Fuel Boost/Transfer Pumps

[skippydiesel]

I would like to hear the experience/opinions (+/-) of the  Forum  on the two, separate function, pumps.

 

1. I am not entirely happy with my boost pumps ability to keep up with the highest power/demand  (still a bit marginal for my comfort) of my Rotax 912ULS engine.

 

2. Contemplating a complete revision of my fuel supply/reticulation (3 tanks) system including existing Facet Cube  style transfer pump.

 

Your recommendations/condemnations (with rational) will be most welcome.

Edited March 27, 2023 by skippydiesel

[skippydiesel]

PS - Forgot to mention fuel supply for boost pump, is through the transfer pump - considering a bypass system, that may allow for a greater volume of fuel to flow, when boost on.

[Blueadventures]

You have also forgotten to include the model of your current Facet pump.  Also best to mention fuel tank locations, some will not know it a low wing type.

[skippydiesel]

2 hours ago, Blueadventures said:

You have also forgotten to include the model of your current Facet pump.  Also best to mention fuel tank locations, some will not know it a low wing type.

Thanks Blue - will check actual model of pump next visit to aircraft.

[Thruster88]

A diagram of the complete fuel system would be helpful.  

[Area-51]

181 has a single 25 year old facet boost pump; still going strong with approx 500hr tsn... valves are still great on pressure and vacuum tests, and it pumps 20% more volume under pressure than the latest edition 912 mechanical pump.

[Old Koreelah]

This is a good reminder to test the flow of the boost pump, in case it’s no longer able to supply enough to the engine.

I plan to do that next month.

[kgwilson]

I have a Facet 4-6 PSI pump to transfer fuel from the 2 wing tanks to the main fuselage tank via a Left/Right/Off fuel selector. The aircraft is low wing so fuel must be pumped uphill via the selector on the lower part of the panel. Each wing tank holds 35 litres and the delivery line is connected to the bottom of the fuselage tank. When I did the test it took 56 minutes to transfer 35 litres into the main tanks that was already half full with 50 litres in it through 1/4 inch fuel line. That works out to 37.5 litres per hour.

 

At the time I thought that was ridiculously slow but in reality when flying I run the pump for 10 minutes on each tank to put about 15 litres into the main tank and in that time the engine consumes about 7.5 litres in normal cruise so I am adding 7.5 litres in 20 minutes or about 23 litres an hour. I watch the fuel guage going up as I fly. Facet cube pumps get quite clattery when they begin to pump air and I can hear that over the noise of the engine so I know when the tank is empty.

 

At full power delivery would barely keep up with fuel consumption but that is not a concern and is what fuel management is all about.

 

Facet have models from 1 - 15 PSI and deliver 26 - 150 litres per hour depending on the model. I have never had a problem with either of my facet pumps.

[Old Koreelah]

Never seen a simpler pump than a facet; vibration and noise a bit high, but that also is useful.

[Area-51]

Its not on many people's radar but testing fuel pump ability to hold both pressure and vacuum over at least 20min minimum time along with flow capacity per hour is a critical area of line maintenance, whether it is mechanical or electrical. It should be part of your 100hr/annual; and you should be recording the results so you can see when its performance is deteriorating.

 

The flow should be at least 50% above your maximum fuel burn rate. 181's facet and 912 pumping capacity are both over 75L/hr through 1/4" lines.

[facthunter]

I'm glad you emphasised that because that is at the core of it all..  Nev