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gents,
at what angle do you put your fuse when testing the fuel flow, please?
I heard some pretty different figures here: from 'tail down to the ground' to '5 degrees more than max lift/descend'
This test is the first major one in the nextcoming days, so i'd rather be prepared..
Hans,
I don't know if you have any particular requirements for fuel flow/drain testing in your jurisdiction; however, my understanding is this is pretty much up to the builder to determine to what conditions they intend to test to.
I think most of us want some sort of figure for unusable fuel; and, that is pretty much determined with the fuselage level which approximates level flight.
Testing to determine what happens with nose up or nose down to the limits a person would normally experience in flight will tell you what you would want to be aware of for operational purposes later (and to be included in your builder developed POH).
Since kitfoxes have a header tank, it creates a situation where a long descent or slip with is entirely possible even though the fuel flow from the wing tanks is cut off due to the attitude.
FWIW - I tested mine at fuselage level, and 10 degrees nose down which is beyond what a person would ever experience in normal flight. Others may have decided to test with different configurations. With the rear drain from the wing tanks, nose down is far more limiting......nose up is likely not all that much more unusable fuel than level.
Probably a good thing to try is do a search on this forum for the subject....you should find a lot of related info.:)
Sincerely,
Dave S
KD7 Trigear Flying
912ULS Warp
St Paul, MN
Like you suggest, there may be several thoughts on this. Mine is that - at least for me - the most critical stage of flight is right after lift off and during the first several seconds of flight. This is usually at full throttle, so this is where I test mine - nose high. This also is the angle of worst gravity feed as the wing tanks are much closer to the level of the carburetors.
Lowell
EAA did a webinar on this subject not long ago.
Here is a link to the recording of it. Lots of good info.
http://www.eaavideo.org/video.aspx?v=2195707082001
Louie
I tested with level flight and nose high, tail low like Lowell. Take off was also the part of the flight I was most concerned with having reliable fuel delivery.
There is a lot of buzz about this right now in EAA and Kitplanes magazines and I am ready to do the fuel flow test myself. I was going to use 25 degrees nose up and 10 degrees nose down for my tests. According to the FAA recommendations you are supposed to use 5 degrees more that tha normal max climb and descent angles. Does my plan to use 25 and 10 seem reasonable to those of you who are actually flying the SS7?
Also the recommended test flow rate should be at least 125-150% of max full power engine consumption (without engine or aux fuel pump on). This seems like a lot of flow for a simple gravity system like the Kitfox. Has anyone done these tests at the above mentioned angles (or close to them) and what results did you get? I'm worried that I'm going to be worried if I don't get the FAA suggested results. My fuel system, hoses and tubes are totally by the Kitfox build manual.
Jim
I doubt you'll have any problem achieving 150% max fuel flow on just gravity feed. It will likely be higher than that even testing with half full fuel tanks.
Let us know how you fared.
Jim,
I'd second DF-4's comments.......my fuel flow tests were not precisely to the protocol you currently see being touted by faa/eaa/etc.......I don't have the exact figures right now but for the testing I did, I recall all configurations way more than 150%.
If you get less, you'd need to look for what is obstructing the flow; but, the kitfox system built to design specs should easily deliver to this standard.
Remember these are experimentals; and, what type of testing a person does on the fuel system is really up to the bulder - to do it so it is predictable and safe....what you find should be written into your aircraft POH. I included 10 degree nose down useful fuel, for example, in addition to level useful fuel.
Dave S
KF7 Trigear
912ULS Warp
St Paul, MN