External GPU

[FlyBry]

The external GPU is a great addition! I was able to start it and turn the connection switch on and get both green lights, however I don't see any indication of any external power being present in the cockpit. I looked all over the cockpit and didn't see any switch inside to connect external power. Am I missing something?

[vdrummer4]

There is neither a switch nor an indicator light, but you should be able to see the voltage rise to 29 V.

See also the attached screenshot from the PTM (Expanded Checklists, Cockpit Inspection.

[FlyBry]

3 hours ago, vdrummer4 said:

There is neither a switch nor an indicator light, but you should be able to see the voltage rise to 29 V.

@vdrummer4, thanks for the tip. Indeed I do see the voltage rise to around 29 volts when the GPU is connected. I didn't see that version of the checklist in the aircraft documentation.

The checklist that comes with the aircraft states in step 35 of the Cockpit Inspection (see below), to turn the battery switch to "OFF", however when that is done (even with the GPU connected) everything shuts off. In fact, there is nowhere else in the checklist after that where is says to turn the battery switch back to "BATT", so not much can be done with the aircraft in that state. In other aircraft that use external power, the electrical buss at least remains partially on with the battery off. This workflow seems a bit different. Feels like the GPU for this aircraft is a big alternator to keep the battery charged. Just my guess

[Coop]

Correct, the volt rise is your only indication. The battery switch off step there is due to the way most operators fly the jet. Prep everything, then turn it off and wait for the passenger to show up in their limo  

[FlyBry]

Thanks @Coop. At what point is the battery turned back on?

[vdrummer4]

6 hours ago, FlyBry said:

@vdrummer4, thanks for the tip. Indeed I do see the voltage rise to around 29 volts when the GPU is connected. I didn't see that version of the checklist in the aircraft documentation.

The real-world documents are linked on a pinned post on the Torquesim discord. You can also find it by googling "c525 ptm". There are 2 volumes (V1 and V2), one with procedures and one with system descriptions.

I recommend reading through the expanded checklists at least once, because it helped me to understand some seemingly unnecessary steps in the checklists (e.g. "Throttles ... as required" on descent.

6 hours ago, FlyBry said:

Feels like the GPU for this aircraft is a big alternator to keep the battery charged. Just my guess

As far as I understand it, that's basically the point of the GPU. The batteries in the CJ are pretty small, so if you're sitting on the ground for some time with BAT / avionics on, you might not have the > 24V required for the engine start anymore.

5 hours ago, FlyBry said:

Thanks @Coop. At what point is the battery turned back on?

Obviously you have to turn it back on before engine start. At night, I don't turn it off at all, because otherwise I'd be sitting in a dark cockpit.

This is a CJ1+ (different engines and Proline 21 avionics), but it's the closest I could find that shows the engine start from within the cockpit (time: 28:16).

Notice the PFDs are off, so the BAT switch is in EMER. You can see CM1 (left seat) turn the switch to BAT (you can hear the fans powering up) at 28:28, right before the "Before Start" check list.

[FlyBry]

@vdrummer4 thanks for the info and video. I just thought it was strange for a checklist to specify turning the battery OFF (and the GPU not holding the power on), but then not turn the battery back on again. Not a real life pilot here, so was just following what was written, but obviously it makes sense to have the battery ON.

[diamonddriller]

I asked about this earlier: