dual fuel pumps

[animal]

ok I know some of you guys have Dual fuel pumps, how is the best way to install them? and do you have them on seperate switches?

Tim H.

[StanFoster]

Tim: I have dual pumps on my RAF. The pumps are run in parallel with each pump on its own circuit. I have a fuel pressure gauge which on preflight I check the output of each pump. During flight I can switch the pumps and watch the fuel pressure guage again.

When I am done flying I do a post flight check on each pump.

Some have a fuel pressure regulator....but I havent had a bit of problems the first year of flying.

Stan

[mceagle]

As Stan said, plus I would run a filter at the inlet of each pump, and have one wired through the ignition switch and the other with its own switch, both via relays.

[ben]

tim h, i also run 2 fuel pumps and have them wire like tim mclure

[Aussie_Paul]

Tim, does it matter to have a filter rather than a strainer for fuel injection? Do fuel injection pumps like "sucking" through a filter?

With my fuel injection setups I run a strainer before the pumps, and the high pressure filter after the pumps.

Aussie Paul. :)

[mceagle]

Correct Paul. I run 100/42 brass mesh as an inlet strainer for FI pumps because the normal small filters cannot handle the high volume required of the FI pumps. (and as you said, a high pressure filter after the pumps.

[animal]

Tim, does it matter to have a filter rather than a strainer for fuel injection? Do fuel injection pumps like "sucking" through a filter?

With my fuel injection setups I run a strainer before the pumps, and the high pressure filter after the pumps.

Aussie Paul. :)

my engine is not injected, I have the early carb. version of the RW-162,dual ignition,single carb. I do have an inline filter mounted before it gets to the pump and gasolator fuel drain.

[mceagle]

Animal, there is no problem with the filter before the pump in Carburettored engines because they normally have a very low volume to contend with. It is in fact a good idea to have the fuel filtered before the "click click" type pumps because they have a very fine clearance between the plunger and the barrell.

[mrford61]

As Stan said, plus I would run a filter at the inlet of each pump, and have one wired through the ignition switch and the other with its own switch, both via relays.


G,day Tim,
What are the risks of not using relays?

Would fuses be a bad idea for an "in parrallel" set-up.

Thanks

Mark Clifford.

[Harry_S.]

Tim H:

I have dual pumps on my RAF. The two fuel lines coming from the seat tank route down to a *manifold* mounted under the keel. Two lines come out of the manifold and each goes to it's own filter. Out of the filter, each line routes to the bottom of it's own pump...the filters and pumps are mounted on either side of the mast/keel.

The exit ports of the pumps are tee'd and one fuel line routes to the pressure gauge and then to the carb.

Each pump is wired thru a breaker and a toggle switch. Each pump is checked after engine start...I have both pumps going on takeoff and switch one off after climbout.

I have a spring loaded drain plug in the bottom of the manifold...the lowest point of the fuel system...that I open, to check for water during my pre-flight.

I will try to post some pics of this setup as I'm down for my *annual* right now.


Cheers :)

[animal]

[QUOTE=Harry_S.]Tim H:

I have dual pumps on my RAF. The two fuel lines coming from the seat tank route down to a *manifold* mounted under the keel. Two lines come out of the manifold and each goes to it's own filter. Out of the filter, each line routes to the bottom of it's own pump...the filters and pumps are mounted on either side of the mast/keel.

The exit ports of the pumps are tee'd and one fuel line routes to the pressure gauge and then to the carb.

Each pump is wired thru a breaker and a toggle switch. Each pump is checked after engine start...I have both pumps going on takeoff and switch one off after climbout.

I have a spring loaded drain plug in the bottom of the manifold...the lowest point of the fuel system...that I open, to check for water during my pre-flight.

I will try to post some pics of this setup as I'm down for my *annual* right now.



ok thanks for all the info guys,right now I have my pumps plumbed so one pump fed the second pump, I guess I need to change that,I figured since I can blow air true it with the compressior,that fuel should still flow thru it if one stops pumping., but I could be wrong.
I will get a pic of how I have it set up today since I now figured out how to get the photos to upload.

I do have my fuel drain gasolator at the lowest point.
right now the way the Scorpion tank is set up is it has a fuel outlet at both ends of the tank,I have a cross over line under the tank feeding into the fuel shut off valve then into a filter,down to the gasolator drain then loops back up to the 2 pumps then curves around into the carb inlet fitting.

thanks again guys for the input on how ya all have yours set up. rotorway does not show dual pumps in the plans for the Scorpions,but after reading about dual pumps on gyros, I figure it won't hurt.

Tim H.

[mceagle]

G,day Tim,
What are the risks of not using relays?

Would fuses be a bad idea for an "in parrallel" set-up.

Thanks

Mark Clifford.

G'day Mark, the main reason that I suggest relays is because then the pump is not directly wired through the main gyro wiring system and has its own independant power supply. The relays switch that independant supply on and off. Less chance of a pump electrical fault affecting the rest of the system (eg the ignition)

[Aussie_Paul]

.....I always ran the electric pump into the crankcase "pulse" pump. I had a filter before the electric pump. I had the electric wired so I could test it before start up by hearing it pulse. I would then leave it off to make sure the crankcase "pulse" pump was working as I taxiied to position. You have to allow enough time for the engine to use the fuel in the carby bowls. Once I new that the crankcase "pulse" pump was working I turned on the electric, confident that I had correctly checked both pumps. I did well over a 1,000 hours with this system.

With fuel injection, the engine stops as soon as the pump stops pumping.

IMHO you should run both pumps all the time due to the chances of a restart with a gyro being unsuccessfull. The altitude that you have is the deciding factor of course. People have crashed trying to restart when they should have been concentrating on the forced landing. :eek:

The ultimate is to have a fuel pressure sensor so that is the fuel pressure drops below a pre determind level the second pump automatically come on, and shows a light on the dash.

Aussie Paul. :)

[animal]

.....I always ran the electric pump into the crankcase "pulse" pump. I had a filter before the electric pump. I had the electric wired so I could test it before start up by hearing it pulse. I would then leave it off to make sure the crankcase "pulse" pump was working as I taxiied to position. You have to allow enough time for the engine to use the fuel in the carby bowls. Once I new that the crankcase "pulse" pump was working I turned on the electric, confident that I had correctly checked both pumps. I did well over a 1,000 hours with this system.

With fuel injection, the engine stops as soon as the pump stops pumping.

IMHO you should run both pumps all the time due to the chances of a restart with a gyro being unsuccessfull. The altitude that you have is the deciding factor of course. People have crashed trying to restart when they should have been concentrating on the forced landing. :eek:

The ultimate is to have a fuel pressure sensor so that is the fuel pressure drops below a pre determind level the second pump automatically come on, and shows a light on the dash.

Aussie Paul. :)

well I am running this in a full helicopter( Rotorway Scorpion with Exec 162 engine),not a gyro, so restarting would be even worse to try then in a gyro, I do like the idea of some type of alarm for the fuel pressure. I may look into this.
thanks for the reply.

Tim H.