Extra fuel pump needed?

[jrevens]

I haven't yet purchased an engine for my 7 S.S. project, but would like to know if I need to plan for an additional electric fuel pump for a 912uls, or if the engine mounted pump is sufficient. I would welcome any comments or suggestions in regard to that particular airframe/engine combination. Thanks!

[jiott]

According to the factory (Kitfox) an extra fuel pump is not needed. The fuel flow from a high wing, non-aerobatic airplane works just fine with gravity alone. You don't need redundancy for gravity, it never fails. The only thing the extra fuel pump gives you is a little more sucking power in case of a partial clog upstream of the pump. However, the sucking power of an electrical fuel pump is not very great and won't overcome a serious clog. If the clog is downstream of the extra pump you would have somewhat more power to push the fuel thru the clog. In most cases the kind of clog that the extra fuel pump could overcome would probably occur progressively over time (like a filter) and give plenty of warning before a total blockage of fuel. A sudden blockage, like icing or big chunk of debris, probably would be too great for the extra fuel pump to help much. So IMHO the extra pump is just weight and unneeded complexity for a very small possible benefit. Yes, the engine driven pump could also fail, so I guess each person must decide how much redundacy he feels comfortable with vs. the extra weight, cost, etc.

I wonder what percentage of Kitfox builders go with an extra fuel pump?

Jim

[Dorsal]

I thought about it and did not add one basically for the reasons stated above.

[DesertFox4]

Have one. Never used or needed it in 8 years and over 800 hours flight time.
I installed it (facet fuel pump) below the seat between the header tank and the console mounted fuel valve.
Not sure it would work as intended if the mechanical quit working.

[HighWing]

I had one, just like Fox 4 in my first Model IV, and used (needed) it once after replacing all firewall forward fuel lines during an annual and had over crimped a firesleeve clamp. I have one one on my new project as well and hope I never have to use it.
Lowell

[DBVZ]

As a point of information, I had a Piper Cherokee 180 with a MOGAS STC. The STC required addition of twin aux fuel pumps. The reason given was that MOGAS vapor issues would be overcome by these pumps. If you intend to burn MOGAS, this may be another reason to consider installing a pump.

[jrevens]

Thanks for all the replies... I really appreciate the experience and knowledge available here.