I have a new HDX with the engine monitor package. The fuel flow is off by about 3gph and I want to adjust the k factor to correct the reading. I have looked in the pilot handbook but there seems to be no info on how to do this. I have gone into set up on the HDX and did not see anything that would allow me to adjust the fuel flow. Does anyone know how to do this?
K Factor on Fuel Flow
- Thread starter Hcsims
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bob m
New Member
Check the Skyview Installation Manual Revision AD Feb 2018 around page 7-78
Were you able to resolve this?
bsgibson26L
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I am new to the Forum, and this is my FIRST post.
I have a 72 Traveler with a full HDX package, including Fuel Flow. However, my plane is getting an engine upgrade - from the original 150 HP O-320 engine to a 180 HP O-360-A4K (same engine used in the Grumman Tiger). I was wondering if there are any TIGER owners on this forum, and if so, could you tell my your CURRENT K FACTOR setting? I thought that would be a good place for me to start. I'm hoping to have my plane out of the shop by March.
I have a 72 Traveler with a full HDX package, including Fuel Flow. However, my plane is getting an engine upgrade - from the original 150 HP O-320 engine to a 180 HP O-360-A4K (same engine used in the Grumman Tiger). I was wondering if there are any TIGER owners on this forum, and if so, could you tell my your CURRENT K FACTOR setting? I thought that would be a good place for me to start. I'm hoping to have my plane out of the shop by March.
airguy
Active Member
If the K-factor was working and accurate before, it will still be. The K-factor is an adjustment to how the device measures fuel flow, if you get it accurate at a lower fuel flow (150hp) it will still be accurate at a higher fuel flow (180hp).
bsgibson26L
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Airguy - Thanks for that reply, it is helpful. BUT - I have one more complication: Since my Dynon HDX system was installed, the aircraft has not flown, In fact, the 150 HP engine has not even been STARTED since the pane upgrade . . . After the panel install, the plane was shipped to Fletchair just outside Fredericksburg TX, where the O360-A4K engine was installed. So, what I'm looking for is a "Starting number" for K factor, just to get me 'close' on the final number.
Best guess right now is that "BOBKAT" (Bob's Kick A$$ Traveler) will be ready for handoff to me in March.
Best guess right now is that "BOBKAT" (Bob's Kick A$$ Traveler) will be ready for handoff to me in March.
If memory serves the default number in the HDX system is 65000. It will get you in the ballpark. Just to be safe do not consider your fuel flow or fuel computer numbers accurate for the first flight. Takeoff with full (visually verified) tanks and fly for one hour. Land and refill. Adjust the K factor. Now your fuel computer will be fairly accurate and you can longer with confidence. You can refine your K factor as you like. The 65000 default is fairly close for the red cube.
airguy
Active Member
I was thinking (memory) that the default was 68000 for the K-factor. Either one will get you in the ballpark and let you adjust from there.
Now fill the tanks completely full and go fly. The longer the better, burn as much fuel out of the tanks as you are comfortable with, landing near empty. One flight, 7 flights, doesn't matter - just burn the fuel, the HDX will track what it thinks is the total gallons used and show how many gallons it thinks are left in the tanks. Now fill up the tanks completely again and make note of the gallons actually pumped, versus what the fuel computer thinks should be required. Do the math to figure out a percentage of adjustment required and which direction, make an adjustment to the K-factor. Repeat. Now you'll be dialed in pretty close. Moving the K-factor larger will reduce the indicated fuel flow, making it smaller will increase it.
There will always be a little error in filling the tanks - bubbles stuck between the baffles, a not-perfect gallon meter on the fuel pump (and we only measure to a 0.1 gallon anyway), differences in density of the fuel due to temperature - but if you pump a large number of gallons instead of a small number, you will minimize these errors and get closer to the real value. That's the reason for burning as much fuel out of the tanks as reasonably possible before a refill while trying to calibrate the K-factor.
Now fill the tanks completely full and go fly. The longer the better, burn as much fuel out of the tanks as you are comfortable with, landing near empty. One flight, 7 flights, doesn't matter - just burn the fuel, the HDX will track what it thinks is the total gallons used and show how many gallons it thinks are left in the tanks. Now fill up the tanks completely again and make note of the gallons actually pumped, versus what the fuel computer thinks should be required. Do the math to figure out a percentage of adjustment required and which direction, make an adjustment to the K-factor. Repeat. Now you'll be dialed in pretty close. Moving the K-factor larger will reduce the indicated fuel flow, making it smaller will increase it.
There will always be a little error in filling the tanks - bubbles stuck between the baffles, a not-perfect gallon meter on the fuel pump (and we only measure to a 0.1 gallon anyway), differences in density of the fuel due to temperature - but if you pump a large number of gallons instead of a small number, you will minimize these errors and get closer to the real value. That's the reason for burning as much fuel out of the tanks as reasonably possible before a refill while trying to calibrate the K-factor.
Last edited:
MikeD
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The K factor is a function of the fuel flow transducer, not Skyview. You will be able to find the K factor on the the manufacturer's website of the fuel flow transducer installed in your aircraft. I.E. Floscan, Red Cube, Electronics International, ......
The best description of how to modify your K-factor to match your fuel consumption can be found in the D-120 installation manual. It kind of got diluted when written up for HDX Skyview
The best description of how to modify your K-factor to match your fuel consumption can be found in the D-120 installation manual. It kind of got diluted when written up for HDX Skyview
airguy
Active Member
And MikeD brings in RTFM for the ultimate win! 
bsgibson26L
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Thanks guys - I feel like I've had a good 'first experience' with this forum.
I HAVE calibrated other fuel flow devices on different aircraft in the past (JPI, Shadin, etc.) but this will be my first Dynon and I was looking for the best 'starting point' for the first K-Factor setting . . and you have provided that. I have recently captured 'Actual' fuel burn on a friends Cheetah, but he has the O-320 engine.
I ended up flying that Cheetah home from Texas to Florida for the owner (he didn't have a current BFR). In a single day, completed 1,072 NM with 2 fuel stops, averaging 136.5 knots WITHOUT a tailwind!
I HAVE calibrated other fuel flow devices on different aircraft in the past (JPI, Shadin, etc.) but this will be my first Dynon and I was looking for the best 'starting point' for the first K-Factor setting . . and you have provided that. I have recently captured 'Actual' fuel burn on a friends Cheetah, but he has the O-320 engine.
I ended up flying that Cheetah home from Texas to Florida for the owner (he didn't have a current BFR). In a single day, completed 1,072 NM with 2 fuel stops, averaging 136.5 knots WITHOUT a tailwind!
I have a Tiger and I followed the instructions. There is a procedure and it takes a few flights to dial it in but once you get adjusted it is very accurate, within a gallon per tank.
jakej
Well-Known Member
FYI - I’d be trying to better that - it’s easily possible to get that to within a 1/4 gallon, just saying, if you want to.
airguy
Active Member
Agreed - I typically fill within .1 to .2 of what the fuel computer thinks I will need.FYI - I’d be trying to better that - it’s easily possible to get that to within a 1/4 gallon, just saying, if you want to.
I had a VM-1000 with the Floscan transducer and tuned in my accuracy was within .1 gallons total with both tanks on my RV-4. I upgraded to Dynon primarily because my Floscan transducer failed and parts for the VM-1000 were not available any more. I installed a Dynon with the red cube. I have been challenged trying to get it within 1 gallon. Having said that, I have been making only short flights and refueling frequently to take advantage of the cheaper gas prices. Also some fuel ramps are not as level as others so when calibrating, make sure the ramp is level otherwise what is said here is spot on.