in paragraph B). Phase 1 + Phase 2 + Continuation training: Personnel of the Part-145 approved maintenance organization required to plan, perform, supervise, inspect and certify the maintenance of aircraft and fuel system components specified in paragraph A). Some useful Manufacturer information regarding inerting of fuel tanks. Electrical Wiring Interconnect System Simply described EWIS is the term used for the basic maintenance requirements of aircraft wiring and electrical systems, with respect to the maintenance and associated working practices, general care, inspection standards, safety, housekeeping and repair of all electrical items (including wiring) on an aircraft The actual term EWIS has been derived from documentation issued by EASA in order to address aircraft general Wiring Standards. EWIS covers the Maintenance of A/C wiring and electrical components Its Associated practices for wiring maintenance General care of wiring on and around A/C Maintenance Inspection standards General wiring safety General A/C and wiring housekeeping Repair Techniques General Wiring Standards Aircraft Improvements to reduce known problems Page 8 of 15

9 EWIS was published by EASA by amendment 4 (ED Decision 2008/007/R of 29/08/2008) to AMC-20 General Acceptable Means of Compliance for Airworthiness of Products, Parts and Appliances. This document can be found via the following webpage. The amendment included the following headings:- AMC AMC AMC Programme to Enhance Aeroplane Electrical Wiring Interconnection System Maintenance Aeroplane Electrical Wiring Interconnection System Training Programme Development of Electrical Standard Wiring Practices Documentation This AMC was heavily based around maintenance providers and maintaining organisations with the emphasis being on enhancing maintenance procedures and inspection based on extensive research into aircraft wiring standards. Objective was to promote new Enhanced Zonal Analysis Procedures (EZAP). To ensure appropriate attention was given to aircraft wiring and its related maintenance.new Guidance for General Visual Inspections (GVI) and it touches on the issue of staff and their awareness and training. Below are the target group categories as listed in Annex III to ED Decision 2008/007/R of 29/08/2008 AMC 20-22, Aeroplane Electrical Wiring Interconnection System Training Programme, including the tables referring to the depth of knowledge to be covered for each group. Target Group 1: Qualified staff performing EWIS maintenance. Target Group 2: Qualified staff performing maintenance inspections on EWIS. Target Group 3: Qualified staff performing electrical/avionic engineering on in-service aeroplane. Target Group 4: Qualified staff performing general maintenance/inspections not involving wire maintenance (LRU change is not considered wire maintenance) Target Group 5: Qualified staff performing other engineering or planning work on in-service aeroplane Target Group 6: Other service staff with duties in proximity to electrical wiring interconnection systems Target Group 7: Flight Deck Crew Target Group 8: Cabin Crew Page 9 of 15

10 5. Related Airworthiness Directives US AD No.: Airworthiness Directives can be viewed at ATA 57 Wings - Fuel Tank Access Door - Replacement / Check / Maintenance or Inspection Program Revision Manufacturer/s: The Boeing Company Applicability This AD applies to all The Boeing Company Model , - 400, and -500 series airplanes, certificated in any category. Reason: This AD was prompted by a manufacturer's review that showed that the fuel tank access door at a certain wing buttock line did not have an engineered ground path with the mating wing structure. This AD requires replacing the fuel tank access door, doing a check of the electrical bond, doing related investigative and corrective actions if necessary, and revising the maintenance or inspection program by incorporating an airworthiness limitation (AWL). We are issuing this AD to address the unsafe condition on these products. US AD No.: Airworthiness Directives can be viewed at ATA 57 Manufacturer/s: Wings - Leading Edge Area - Modification The Boeing Company Applicability This AD applies to The Boeing Company Model , B, B SUD, B, C, F, , , D, F, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Special Attention Service Bulletin , Revision 2, dated February 22, Reason: This AD requires additional work to seal those drainage holes in the wing access panels. This AD was prompted by a design review following a ground fire incident and reports of flammable fluid leaks from the wing leading edge area onto the engine exhaust area. We are issuing this AD to address the unsafe condition on these products. Page 10 of 15

11 US AD No.: Airworthiness Directives can be viewed at ATA 57 Manufacturer/s: Wings - Fuel Tank Boundary Structure Wire Bundle Clamp Teflon Sleeves - Installation / Inspection The Boeing Company Applicability This AD applies to The Boeing Company airplanes, certificated in any category, as identified in the applicable service information specified in paragraphs (c)(1), (c)(2), (c)(3), and (c)(4) of this AD. (1) For The Boeing Company Model , -200LR, -300, - 300ER, and 777F airplanes: Boeing Service Bulletin A0050, Revision 4, dated September 28, (2) For The Boeing Company Model and -300 airplanes: Boeing Alert Service Bulletin A0051, dated May 15, (3) For The Boeing Company Model , -300, and -300ER airplanes: Boeing Alert Service Bulletin A0057, Revision 1, dated August 2, (4) For The Boeing Company Model , -200LR, -300, and -300ER airplanes: Boeing Alert Service Bulletin A0059, dated October 30, Reason: We are superseding Airworthiness Directive (AD) , which applied to certain The Boeing Company Model , - 200LR, -300, and -300ER series airplanes. AD required installing Teflon sleeving under the clamps of certain wire bundles routed along the fuel tank boundary structure, and cap sealing certain penetrating fasteners of the main and center fuel tanks. This AD requires certain inspections for certain airplanes, corrective actions if necessary, and installation of Teflon sleeves under certain wire bundle clamps. This AD was prompted by a report indicating that additional airplanes are affected by the identified unsafe condition. We are issuing this AD to address the unsafe condition on these products. Page 11 of 15

12 6. Air Trans Flight 956 ALT Fuel Tank Safety / EWIS Continuation Training. On November 29, 2000, the flight crew of a McDonnell Douglas DC-9-32, operating as AirTran Airways flight 956, executed an emergency landing at Hartsfield Atlanta International Airport (ATL). As the airplane was climbing through about 3,800 feet, the cockpit voice recorder (CVR) recorded popping sounds consistent with the sound of circuit breakers tripping, which continued for about 34 seconds. The flight crew also noted that the MASTER CAUTION light, several annunciator panel lights, the left and right fuel pressure lights, and the radio rack fan OFF annunciator lights had illuminated. The captain told the first officer to tell ATC that they wanted to level off at 4,000 feet and return to the airport because "right now we have electrical problems.".. Subsequently, about 2 minutes after take-off, the flight crew requested a return to ATL. After the landing, one of the flight attendants reported to the flight crew that smoke could be seen emanating from the left sidewall in the forward cabin; air traffic control (ATC) personnel also notified the flight crew that smoke was coming from the airplane. The flight crew then initiated an emergency evacuation on one of the taxiways. Airport rescue and firefighting assisted in subduing the fire. Of the 2 flight crewmembers, 3 flight attendants, and 92 passengers on board, 13 passengers received minor injuries. The airplane sustained substantial damage. Examination of the airplane revealed fire damage to the left forward areas of the fuselage and cargo compartment and damage to the cabin floor and sidewall. Fire damage was concentrated in an area just aft of the electrical disconnect panel located at FS 237, which is a junction panel for seven wire bundles. A soot trail extended aft from the radio rack vent, located just aft of the lavatory service panel. Soot was also present throughout the forward cargo compartment and on the cabin outflow valve near the rear of the airplane. Further examination of the interior area between the forward cargo compartment and the fuselage revealed bluish stains, similar in colour to lavatory rinse fluid on sidewall insulation blankets and components near FS 237. No drip shield, which was designed to protect the connectors at FS 237 from overhead fluid leakage, was installed over the FS 237 disconnect panel at the time of the accident, although the support brackets for the drip shield were in place. The drip shield was incorporated into the design of DC-9 series airplanes beginning with fuselage line number 271, which included N826AT. N826AT was delivered with the drip shield installed, but investigators could not determine why the shield was not in place at the time of the accident? The damaged wiring from the area around FS 237 was removed and sent to the Safety Board's materials laboratory for detailed examination. Beading was observed on the ends of many individual wires, which is consistent with heat damage from arcing. Each of the seven electrical connectors from the removed wire bundles was opened to determine the internal condition of the connector pins and grommet material. One connector exhibited more thermal damage than the other six and contained light-blue and turquoise-green crystalline deposits on the mating surfaces of its two sides Page 12 of 15

13 and around nearly all of its pins. This connector also exhibited evidence of pin-to-pin shorts. Laboratory tests of the grommet material from this connector revealed elevated levels of sulphate (a basic chemical constituent in lavatory rinse fluid, which can be very conductive) as compared to undamaged grommet material. Maintenance Information Records from the airplane's most recent C check, were reviewed for non- routine maintenance actions accomplished in the area of the forward lavatory or that mentioned lavatory fluid leaks in this area. The following items were noted: "Fwd lav dump chute flange very dirty and boot torn." Corrective action involved cleaning the forward lavatory dump chute flange and replacing its boot. "Fwd lav dump pull cable binds." Maintenance discovered that the cable was twisted. Corrective action involved installing a new cable. "Fwd lav shroud has blue water and filth under seat and backside of shroud." Corrective action involved cleaning the shroud seat and backside. "Fwd lav large floor pan has build-up of blue water stains, sealant, and grime." Corrective action involved cleaning the lavatory floor pan. The airplane's flight logbook was also reviewed to determine if any electrical anomalies involving items in the area of the fire had occurred during the several months before the accident. An October 12, 2000, write-up noted that the radio rack fan OFF annunciator light had illuminated. The corrective action was noted as "reset [circuit breaker]; Ops check fan, checks good as per [Maintenance Manual] " A November 20th write-up noted that the circuit breakers for the forward lavatory flush motor popped twice and that each time the flush motor operated, the circuit breakers popped. The corrective action was noted as "reset CB's and serviced lav to proper level. No defects noted. OK for svc." A November 28th (the day before the accident) write-up indicated that both the forward and aft lavatory circuit breakers popped when the lavatories were flushed. It further indicated that maintenance personnel suspected anomalies related to the jet way power supply, which was providing ground power to the airplane at the time, and that a check using power from the airplane's auxiliary power unit revealed no further anomalies. Follow-up AirTran's lavatory servicing procedures, which were in place at the time of the accident, stipulate that at least 3.5 gallons but no more than 4.0 gallons of rinse fluid should be added to each waste tank during lavatory servicing. Incompletely draining the tank can lead to excess fluid levels in the tank, which can then flow over the tank onto the lavatory floor; the fluid can then migrate to beneath the floor and drip onto components below, especially in areas where the floor panels are not properly sealed. Page 13 of 15

14 Boeing issued Alert Service Bulletin (ASB) DC9-24A190 on July 31, 2001, to all operators of DC-9 airplanes. The ASB recommends that operators visually inspect the connectors at the FS 237 disconnect panel for evidence of lavatory rinse fluid contamination and that they install a drip shield over the disconnect panel. To prevent waste tank overflows, Boeing also issued Service Letter DC?9-SL on March 22, 2002, to operators to stress the importance of properly sealing floor panels and adhering to lavatory servicing procedures specified in its DC-9 Maintenance Manual. 7. Down to the wire A healthy wire is perhaps the simplest, yet most important, element in an electrical system. Typically, a copper conductor (from 1 to 10 mm in diameter) is covered by a thin outer insulation (from 0.5 to 2 mm thick). Damaged insulation can expose the copper, giving rise to arcs, shorts, and electromagnetic emission and interference. Arcing occurs when current flows from the wire through ionized air to another conducting object, such as a second wire or the aircraft structure. A short circuit channels the current to an undesired conductor. If an external shield or braid protecting a wire is broken, the resulting antenna radiates the signal on the wire. As the wire ages, the insulation may become brittle and crack. Vibration can also chafe the insulation as wires vibrate against each other, a tie-down, or any other hard surface. Maintenance can also be hard on wires, as they may be nicked by workers' pliers, or bent beyond their tolerable radius, or sprinkled with metal drill shavings, chemicals or water, or even used as stepladders in hard-to-reach places. But perhaps the greatest concern is the breakdown of the wire's insulation when exposed to moisture. Insulation made from polyimide film, often referred to by the brand-name Kapton, was once thought to be the ideal wiring insulation and was widely used in both military and commercial aircraft during the 1970s and early '80s. A long-chain polymer that is both tough and durable, with a very high resistivity, Kapton provides excellent electrical insulation even at a thickness of less than a millimetre. What was not known initially was how Kapton held up to the moisture that tends to condense in or near aircraft wiring harnesses. This moisture is so prevalent that most wires are outfitted with a drip loop, which prevents water droplets from running down the cables and into critical electronics. Exposed to this moisture, Kapton's long polymer chains break down, and the insulation becomes brittle, developing small cracks that in turn let in even more moisture. So-called wet arcs begin to flow along these cracks, creating intermittent arcs too small to trip normal circuit breakers and often too small even to interfere with the signal transfer along the wire. Nonetheless, the tiny arcs do begin to carbonize the insulation, and carbon is an excellent conductor. Once enough carbon has built up ("enough" depends on the type and thickness of the insulation, the power handling of the wire, and other factors), there can be a large explosive flashover, with exposed wires spewing molten metal. Page 14 of 15

15 One would hope that Kapton cracks are relatively rare. Not so, according to a recent report by Lectromechanical Design Co. Using a proprietary tool called the DelTest, Letromec engineers tested the wiring in a Boeing 747, an Airbus A300, a Lockheed L-1011, and two DC-9s that were each over 20 years old and had been retired by commercial airlines within the previous six months. The results: 13 cracks per 1000 meters of wire in the L-1011, down to 1.6 cracks per 1000 meters in one of the DC-9s. With approximately 240 km of wire in the L-1011, this amounted to over 3000 cracks, each a potential cause of catastrophic arcing. Sometime after Kapton's problems came to light, in the late '70s, its use was cut back, and aircraft manufacturers began replacing it in some of the most critical wiring systems in planes in service. Alternatives to Kapton include polyvinylchloride, glass, nylon, polyester, and Teflon. But polyimide can still be found on thousands of aircraft in service, including the McDonnell Douglas MD-11 and older Boeing 737s and 767s. Page 15 of 15