Challenger Ultralight Aircraft Maintenance

Tip #2 – The Phantom Load

I originally ran my Icom A-5 radio off of its internal battery and took it home at night to recharge. This worked fine but I feared running out of battery power after a long cross country flight. The solution to this was to connect the A-5 to the battery of the aircraft. I wanted to run the radio directly off of the aircraft battery without going through the Master switch. This way I could still monitor the air waves while power off gliding or listen to traffic while doing my pre-flight checks. I did the same with the GPS.

The new electrical arrangement worked fine. It gave me great peace of mind not worrying about running out of radio battery power in flight.

A problem began to occur though when I would leave the plane for a few weeks without flying. The battery would drain somehow. A couple of times the aircraft would not start. I was puzzled at what might be causing my aircraft battery to lose power while I was away. I double and triple checked that I was not leaving the Master switch on, yet it kept happening.

Finally one night at home I heard a commercial from the power utility company about “Phantom Loads” in the home. Quite a number of home appliances use power even when they are turned off. Televisions and other electronic devices,for instance, are still big power users when we think they are turned off. The utility company recommended house holders switch off the power to these devices from an external switch such as a power bar or a switched wall outlet. This would save money on the electrical bill.

I pondered that concept with regard to my plane. Could my aircraft radio or GPS be using power when I had it switched off? On my next trip to the airport I unplugged the radio power cord before leaving. I took the GPS home to learn more of its secrets.

The problem stopped. I now double check to unplug the radio power cord every time I leave the aircraft so it will not draw power from the main battery. Another solution, of course would be to have a switch on the panel to control power to the radio and GPS. Another idea is to have a solar powered trickle charger connected to the aircraft battery when the plane is stored. At any rate, it is still surprising that the little A-5 radio could drain a medium sized 12 volt utility battery over the course of 3 weeks or so.