After some time off from the Jetstream, I'm flying it more regularly these days (party to gaze in awe at my new UTX+GEX combo), and I'm having trouble with the electrical system after engine start. So, here's what I do. I have a flight. I land, kill the engines the way I should (i.e., I know how to engage the start locks). Connect the external power, shut down the other stuff, and take a short break and plan my next flight and then go back to the bird. Then, I preflight and program FMS on Ext Power, fire up the engines and then turn on the battery and generator. I disconnect the the ext power, turn on the avionics and fire up the FMS again and it turns off in the self test? The battery/gen knob is in batt. Trying to troubleshoot, I tried switching the knob around to Generator and Battery, and I think the Gen says it has a negative value. Am I accidently in Beta? Anyway, I'm sort of perplexed by this. My recollection is that the knob always stays in battery and that once the battery and gens are on everything should work fine. Am I missing something with the bus tie (which I don't touch normally). I'm certain this is me being an idiot and not a problem with the system (unless Peter Dawson's battery fix is somehow creating a non-battery, which I would sincerely doubt). Any troubleshooting ideas will be much appreciated.

Program the FMS once you have the engines going, otherwise you loose the programming when you switch from genset to engine driven alternator.A neg value on the ampmeter when in battery means you are discharging.If you are on the external power, then the battery is isolated as described in the AOM (see battery contactors section 8.5 pg 3 and 4). The AC busbar contactors are on pg 13 same section.The knob is just a selector for the ampmeter. It doens't matter where you put it.

Program the FMS once you have the engines going, otherwise you loose the programming when you switch from genset to engine driven alternator.A neg value on the ampmeter when in battery means you are discharging.If you are on the external power, then the battery is isolated as described in the AOM (see battery contactors section 8.5 pg 3 and 4). The AC busbar contactors are on pg 13 same section.The knob is just a selector for the ampmeter. It doens't matter where you put it.

Thanks, Dan, so why would I be discharging after disconnecting the GPU and firing up the generators? Shouldn't it be charging?

I'm not sure, remember this is British electrical. There is logic having a charging battery shown as negative since it is 'sinking' current and the generator 'sourcing' current is positive. I have slept at least three times since I last paid attention to the ammeter. Sorry. This is where Lucas electrical for Jags came from, who knows.

I'm not sure, remember this is British electrical. There is logic having a charging battery shown as negative since it is 'sinking' current and the generator 'sourcing' current is positive. I have slept at least three times since I last paid attention to the ammeter. Sorry. This is where Lucas electrical for Jags came from, who knows.

Nice one. Thanks, I'll play with some more this weekend and see what I can come up with.