The International Cessna^® 170 Association

If so, can you tell me if there is anyway to program partial gallons? For example, if you have 10.7 gallons remaining, and you add 10.1 gallons, how do you program it to 20.8?

Manuals and googles have left me still unable..So I'm stuck trying to hit the perfect squeeze at the gas pump and not overshoot the hundredth of a gallon so that I always end up on a whole number.

Any help would be appreciated!

I think the answer you're looking for is on page 10 of this manual? Without trying it, it's hard to understand exactly what they're saying, but it looks like you can poke one button or another to increase or decrease the fuel remaining indication after fueling.

My fuel flow and engine monitor are JPI, which work well but have very unintuitive buttonology. After using them for more than 20 years, I still sometimes have to look at the manual to do really simple stuff.

You can do it pretty easily. Just enter the programming mode as if you would any time you filled up the tank. Instead of putting the full amount put the total that you have. It should not be any big deal.

DaveF wrote:I think the answer you're looking for is on page 10 of this manual?

Thanks for the help. Yep, this is the exact process I use per the manual...Right down to the picture shown in the manual where it is only whole numbers. Even if you watch the videos from EI on fuel programming, it's always in whole gallons.

I'm feeling dumb or possibly super bummed about a wildly inconvenient and possibly dangerous design flaw.

I found the manual to be a little hard to understand. Or maybe the manual was written for smarter people. It sounds to me like you have it calibrated for whole gallons rather than 0.1 gallons. Somewhere I think you can change that?

Overall I like it, especially for leaning. I have a UBG16 as well, but tend to just lean for fuel flow now I know where it should be. It is surprisingly accurate.

Thank you Dave F for that manual on the FP-5 /FP-5L . I have a manual but it must be a old one as it doesn’t have half the information in it as the one you posted . So now to try and work out which unit I have . While I have flow rate ,I haven’t seen the HP . But saying all that ,this gauge is gold. it’s frightening what it shows on full throttle on take off. But it makes me smile when at 8500ft and at 2450rpm. And mixture leaned out .

I have a FP-5L fuel flow computer but I haven't ever tried to input tenths of a gallon. I always fill the tanks so 37gal is the number I always use.

Other than that, I am totally satisfied with the operation. Once calibrated correctly, it consistently agrees with the gas pumps I use.

The moving map GPS and fuel flow computer are the two things that have reduced anxiety while flying more than anything else.

I talked to EI. Apparently there is no way to add partial gallons...So if you have 10 gallons of fuel and you add 10.5, your only option is to program either 20, or 21. This leaves up to a half gallon error in one fueling. Do this a few times and you could be multiple gallons off. Sometimes I'll go 5 or 6 fueling without topping off to rest bat to full. That could be as much as a 3 gallon discrepancy. (obviously I try to get the perfect squeeze and round the best I can to minimize).

Im really not too happy about that level of error. Any one know if the JPI gauge is better?

My unit is calibrated for litres as that’s the way the fuel is sold here. Found the EI unit extremely accurate . However using US gals it wouldn’t be a accumulative error as you suggested but a fixed error as you would be filling your tank to the set figure . I don’t not think capacitance type fuel systems would be operating to those accuracies .

I occasionally fly a turboprop with an FP-5. I never set it by the fuel I add. I stick the tanks, verify the stick against the fuel gauges, and set it to what is actually in the airplane. That avoids accumulated error, but more importantly avoids error from an incorrect assumption about how much fuel was in the tanks to start.

I’ve been flying with this fuel computer for over three years and I have never found a way to set tenths of gallons. I stick the tanks at least every other flight or so and find that helps reduce any rounding errors. In short if my stick readings are lower than what the fuel remains says I will up date the quantity to my new reading. Usually they are fairly close so. I am very happy with the fuel flow accuracy and find it helps reduce anxiety on long legs.