fuel feed

[draconus]

Flying lately in SP @latest beta I noticed a few times where my right eng feed going low (300-400lbs) with corresponding warning light. Moving the fuel transfer switch from Auto to Oride balanced the fuel resolving the problem every time. Feed switch Norm - not touched. Total fuel - lots of - like teens of thousand.

 

 

Normal or bug?

 

 

Particularly it was in Nevada Refueling Training IA mission.

[sLYFa]

Thats interesting. The fuel transfer switch should not influence L/R fuel balancing in any way, especially if there is lots of fuel left in the fuselage tanks.

All this switch does is force open the wing transfer shutoff valves and pressurize the tanks in case of some elecrical fault. Since the wing transfer valves should be automatically opened anway in flight, this switch has effectively no function in flight.

Placing the feed switch out of NORM on the other hand should immidiately equilize fuel levels in the left and right feed group, as it opens both the sump tank interconnect valve and the box vent valves, thereby effectively combining the left and right feed group into a single one. However, depending on engine demand, an imbalance could still occur if the fuel consumption from the non-selected engine side exceeds the supply from the selected side through the sump tank interconnect valve.

Edited August 8, 2019 by sLYFa

[draconus]

Didn't happen on my last flight so when it does I'll be more focused on the problem. It may be connected to prolonged afterburner use as I got to a point where L feed state was 1800 while R was 1500, but I guess it's nothing unusual.

[sLYFa]

I have to correct myself. Putting the feed switch out of NORM will not transfer fuel to the unused sides' box beam tank (unless fuel is left in the wing tanks), meaning that you will be stuck with 300lbs of fuel (thats the capacity of one sump tank) on the unused side once the box beam tank on that side is empty.

In short, you cannot get a feed groups fuel state above 300lbs with the FEED switch once it reaches that state unless you have fuel in the wings left. But again, the WING/EXT TRANS switch should not influence this in any way if there is no malfunction present.

[IronMike]

Didn't happen on my last flight so when it does I'll be more focused on the problem. It may be connected to prolonged afterburner use as I got to a point where L feed state was 1800 while R was 1500, but I guess it's nothing unusual.

 

 

It is possible that the jet you started in had an engine on the right (or left?) side that was showing higher wear than the engine on the other side. This is something that is actually modeled and randomised everytime you spawn in a new jet. Of course you would never get a deferred engine, but for example one engine's wear could be slightly higher, so that its afterburner would light slightly slower than the other one's, or would give marginally less power etc (which in longer flights could accumulate over time). These descrepancies between two engines are not frequent, they do not impact the flight really, they are tiny at times, but in such a case maybe could have caused different performance results.

 

However please take this with a grain of salt, I have to ask Fat Creason if such a marginal difference in performance could really affect fuel consumption (or flow) in a noticeable way.