曝光台 注意防骗
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and flight deck condition of wiring as a method of determining what
additional actions were necessary to prevent the accumulation of
combustible materials in these areas. The acknowledgement of
ongoing assessments, in addition to the enhanced zonal inspections
emanating from the EZAP, should result in a frequency and intensity
of inspections to address the concern.
8 April 19 2002 30
2b.3 OEM Review design practices regarding the use of drip shields for this
specific situation, investigate periodic selective inspection and nondestructive
testing of wiring. Develop updated wiring separation
guidelines that consider loss of multiple critical functions from a
common mode failure
Boeing - Expected and actual sources of moisture impinging on
electrical wiring is presently taken into consideration during the
design of the electrical system. Boeing presently conducts periodic
inspections of airplanes, including the E/E bay and flight deck.
Selective inspections, as a result of in-service experience, are
evaluated on a case by case basis. Wire separation and segregation
guidelines are presently contained within the SWPM and reflect
current production design standard that account for loss of multiple
or redundant systems. Any changes to the standards will be reflected
in future revisions to the SWPM
Airbus - Potential source of contamination of airplane wiring are
identified during the design and development of the airplane, and
appropriate protection in from of drip or heat shields are included to
minimize the effects of contamination. Airbus currently conducts
periodic inspection of the aircraft wiring including the avionics bay
and flight deck. The information collected as a result of these
inspections is used to improve and update, as required, the current
electrical design, technology of electrical components and technical
design directives and ESPM guidelines.
Routing, separation and attachment guidelines, as well as prevention
of contamination and cleaning of noted contamination on the wiring
and/or electrical components are currently included in the ESP
Lockheed - The Lockheed SWPM manual provides practices specific
to SWAMP locations. Detailed Visual Inspection is the suggested
inspection method for detecting wiring faults that may be related to
moisture ingression. Drip shields are used throughout the SWAMP
areas exclusively for the protection of wiring. It is the responsibility
of each operator to ensure that the design integrity of the airframe is
properly maintained and to incorporate maintenance and inspection
programs that follow industry best maintenance practices
[COMMENT 1] Boeing states that “wire separation and segregation
guidelines are presently contained within the SWPM and reflect
current production design standard that account for loss of multiple
or redundant systems.” The SWPM is referenced, but not quoted, and
the reference to the production design standard is non-specific.
Section 20-10-19 of the SWPM states the following:
The airplane wiring is designed and installed:
• To prevent the propagation of the effects of electrical
faults to other independent power sources
• To prevent possibility that the failure of a component
in a redundant system can disable another related,
redundant system
• To avoid electromagnetic interference (EMI) between
electromagnetic compatibility (EMC) circuits that are
not compatible.
These functional concerns do not take into account the potential fire
or the potential for multiple critical systems failure. In other words
it’s OK to lose all primary flight control circuits simultaneously
(possibly as the result of a localized fire or arc-tracking event) as
long as the back-up are still functional.
8 April 19 2002 31
Under the assumption that the critical failure mode is a simple bolted
(non-intermittent) short circuit, Boeing allows the separation
requirements to be relaxed if a fusible link circuit breaker is placed
between the source and the co-located wires.
[COMMENT 2] Boeing represents that present wire separation and
segregation guidelines already account for loss of multiple or
redundant systems. The ATSRAC needs details to better determine if
these guidelines provide adequate separation.
[COMMENT 3] This does not update anything. It only says we
already have it covered. Also does not address wire separation.
OWNER REMARKS: OEM P3
Wire separation guidelines outlined within the OEM standard wiring
practices manuals reflect those used during and certified for airplane
manufacture. These guidelines reflect only a portion of the methods
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