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2.5.1 Integrity of Wiring and Bonding Jumpers
The vast majority of the bonding jumpers were found to be in excellent condition. There were
isolated instances of broken, missing, or corroded jumpers, but these were random in nature and
did not exhibit any correlation with aging or location. Even though there were reports of minor
corrosion / discoloration of bonding jumpers, the data showed that bond integrity was not affected.
Any discrepancies found were resolved by each manufacturer on a case-by-case basis.
With respect to other wiring in the fuel tank, findings showed that the types of wire being used in
the fuel tank were not degraded by the fuel tank environment (see next topic below). Again, some
discrepancies were found related to the installation and are being addressed on a case-by-case
basis by the manufacturers.
Findings in many cases showed that wire installed in metallic conduits is susceptible to abrasion.
The affected manufacturers have evaluated or are evaluating their fuel system wiring conduit
installations to address this issue.
2.5.2 Condition of FQIS Wiring and Components
The wiring and components of the fuel quantity indication system (FQIS) were found to be in
good condition across the fleet except as noted below.
Boeing issued a service bulletin for the 747 Classic (747-100, -200, -300, SP, and SR), which the
FAA has mandated, specifying the inspection and replacement of wiring in the fuel tank that is
attached to older style fuel probe terminal blocks, which can possibly damage the FQIS wiring.
For those manufacturers whose designs included the routing of FQIS wiring in metal conduit,
additional review and corrective action has been taken to address abrasion and wire separation
issues.
Instances of sulfide contamination were observed on various models where there was exposed
copper or silver on the wiring or the components, but no system issues were reported associated
with this contamination. The FAA is addressing sulfide contamination with a research effort to
determine its effect and, if required, the process for cleaning and sealing affected components.
2.5.3 Condition of Fuel Pumps, Fuel Lines, and Fittings
Overall, the condition of the fuel lines and fittings is excellent. Most discrepancies were isolated
and minor in nature and were either related to an installation design or to collateral damage caused
during an entry into the fuel tank for other purposes. Nothing indicated a chronic problem
requiring immediate or long-term action. There was one instance where Bombardier de Havilland
issued a service bulletin, mandated by Transport Canada, to inspect and rectify a fuel coupler that
was incorrectly installed.
2.0 Overview (continued)
August 4, 2000 Industry AFFSP Report Page 13
The external inspection of fuel pumps showed them to be in good condition. Again, only minor
discrepancies were noted. It should be noted, however, that the AFSSP inspection process did not
require the removal, teardown, and detailed component inspection of fuel pump installations.
Currently, a number of fuel pump installation issues exist across the fleet with respect to internal
wear or corrosion. The industry and responsible regulatory authorities are aware of these issues
and have taken the appropriate action to address them.
2.5.4 Electrical Bonding and Grounding of Fuel System Equipment
Electrical bonding and grounding of fuel system components falls into three areas:
! Static bonding.
! Fault current bonding.
! Lightning bonding.
The inspections showed that static bonds do not exhibit aging. There were no trends to suggest
that the older the airplane, the higher the bonding resistance of the static bonds. Findings did show
that some static bonds were exceeding their original manufacturing resistance limit, but they were
still well within an acceptable limit for the dissipation of static-charge buildup.
With respect to fault current bonds, dependent upon the model /manufacturer, these bonds were
either acceptable or showed some aging effects. For those manufacturers whose fault current
bonds are aging, the designs are being enhanced to increase existing margins, and periodic
inspections are being considered to ensure that these margins are maintained.
Overall, there were no issues associated with lightning bonds. Ongoing studies are now being
conducted by some manufacturers to validate lightning bonding criteria and in-service limits to
further enhance knowledge in this area.
2.5.5 Inspection for Foreign Object Debris (FOD)
There were no significant findings regarding the presence of FOD in the fuel tanks or damage
caused by FOD in the fuel tanks.
2.5.6 General Tank Condition
The general condition of the fuel tanks across the operational fleet was found to be excellent
　
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