Fuel Calibration

[benapilot]

The time is coming soon to calibrate my new HDX with Cies fuel senders on my 182.

I would love to hear any tips and tricks, secrets of success, things you wish you did.

As I understand it, I’ll need to deflate the nose tire and/or the nose strut to get it level, add the unusable fuel (per the TCDS), and start from the setup screen on Skyview. My plan is to do five gallons at a time until full (39.5 gallons per wing).

What am I missing?

 

[greentips]

I have the old stewart-warner style resistive gauges. I followed the dynon procedure for that. I think the calibration for those gauges calls for two gallon increments. I initially tried a marked beaker at the reference volume, but it was a bit tricky to get right on the mark. For the second main and the aux tip tanks, I took a 5 gallon plastic jug, and a 50# postal scale, set the tare weight for the jug, picked a day close to ASTM Standard temp (20C/68F) and replaced the quick drain with a locking quickdrain with a hose nipple. I drained the fuel into spare jugs (32.5 G/main & 12 G/aux). The quickdrain with the hose nipple kept my arm dry during defueling and made life a lot easier.

For the pours, I took 6.0 lbs/ gallons at 66F as the reference standard and filled my container to 12.0 lbs. I used a container that was easy to fill without spilling and easy to pour. This made the job quick and accurate, provided I remembered to set the tare weight between fills. When I didn't, I subtracted that weight from the next fill to compensate. I haven't seen much variance between over the range of the tanks. I'm going to re-calibrate before the next annual and see how the numbers change from the original calibration.

 

[r2brou2]

I think you tell it the max fuel quantity and it tells you how many gallons to put in with the last one saying fill the rest of the way. I think it was 5 gallons at a time for me so I couldn't try 2 to get more fidelity or easier handling.

I had a large calibrated beaker (4L maybe?) and I used that to calculate the density of the fuel then used a scale and measured the required fuel quantities.

Make sure to put your fuel selector on right or left, not on or off, in order to prevent cross feeding while calibrating one tank at a time. You don't get the option to do both tanks going back and forth between fills.

What is considered flight level? IIRC, the "waterline" that they provide you is not defined as flight level. If you are using the waterline such as when you do a weight measurement, then deflating the strut and tire isn't sufficient.

 

[greentips]

I think you tell it the max fuel quantity and it tells you how many gallons to put in with the last one saying fill the rest of the way. I think it was 5 gallons at a time for me so I couldn't try 2 to get more fidelity or easier handling.

I had a large calibrated beaker (4L maybe?) and I used that to calculate the density of the fuel then used a scale and measured the required fuel quantities.

Make sure to put your fuel selector on right or left, not on or off, in order to prevent cross feeding while calibrating one tank at a time. You don't get the option to do both tanks going back and forth between fills.

What is considered flight level? IIRC, the "waterline" that they provide you is not defined as flight level. If you are using the waterline such as when you do a weight measurement, then deflating the strut and tire isn't sufficient.

Good points. I did not deflate the nose wheel or strut. I did level the airplane r/l and set the fuel selector to the opposite tank to isolate the one I was calibrating. I used a plastic gas can for the transfer container. I did use a 4L beaker, maybe we used the same one (Fischer Scientific of old wet chem darkroom ancestry).

I don't remember what the deck angle was (as measured by the dynon attitude indicator), but it was not completely level fore/aft but was in roll axis. I stuck a long 5/8" craftsman socket in the spacer on the nose strut to get it close which is what I use when I juice the nose strut at annual.

I have the 32.5/30 usable gallon bladders replaced with eagle about 20 years ago for the mains and Flint Tips for the aux. I wasn't sure where or how it decided to tell me how many gallons to put in at each calibration checkpoint. I do know that the calculated fuel burn is usually within a half a gallon of the sensor determined qty at max endurance trips (TT and Hobbs time around 5.5 - 6 hours with departure climbs of about 1100 MSL to 11000 - 14000 and destination 445 MSL. I do have one fuel gauge in one of the flint tanks that's sticky and has been since I installed them.

 

[benapilot]

Good stuff!

I temporarily installed the HDX today and started the fuel calibration process to get a look at what I’ll need. On my 39.5 gallon tank, it prompted me to use five gallons at a time (my useable is 39.5 in each tank, but Skyview asks or a whole number. I’ll go the conservative route and define my tanks as 39 gallons each).

As for getting it level, the only reference in the POH or service manual to “level” is the upper door sill. That’s what I plan on using for calibration. My 182 sits 6° nose up at rest- I’m pretty sure I can get it level with just deflating the nose tire and/or strut.

 

[CanardMulti]

One item NOT in the manual: be patient. Give the voltage numbers on the screen plenty of time to settle down completely before saving them. Especially at the zero and low level increments, we're talking 5 or more minutes minimum.

When I calibrated my first tank initially, I just let each 5 gallon increment of fuel stop moving and immediately stored the voltage value. After storage of a low fuel level value for the next tank, a friend stopped by and we talked for a few minutes. When I returned to the task at hand, I was shocked to see how much the voltage had drifted. I started over on the second tank, redid the calibration on the first, and readings have been spot on ever since.

For the record, I have capacitance senders and each tank holds about 52 gallons.

Ken