February 18, 201313 yr First time poster Been flying the ngx since this add-on was released and loving it. Just one thing that i have noticed and wanted a bit of clarification on is the fuel pumps. Ive noticed that the it doesn't matter if the fuel pump switches are on or off is this normal? Are the engines gravity fed but have pumps to make sure there is a good constant flow? I have noticed that if i for what ever reason have a fuel imbalance that i can open the cross feed and only use that pumps on the tank with more capacity but i can start and do an entire flight with them off and the engines still run fine. Thanks for any response C Parker
February 18, 201313 yr Commercial Member Are the engines gravity fed but have pumps to make sure there is a good constant flow? Yep. Further explanation in the manual. Kyle Rodgers
February 18, 201313 yr Ive noticed that the it doesn't matter if the fuel pump switches are on or off is this normal? Are the engines gravity fed but have pumps to make sure there is a good constant flow? I have noticed that if i for what ever reason have a fuel imbalance that i can open the cross feed and only use that pumps on the tank with more capacity but i can start and do an entire flight with them off and the engines still run fine. It is what Kyle would call a "simism" that the fuel pumps have to be on for the engines to run. It really bugs me in addons when switching the pumps off stops the engines (or they won't start if you forget to switch them on). It is not a good idea to run the engines without boost pressure, but it is possible. Even if engines are not gravity fed they can suck fuel from the tanks. The engine itself has low pressure and high pressure pumps to keep the fuel flowing. That flow demand will draw fuel from the tanks as long as air or vapour doesn't get in the system. Boost pumps are there to help prevent that happening, as does gravity feed.
February 18, 201313 yr The problem (I never seen this happen) can be if the pumps are off at high altitude with high engine demand but still not a great speed, In this case the low pressure of the air, low flow in the NACAs that pressurize the fuel could cause vapour/air formation in the tubes before the engine driven pumps. Except for that no problems. Regards Andrea Daviero
February 18, 201313 yr Author Ok brilliant guys thanks for the info. So if i forgot to turn them on is there a chance of engine failure or something? C Parker
February 18, 201313 yr Yes the engine may flame out at high altitude and possibly during high pitch angles and low quantity with high engine demand, such as during a go around if the pumps are off. Bryan Richards "People depend so much on automation that they forget how to get the automation to work." B.W.
February 18, 201313 yr Ok brilliant guys thanks for the info. So if i forgot to turn them on is there a chance of engine failure or something? In reality a flameout at altitude is quite likely. Whether PMDG has modelled this in the NGX I don't know.
February 18, 201313 yr Commercial Member It is what Kyle would call a "simism" that the fuel pumps have to be on for the engines to run. Haha - thanks. Kyle Rodgers
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