As mentioned earlier, I have used single switches to control the SDS engine control units (ECU) and coil packs. However, I compensate for the risk of a single switch failure by using the highest quality Mil-Spec switches I could find – ones manufactured by Honeywell. The use of single switches is a departure from the SDS recommendations but I feel the risk of this change is negligible given the switches I am using.

One of the interesting things I have been able to do with the Garmin G3X is to dispay warning messages on the EFIUs whenever only a single ECU or single coil pack has been selected. This helps minimize the possibility of taking off on a single ECU or coil pack (somewhat analogous to taking off on a single magneto in a traditional aircraft).

The switch at the right is the Honeywell 2TL1-12A switch used to control the ECUs and coil packs. It is an On-Both-On switch. If you look closely, you will see that the switch is locked in each position unless the lever is first pulled out before moving. The switches I used are in the wiring diagrams found below and may be purchased at the usual sources such as MOUSER or DIGIKEY.