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Dan2+2
10-04-2005, 09:04 PM
Tony Bingeles books seem to say it is mandatory to have an aux.electric fuel pump. Do any certified cubs have aux fuel pumps? With a low pressure carb. is a aux elec. pump needed?

irishfield
10-04-2005, 09:10 PM
No pumps required in a gravity feed system. If you have a mechanical pump on your engine..then yes you need a back up "boost" pump.

mvivion
10-04-2005, 10:21 PM
In some cases, where larger engines are installed in an airframe that was originally equipped with a smaller engine, an aux pump is required to compensate for a low pressure, low volume situation at max power.

For example, the Avcon 170, equipped with an O-360, requires an electric pump to back up the mechanical pump. Neither is really required, except there is a section of the fuel line which is technically according to spec too small in diameter to permit full power operation of the higher horsepower engine.

MTV

redrooster
10-04-2005, 11:08 PM
No pumps required in a gravity feed system. If you have a mechanical pump on your engine..then yes you need a back up "boost" pump.

Not a hard and fast rule... the (first year) 1948 (ragwing) Cessna 170 has an engine driven fuel pump, the only 170 model to have one. No electric backup pump. The engine-driven pump is there in case a line unports and the fuel level in the tank is too low to re-establish siphon-action and start gravity feeding again. The pump will suck the fuel up to the high point in the system (top of the forward door post), then gravity takes over.

Rooster

landesskis
10-05-2005, 12:59 AM
Airglas uses an auxiliary fuel pump to pump the belly tank or gas/cargo into the left wing tank. This is why the fitting is supposed to welded into the left wing tank. People have run a "T" fitting into the existing fuel line and mix up the left or right with the pump running will flood out their engine in flight. A gravity feed system should never be messed with.

irishfield
10-05-2005, 08:00 AM
No pumps required in a gravity feed system. If you have a mechanical pump on your engine..then yes you need a back up "boost" pump.

Not a hard and fast rule... the (first year) 1948 (ragwing) Cessna 170 has an engine driven fuel pump, the only 170 model to have one. No electric backup pump. The engine-driven pump is there in case a line unports and the fuel level in the tank is too low to re-establish siphon-action and start gravity feeding again. The pump will suck the fuel up to the high point in the system (top of the forward door post), then gravity takes over.

Rooster

If there's an engine driven pump...then it's not a gravity feed system..simple as that no matter where the tanks are located. In the experimental world. which this question relates too...if there is one pump..there must be two to pass inspection. True gravity feed with no pumps...then that's how many are required and why there is a fuel flow test to pass in the max nose up attitude.

Dan2+2
10-05-2005, 10:28 AM
So,If the system passes the nose up fuel flow test then no pump is needed for the low pressure carb? That is how my J4 and J5 are setup but I wasn't sure if an O320 would the work same as a c85.

KelvinG
10-05-2005, 11:54 AM
Anyone have a suggestion for a electric aux fuel pump? I have just started looking and the new certified ones are going for $500.00 to over $1,000.00.
I need something that supplies 9 to 15 PSI at about 0.5 gallon per minute and it doesn't look to me like the Facet pumps are up to that.

Thanks,
KelvinG

Aviator
10-05-2005, 02:42 PM
[quote="KelvinG"]Signature...
"Only a virtuous people are capable of freedom. As nations become corrupt and vicious, they have more need of masters." Benjamin Franklin[quote]

If Ben were here today, he might rephrase that to:

"Only a virtuous nation is capable of freedom. As masters become corrupt and vicious, people have more need of freedom."

irishfield
10-05-2005, 03:49 PM
So,If the system passes the nose up fuel flow test then no pump is needed for the low pressure carb? That is how my J4 and J5 are setup but I wasn't sure if an O320 would the work same as a c85.

Put Min fuel in the tank (ie 30 minutes worth, no more - approx 5 gallons for an O-320). Tail in a hole and wheels on car ramps to achieve something around the 15* angle of attack on the wing.
Proper way is fitting from carb inlet to be on end of feed hose so you are doing the test with output thru the fine screen from the carb inlet. Fuel hose held at same height as the carb inlet and time the fuel flow into a graduated container.

Gravity flow must be 150% of the engine requirement at WOT (wide open throttle). For an O-320 that's about 15 GPH so you must see at least 22.5GPH fuel flow to pass. Most 3/8 lines will flow at least 25 to 40GPH if no kinks or undersized valve/fitting insides (from wing tanks).

If you are using a pump system...in the same configuration the output must be 125% of requirement.

Dan2+2
10-05-2005, 05:03 PM
Thanks irishfield thats just the info I needed.

irishfield
10-05-2005, 05:05 PM
Thanks irishfield thats just the info I needed.

Anytime Dan! What we hang out here for!