B111_FTS_2011.06.01 Fuel Tank Safety.pdf

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LTT 2006
ATA
Fuel Tank Safety
Fundamentals
28
Detailed Training and enhanced Airworthiness Program
acc. EASA Decision No 2009/007/R
Training Letter
Phase-1-and-2
FUNDMTL_FTS_L2
ScV
1MAY2011
01.06.2011

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Page 1
ATA DOC+Abbreviations
FUEL TANK SAFETY DETAILED-TRAINING
FRA US/O-2 ThM May 13, 2011
FUEL TANK SAFETY
DETAILED TRAINING AND ENHANCED AIRWORTHINESS PROGRAM EASA DECISION NO 2009/007/R
ABBREVIATIONS
ALI Airbus: Airworthiness Limitation Item
Boeing: Airworthiness Limitation Inspection
Airworthiness Limitation Instruction
AMM Aircraft Maintenance Manual
AWL Airworthiness Limitations
ASM Air Separation Module
CDCCL Critical Design Configuration Control Limitations
CMM Component Maintenance Manual
CMR Certification Maintenance Requirements
EASA European Aviation Safety Agency
FAA Federal Aviation Administration
FAL Fuel Airworthiness Limitations
FQI Fuel Quantity Indication
FQIS Fuel Quantity Indication System
Fuel ALI Fuel Airworthiness Limitation Items
INT/POL Interim Policy
JAA Joint Aviation Authorities
LEL Lower Explosion Limit
MPD Maintenance Planning Data
NAA National Aviation Authorities
NTSB National Transportation Safety Board
PPM Parts Per Million
SB Service Bulletin
SFAR Special Federal Aviation Regulation
SPM Standard Practices Manual
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Introduction|L1
FUEL TANK SAFETY
INTRODUCTION
DETAILED-TRAINING
FRA US/E-1 ScV Aug 10, 2007
INTRODUCTION OF THE SFAR 88
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
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. 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.
After arriving at JFK International Airport from Athens, Greece, the plane sat on
the ground for four hours with the air conditioning units operating before
departing for Paris at 8:19 p.m.. The plane exploded 20 minutes later, while
ascending at 13,760 ft.
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.
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Introduction|L1
FUEL TANK SAFETY
INTRODUCTION
DETAILED-TRAINING
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Figure 1 Background for the Introduction of the SFAR 88

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Page 4
Introduction|L1
FUEL TANK SAFETY
INTRODUCTION
DETAILED-TRAINING
Thai B737−400
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!
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Introduction|L1
FUEL TANK SAFETY
INTRODUCTION
DETAILED-TRAINING
The pumps were operating
dry (no fuel passing
through them) at the time of
the explosion!
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Figure 2 Thai 737−400 Fuel Tank Explosion

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Page 6
Accident Findings|L1
FUEL TANK SAFETY
ACCIDENT FINDINGS
DETAILED-TRAINING
ACCIDENT FINDINGS
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.
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 FQIS (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 autoignition are two source
theories that were tested by the NTSB.
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
existingjets, 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. 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.
Autoignition
Another possible source of ignition is from the terminals of the FQIS 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 autoignition. 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 autoignition could have occurred within the central fuel
tank of TWA Flight 800 involves the scavenger pump and faulty check valves.
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 autoignition
temperature than the liquid and the pump is a significant source of energy that
could become hot enough to cause autoignition of fuel vapor.
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Page 7
Accident Findings|L1
FUEL TANK SAFETY
ACCIDENT FINDINGS
DETAILED-TRAINING
ELECTRICAL ARCING
FUEL AIR
Fuel and Air combined in the right
proportions (flammable mixture)
Ignition Source
Requirements for ignition of flammable vapors
An ignition source that is:
- Not submerged in fuel, and
- Of sufficient energy
DRILL SHAVING AND CONTAMINATION ON WIRE BUNDLES
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Figure 3 Accident Findings

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Page 8
Consequences|L1
FUEL TANK SAFETY
CONSEQUENCES
DETAILED-TRAINING
CONSEQUENCES
AIRCRAFT FUEL SYSTEM SAFETY PROGRAM (AFSSP)
(Refer to: Aircraft Fuel System Safety Program Report prepared by the
International Aviation Industry, August 4, 2000)
In wake of the tragic TWA Flight 800 accident the collective realization
emerged that additional information needed to be gathered regarding the
condition of airplane fuel tank systems in the world fleet. Consequently, the
industry in 1997 committed itself to assessing the state of the inservice fleet
around the world. To accomplish this ambitious goal, the AFSSP (Aircraft Fuel
System Safety Program) was formed. Participants in this voluntary industry
program include present and past turbine−powered airliner manufactures,
airlines, industry organizations, and airworthiness authorities from around the
world. The following excerpt outlines the goals of the AFSSP:
“The industry is fully committed to enhancing aviation safety and believes that
efforts should be based on facts. The data available at this time indicates that
the best prevention strategy should focus on improvements - design, operation,
or maintenance - to enhance fuel tank systems.Therefor the industry plans to
voluntarily undertake either a sampling of high−time aircraft or major fuel tank
inspection programs to verify
the integrity of wiring and grounding straps;
the condition of fuel pumps, fuel lines and fittings; and
the electrical bonding on all equipment.
The inspection program will not be limited to the Boeing 747; rather, Airbus,
Boeing, Lockheed Martin, and McDonnell Douglas have agreed to jointly
sponsor a program that covers all of their respective models. In addition, the
airlines represented by the ATA, AEA, and the AAPA have agreed to
participate in these inspections. The inspection programs findings will be
coordinated through the international industry fuel tank inspection task forces.
The industry proposes that task force participation include the FAA and
international authorities. Subject to agreement with the authorities, the industry
would propose to share findings and plans with the public on a timely basis.“
The following mission statement was developed by the AFSSP to guide and
focus the efforts of this program:
“Through worldwide industry collaboration, take appropriate action to ensure,
maintain and enhance the safety of fuel systems throughout the life of the
aircraft.“
In the Aircraft Fuel System Safety Program Report prepared and issued by the
International Aviation Industry August 4, 2000 the following statements are
given among others under paragraph:
2.6 Actions and Recommendations
...
Based on AFSSP findings, the industry recommends additional training for
manufacturing and maintenance personnel, and will be reviewing or modifying
the existing fuel system maintenance practices to:
Substantiate the integrity of bonding straps through
− Long−term periodic visual/tactile inspection to verify bond integrity
− Enhancements to existing maintenance instructions for bonding jumper
maintenance and replacement
Provide periodic inspection criteria for FQIS (Fuel Quantity Indicating
System) wiring and components that are more detailed to better define
conditions and items to be inspected during general tank inspections.
Provide for the periodic in−situ inspection of fuel pumps and associated
wiring, fuel lines, and fittings.
The following items are presently part of the periodic heavy maintenance or
structural inspections that are already being conducted, so no change to
existing practices is recommended.
− Inspection for foreign object debris.
− General tank condition.
...
However, findings outside of this inspection program have shown that improper
repair or maintenance of fuel system components can lead to safety issues.
Therefore, the industry believes it is critical to have well−documented
maintenance procedures and qualified repair stations and personnel
maintaining fuel system components to ensure that design integrity is
maintained.
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Consequences|L1
FUEL TANK SAFETY
CONSEQUENCES
DETAILED-TRAINING
Official Report:
„The probable cause of the TWA Flight 800 accident was an explo-
sion of the center fuel tank (CWT)... neither the energy release mech-
anism nor the location of the ignition inside the CWT could be deter-
mined from the available evidence.“
National Transportation Safety Board(NTSB)-2000
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Figure 4 TWA Flight 800 accident

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Page 10
Regulation|L1
FUEL TANK SAFETY
REGULATION
DETAILED-TRAINING
REGULATION
AIRWORTHINESS DIRECTIVES ISSUED
General
As a result of this accident, multiple ADs (Airworthiness Directives) on multiple
models were issued.
BACKGROUND
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).
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 harmonised
design review results. 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.
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.
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 ED Decision No 2009/007/R of the Executive Director of the
Agency.
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Regulation|L1
FUEL TANK SAFETY
REGULATION
DETAILED-TRAINING
Fuel System Safety Compliance Data
June 6, 2001
SFAR 88 Rule became effective.
Applicable TC, STC holders had
to comply by December 6, 2002
June 6, 2001
FAR Parts 25,91,121,125,129 amended
to require instructions for maintenance
and inspection of the fuel tank system
had to be incorporated into the operators
Maintenance Program and be FAA
approved by June 7, 2004
Phase One
SFAR Rule
Implementation
Phase Two
FAR Rule
Implementation
EASA
FAA
The FAA and European Aviation Safety
Agency (EASA) have indicated that
operators must train their maintenance
and engineering personnel regarding the
changes brought about by SFAR 88.
March, 2009
Enhanced
Airworthiness
Program.
Covering Phase 1+2
and Continuation
Training
EASA DECISION
NO 2009/007/R
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Figure 5 Fuel System Safety Compliance Data

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Page 12
Requirements|L1
FUEL TANK SAFETY
CONSEQUENCES FOR MAINTENANCE AND
OVERHAUL
DETAILED-TRAINING
CONSEQUENCES FOR MAINTENANCE AND OVERHAUL
Engineering
Modifications of existing systems
and introduction of new
technologies for the fulfillment of the
SFAR 88 specifications
Engineering
Reassessment and revision in the
maintenance and overhaul
program and in the documents
Employee at aircraft
Awareness of problems in the
working areas of “Fuel Vapor“ and
“Wiring“
Requirements on the Maintenance and Overhaul Personnel
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Figure 6 Requirements on the Maintenance and Overhaul Personnel

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Page 13
Requirements|L1
FUEL TANK SAFETY
OVERHAUL
DETAILED-TRAINING
Example:
Fuel Pumps
− Internal components of the “stator wiring“ as a source of spark discharge.
− Damages at external cables and corroded connections as a source of spark formation.
− Avoidance of “fuel pump“ operation in empty fuel tanks.
Specific control specifications are demanded in the aircraft documentation. Possible damages
can be discovered at SFAR 88 relevant components and system components.
Fuel Quantity Indication System
− Faulty insulation of the cables and corroded connections.
− Unprotected laying of FQI cables together with high voltage lines.
Fuel Quantity Indication Probes
− Contaminations in the fuel tanks produce a risk of short circuits.
Bonding Straps
− Failure because of corrosion or improper fastening.
− Failure because of mechanical wear and tear due to movements.
Pneumatic system failures
− Due to leakages of the “pneumatic system“ the components of the fuel tanks are heated up.
Modifications of existing systems
and introduction of new technologies for the fulfillment of the SFAR 88 specifications
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Requirements|L1
FUEL TANK SAFETY
OVERHAUL
DETAILED-TRAINING
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.
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 “bonding straps“.
In SFAR 88 relevant areas an increased execution of “double checks“.
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Requirements|L1
FUEL TANK SAFETY
OVERHAUL
DETAILED-TRAINING
Fuel Airworthiness Limitations (FALs)
AIRBUS BOEING
DOUGLAS Lufthansa Technik Internal Documents
Airworthiness Limitations (AWLs) and
Certification Maintenance Requirements (CMRs)
Maintenance Planning Data (MPD)
Trijet Special Compliance Items Report Lufthansa Technik Standard Practices Manual
ATR
Airworthiness Limitations (AWLs) and
Certification Maintenance Requirements (CMRs)
− A318/A319/A320/A321 Doc. 95A.1931/05
− A300−600 Doc. 95A. 1929/05
− A310 Doc. 95A. 1930/05
− A330 Doc. 95A. 1932/05
− A340 Doc. 95A. 1933/05
− B737−100/200/200C/300/400/500 Doc. D6−38278−CMR
− B747−100/200/300/SP Doc. D6−13747−CMR
− B747−400 Doc. D621U400−9
− B777 Doc. D622W001−9
− B757/B767
− MD11 Doc. MDC-02K1003
− LHT-SPM Approved by FRA WE
− ATR42 MRB Rev.10 Part02
− ATR72 MRB Rev.14 Part02
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Figure 7 Documentation to implement the SFAR 88

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Page 16
AWL|L1
FUEL TANK SAFETY
AIRWORTHINESS LIMITATIONS
DETAILED-TRAINING
INTRODUCTION
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) for Boeing, and FALs (Fuel
Aiworthiness Limitations) for Airbus into maintenance program documents.
These AWL‘s are divided into two categories:
CDCCL (Critical Design Configuration Control Limitations) for Boeing and
Airbus:
− 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, and Special Compliance Items
document (for Long Beach models). Some examples of CDCCLs are the
bonding and grounding of fuel system components, and the routing of
fuel system wiring.
ALIs (Airworthiness Limitation Inspections)only for Boeing:
− These are repetitive inspections which are required to help ensure that
components 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 ALIs are verification of fault current
bonds, and inspection of wiring insulation and clamping.
ALIs (Maintenance / Inspection Tasks) only for Airbus:
− 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.
The AWLs for each model have been released in the appropriate maintenance
documents for each model. The documents, by model, are listed in the training
information attachment. AWLs are expected to be mandated by FAA
Airworthiness Directives. 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.
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AWL|L1
FUEL TANK SAFETY
DETAILED-TRAINING
Fuel Airworthiness Limitations
(FALs)
Fuel System Airworthiness Limitations
(AWLs)
Maintenance/Inspection Tasks (ALIs)
Airworthiness Limitation Instructions (ALIs)
Critical Design Configuration Control Limitations (CDCCL)
(Airbus / Boeing)
What do the “Airworthiness Limitation Instructions“ (ALIs) say?
In terms of SFAR 88, an „Airworthiness Limitation Item“ is a mandatory maintenance or inspection of the fuel system that
can include „Critical Design Control Configuration Limitations“.
In addition, further required actions can be performed to ensure that unsafe conditions do not occur and are not introduced
into the fuel system as a result of maintenance actions, repairs or alterations throughout the operational life of the aircraft.
ALI‘s are controlled according to a fixed interval. This can be “Flight Hours“, „Flight Cycles“ or “Calendar Time“.
What do the “Critical Design Configuration Control Limitations“ say?
A CDCCL is a “Fuel Airworthiness Limitation“, and a requirement to preserve a critical ignition source prevention feature
of the fuel system design.
Possible ignition sources for example can be present by a change of the original configuration of the “fuel vapor area“ or at
components of the “fuel system“ after performing
CDCCL‘s are necessary to prevent the occurrence of an unsafe condition of the aircraft identified by the SFAR 88.
Alterations, Repairs or Maintenance actions
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AI|FAL Example|L1
FUEL TANK SAFETY
FUEL AIRWORTHINESS LIMITATIONS
DETAILED-TRAINING
FUEL AIRWORTHINESS LIMITATIONS EXAMPLE
EXAMPLE OF AIRBUS FUEL AIRWORTHINESS LIMITATIONS
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Page 19
AI|FAL Example|L1
FUEL TANK SAFETY
DETAILED-TRAINING
(FALs)
Maintenance / Inspection Tasks
(ALIs)
Critical Design Configuration Control Limitations
(CDCCL)
Customer Services Directorate
A340 Fuel Airworthiness Limitations
SECTION 1
MAINTENANCE / INSPECTION TASKS
SECTION 2
CRITICAL DESIGN CONFIGURATION CONTROL LIMITATIONS
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Figure 8 Example of Airbus FALs

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Page 20
AI|FAL Example|L1
FUEL TANK SAFETY
DETAILED-TRAINING
THIS PAGE INTENTIONALLY LEFT BLANK
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Page 21
AI|FAL Example|L1
FUEL TANK SAFETY
DETAILED-TRAINING
SECTION 2
CRITICAL DESIGN CONFIGURATION CONTROL LIMITATIONS
Selection of Airbus “Critical Design Configuration Control Limitations“
TASK 28−42−16−400−801
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Figure 9 Example of A340 Removal/Installation Center Tank Middle-FQI-Probe

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Page 22
BAC|ALI Example|L1
FUEL TANK SAFETY
DETAILED-TRAINING
EXAMPLE OF BOEING AIRWORTHINESS LIMITATIONS
For the B737, B777, B747 the Maintenance Planning Data are similarly structured. As an exam-
ple a page is shown from the B737 MPD. (B737 External Wires Over the Center Tank Inspection).
Reference: AMM 28−11−00
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Page 23
BAC|ALI Example|L1
FUEL TANK SAFETY
DETAILED-TRAINING
Page 60X
EFFECTIVITY
ALL
737−300/400/500
Jan 12/06
MAINTENANCE MANUAL
E. External Wires Over the Center Tank Inspection
(1) Do a detailed inspection of the wire bundles routed on the
main deckover the center tank and under the floor beams
between Station 540 and Station 664.
(a) Look for these items:
1) Damaged clamps,
2) Wire chafing,
3) Wire bundles that are in contact with the surface of
the center tank.
28−11−00
According 28−AWL-01
ALI
According 28−AWL-02
CDCCL
Refer to AMM 28−00−00
ASK 28−11−00−206−281
7. External Wires Over the Center Tank Inspection
A. General
(1) ALI − Refer to the task: Airworthiness Limitation
Precautions (AMM 28−00−00/201), for important
information on airworthiness limitation instructions (ALIs).
AMM 28−00−00
D. Airworthiness Limitations Instructions (ALIs)
S 912−072
WARNING: OBEY THE MANUFACTURERER‘S PROCEDURES
WHEN YOU DO ANY MAINTENANCE THAT MAY
AFFECT AN ALI. IF YOU DO NOT FOLLOW THE
PROCEDURES, IT CAN IN CREASE THE RISK OF
A FUEL TANK IGNITION SOURCE.
(1) Make sure you follow the procedures for tasks identified as ALIs.
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Figure 10 Example of B737 External Wires Over the Center Tank Inspection

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Fuel Characteristics|L1
FUEL TANK SAFETY
FUEL CHARACTERISTICS
DETAILED-TRAINING
TYPES OF TURBINE ENGINE FUEL
Turbine engine fuels used for jet engines are kerosene type fuels which are
closely related to diesel gasoline.
There are 4 main types of turbine engine fuel. These are called
Jet A1,
Jet A,
Jet B and
JP 5.
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Figure 11 Types of Engines Fuel

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FUEL TANK SAFETY
DETAILED-TRAINING
Types of Turbine Engine Fuel (cont.)
The fuel types differ in their main characteristics.
Jet A1 is the most commonly used fuel type for jet engines in Europe.
This fuel type is reasonably safe for you to handle because it has a high flash
point of plus 38° C and a low freezing point of minus 47° C. The American
name for this type of fuel is JP 1A.
Jet A is the most commonly used fuel type for jet engines in America.
It is very similar to Jet A1 with the same high flash point of plus 38° C but with
a lower freezing point of -40° C. In the USA this fuel is also called JP 1.
Jet B fuel is mainly used for military jet engines.
Theoretically, it can also be used for civil aircraft engines but Jet B has an
extremely low flash point of minus 20° C to provide good ignition capabilities.
This means it requires extreme care in handling. Jet B has a very low freezing
point of minus 60° C. The American name for this type of fuel is JP 4.
JP 5 is another type of military jet fuel.
It is preferred by the military on aircraft carriers because its very high flash
point of plus 65° C makes it very safe for handling. JP 5 has a relatively low
freezing point of minus 48° C.
You must record the type of fuel used when refueling. This is important,
because each type of fuel has different handling and operating characteristics.
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FUEL TANK SAFETY
DETAILED-TRAINING
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Figure 12 Fuel Main Caracteristics

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FUEL TANK SAFETY
DETAILED-TRAINING
CHARACTERISTICS OF TURBINE ENGINE FUELS
The main requirements of turbine engine fuels are a low freezing point and a
flash point low enough to provide good ignition capabilities but as high as
possible for safe fuel handling.
Turbine engine fuels must also have a low tendency to vaporize in high flight
altitudes.
Engine fuels need to be widely available all over the world and must have a low
tendency to carry water.
Different fuels have different freezing points depending on their composition.
The freezing point is the temperature at which some elements of the fuel start
to crystallize and the fuel flow slows down. The required freezing point of fuel
for turbine engines should be below minus 40° Celsius.
The flash point of fuel is the lowest temperature at which the fuel creates just
enough vapors to build up a fuel/air mixture that can be inflamed. To reduce
any fire hazards, the flash point of the fuel used for civil aircraft should be as
high as possible. If the flash point is reached, the fuel/air mixture burns, but if
the external flame is removed, the fuel/air mixture extinguishes.
The volatility is another very important characteristic of jet fuels. Volatility of
fuel is its ability to vaporize. A highly volatile fuel is very desirable for engine
starts in cold weather and in flight, and fuel with low volatility is desired to
eliminate vapor lock and to reduce fuel losses by evaporation.
Jet fuel, like all other fluids vaporizes if the ambient pressures decreases. The
higher you fly the more the ambient pressure decreases. Ambient pressure
decrease causes fuel to vaporize.
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Figure 13 Fuel Characteristic

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Characteristics of Turbine Engine Fuels (cont.)
Another very important characteristic of fuel is its density. This is the ratio
between mass and volume. This ratio changes with the fuel type and fuel
temperature.
Jet A1 and Jet A have the same density of 0.81kg/ltr. at a temperature of
15 C.
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Figure 14 Fuel Density

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FUEL TANK SAFETY
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Characteristics of Turbine Engine Fuels (cont.)
Other requirements on jet engine fuels are that it must be readily available so
that the airlines can get the same fuel type all over the world. It must have
adequate lubrication capabilities for the moving parts in the fuel system, and
the fuel must have a low tendency to hold water to minimize water
contamination problems.
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Figure 15 Fuel Requirements

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Accident Board Rec.|L1
FUEL TANK SAFETY
ACCIDENT BOARD RECOMMENDATIONS
DETAILED-TRAINING
RECOMMENDATIONS TO MINIMIZE IGNITION SOURCES
The odds of one of these conditions causing the fuel to ignite in the central fuel
tank are slim, but they still must be prevented from ever occurring. One key
area for prevention is by regularly inspecting the wiring. Stripped insulation,
which can lead to arcing, and copper sulfide buildup on FQIS terminals, which
can create autoignition, would be discovered and be fixed. Inspectors should
examine check valves and localized heat sources within the scavenger pump.
Also, a cleaner environment should be maintained around the central fuel tank
to prevent the buildup of possible conducting agents such as drill shavings and
“syrup“. Finally, the risk of arcing could be reduced if more durable insulation
that covers electrical wiring is installed in new and old commercial airlines. This
improvement may be especially important, as the average age of operational
planes is steadily increasing.
There were numerous recommendations, which primarily involve the following:
Reduce fuel tank flammability.
Minimize fuel tank ignition sources.
Re−evaluate airplane design and certification standards.
Re−evaluate maintenance and aging of aircraft systems.
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FUEL TANK SAFETY
DETAILED-TRAINING
Fuel Tank Ignition Source
Consideration
INTERNAL
IGNITION SOURCES
PUMPS
ELECTRICAL
COMPONENTS
ELECTROSTATIC
OR LIGHTING
Electrical
Power
Impeller/Inlet Fuel Level
Sensor
Temperature
Probe
Fuel
Quantity
Indication
Redundant
Bond Paths
Periodic
Integrity
Check
Fault
Protected
Separated
Shielded
Main Feed
Tank
Pump Inlet
Covered
Transient
Protection
Isolation
Fuel
Quantity
Transmitter
Inlet
Enclosed in
Collector Cell
Inlet
Enclosed in
Collector Cell
Auxiliary
Tank
Fault
Protected
Wiring
outside of
Tank
Protected
from Arcing
into Tank?
Pump
Housing
Burnthrough
Protected
Arc/Ground
Fault Circuit
Protection
Pump Inlet
Covered
Flame Arrestor in
Motor Driven
Scavenge Pump
Ejector Pump
Scavenge
Auto
Shut-Off
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Figure 16 Internal Ignition Source Consideration

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FUEL TANK SAFETY
DETAILED-TRAINING
EXTERNAL
IGNITION SOURCES
Surface
Heating
Arc into
Tank
Affects of Wiring
routed outside of
Tank on Wiring
entering Tank
Pneumatic
Ducting
External Fire in
Zones adjacent
to Tank
Electrical
Wiring
protected GFI?
EMI Induced
Transients
Hot Short
Auto
Shut-Off
Duct Leak
Detection
Electrical
Power Wiring
Electrical
Connectors
Fuel Tank Ignition Source Consideration
Pump
Connectors
Meet IVT
Wiring
Standard?
Fail Safe
Support
Brackets?
Sealant Fuel
resistant
Explosion
Proof
Corrosion
Resistant
Periodic
Integrity
Check
Periodic
Integrity
Check
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Figure 17 External Ignition Source Consideration

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Factors|L1
FUEL TANK SAFETY
FACTORS FOR A FUEL TANK EXPLOSION
DETAILED-TRAINING
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Factors|L1
FUEL TANK SAFETY
DETAILED-TRAINING
OXYGEN
COMBUSTIBLE
MEDIUM
IGNITION
SOURCE
A mixture of fuel and
oxygen can be
extremely
...explosive
...electrical sparks.
...cable fire.
...hot surfaces.
...friction sparks.
...static discharge.
Some typical ignition
sources are
Main factors as ignition sources for a fuel air mixture explosion
In aircraft maintenance and overhaul all areas of the fuel tanks have to be inspected for present
damages and their possible causes.
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Figure 18 Awareness of problems in the working areas of “Fuel Vapor“ and “Wiring“

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Wiring Degradation|L1
FUEL TANK SAFETY
DETAILED-TRAINING
CAUSES OF WIRING DEGRADATION
Vibration
High vibration areas tend to accelerate degradation over time, resulting in
”chattering” contacts and intermittent symptoms. High vibration can also cause
tie−wraps, or string−ties to damage insulation. In addition, high vibration will
exacerbate any existing problem with wire insulation cracking.
Moisture
High moisture areas generally accelerate corrosion of terminals, pins, sockets,
and conductors. It should be noted that wiring installed in clean, dry areas with
moderate temperatures appears to hold up well.
Maintenance
Unscheduled maintenance activities, if done improperly, may contribute to long
term problems and wiring degradation. Repairs that do not meet minimum
airworthiness standards may have limited durability. Repairs that conform to
manufacturers recommended maintenance practices are generally considered
permanent and should not require rework if properly maintained.
Metal shavings and debris have been discovered on wire bundles after
maintenance or repairs have been conducted. Care should be taken to protect
wire bundles and connectors during modification work, and to ensure all
shavings and debris are cleaned up after work is completed.
As a general rule, wiring that is undisturbed will have less degradation than
wiring that is reworked. As wiring and components become more brittle with
age, this effect becomes more pronounced.
Indirect damage
Events such as pneumatic duct ruptures can cause damage that, while not
initially evident, can later cause wiring problems. When such an event has
occurred, surrounding wire should be carefully inspected to ensure no damage
is evident.
Chemical contamination
Chemicals such as hydraulic fluid, battery electrolytes, fuel, corrosion inhibiting
compounds, waste system chemicals, cleaning agents, deicing fluids, paint,
and soft drinks can contribute to degradation of wiring. Wiring in the vicinity of
these chemicals should be inspected for damage or degradation.
Recommended original equipment manufacturer cleaning instructions should
be followed.
Hydraulic fluids, for example, require special consideration. Hydraulic fluid is
very damaging to connector grommet and wire bundle clamps, leading to
indirect damage, such as arcing and chafing. Wiring that may have been
exposed to hydraulic fluid should be given special attention during wiring
inspections.
Heat
Wiring exposed to high heat can accelerate degradation, insulation dryness,
and cracking. Direct contact with a high heat source can quickly damage
insulation. Even low levels of heat can degrade wiring over long periods of
time. This type of degradation is sometimes seen on engines, in galleys, and
behind lights.
Installation
Wiring not installed properly can further accelerate the wiring degradation
process. Improper routing, clamping, and terminating during initial installation or
during a modifications can lead to wiring damage.
Wiring routing
Eliminate potential for chafing against structure or other components
Position to eliminate/minimize use as handhold or support
Minimize exposure to damage by maintenance crews or shifting cargo
Avoid battery electrolytes or other corrosive fluids
In general, wiring should be routed in such a manner to ensure reliability and to
offer protection from the potential hazards shown in this slide.
The following pictures illustrate some of the hazards previously described.
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Wiring Degradation|L1
FUEL TANK SAFETY
DETAILED-TRAINING
INDIRECT DAMAGE
CHEMICAL
CONTAMINATION/CLEANING
HEAT
INSTALLATION
VIBRATION
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Figure 19 Causes of Wiring Degradation

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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
EXAMPLES OF WIRING PROBLEMS
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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
IMPROPER
PROPER
Power cables can become damaged
when riding on structure.
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Figure 20 Wires riding on Structure

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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
PROPER
IMPROPER
Wire bundles that cross should be
secured together to avoid chafing
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Figure 21 Wires riding on other Wires

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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
IMPROPER
If the grommet is too short, wire bundle
chafing can occur.
PROPER
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Figure 22 Wires riding on Lightening Hole

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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
WIRING ROUTING
Protect wires in wheel wells and other exposed areas
Route wires above fluid lines, if practicable
Use drip loops to control fluids or condensed moisture
Keep slack to allow maintenance and prevent mechanical strain
Ensure that wires and cables are adequately protected in wheel wells and other
areas where they may be exposed to damage from impact of rocks, ice, mud,
etc. (If re−routing of wires or cables is not practicable, protective jacketing may
be installed.) This type of installation must be held to a minimum.
Where practical, route wires and cables above fluid lines. Wires and cables
routed within 6 inches of any flammable liquid, fuel, or oxygen line should be
closely clamped and rigidly supported. A minimum of 2 inches must be
maintained between wiring and such lines or related equipment, except when
the wiring is positively clamped to maintain at least 1/2−inch separation or
when it must be connected directly to the fluid−carrying equipment.
Ensure that a trap or drip loop is provided to prevent fluids or condensed
moisture from running into wires and cables dressed downward to a connector,
terminal block, panel, or junction box. Wires and cables installed in bilges and
other locations where fluids may be trapped are routed as far from the lowest
point as possible or otherwise provided with a moisture−proof covering.
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Examples|L1
FUEL TANK SAFETY
DETAILED-TRAINING
This example shows a number of problems:
Wires in the bundle are not
tied properly.
The wire bundle is riding hard
on the hydraulic lines.
The wire bundle appears to
be contaminated with
hydraulic fluid residue.
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Figure 23 Wires in the bundle are not tied properly

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FRS|L1
FUEL TANK SAFETY
FLAMMABILITY REDUCTION SYSTEM
DETAILED-TRAINING
FLAMMABILITY REDUCTION SYSTEM (FRS)
AVOIDANCE OF THE EXPLOSION HAZARD BY NITROGEN
INERTING
Beside the avoidance of igniting sources, the explosion hazard can be
prevented by nitrogen enrichment of the fuel tanks, called FRS (“Flammability
Reduction Systems“ ). The pressurized air in the system is forced through the
membrane fibers and allows fast gases to escape through the membrane wall
and the nitrogen rich stream to pass through. By this possibility the level of the
fuel center tank can be adjusted from “high flammability“ to “low flammability“.
It is planned that B737 delivered from February 2007 shall be equipped with
the system. For aircrafts already delivered and still in operation, refitting will be
carried out at given time.
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FRS|L1
FUEL TANK SAFETY
FLAMMABILITY REDUCTION SYSTEM
DETAILED-TRAINING
FLAMMABILITY REDUCTION SYSTEM 747 SP
FLAMMABILITY REDUCTION SYSTEM A320 TEST VERSION
AIR SEPARATION MODULE (ASM)
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Figure 24 Flammability Reduction System

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Summary|L1
FUEL TANK SAFETY
SUMMARY
DETAILED-TRAINING
SUMMARY
When aircraft maintenance is carried out in the area of the “fuel vapor seal“ or
at components of the fuel system, which are indicated in the documents as
AWLs, FALs, ALIs or CDCCLs
then you must always work according to an authorized documentation, such as
“AMM“, “CMM“ or “Job Card“ !
Deviations of every type of the specifications listed in the manufacturer
documentation are not permitted!
If uncertainties arise in the context of the work execution with a
documentation, then the work should never be continued on assumptions!
In such cases “Product− or System Engineering“ authorized by the aircraft
operator must be informed to guarantee the correct execution of the work
and documenting these!
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Summary|L1
FUEL TANK SAFETY
SUMMARY
DETAILED-TRAINING
condition after the execution
Measures to make sure the airworthiness
of the aircraft with
su pp
or t
o f Pr
o d
uc t
− or S y
stem En g
ineeri n g by:
good workmanship
, design modifications ,
operational procedures ,
interim action s
Measures to make sure the airworthiness of the aircraft with support of Product or System Engineering by:
good workmanship,design modifications,operational procedures ,interim actions
Predefined inspection intervals in
Flight Hours, Flight Cycles or Calendar Time
for
Maintenance / Inspectio n Tasks (ALI‘s)
Predefined inspection intervals in
Flight Hours, Flight Cycles or Calendar Time
for
Maintenance / Inspectio n Tasks (ALI‘s)
Aircraft release
Aircraft release
Specifications at repairs,
component changes, modifications
for
Critical Design Control Limitations
Specifications at repairs,
component changes, modifications
for
Critical Design Control Limitations
safe condition after the execution
Examples of Maintenance / Inspection Tasks:
vapor seal
vent drain system
fuel pump circuit breaker reset
fuel quantity gage system wiring overbraid
external wires over center fuel tank
center wing tank fueling valve−
fault current bond
inboard main tank override/jettison pumps
fuel boost pump automatic shutoff system
Examples of Maintenance / Inspection Tasks:
−vapor seal
−vent drain system
−fuel pump circuit breaker reset
−fuel quantity gage system wiring overbraid
−external wires over center fuel tank
−center wing tank fueling valve−
fault current bond
−inboard main tank override/jettison pumps
−fuel boost pump automatic shutoff system
Examples of CDCCL s:
air gap fuel quantity indicating probes
features of fuel pumps
direct bonding of items
separation of wiring from other wiring
in fuel tank wire splices
fuel tank access door bonding
external wires over center fuel tank
AC pump and DC pump maintenance
Examples of CDCCL :
−air gap fuel quantity indicating probes
−features of fuel pumps
−direct bonding of items
−separation of wiring from other wiring
−in fuel tank wire splices
−fuel tank access door bonding
−external wires over center fuel tank
−AC pump and DC pump maintenance
Execution according:
AMM / CMM / Job Card
Execution according:
AMM / CMM / Job Card
(AWL s)
(AWL s)
“Safe“
“Unsafe“
‘s
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Figure 25 Control Sequence at “AWL“ Relevant Components

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Prac. EASA demand|L2
FUEL TANK SAFETY
ED DECISION 2009/007R
DETAILED-TRAINING
COVER OF PRACTICAL DEMANDS FOR THE EASA DECISION 2009/007/R
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Prac. EASA demand|L2
FUEL TANK SAFETY
ED DECISION 2009/007R
DETAILED-TRAINING
EASA
FAA
Fuel Tank Safety during maintenance: fuel tank entry and exit procedures,
clean working environment, what is meant by configuration control, wire separa-
tion, bonding of components etc,
Where relevant information can be found and how to use and interpret this in-
formation in the instructions for continuing airworthiness (aircraft maintenance
manuals, component maintenance manuals, Service Bulletins...)
Flammability reduction systems when installed: reason for their presence,
their effects, the hazards of an FRS using nitrogen for maintenance, safety
precautions in maintenance/working with an FRS,
Annex 1 to Decision 2009/007/R
ED Decision 2009/007R
24/03/2009
PRACTICAL EXTRACTS FOR DECISION 2009/007/R
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Figure 26 Cover of practical demands for the Decision 2009/007/R

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Service Bulletins|L2
FUEL TANK SAFETY
SERVICE BULLETINS
DETAILED-TRAINING
SERVICE BULLETINS
IMPLEMENTATION OF THE DECISION 2009/007/R REQUIREMENT BY SERVICE BULLETIN
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FUEL TANK SAFETY
SERVICE BULLETINS
DETAILED-TRAINING
Commercial
Airplane
Group Service Bulletin
747
ALERT
SUBJECT:
Number: 747−28A2292
Date: September 14, 2007
ATA System: 2814 2816 2821 2822 2825 2831
FUEL − Main, Center, and Auxiliary Fuel Tank Valve Actuators − Electrical Bond Inspection
BACKGROUND
This service bulletin gives instructions to inspect and if necessary, improve all the electrical bonds between the
motor operated valve (MOV) actuators and the airplane structure. Improving the electrical bond will prevent
electrical current from flowing through the actuator and into the fuel tank. If this service bulletin is not done, it is
possible for electrical current to flow into the fuel tank, providing an ignition source for the fuel fumes inside the
tank.
The Boeing system safety assessment necessary to comply with Special Federal Aviation Regulation (SFAR) 88
”Fuel Tank System Fault Tolerance Evaluation Requirements” showed that under specific conditions it was
possible for electrical current to flow through the MOV actuator and into the fuel tank. This assessment has lead
to requiring electrical bond improvements for the MOV actuator installation.
This service bulletin gives instructions to measure the electrical bond resistance, and if necessary, change each
electrical bond and rework each part surface between the MOV actuator and the airplane structure. If it is
necessary to remove an adapter plate, you will have to do a tank entry to gain access. Note that it is unlikely
that you will have to remove the adapter plates.
This service bulletin gives instructions to measure the electrical bond resistance, and if necessary, change
each electrical bond and rework each part surface between the MOV actuator and the airplane structure.
If it is necessary to remove an adapter plate, you will have to do a tank entry to gain access. Note that it is un-
likely that you will have to remove the adapter plates.
Section 9 of the 747−100/200/300/SP Airworthiness Limitation (AWLs) and the Certification Maintenance
Requirements (CMRs) documents were changed.
Section 9 of the 747−400 MPD (Maintenance Planning Data) document was changed.
Requirement of FAA
Practical demands for
the decision 2009/007/R
Implementation of SFAR 88
Requirement by the
manufacturer
IMPORTANT AUTHORITIES EXTRACTS
FOR SERVICE BULLETINS
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Figure 27 Important Autorities Extracts for Service Bulletins

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FUEL TANK SAFETY
SERVICE BULLETINS
DETAILED-TRAINING
Compliance
The FAA (Federal Aviation Administration) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make
the compliance tasks and times given in this service bulletin mandatory.
Boeing recommends that operators accomplish this service bulletin within 60 months after the date on this service bulletin.
Description
Gain access to each MOV actuator. For each MOV actuator, measure the electrical bond resistance from the MOV actuator to the airplane structure. If the
electrical bond is not adequate, remove and keep the MOV actuator. Measure the electrical bond resistance of the next part in the assembly. If the electrical
bond is not adequate, remove and keep the part. Continue until you reach a point where the electrical bond is adequate, or you have reached the airplane
structure.
If necessary, change each electrical bond and rework each part contact surface between the MOV actuator and the airplane structure. In some cases, the MOV
actuator is attached directly to the MOV mounting bolts. But in most cases, there is an index plate and an adapter plate between the MOV actuator and the air-
plane structure.
After you install each part, you must measure the electrical bond resistance. Each electrical bond must be adequate at each part before you can install the next
part of the assembly. If the electrical bond is not adequate you must remove the part and rework that electrical bond. You must build the assembly until the MOV
actuator is installed and operates. Keep in mind that it is unlikely that you will have to remove the adapter plate and rework the bottom contact surface of the
adapter plate. If it is necessary to remove the adapter plate, you will have to do a tank entry to gain access.
Approval
This service bulletin was examined by the FAA (Federal Aviation Administration). The changes specified in this service bulletin comply with the applicable regula-
tions and are FAA approved, as well as EASA (European Aviation Safety Agency)/JAA (Joint Aviation Authorities) approved for all EASA/JAA approved airplanes
listed in the service bulletin effectivity. This service bulletin and its approval were based on the airplane in its original Boeing delivery configuration or as modified
by other approved Boeing changes.
If an airplane has a non−Boeing modification or repair that affects a component or system also affected by this service bulletin, the operator is responsible for ob-
taining appropriate regulatory agency approval before incorporating this service bulletin.
BOEING SERVICE BULLETIN 747−28A2292
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Figure 28 Boeing Service Bulletin 747−28A2292

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ACCOMPLISHMENT INSTRUCTIONS
A. GENERAL INFORMATION
ALERT ALERT
KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL PARTICLES OR CONTAMINATION WHEN YOU
USE TOOLS. UNWANTED MATERIAL, METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE DAMAGE
TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR OTHER ELECTRICAL DAMAGE.
CAUTOIN:
WORK INSTRUCTIONS
1.Get access to the MOV actuator. Refer to 747−100/200/300 AMM 28−16−01 as an accepted procedure.
Page 60X
747
MAINTENANCE MANUAL
28−16−01
TASK 28−16−01−404−009
Reserve Tank Transfer Valve Actuator Installation
SUBTASK 28−16−01−420−004
(1) Do this task: Motor Operated Valve Actuator Installation − Faying Surface
Preparation and Bonding Resistance Measurement, TASK 28−00−01−400−801.
CDCCL−Refer to the task: Airworthiness Limitation
Precautions (AMM 28−00−00/-910−801)
WARNING: OBEY THE MANUFACTURER‘S
PROCEDURES WHEN YOU DO ANY
MAINTENANCE THAT MAY AFFECT
A CDCCL. IF YOU DO NOT FOLLOW
THE PROCEDURES, IT CAN IN-
CREASE THE RISK OF A FUEL
TANK IGNITION SOURCE.
(1) Make sure you follow the procedures for items
identified as CDCCLs.
All occurrences of CDCCLs found in this chapter of the
AMM are identified by this note after each applicable
CDCCL design feature:
C. Critical Design Configuration Control Limitations
(CDCCLs)
EFFECTIVITY
ALL
2. Remove the bonding jumper, and measure and record the electrical bond resistance from the actuator mounting feet to the airplane
structure as given in Figur 1
CDCCL−Refer to the task: Airworthiness Limitation Precautions, TASK 28−00−00−910−801,
for important information on Critical Design Configuration Control Limitations (CDCCLs).
NOTE:
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Measure and Record the Electrical Bond Resistance for the No. 1 Reserve Tank Transfer MOV Actuator
ALERT ALERT
A
F
WD INBD
2 3
NO.1 RESERVE TANK
TRANSFER
MOV ACTUATOR (INBOARD)
SEE A
A
4
5 1
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Figure 30 No. 1 Reserve Tank Transfer MOV Actuator

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FRA US/O-2 ScV Aug 27, 2007
HUMAN FACTORS
INTRODUCTION
Air transport is considered as one of the safest means of travelling in the world
today, yet every now and again an accident occurs which shakes our
complacency. All too often, as we look at the cause of the accident, we will
say:
”How could such simple error have combined to cause such a
catastrophe?”
An in−depth review of the events after the fact will reveal, time and again, that
a series of human errors (known also as a chain of events) was allowed to from
until the accident occurred. In about one accident out of ten, maintenance
errors are part of the chain of events.
If we brake the chain of events at the maintenance level, the accident will
not happen.
What you will gain from this workshop is very much related to what you are
prepared to invest into it. Be open minded − but if you disagree with anything
that is being said, feel free to speak up.
Take the time to glance through this book from time to time in the future. It may
help you to avoid mistakes and safe you from having to pay the price for them.
What is maintenance Human Factors?
In the most straightforward terms, Human Factors are those conditions that
affect a human in the aviation maintenance work environment.
Often, a Human Factors class begins by asking participants to list human
factors that affect work performance. The following list is only a small sample
of the possible topics of human factors those participants might list:
Fatigue, poor communication, personal life problems, smelly fumes, loud
noises, slippery floors, snow, incomplete or incorrect documentation, poor
instructions, substance abuse, poor training, poorly designed testing for skill
and knowledge, bad lighting, unrealistic deadlines, lack of spare parts and
tools, poor tool control, boring repetitive jobs, a rush to complete jobs.
The list may be endless. Some problems are minor but can become major.
In most cases more than one of these factors contributes to a problem. During
this course we will consider most of these human factors that may contribute to
an incident or accident event.
Costs
Not only does human error in maintenance compromise safety, it also costs
money. For example, the manufacturers estimate that;
the cost of an in−flight engine shutdown is about $500,000.
A flight cancellation costs a minimum of $50,000.
An average ground damage accident is about $100,000 when ramp
equipment contacts an aircraft.
The airlines lose at least $billion per year from human error.
The industry can hardly afford such losses now, or at any time.
We must do better. Attention to human factors can help us to improve safety
and to return the airline business to profitability.
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Chain of Events
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Figure 32 Introduction to Human Factors (HF)

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ACCIDENTS
Boeing data shows that the primary causes of accidents are:
Flight crew,
Airplane,
Weather,
and Maintenance
along with many other factors.
Another study, conducted during the eighties to early nineties, showed that
maintenance related accidents were the 2nd leading cause of fatalities.
What causes these accidents?
Experts agree that about 80% of these accidents are a result of human error.
Therefore we must pay attention to human factors if we are going to improve
the overall safety of the world’s airlines.
100%
20%
80%
1910 2000
human
technical
Figure 33 80/20 Rule
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ERROR MODELS AND THEORIES
General
To err is human. As humans we make mistakes. No matter how we try, that will
never change! However, as aviation maintenance personnel you must take the
proper steps to minimize error.
It is a matter of safety!
It is also a matter of pride in your work and a matter of cost control for your
company.
To minimize error, it is necessary to understand error. This unit will first define
error. Then, the section will offer graphical models to help you visualize error.
Finally, the section will show you the 12 most common errors that humans
make, and will offer guidelines for minimizing such errors.
Throughout the human factors training you may hear the words ”Dirty Dozen.”
The Dirty Dozen is a listing of the 12 most common causes of human error in
maintenance. The concept was developed by Mr. Gordon Dupont at Transport
Canada.
Gordon Dupont,
Transport Canada
Concept developed by Gordon Dupont
Figure 35 „The Dirty Dozen“
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2
3
4
5
6
minimise Error
Error containment
As humans we make mistakes
- that will never change!
To Err is Human!
1
SAFETY FACTOR
EXAMPLE:
Look at this easy example of one bolt with many nuts.
This nut and bolt assembly can only be disassembled
one way. However, there are over 40,000 combinations
for reassembly, of which only one is correct!
This is a good example of the complexity, and chance of
error, in aviation maintenance environments.
MAINTENANCE ERRORS COST MONEY!!
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Figure 36 Human Error

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DIRTY DOZEN
We all make the same kind of errors and we are all human. ”To Err is Human.”
Throughout the human factors training you may hear the words ”Dirty Dozen”
many times. If we could eliminate or control these 12 causes of error we would
eliminate a very high percentage of maintenance−related events.
We will look at each factor that contributes to an error, and offer possible
corrective actions to prevent such error.
By the end of your Human Factors training you should remember many of
these errors, and also know the best methods for preventing them.
The following is a listing of the Dirty Dozen:
Lack of communication
Lack of teamwork
Norms
Pressure
Complacency
Lack of knowledge
Lack of awareness
Lack of ressources
Distraction
Assertiveness
Fatigue
Stress
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Lack of Communication
Lack of Teamwork
Norms
Pressure
Complacency
Lack of Knowlegde
Lack of Awareness
Lack of Resources
Distraction
Lack of Assertiveness
Fatigue
Stress
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Figure 37 Dirty Dozen

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LACK OF COMMUNICATION
Communication errors are the most common type of error. There are many
opportunities to fail in communication.
You must be continuously aware of the communication challenge, therefore a
whole chapter (M9.7 Communication) deals with this factor exclusively.
Tips
What are some of the corrective actions that can be taken?
First of all: Be aware of the challenges.
Remember that complete communication requires a transmitter, a receiver
and feedback. All three are important!
When you communicate, remember the 3 C’s: Correct − Clear − Complete.
Assumptions are dangerous. Try to avoid assuming that your message was
understood. Be sure by looking for the feedback.
Continental Express
EMB120 - 1994
BILL!
Are the screws
tightened
YES!
I checked the oil
Figure 38 Lack of Communication
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LACK OF TEAMWORK
Maintenance requires teamwork. ”Lack of Teamwork” is another of the Dirty
Dozen. Lack of teamwork is the failure of a group to work together to achieve a
common goal.
Tips
What are the Corrective Actions for Lack of Teamwork?
Communicate the group goal.
− Make sure that everyone understands what is going on.
− The team leader should promote this understanding.
Recognize that the team’s success is a shared success.
Recognize that each person must contribute to the team goal.
Do you give your best effort to serving your customers?
You must remind yourself to treat your teammates the same as your most
important customers.
A good team should communicate the challenges. When something goes
wrong it should be discussed, not ignored.
Figure 39 Lack of Teamwork
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NORMS
Norms are the commonly accepted work practices within an organization.
Norms are not usually written down − they are simply the methods by which the
organization works. Often „norms“ are bad practices, bypassing „inconvenient
procedures“ but there are examples of „good norms“ as well.
Here is an example of a good norm for shift turnover.
(Klaus): ”Hi Stefan, let me tell you what we did today and what are the next
tasks. We also wrote this information on the job cards”
(Stefan): ”Thanks Klaus, I want to be sure I understand this so I can explain
it to the team. By the way, are the lock pins and power−on warnings
installed as usual?”
(Klaus): Also Stefan, remind everyone that the lock pins for the thrust
reverser are hard to see, and must be removed before the aircraft is ready
for service. I also wrote that down.”
(Stefan):”OK Klaus, have a good evening and I will see you the same time
tomorrow.”
Tips
Now let’s look at some of the corrective actions for bad norms. Remember that
a violation was defined as a disregard of regulations and operating procedures.
Often the difference between a norm and a violation is based on whether or not
there is an incident.
If you do something merely ”because everyone does it that way” you may be
subject to legal action.
Therefore, a corrective action may be finding proper documentation for the
norm.
It is OK to ask why a procedure is not documented. There should be a
reasonable answer or you should not follow the action.
Pressure from your co−workers can force you to follow undocumented
procedures.
Assume leadership. Be assertive and push for converting the good norms to
good written procedures. Finally, adopt the ”Good Norms”.
Chicago, 1979 American Airlines DC10
Figure 40 Norms
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PRESSURE
There is often pressure in maintenance, which can come from many sources.
Often, you put the greatest pressure on yourself. You press yourself for high
quality performance in minimal time.
Your managers may apply pressure. Pressures to meet a deadline are the
most common. And, your co−workers may also apply pressure. They can
create a sense of urgency that forces you to work at a pace faster than you are
comfortable with. Conditions cause pressure. The closer it gets to departure
the more pressure builds up to get the task completed quickly. So, pressure is
one of the dirty dozen. It is a possible contributing factor to an event.
Tips
We have established that negative pressure can have negative consequences
on your maintenance work. It can lead to error, but you can control it.
What are the Corrective Actions for Pressure?
First, when pressured, stop and assess the situation.
Be rationale. Cool down - ”Chill”.
Remind yourself of the consequences of error.
As the saying goes, ”If you do not have time to perform the job correctly the
first time, how will you have time to redo the task?” Haste makes waste.
Don’t let pressure become the norm. If there is always undue pressure,
it becomes a condition that is setting you up to fail.
Bring the situation to management attention.
The Airline industry will always have daily pressures, but you must do your best
to ensure that the pressure does not affect system safety or efficiency.
Figure 41 Pressure
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COMPLACENCY
Complacency can contribute to a maintenance event when the mechanic is
overconfident about a task. This is usually a result of performing the tasks
repeatedly. Psychology experts say that many tasks become ”Automatic”.
Like driving to work, you sometimes can forget the trip. That is because you
were on ”Automatic.” You may have been inattentive. You have been ”unsafe.”
Most likely you were Complacent!
Tips
What are the Corrective Actions needed to avoid errors of complacency?
You should remind yourself to be aware of complacency.
Continued use of Job Cards is a good way to avoid complacency.
Ask for check by colleagues.
Rather think:“...today I will detect something...“
The error of Complacency can be minimized.
You must remind yourself, or an unsafe event may be the grim reminder of
complacency.
...LIKE ALWAYS...
Figure 42 Complacency
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LACK OF KNOWLEDGE
Lack of knowledge is one of the 12 common mistakes that contribute to events,
but is rather rare.
However, the Lack of Knowledge factor is usually compounded by a worker’s
failure to consult the manual, or failure to work as a team, or failure to
communicate the lack of knowledge.
Fatigue may also contribute to a Lack of Knowledge error type.
Tips
Lack of knowledge should not be an error in today’s aviation maintenance.
There are many ways to avoid such error. What are the Corrective Actions for
Lack of Knowledge?
First of all, strive to recognize what you do not know.
When something is unfamiliar, acknowledge that you need assistance.
Often your co−workers are the best source of new knowledge.
They can offer explanations and can show you how to do a task.
Use the manual. If you have the appropriate type training you can read the
manual to learn how to do a job.
If you have many situations where you lack appropriate knowledge, you
may request additional training.
Don’t let lack of knowledge become a company norm. If many people lack
knowledge, then additional training is necessary. Figure 43 Lack of Knowledge
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LACK OF AWARENESS
Lack of Awareness is an error that is often combined with other errors in the
dirty dozen. Quite simply it can be called ”Failure to Pay Attention.”
All too often, an event investigation will result in quotes like the following: ”I was
not paying attention,” ”I did not see the obstacle,” ”I did not notice the wing tip
was so close to the hangar door.”
Whatever the confounding excuse, usually the person acknowledges that there
was a lack of awareness.
Tips
Lack of Awareness is a challenge that can be overcome.
What are the Corrective Actions?
First of all, and most simply, remain alert to workplace conditions.
Maintain situation awareness by observing conditions, knowing what they
mean, and project to the impact of the conditions.
For example, if you recognize a close clearance between equipment,
buildings, and aircraft then you should project the potential danger and
remain aware of it.
Cooperate with colleagues to maintain awareness. Help one another.
Lack of awareness does not have to be a common error. However, you must
work hard to maintain constant awareness of the maintenance work
environment.
Figure 44 Lack of Awareness
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LACK OF RESOURCES
Lack of Resources is often cited as a reason for error.
Resources can mean many things: tools, manuals, computers, people, time,
and more.
Lack of Resources is likely to become a problem when it is combined with other
errors in the Dirty Dozen.
For example, if you need a part or a tool that is not available, then you must
speak up. You must be assertive, you cannot be complacent, and you must not
become a victim of pressure or of schedules. You must do the job correctly.
When there is a lack of resources you must be realistic about the situation and
find the best legal and safe way to get the aircraft back in the air.
Tips
What are the corrective actions for lack of resources?
First of all, you must be realistic and accept that resources are not unlimited
in any organization.
However, you have the responsibility to decide which resources are
imperative for safety. That minimum cannot be compromised.
Good job planning can reduce resource challenges. Order stock and special
tools before you start the job.
Have a means to pool parts and to get them quickly.
Work the resource logistics with planners.
Don’t let lack of resources become your workplace norm.
TOOLS
COMPUTERS
TIME
MONEY
PEOPLE
MANUALS
Figure 45 Lack of Resources
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DISTRACTION
Jobs and life are full of distractions! That is why ”Distraction” is another of the
Dirty Dozen. Distraction can come in the form of thoughts, noise, bright lights,
people, radio messages or telephone calls.
Since you cannot easily eliminate distractions, you must accept them and find
ways to cope with them.
Tips
”Keep your mind on the job.” ”Concentrate to avoid distractions”.
That is easier said than done. Whatcan be done to overcome Distractions?
Beware of other dirty dozen errors. If you are pressured, fatigued, or lack
assertiveness, then you are more likely to be bothered by distractions.
To avoid error, finish a task before you attend to the distraction.
If you leave a task unfinished, mark the task as incomplete.
Try to avoid stopping before the final step.
When you return to a task that was interrupted, go back a few steps in that
task to check that everything was completed.
When you know that you have mental distractions, then ask a colleague to
check on you, and you can also check on yourself. Recognize that mental
distractions can cause work problems.
Again, use the checklists and the job cards to help ensure that you
completed the job correctly, in spite of the complications.
Figure 46 Distraction
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LACK OF ASSERTIVENESS
Assertiveness is a good thing! It means that you speak up when you believe it
is necessary. When an assertive worker sees an opportunity, they bring it to the
attention of their co−workers or the management.
There are times when assertiveness is an absolutely necessary part of aviation
safety.
Tips
What are the corrective actions needed for assertiveness?
Usually you must speak up to assert your opinion. Do it politely and at the
right time.
− If you speak too soon you may be embarrassed.
− However, if you wait too long you may not be able to properly influence
the situation.
When you do speak up, follow the ’3 Cs’: Clear, Correct, and Complete.
Sometimes your actions show your assertiveness. That is demonstrated
when you insist on doing a job properly, or by refusing to do a job in a
manner that is unacceptable to your standards.
Sometimes you must document situations to show assertiveness.
For example, you write in the logbook only the items that you believe to be
air worthy.
Assertiveness is a good thing. It is not to be confused with stubbornness,
aggressiveness, bossiness or other negative characteristics.
Figure 47 Lack of Assertiveness
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FATIGUE
’Fatigue’ is one of the dirty dozen errors that we make in maintenance.
It is a potential problem for many. Fatigue can be a serious on−going ’chronic’
problem or it may be ’acute’ − just caused by a few nights of missed sleep.
Usually you make errors because you are fatigued.
For example, you may forget to complete a task, you may be unclear in your
communication, or you may be temporarily too lazy to do the job correctly. But
fatigue is the real problem. When you are fatigued, your physical strength and
mental ability are impaired. Fatigue can be managed, but first you must be
aware of the risks.
Tips
What are the corrective actions for fatigue?
If you are fatigued you may not admit it, so be careful!
Remain physically active. When tired, get up and walk around, stretch at
frequent intervals and engage in conversation if possible, take breaks, drink
caffeinated beverages and lots of water, avoid the most tedious work when
fatigued.
Work with colleagues and let one another know when fatigue may be a
problem.
To minimize fatigue, review this list:
− Get 7−8 hours of sleep every night.
− Eat properly.
− Exercise regularly.
− If you are always tired you should seek professional medical care.
Figure 48 Fatigue
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STRESS
Stress is a psychological and sometimes physical condition caused by some
kind of ”stressor.” The stressor can be a once−only situation or it can be an
ongoing one. For example, a short−term stressor may be a very difficult repair
that must be done quickly. Once the repair is completed the stress goes away.
An example of long−term stress could be a divorce situation or other personal
problems. Like fatigue, there is short−term stress, called acute stress, and
long−term stress, called chronic stress. Whether acute or chronic, stress can
affect your life and your work performance. You must deal with it.
What are the symptoms of stress? Different individuals may have different
symptoms; however, many behaviours are reliable indications of stress. Usually
you know when you are stressed.
Stress may make you irritable. It may affect your memory, your ability to pay
attention, or your ability to make rational decisions. Stress affects health.
It may cause loss of appetite, headaches, stomach problems, and inability to
sleep. Stress causes one to be nervous or restless. Stress can lead to alcohol
or drug abuse. Obviously, all of these conditions may put at risk the quality of
your work.
Stress is often a part of daily life and therefore a part of work. While stress is
not an error, it can lead to error. What can you do about it?
First of all, always be aware that stress can impact the quality of your work.
When stressed, you should slow down, or stop, and regain your composure.
You should try to think rationally, not emotionally, about the situation.
Sometimes you may want a ”TIME OUT” − a short break to think over the
stressful situation. It is often helpful to discuss the conditions that are
causing the stress.
You should ask your colleagues to monitor your work if you are stressed
out.
Engage in physical activity − exercise relieves stress. Do not let a stress
compound itself by performing poorly in your maintenance responsibilities.
Figure 49 Stress
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ERROR MANAGEMENT
General
Airlines are the safest mode of transportation. That is a FACT!
However, incidents, accidents and events happen, albeit to a minute
percentage of flights. The ”Event Investigation” describes a process that was
introduced by the Boeing Company in the early nineties.
The process is called Maintenance Error Decision Aid or MEDA for short. The
prime philosophy is that we can learn a lot from our errors. MEDA helps us to
document, classify, understand, and minimize our errors.
There are other investigation programs available, which have a structured
design to evaluate incidents. Which of the many programs is used within a
maintenace organistation is rather secondary. MEDA is widely spread
throughout the MRO community, therefor we will give a brief overview of its
operation.
We use the word ”Event” to include accidents and incidents where
maintenance is a contributing factor.
Iceberg Model
The ”Iceberg Model” provides a rationale for recording and understanding
human error using processes like MEDA. On a large iceberg, the tip of the
iceberg is above the water level.
The tip of the iceberg represents the one human error that causes a serious
airliner event. At the large base of the iceberg are the multitudes of minor
human errors that are committed daily within an airline maintenance
organization.
Most of these errors do not compromise safety but can cause large expenses
of wasted time and resources. However, some are ”operationally significant”
causing delays, cancellations or in−flight shutdowns.
We must reduce the number of errors below the water level to reduce the
serious events above the water level.
By understanding our current errors we can prevent future errors.
MEDA
MEDA - Philosophy:
LEARN FROM ERRORS!
Figure 50 Error Management
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FUEL TANK SAFETY
HUMAN FACTORS
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FUEL HANDLING SAFETY PROCEDURES
DETAILED-TRAINING
FRA US/E-1 ScV Feb 25, 2010
OVERVIEW
You can divide fuel handling safety procedures into three areas such as
fire prevention,
fire extinguishing and
personnel safety.
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Figure 51 Overview

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Overview cont.
Fire prevention is the elimination of all the sources which create or support a
fire.
Fire is assisted by inflammable vapor, heat sources and oxygen. So elimination
of any one of these sources can prevent fire.
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Figure 52 Fire Prevention

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Overview cont.
Because oxygen and fuel vapor can not be eliminated, no naked flame and
no smoking is allowed during aircraft maintenance and it makes perfect sense
that no refueling and defueling takes place during filling or changing of oxygen
bottles.
To fight any possible fire you must ensure that the correct fire extinguishers are
available.
You will learn more about fire fighting and the different types of fire
extinguishers in the lessons about fire protection in M11.8.
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Figure 53 Fire Fighting

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Overview cont.
Apart from fire, there are two other main hazards of working with fuel.
Fuel vapor inhalation can make you ill or even unconscious and any fuel
contact to your skin should also be avoided.
Fuel contact destroys the protective film on your skin and eyes. Fuel is also
poisonous and should not be swallowed.
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Figure 54 Fuel Vapor and Contact

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SAFETY AREAS
As you probably realize, fuel vapor comes mainly from the fuel vent tanks or
from fuel leaks.
You designate a safety area around on aircraft when a high fire hazard exists.
This would be during refueling or defueling or at any time when the fuel tanks
were open.
The limits of the safety area are marked in different ways, colored floor
markings are found at the gate.
The gate area is always a no−smoking area.
The refueling side of the aircraft is kept clear to ensure safe monitoring and
a free escape route.
The fuel truck has to be positioned to enable a quick escape.
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Figure 55 Safety Area - Outside

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Safety Areas cont.
You mark the safety areas inside the hangar with posts and barriers.
A no−smoking rule is normal inside hangars. Additional warning signs and
signal lights alert the hangar crew if the aircraft fuel tanks are open.
Refueling in the hangar must be avoided, but if you HAVE TO the entire hangar
area will become the safety area.
You have seen that the fire hazard with fuel vapours can be reduced by
recognizing the safety areas.
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Figure 56 Safety Area - Hangar

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INFLAMMABLE FUEL VAPOR LEAKS
Fuel leaks are either caused by refueling malfunctions or by damage to the
aircraft.
If refueling leaks occur, they would usually be at the vent tank openings.
You should be aware that leaks can occur in faulty refueling couplings,
refueling hoses and fuel truck components.
You must deal with any spilled fuel or fuel leakage immediately.
You first stop the leakage flow
then add a binding agent to the fuel spillage.
You minimize fuel leakage of any kind by ensuring that refueling is not done
unattended especially during overwing refueling.
You should also be aware that fuel may spray around, if you drain tanks in
windy conditions.
Fuel leakage may also be caused by damage.
Aircraft damage can be caused by the aircraft moving during refueling. So you
must ensure that the wheel chocks are in place during refueling.
Even with the wheel chocks in place damage to the tanks may occur. This can
be caused by any equipment which is located too close to the aircraft as it gets
heavier because of the increasing fuel load compressing the shock struts of the
landing gears.
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Figure 57 Fuel Leaks

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HEAT SOURCES
As mentioned before, no naked flames and no smoking is allowed at the
aircraft to reduce the fire hazard, but be aware, that there are many other heat
sources near an aircraft which are capable of igniting a fuel air mixture.
It should be obvious to you, that refueling is not allowed when the aircraft
engines are running.
For the same reason no car engine should be operated near or below a vent
tank opening.
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Figure 58 Heat Sources

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Heat Sources cont.
Other heat sources that may inflame a fuel air mixture, are sparks.
Conditions that can create sparks on an aircraft can be either
electrical switching,
HF transmission or
weather radar operation
by metal parts such as tools being struck together or
by electric static discharge.
Electric static charges are not visible, and as you probably know by experience,
you cannot feel if your body is loaded with a high static charge, you just feel the
discharge if it happens in a high energy spark.
During refueling electric static charge is created.
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Figure 59 Sparks

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DETAILED-TRAINING
Heat Sources cont.
To prevent any sparks by electric static discharge the fuel truck must be
connected to the aircraft by a grounding lead.
When working in a fuel tank, you must use special tools which do not create
any sparks. These tools are called explosion proof tools. Even walkie−talkies
which are used during tank maintenance must be explosion proof.
When entering a tank, you have to wear special clothing made of cotton which
will not create electric static charges.
Avoiding sparks is one of the most important things to prevent a fire.
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DETAILED-TRAINING
Aircraft Grounding for Refueling
Fuel Tank Access Tools
Fuel Tank Access Equipment
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Figure 60 Avoiding Sparks

B111_FTS_2011.06.01 Fuel Tank Safety.pdf

B111_FTS_2011.06.01 Fuel Tank Safety.pdf

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B111_FTS_2011.06.01 Fuel Tank Safety.pdf