Fuel pump and ICE detector with single engine flight

[dlrk]

In single-engine flight, disarming the affected side fuel pump illuminates INOP lights and displays both yellow fuel pump EICAS warnings.

When ice is detected in single engine flight, the ICE light comes on yellow even if wing anti-ice is on illuminated green, and the 14th crossfeed valve is open.

Is this intended/expected?

[Graeme_77]

Interesting question, and sorry I missed it earlier. Yes, once is most likely expected behaviour and the other definitely is.

1) Fuel pumps. As you can see from the study menu, the boost pumps are not dedicated to a single engine. You have two boost pumps, and they both provide pressure for both engines. They should both run, or both not run.  As such, the switches are not really turning the pumps on and off, but rather controlling the automatic logic. When the switches are pressed in, if pressure is lost on the engine driven pump on that side then both boost pumps will run. (So there is always a dual source providing fuel for the engine, one engine pump and electric boost pumps on standby, or both electric boost pumps).

By switching off the right side, you are telling the system that despite the fact there is no fuel pressure from the right side engine pump, you don't want boost pumps. It's not happy about this and shows inop for the pumps.  I will verify this behaviour with the type rated pilots as despite it being essentially the same check performed on the ground, it does "feel" wrong to me.

However, at this point, go into failures, fail the other side primary ejector pump and you'll see the pumps come back to life as you would expect.  

2) Ice detection. The ice detectors are not looking at ice on the wing, and are not affected by the wing ice protection. They operate on a cycle of 5 seconds of heat, 55 seconds with no heat and as long as ice continues to build, they will indicate ICE. They are telling you that you are flying in active icing conditions and ice protection is required. As long as you have the 14th stage isol open you'll be protecting both wings.

[Graeme_77]

To add, following some extensive conversation, it's possible the flight condition behaviour can be improved. It seems for the single engine shutdown the on-side boost pump switch off should only generate the INOP message on that side, and will stop both pumps from running. We're not 100% as the documentation is pretty poor, and pilots can't simply shut down a real engine in flight!. However, the devs and testers will keep investigating and update where possible.

Thanks for the post - a real head scratcher!

[dlrk]

That's my impression from the checklist, that INOP message should only be on the deactivated pump.

With regard to the ICE message, it's not that the ICE EICAS comes on, it's that it comes on in yellow, even if the anti-ice is on and green, whereas in two engine flight, ICE is green and doesn't cause a warning

[sunake]

22 hours ago, Graeme_77 said:

To add, following some extensive conversation, it's possible the flight condition behaviour can be improved. It seems for the single engine shutdown the on-side boost pump switch off should only generate the INOP message on that side, and will stop both pumps from running. We're not 100% as the documentation is pretty poor, and pilots can't simply shut down a real engine in flight!. However, the devs and testers will keep investigating and update where possible.

Thanks for the post - a real head scratcher!

I brought up something similar in the discord. The same thing happens on the ground so perhaps your pilots can do a single engine taxi after landing if their company allows that procedure.