BravoWhiskey Posted August 10, 2022 Report Posted August 10, 2022 I am not sure if my Fuel Flow is wrong or if I have more capacity in my tanks than indicated. I had full tanks, 2 standard 44.5g per side and flew from UES to DYL yesterday. Burned an indicated 71g. With this I should have had about 18g remaining. Both my wing gauges and panel indicate about 28-30g. So this makes me think my Fuel flow is off. Which is also strange since it always seems to be accurate on refilling amounts. Are the tank capacity wrong? Quote
anthonydesmet Posted August 10, 2022 Report Posted August 10, 2022 Did you top the tanks off yet? How much did you pump back in? What kind of fuel flow indicator do you have? Before my Shadin went out sometimes the display was intermittent…. in other words it was not calculating fuel burn 100% throughout the flight resulting it the fuel indicator reading higher than actual fuel use. Very seldom will a fuel flow computer drop its K factor or default to factory so probably not that. From reading your discretion it just sounds like your factory gauges and possibly wing site gauges are off do to tank transducer/sender. Personally I use the factory fuel gauges just to indicate I am full fuel or half fuel. I never use the factory gauges and site gauges for actual fuel gallon quantity. I am old school and have had too many fuel indicator issues in too many airplanes so I still calculate mentally by using my expected fuel burn at my cruise power setting over time and reference my JPI to make sure everything makes sense. Then when I top off post flight between my calculations, JPI, cockpit gauges and wing site gauges everything should coincide. If not, I start investigating the outlier. 1 Quote
Pinecone Posted August 10, 2022 Report Posted August 10, 2022 You can always go old school and run a tank until the engine sputters and then see how much fuel it takes. And watch the gauge to see it reads Empty. 1 Quote
buddy Posted August 10, 2022 Report Posted August 10, 2022 If it’s anything like my O2 and you fill it to the top the total amount of fuel in your tanks should be about 100-102 gal. It’s 89gal. to the bottom of the goose neck. 1 Quote
GeeBee Posted August 10, 2022 Report Posted August 10, 2022 4 hours ago, BravoWhiskey said: I am not sure if my Fuel Flow is wrong or if I have more capacity in my tanks than indicated. I had full tanks, 2 standard 44.5g per side and flew from UES to DYL yesterday. Burned an indicated 71g. With this I should have had about 18g remaining. Both my wing gauges and panel indicate about 28-30g. So this makes me think my Fuel flow is off. Which is also strange since it always seems to be accurate on refilling amounts. Are the tank capacity wrong? So when you refueled, to the 89 gal level, how much fuel did you take on? That tells you what is correct. Also when you top your tanks do you top to the level as stated in the servicing section of the POH or do you stuff them to the physical top? 1 Quote
kortopates Posted August 10, 2022 Report Posted August 10, 2022 Determining/calibrating Fuel flow and tank capacity are two different independent variable. You can't infer one from the other. To determine tank capacity, nothing short of draining the tank empty and fueling it to the repeatable "full" level like the full point stated in your POH; and taking into account unusable fuel if starting with a totally dry tank. To calibrate fuel flow, its a matter of comparing the reported Fuel Used against your fuel receipts but to get accurate results you need to minimize error by starting the process by filling to repeatable "full" level (on level ground), burn through about 100 gallons tracking fuel used and added, and then fill one last time to the same repeatable fill level and then compare total fuel used to total fuel receipts. Then adjust your monitors K-Factor. 2 Quote
PT20J Posted August 10, 2022 Report Posted August 10, 2022 How old is your fuel flow transducer? Although the Flowscan transducers are rated for 10,000 hours, a JPI tech told me that they get flakey after about 10 years sitting in 100LL and read low. Quote
BravoWhiskey Posted August 10, 2022 Author Report Posted August 10, 2022 4 hours ago, buddy said: If it’s anything like my O2 and you fill it to the top the total amount of fuel in your tanks should be about 100-102 gal. It’s 89gal. to the bottom of the goose neck. That’s starting to make the most sense. The line guys certainly topped it when I left. My refills have been pretty consistent with fuel flow but this was my first long flight. The goose neck is pretty short. I wasn’t expecting an extra 5 gallons if I top it off. But I’ll try seeing the difference between bottom of the filler and top this weekend. Quote
kortopates Posted August 10, 2022 Report Posted August 10, 2022 That’s starting to make the most sense. The line guys certainly topped it when I left. My refills have been pretty consistent with fuel flow but this was my first long flight. The goose neck is pretty short. I wasn’t expecting an extra 5 gallons if I top it off. But I’ll try seeing the difference between bottom of the filler and top this weekend. If you don’t fill it yourself all bets are off as to what you are measuring.Sent from my iPhone using Tapatalk 2 Quote
BravoWhiskey Posted August 10, 2022 Author Report Posted August 10, 2022 41 minutes ago, kortopates said: If you don’t fill it yourself all bets are off as to what you are measuring. Sent from my iPhone using Tapatalk Of course. But it was all the way to the filler cap when I did my preflight. And when I asked them to top off I told them I should only need 10 gallons. This was based on my previous short flight with my standard “full” level that I was used to. So even though I thought I needed 10 the bill was for 20 gallons… but I’ll certainly check this all out when I fill next time. Quote
carusoam Posted August 15, 2022 Report Posted August 15, 2022 BW, This is a long standing question that every plane owner goes through…. 1) How much fuel is in the tank… 2) How much is useable… 3) When do my low lights actually come on… 4) How important is the level ground while filling… 5) How accurate are the fuel level indicators on the ground… 6) Everybody gets to calibrate their fuel level equipment once…. One gallon at a time…. 7) The POH has many answers regarding volume and filling procedures…. 8) Long bodies can pack 100+ gallons in the tanks…. Some require more care than others…. 9) Some small details can cause challenges…. So know your tanks… don’t expect them to work, until proven to work like the POH or STC…. 10) Don’t recalibrate your FF equipment until you KNOW how much fuel is in the tanks…. And how to fill the tanks consistently… One of my first conversations with @Cris more than a decade ago…. We were discussing his Eagle’s fuel tanks…. The M20S artificially limited the fuel capacity to something like 60g…. And Cris was bringing his plane up to Screamin’ Eagle level…. The fuel neck makes a huge difference… some need a vent hole…. PP thoughts only… Best regards, -a- Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.