Fuel system capacity
Fuel system capacity
(OP)
Hi all, Can somebody steer me to guidance on fuel tank capacity requirements when doing an engine upgrade? For example take out an A65/65Hp and put in an 0-235/118Hp. The original 13 gal tank is not quite adequate for decent ops. Is there some rule for Part 23 aircraft? Thanks for your comments.
John Q.
John Q.





RE: Fuel system capacity
(d) The total usable capacity of the fuel tanks must be enough for at least one-half hour of operation at maximum continuous power.
(e) Each fuel quantity indicator must be adjusted, as specified in §23.1337(b), to account for the unusable fuel supply determined under §23.959(a).
They are from FAR23.963. There is a whole section on Fuel Tanks starting in 23.951.
Garland E. Borowski, PE
Star Aviation
RE: Fuel system capacity
Someone once told me an appropriate analogy: "you go and get the double-D boob job, then wonder why your back is sore".
RE: Fuel system capacity
RE: Fuel system capacity
In short, when making alterations, it is best to start with the original certification basis and work from there. Many times FAA will require upgrading to the regulations in effect at the time of application for the STC, but not always. If you were to try to modify a Champ to FAR 23 fuel system standards it would be impossible, so CAR 4a will be the prevailing document.
I don't think upgrading a 7AC to an O-235 is a viable project based on gross weight alone. Stick with the A-65. There is an STC for the O-235-C (115hp) on the 7AC, STC SA3-372, but doing a search, I can't come up with the owner of that STC. I don't know about your FSDO, but I know none of the ones I work with would give a field approval for this alteration. You might also want to check out Order 8900.1 chapter on major alterations to see how it would fit in if you need to develop engineering data to apply for an new STC.
RE: Fuel system capacity
How about a Rotax 912? 121 lbs which gives a little wiggle room for radiators, etc., and electrical system for the glass cockpit and three-axis autopilot that surely follows. 80 Hp which gives the "kick" you are looking for, but not too extreme. "Just because you have a spare O-235 laying around" is not enough economics to pull this off. Then again, you can do whatever you want under experimental.
RE: Fuel system capacity
RE: Fuel system capacity
Thanks again for all the prompt comments, John Q.
RE: Fuel system capacity
on W&B, what are you going to compare your results (calc or weighed) to ? i'd expect that the flight envelope would be quite different ... you're obviously after a faster plane, how are you planning on expanding the envelope (at least in the V direction?
Is there an up-engined version around for comparison ?