Electrical System – Bus Assignment for Instruments and Equipment
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Hi everyone,
following up on my earlier post about the electrical system logic (bus-ties, AC priority, STBY INV relay etc.), I did some further testing specifically looking at how instruments and equipment are distributed across the two electrical channels. I think this one is worth flagging separately because it directly affects how failure scenarios play out during flight, not just the electrical panel behaviour.
Let me say upfront that the depth of the electrical system implementation is genuinely impressive. The bus-tie and transfer logic, the AC and DC splitting, the generator inhibit during starting, the STBY GEN auto-start, the START MASTER ESS DC logic, the APU GEN airborne single-bus limitation, the cross-starting capability, the battery inhibit on STBY GEN operation - all of this works correctly and in detail. It's clear that a huge amount of work went into getting the electrical architecture right, and testing it has been a real pleasure.
However, I did notice an issue with how individual consumers are assigned to their respective busbars, and this one matters because it affects what the crew can and can't do after a generator failure.
When Channel 1 is lost (GEN 1 OFF/RESET, both bus-ties OPEN, only GEN 4 supplying Channel 2), essentially everything goes dark. Both the left and right flight instruments show fail flags, all radios (VHF COM 1 and 2) lose power, the weather radar and transponder go offline, and all four engine intake anti-ice systems fail. The only correct Channel 2 response I could find on the overhead was R PITOT HTR FAIL.
In the real aircraft, Channel 1 loss should only take out the Captain's instruments and Channel 1 equipment. The First Officer's side should remain fully operational on AC BUS 2 and DC BUS 2, and the crew would retain at least VHF COM 2, one DME, one transponder, and functioning right-side flight instruments. The whole point of having two independent channels is that a single channel failure should never leave the crew without instruments or communications.
When I tested it the other way around (Channel 2 lost, only GEN 1 on Channel 1), neither side showed any fail flags at all and everything kept working normally, with the exception of R PITOT HTR FAIL illuminating correctly. So it appears that most equipment is wired to Channel 1 only, rather than being distributed across both channels.
This effectively means that a Channel 1 failure in the sim is far more catastrophic than it should be, while a Channel 2 failure has almost no operational impact. In reality, both failures should be survivable with roughly equal levels of degradation on opposite sides of the cockpit.
Some bus assignment logic is clearly in place already (the electrical system logic I mentioned above, plus a few overhead items responding correctly to channel loss), so hopefully this is something that can be expanded to the instruments and avionics in a future update.