Modern combat aircraft like the F-16, F-18, F-22, F-35 (and some newer F-15’s) are all fly-by-wire aircraft. This means loss or degradation of the electrical system could result in the pilot being unable to control the aircraft even if the propulsion system is still operable. This makes it very important that the Electrical Wiring Interconnect System (EWIS) design is robust and resistant to: 1) crosstalk, 2) common mode failures, 3) EMI, and 4) environmental and maintenance hazards.
Typically EWIS design criteria require wiring to be routed in the airframe to mitigate these issues, but what happens when a disconnect is needed? Competing for bulkhead space, weight and structural considerations often means disconnects are congested with many types of signals from a multitude of systems. Here are some guidelines:
1) Redundant signals still have to remain separated. To reduce the number of disconnects, this may require the use of connectors that contain more than one contact size within the same connector.
2) If redundant signals can’t be routed through separate disconnects, keep them as far from each other in the connector as possible so that an overcurrent event is less likely to affect more than one of the signals.
3) In general, power carrying conductors should be routed through different disconnects than data or other low-level signals.
4) For power circuits, try to keep “like” signals (low power vs high power, AC vs DC, etc) routed together.
5) Try to keep data signals with similar EMI and RFI sensitivity in the same disconnect. Keep Ground shields on each side of the disconnect; either through the connector backshell or a ground point on the airframe. Avoid running shield conductors through the connector pins if possible.
6) Signals known to have a sensitivity to electromagnetic or RFI coupling should also be run in separate connectors, or sufficiently shielded/grounded/separated in the disconnect pinout as much as possible.
Should you have any further questions, please contact InterConnect Wiring at 817.377.WIRE (9473).
