Boeing Wire Separation requirment

Example Separation Codes
• Looking up the ‘*’ for this bundle shows that it is:
• WIRS MPI Screen:
Additional Information & Special Considerations
• Wire wrap wires: All separation requirements apply to wire wrap wires including ¼” minimum airspace separation between all conductors of different functional codes. • All affected wire wrap wires require a routing graphic. These include, adds, deletes and impact wires.
SFAR88 continued
• The varglas serves the purpose reducing the possibility of electrical arcing between threat and target wires as well as from other near by wire bundles.
SFAR 88 Cont.
• Threat and Target wires are pulled out of the standard bundle runs and routed separately from other bundles.
But what is SFAR 88 really mean?
• SFAR 88 wires consist of fuel tank wires • These wires are signal wires and power wires. • The basic idea of SFAR 88 is to separate signal wires (Target) from power wires (Threat) to reduce the risk of a Threat wire shorting to a Target wire to produce an ignition source in the tank.
SFAR88
• SFAR88 (Special Federal Aviation Regulation 88) is a revision to the fuel system design requirements to mitigate the possibility of an in tank ignition source. • SFAR88 wire bundles are identified on DWG 828B6103. • SFAR 88 wire bundles are identified in the Fuel System Wiring table on Frame 1 of all PI picture sheets.
Why Separate Wiring?
Separation Code Data
• For 747-400, the wire separation code is divided into 3 categories.
Category 1 Functional Separation
• Functional separation is defined as the bus which supplies power to the bundle. • Code 1 is for bundles powered from bus 1. Code 2 is for bundles powered from bus 2. Code 3 is for bundles powered from bus 3. Code 4 is for bundles powered from bus 4. Code S is for bundles powered from standby power. Code N is neutral (Non-redundant non-power circuits).
Category 3 Special Cases/Sub-Functional
• The 3rd character in the separation code is reserved for special cases. These special cases are usually used to ensure physical separation of dual channel (redundant) Avionic data or systems. • The 3rd character is typically an ‘A’ or a ‘B’, but can be any letter or ‘*’. • The 3rd character separation is built into the design and data is not available to the repair station.
Example Separation Codes
• This means that the bundle has a Functional Separation Code of 1, which means it’s powered by bus 1. • The second digit is also a 1 which means that it is a source of EMI interference. • The 3rd digit is an ‘*’ which means that there are special separation requirements which are accounted for in the design.
Category 2 EMC Separation
• EMC separation is defined by whether the bundle (Code 1) is a source of EMI interference, (Code 2) neither a source and is not affected by EMI interference and the last (Code 3) is affected by EMI interference.
SFAR88 continued
• SFAR88 installation requirements are found on SH 1 of every 828B810* DWG.
SFAR88 continued
• Use only ES4400 Varglas on SFAR88 bundles which require sleeving.
Tools/Resources
• PI DWG Frame 1 of each picture sheet has a table which lists the Category 1 separation. • CH 91 (D280U106) WD lists (but does not define) the Category 1, 2 & 3 separation codes for each bundle.
Boeing Wire Separation
Description and overview Including SFAR88
Applicable Documents
• D6-35625 (Wire separation requirements for 747-400) Boeing internal document. • BAC5158 Wire Installation Requirements. • D6-54446 SWPM (Standard Wiring Practices Manual 20-10-19
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Category Separation Table
PI DWG Functional Separation Identification
PI DWG Functional Separation Identification Continued
Example Separation Codes
• Bundle W4874 has a separation code of 11*.