External power supply for training
I purchased a 1976 182P with dual Garmin G3X Touch displays, a G5 standby ADI, GNX 375 GPS plus other avionics. The pilot’s G3X and the G5 are powered through the battery switch while all the other avionics have a dedicated avionics master switch. A friend loaned me a power supply to provide continuous plower while learning the systems. He also advised to check the POH for its use.
The POH says the following under the ground power plug receptacle section: “Electrical power for the airplane electrical circuits is provided through a split busbar having all electric circuits on one side of the bus and other electrical circuits on the other side of the bus. When an external power source is connected, a contactor automatically opens the circuit to the electronic portion of the split bus bar as a protection against damage to the transistors in the electronic equipment by transient voltages from the power source. Therefore the external power source cannot be used as a source of power when checking electronic components.”
So should I or should I not use an external power source to power my avionics on the ground? I’m not “checking electronic components” I’m practicing or studying.
Comments
Connecting power to the external power connector will not allow power to the avionics bus. There is a diode from the ext. connector to the split bus contactor. This prevents voltage spikes from activating the starter motor affecting the avionics.
You will have to connect a power supply directly to the battery and turn on the master. It must be a newer precision, processor regulated unit, not an older 'battery charger'. The older units have no voltage regulation and can apply 15 volts or more.
The power supply should have at least a 20 amp capacity to handle the avionics load.