dbaflyer
Well Known Member
I think this should have been done as part of flight testing, but now that I've got a new G5 and thinking about getting an IFR rating, I thought it necessary to understand what happens in the cockpit when various switches are turned off. Yes there is the theory of your electrical diagram, but then there is the reality of what happens.
I have a dual display G3X touch system with GMC305, GTN650, G5, GTR200 and audio panel. Dual alternators feed the main bus. The G5 has a backup battery and an IBBS keeps the displays, GEA24 and GSU25 powered up.
The avionics buss is feed from the main buss with with an avionics switch and relay. A second essential buss switch feeds the same avionics buss from an always hot battery buss.
Testing out scenarios like:
1. Turn off main alternator
2. Turn off main battery switch
3. Turn off backup battery (IBBS) switch
At this point everything is running very good and powered up. So I work up my nerves to actually turn off the essential buss switch which is going to make my entire panel go dark except the G5 which has its own battery. The single electronic ignition is running off the always powered battery buss so the engine is very happy.
I was doing this over the top of an airport with plenty of altitude so I went ahead and hit the switch. Like planned the panel went dark, but something happened that wasn't expected. Any guesses as to what it was?
My bird immediately went into a right handed turn and did a slight pitch down. Keep in mind before the panel went dark the auto-pilot was flying in both pitch and roll.
At the time I had know idea what jut happened, but now later can speculate that my airplane was not completely in trim and the AP servos were doing some work to keep the plane straight and level. When the servos powered down those forces went away.
If anyone has any other ideas on what could cause this let me know, but it was fairly scary at the time.
I have a dual display G3X touch system with GMC305, GTN650, G5, GTR200 and audio panel. Dual alternators feed the main bus. The G5 has a backup battery and an IBBS keeps the displays, GEA24 and GSU25 powered up.
The avionics buss is feed from the main buss with with an avionics switch and relay. A second essential buss switch feeds the same avionics buss from an always hot battery buss.
Testing out scenarios like:
1. Turn off main alternator
2. Turn off main battery switch
3. Turn off backup battery (IBBS) switch
At this point everything is running very good and powered up. So I work up my nerves to actually turn off the essential buss switch which is going to make my entire panel go dark except the G5 which has its own battery. The single electronic ignition is running off the always powered battery buss so the engine is very happy.
I was doing this over the top of an airport with plenty of altitude so I went ahead and hit the switch. Like planned the panel went dark, but something happened that wasn't expected. Any guesses as to what it was?
My bird immediately went into a right handed turn and did a slight pitch down. Keep in mind before the panel went dark the auto-pilot was flying in both pitch and roll.
At the time I had know idea what jut happened, but now later can speculate that my airplane was not completely in trim and the AP servos were doing some work to keep the plane straight and level. When the servos powered down those forces went away.
If anyone has any other ideas on what could cause this let me know, but it was fairly scary at the time.