introduction of the sfar 88. introduction with the introduction of the fuel tank safety requirements...
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INTRODUCTION OF THE SFAR 88
INTRODUCTIONWith the introduction of the Fuel Tank Safety requirements Part 145 organizations are to provide Fuel Tank Safety training for theirpersonnel
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.
The purpose of this document is to comply with the phase 1 training requirement and to inform you of the Fuel Tank Safety history background and the (upcoming) changes in maintenance andregulatory procedures
INTRODUCTIONYou are therefore required to read this document and to take notice ofits contents.After reading the document you are required to complete the examination.Furthermore you are requested to complete the Course Evaluation Form.
If you have any questions regarding the information detailed in thisdocument please feel free to contact the QA department.
BACKGROUND INFORMATION
General
• Since 1959 there have been 17 fuel tank ignition events, resulting in:
• 542 fatalities
• 11 hull losses
• 3 others with substantial damage.
Causes• 3 unknown• 4 caused by external wing fires• 4 electrostatics• 2 lightning• 2 pumps or wiring suspected• 1 by small bomb• 1 maintenance action
BACKGROUND INFORMATION
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 center fuel
tank exploded, shortly after the main fuel tanks were refueled. • The cause of the explosion was the ignition of the flammable fuel/air
mixture in the center 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 center tank fuel pumps.
NOTE: The pumps were operating dry (no fuel passing through them) at the time of the explosion!
BACKGROUND INFORMATION
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.
BACKGROUND INFORMATION
• Researchers examined retrieved parts of the airplane and other similar models to seek explanations for Flight 800's explosion.
• It has been billed as the longest and most expensive accident investigation in American aviation history.
• There were several factors that made TWA Flight 800 a ticking time bomb.
• The two key factors that contributed to the dangerous environment for the 25 year-old Boeing model 747-131 were the condition of the aircraft’s electrical hardware and the presence of a highly explosive fuel-air ratio in the central fuel tank.
BACKGROUND INFORMATION
• The central fuel tank, which is capable of holding 13,000 gallons of jet fuel, only contained 50 gallons at the time it exploded, meaning that it was less than one-half percent full.
• TWA Flight 800 was using Jet A fuel, which is most commonly used for commercial jets. The central fuel tank is located on the underside of the fuselage, directly between the wings.
BACKGROUND INFORMATION
WHAT CAUSED THE CRASH OF TWA 800?• The National NTSB (Transportation Safety Board) considered TWA
800 the “most extensive and encompassing accident investigation ever undertaken by the safety board."
• The NTSB determined that the probable cause of the TWA Flight 800 accident was an explosion of the CWT (Center Wing Fuel Tank), resulting from ignition of the flammable fuel/air mixture in the tank.
• The source of ignition energy for the explosion could not be determined with certainty.
• However, of the sources evaluated by the investigation, the most likely was a short circuit outside of the CWT that allowed excessive voltage to enter through electrical wiring associated with the fuel quantity indication system.
BACKGROUND INFORMATION
The Ignition Source • Upon realizing that the central fuel tank of TWA Flight 800 exploded
and that the explosion was not likely by a bomb, the NTSB focused on finding the source of ignition.
• However, after scrutinizing all of the recovered wreckage, which accounts for over 95 % of the plane, they found nothing to support any plausible theory of ignition.
• The investigation focused on examining the electrical wiring near the central fuel tank, which consists largely of wiring for the FOIS (Fuel Quantity Indicating System) and for control of the fuel pumps.
• Unfortunately, most of this wiring was burned or damaged from the explosion, thus hindering an analysis into the role that it could have played in causing the explosion.
• However, this did not leave the NTSB completely in the dark concerning ignition sources.
• Electrical arcing and auto ignition are two source theories that were tested by the NTSB.
BACKGROUND INFORMATION
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.
BACKGROUND INFORMATION
• 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.
BACKGROUND INFORMATION
• The NTSB initiated simulations with these conditions to see if it was possible to create an electrical arc.
• In one rare case, when bare wires were bundled close to each other, an arc was created.
• The phase of electrical energy necessary to ignite fuel vapors is defined in various standards.
• The generally accepted value is 0.2 milli-joules. An adequate margin needs to be considered, when evaluating the maximum allowable energy phase for the fuel tank design.
BACKGROUND INFORMATION
Auto ignition• Another possible source of ignition is from the terminals of the FOIS
wires in the central fuel tank on which copper sulfide can build up. • This phenomenon has been observed in aging electrical systems,
and is a result of the natural deterioration of wiring. • The buildups 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.
BACKGROUND INFORMATION
• 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 vapor to pass through it, resulting in a concentration of vapor around the check valve of the scavenger pump. .
• The vapors 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 vapor.
BACKGROUND INFORMATION
• Guidance provided in FAA AC25 - 8 "Auxiliary Fuel Systems Installations" has defined hot surfaces which come within 30 degrees Centigrade (50F) of the autogenous ignition temperature of the fuel air mixture for the fluid as ignition sources.
• Surface temperatures not exceeding 200C have been accepted without further substantiation against current fuel types
BACKGROUND INFORMATION
• Subsequent to accidents involving Fuel Tank System explosions in flight (Boeing 747-131 flight TWA800) and on the ground, the FAA (United States Federal Aviation Administration) published Special Federal Aviation Regulation 88 (SFAR88) in June 2001.
• SFAR 88 required a safety review of the aircraft Fuel Tank System to determine that the design meets the requirements of FAR § 25.901 and § 25.981 (a) and (b) and develop maintenance and inspection instructions that operators would use to ensure continued
fuel tank safety.
SFAR 88
• A similar regulation has been recommended by the European JAA (Joint Aviation Authorities) to the European National Aviation Authorities in JAA letter 04/00/02/07/03-L024 of 3 February 2003.
• The review was requested to be mandated by European National Airworthiness Authorities using JAR § 25.901 (c), § 25.1309.
• In August 2005 the EASA (European Aviation Safety Agency) published a policy statement on the process for developing instructions for maintenance and inspection of Fuel Tank System ignition source prevention that also included the EASA expectations with regard to compliance times of the corrective actions on the unsafe and the not unsafe part of the harmonized design review results.
SFAR 88
• On a global scale the TC (Type Certificate) holders committed themselves to the EASA published compliance dates (see EASA policy statement).
• The EASA policy statement was revised in March 2006 resetting the date of 31 December 2005 for the unsafe related actions to 1 July 2006.
• 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 2003-112-15 "SFAR 88 – Mandatory Action Decision Criteria".
• These are identified in Failure Conditions for which an unacceptable probability of ignition risk could exist if specific tasks and/or practices are not performed in accordance with the manufacturers requirements.
SFAR 88
• This EASA Airworthiness Directive mandates the Fuel Airworthiness Limitations CDCCL (Comprising maintenance inspection tasks and Critical Design Configuration Control Limitations) for the type of aircraft, that resulted from the design reviews and the JAA recommendation and EASA policy statement mentioned above.
SFAR 88
Enhanced Airworthiness Program• The FAA and EASA have indicated that operators must train their
maintenance and engineering personnel regarding the changes brought about by SFAR 88.
• See EASA EO Decision No 2007/001/R, 2007/002/, 2007/003/R of the Executive Director of the Agency.
SFAR 88
Modifications of existing systems and introduction of new technologies for the fulfillment of the SFAR 88 specifications• Specific control specifications are demanded in the aircraft
documentation. • Possible damages can be discovered at SFAR 88 relevant
components and system components.
• Example:• Fuel Pumps Internal components of the "stator wiring" as a source of spark discharge.Damages at external cables and eroded connections as a source of spark formation.Avoidance of "fuel pump" operation in empty fuel tanks.
SFAR 88
• Fuel Quantity Indication SystemFaulty insulation of the cables and corroded connections.Unprotected laying of FQI cables together with high voltage lines.
• Fuel Quantity Indication ProbesContaminations in the fuel tanks produce a risk of short circuits.
• Bonding StrapsFailure because of corrosion or improper fastening.Failure because of mechanical wear and tear due to movements.
• Pneumatic system failuresDue to leakages of the "pneumatic system" the components of the fuel tanks are heated up.
SFAR 88
Reassessment and revision in the maintenance and overhaul program and in the documents• Selection of available and scheduled changes in the maintenance
specifications for "fuel tank maintenance" and "inspection":• Improved instructions for the topic "bonding", as well as regular
"bonding checks",• Leakage inspection at the fuel center tank and condition of the
"vapor seals" and "drip shields",• Execution of "FQI probe gap check" before closing fuel tanks.• Execution of bonding check" and "control of foreign objects" before
closing fuel tanks,
SFAR 88
• Leak check after disturbances at a "hot air duct" nearby fuel tanks,• Maintenance and overhaul on "fuel pumps" only in accordance with
CMM,• Measures for avoiding dry running of "fuel pumps" in accordance
with AMM,• A redundant lay-out in safety relevant areas of "bon ding straps",• In SFAR 88 relevant areas an increased execution of "double
checks",
SFAR 88
• This SFAR 88 rule required manufacturers to enhance airplane maintenance programs to maintain design features that are necessary to prevent an ignition source in the fuel tanks.
• The result of this effort was the incorporation of several AWLs (Airworthiness Limitations) into maintenance program documents.
SFAR 88
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 creation 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.
SFAR 88
• 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.
• All changes to a CDCCL or ALI or a procedure involving a CDCCL or ALI must be approved by the appropriate regulatory office.
• The relevant authority varies by country and model.
SFAR 88
Regulatory Changes• FAA issued Special Federal Aviation Regulation No 88 for turbine
power transport category airplanes after January 1, 1958, that meet the following criteria:
• Passenger capacity of 30 or more, or • Maximum payload capacity of greater than 7500 pounds • The SFAR requires that all TC and STC holders accomplish the
following tasks:• Conduct a safety review of the fuel tank system to determine that
the design meets the requirements of FAR §25.901 and §25.981(a) and (b).
• If design does not meet the above requirements, identify design changes required to bring fuel system components into compliance.
• Develop all maintenance and inspection instructions required to maintain the design features of the fuel system that preclude the existence or development of an ignition source within the fuel tank.
SFAR 88
• JAA INT/POL 25/12 addresses the same for TC and STC-holders of JAA Member States.
• EASA has issued changes to the Applicable Means of Compliance (AMC) of Part 66, Part M, and Part 145 to address fuel tank safety issues:
• Please note that the basic regulations as specified in Part 66, Part M and Part145 have not changed.
• Part 66 (Decision 2007/003/R) provides changes in the AMC of Part 66 to include CDCCL items in the Part 66 training requirements
• Part M (Decision 2007/001/R) provides changes in the AMC of Part M regarding CDCCL
SFAR 88
• Part 145 provides changes in the AMC of Part 145 to include maintenance requirements regarding CDCCL items: (new text
marked in Red) • AMC 145.A.30(e): to include training for personnel regarding
CDCCL:• New paragraph 11:• 11. Additional training in fuel tank safety as well as associated
inspection standards and maintenance procedures should be required of maintenance organisations’ technical personnel, especially technical personnel involved with the compliance of CDCCL tasks.
• EASA guidance is provided for training to maintenance organisation personnel in Appendix IV to AMC to 145.A.30(e) and 145.B.10(3).
SFAR 88
SFAR 88• AMC 145.A.42(b): to include the requirement to verify CDCCL
requirements when receiving and accepting components:• The EASA Form 1 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 exercised in ensuring compliance with applicable airworthiness directives, and the status of any life limited parts fitted to the aircraft component as well as Critical Design Configuration Control Limitations.
SFAR 88• AMC 145.A.45(b): include the requirement that the Part 145
organization should hold the CDCCL requirement of the products (aircraft, engines and components) within the Part 145 approval:
• Except as specified in sub-paragraph 5, each maintenance organisation approved under Part-145 should hold and use the following minimum maintenance data relevant to the organisation’s approval class rating. All maintenance related Implementing Rules and associated AMCs , approval specifications and Guidance Material, all applicable national maintenance requirements and notices which have not been superseded by an Agency requirement, procedure or directive and all applicable EASA airworthiness directives plus any non-national airworthiness directive supplied by a contracted non-EU operator or customer as well as Critical Design Configuration Control Limitations
• AMC 145.A.45(d): to provide a note that when modifying maintenance procedures regarding CDCCL’s this is considered a modification and requires Part 21 approval:
• Add note:• 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.
SFAR 88
SFAR 88
AMC 145.A.45(e)
Added
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.
SFAR 88
• AMC 145.A.45(g): special attention to be given for control of approved data regarding airworthiness limitations, etc:
• 1.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.
• 2. ….
SFAR 88• AMC 145.A.65(b)(3): The Part 145 organization is to ensure that
during maintenance no CDCCL items are compromised• This includes the requirement to provide training to staff regarding
CDCCL items :• new paragraph 4:• 4. The maintenance organisation should ensure that when carrying
out a modification, repair or maintenance, Critical Design Configuration Control Limitations are not compromised; this will require the development of appropriate procedures where necessary by the maintenance organisation. The maintenance organisation should pay particular attention to possible adverse effects of any wiring change to the aircraft, even a change not specifically associated with the fuel tank system. For example, it should be common practice to identify segregation of fuel gauging system wiring as a Critical Design Configuration Control Limitation.
SFAR 88• Maintenance organisations can prevent adverse effects associated
with wiring changes by standardising maintenance practices through training, rather than by periodic inspection. Training should be provided to end indiscriminate routing and splicing of wire and to provide comprehensive knowledge of critical design features of fuel tank systems that would be controlled by a Critical Design Configuration Control Limitation.
• EASA guidance is provided for training to maintenance organisation personnel in an Appendix IV to be added to AMC to Part-145.
• The maintenance of ignition prevention features is necessary for the inherent safety and reliability of an aircraft’s fuel tank system. The aircraft cannot be operated indefinitely with the failure of an ignition prevention feature. The failure will have a direct adverse effect on operational safety. It could prevent the continued safe flight and landing of the aircraft or cause serious or fatal injury to the occupants. The fuel system review required will identify ignition prevention features of the design. The failure of any of these features may not immediately result in an unsafe condition, but it may warrant certain maintenance to support continued airworthiness.
• AMC 145.A.70(a): Part 145 organization should include procedures in their MOE regarding handling and dealing with CDCCL items:
• add new section:• The exposition should contain information as applicable, on how the
maintenance organisation complies with Critical Design Configuration Control Limitations (CDCCL) instructions.
SFAR 88
• Appendix I to AMC 145.A.30(e): Provides instructions and information regarding the contents of Fuel Tank Safety training.
• Phase 1 training is provided for:
• The group of persons representing the maintenance management structure of the organisation, the quality manager and the staff required to quality monitor the organisation.
• Secondly a more detailed and specific Phase 2 training and continuation training every 24 months) is to be provided to personnel of the Part-145 approved maintenance organization required to plan, perform, supervise, inspect and certify the maintenance of aircraft and fuel system components.
• Effect on SAMCO procedures• SAMCO is to amend the MOE to include the new requirements:• MOE to reflect the training requirement of personnel regarding
CDCCL tasks• MOE to include procedure regarding handling CDCCL tasks as
critical task• MOE amend incoming inspection procedure to include CDCCL
requirements• MOE to be amended to exclude CDCCL tasks from maintenance
tasks exemption/modification• MOE add requirement to specify CDCCL tasks as such on the
technical records and/or release to service• SAMCO is to provide Fuel Safety training to applicable staff
SFAR 88