Auxiliary fuel pump necessary?

[SWeidemann]

I finished a two day Rotax 912 Series service seminar (Leading Edge Airfoils in Lyons, WI) where it was pointed out that a auxiliary fuel pump is recommended in any installation using the 912 however my impression is that most Kitfoxes with the 912 do not use an aux pump (in addition to the engine driven one).

In my Model 5 Tri Gear, I do not believe I have a pump on board other than the mechanical engine driven one. It works fine, but now I'm wondering if I should put one in? Should I be doing fuel flow testing or just keep flying what I have? (It does have a lot of time on it with no known incidents of any kind.)

Another point, is: Should I have a metal header tank instead of the plastic one ? My plastic one works however is a little "weepy" around the pipe joints.

Skot
N24V

[akarmy]

I have been flying for 325 hours with only the engine driven pump. I think the SLSA aircraft have an electric pump, but the factory experimental ones don't (but John can confirm that).

The general theory is that with a high wing plane you have enough head pressure to feed the engine if the mechanical pump stops. However as with most things... It's your choice to make!

[HighWing]

I have one in mine - Model IV - and glad I did once. It is not on during normal operations. I will sometimes turn it on for several seconds prior to cranking if the engine has not been run for a while with the fuel valve off. This is just to ensure the float bowls are full.

My glad I did episode was after I replaced all the fuel hoses and had inadvertently tightened a fire sleeve clamp too tightly which crimped the fuel line. During the after maintenance test flight at full throttle climb, the engine started to stutter. Aux pump on and the engine ran at reduced throttle and I was able to execute the "Death Turn" and land.

I guess I would agree with Rotax. For me it is pretty cheap insurance.

[Paul Z]

On mys SLSA Factory Built I have one mechanical fuel pump, it is mounted on the passenger side of the engine.

[jiott]

If your plastic header tank is weepy, as most of them are, yes you need to get the aluminum one. A weepy plastic tank can rarely be sealed up and you will be constantly dealing with the smell and wet fuel dribbling on the bottom fabric. Just do it!

[Dave S]

Skot,

In the end; each builder or owner should make these decisions for their own reasons.....I don't want to tell another person what I think they should do. What I can do is say what my reasons for my choices were.

1) I originally had the plastic header tank with my kit from the old skystar/egt company just before it went bankrupt. I found the sealing up of the fittings a bit iffy; but, the major deal was the tank itself had bubbles in the plastic which meant the amount of plastic between the cabin and the fuel could be measured in thousands of an inch......which is pretty much a quality control issue - it was not possible to eliminate a fuel odor with the old plastic tank. John Mc Bean got me a new aluminum header tank and I have been very happy with that. I think some people have good luck with the plastic tank, but I found the aluminum header tank far superior.

2) On the electric fuel pump, I elected to install one at build time for the same reason Highwing stated....to be sure the fuel system is full through the carbs for a quick initial start. I don't use it for normal operations, just on cold start up and as a backup for the mechanical pump. An electric pump won't necessarily cover all possible failure modes for the mechanical pump but it will cover some failure modes. A point to keep in mind if you do decide to go with the facet electric pump is there are more than one model and they differ in pressure. I went with the lower pressure facet pump to avoid over-boosting the fuel pressure.

3) There are several threads on the list regarding fuel flow testing. using the search function should turn up most of these. I elected to do a flow test with and without the electric pump; and, then check it at annual condition inspection time to make sure it hasn't changed...also after any fuel system maintenance.

I am pretty careful with the fuel system to make sure it has not deteriorated....periodic draining of the entire system, removal and flushout of the header tank along with the flow testing; also testing the pressure of the pumps on the ground with the engine at various power settings - (I don't have a panel gauge for fuel pressure).

It's all what a person determines they want in their plane...there are a lot of kitfoxes flying just fine with the plastic header tank and without an electric pump; for my purposes, I was happier with the changes.

Sincerely,

Dave S
KF 7 Trigear
912ULS

[Paul Z]

If your plastic header tank is weepy, as most of them are, yes you need to get the aluminum one. A weepy plastic tank can rarely be sealed up and you will be constantly dealing with the smell and wet fuel dribbling on the bottom fabric. Just do it!

I had two of those plastic header tanks, weepy is an understatement!
WEEPY, LEAKY, HAZARDOUS is how I would describe them.
I finally got an aluminum one, no weepy, no drippy!

[Wheels]

I have a facet electric back up. Just a little insurance. things happen, situations develope, etc etc.