Fuel system behavior and other issues
-
I don't have an 146 FCOM but have one for the RJ. In there it says:
"If an engine is not supplied by an electrically driven pump, the engine will keep running under gravity feed." Which makes sense due to the physical positioning of tank and engine.
Turning off pumps and the feed valves does not close the low pressure valve to the engine. Those can only be closed by pulling the fire handle.Now why the engine died in one situation and not the other I am not certain and would have to dive deeper. Perhaps it depends on fuel level and power-settings (maybe even any manoeuvring you were doing?). Perhaps pump failure has a random chance that mechanical parts of the pump broke and are blocking the lines?
I imagine that in some situations gravity feed would not be able to provide a sufficient rate of fuel to keep the engine from flaming out. -
This is something that came to light in a community stream around the time of the 146 V2 release when one of the streamers accidently switched off one of the fuel pumps in flight. Up until that point, I don't think anyone has ever tried turning a fuel pump off in flight! And now, just like buses... 😉
The logic in the real 146 is that if a fuel pump is switched off, the standby pumps will continue to supply fuel to the engines. There is one standby pump in each wing supplying the inner feed tanks, and they are powered by the yellow hydraulic system.
If the standby pumps fail, then gravity will keep the feedtanks full until approx 2,000KG of fuel remains per side.
This isn't how its currently working in our simulation of the 146 but we do have this noted as an area to improve in the next update. The reason you are likely seeing differences in the engine shutdown logic is due to speed and altitude. At high altitudes, the engines are more reliant of fuel flow, so if one of the fuel pumps is switched off at high altitude it will likely lead to an engine shutdown. At lower altitudes, switching off the fuel pump will likely not effect the engine.
Mark - Just Flight
-
Thank you for the explanations!
I did expect some gravity flow: after all, APU starts and runs fine on the ground even with L inner pump off. I just never expected it to be enough for engines on cruise thrust.
All test flights were at FL170 so I am still a bit puzzled by the inconsistency in failures. But it could indeed be that shutdowns were related to holding pattern turns or less fuel remaining. All in all I do not think this is too important.
Does it make sense to report the load flight and the EFB freeze issues elsewhere or are they known to the dev team?
-
@grue There are a couple of reasons that I can think of that would cause the EFB to be unresponsive:
-
If the EFB displays a "license failure" message this would point towards an activation/installation issue. If this is the case we would recommend getting in touch with our support team via the following link and they will be able to help troubleshoot that with you: https://www.justflight.com/support
-
A recent update to the Horizon Sim 787-9 mod caused a compatibility issue with the EFB/tablet in our aircraft. Horizon Sim has since released a further update fixing this compatibility issue, so if you are using this mod, we would recommend making sure that it is fully up to date.
-
Simconnect become a bit unstable after multiple flights and can prevent the aircraft's gauges to correctly load (usually evident by a "loading aircraft" message on the EFB). If this occurs, try pressing the pause/break key on your keyboard a couple of times to see if that 'kicks' the aircraft back into life. If not, the only other solution we could provide is to restart the simulator.
With regards to the other points you have raised in your original post, we currently have a fix in testing for improved holding patterns with the UNS-1 and this will be included in the next update. The crashing when loading a saved flight isn't something I have seen reported before, and I personally haven't tried to load a saved flight, but we'll get that logged so we can try and replicate that on our end. If we can replicate it, we will investigate it further and include a fix in a future update to the 146.
Mark - Just Flight
-
-
@grue without wanting to talk down this otherwise great product: but I do not think turn bank or fuel remaining is factured in. It's like I said once: not a lot of people will try these features but when you do, there's not a lot of addon planes that hold up to the promises made ih those mouth watering trailers. Not even the ones of his lord almighty RR. (Leonardo being the only real exception to that, as far as I can judge)
-
@Mark , I do not have the 787 installed neither did EFB did not display any messages when frozen, it just got stuck at the aircraft config page and did not accept any input. The aircraft was otherwise controllable. I will see if I can reproduce this.
-
If the outer low pressure illuminates due to a pump failure, the recovery is:
- left and right STBY pumps ON
- relevant common feed OPEN
That should restore operation.
