Fuel tank gauge cross check

[douglips]

Hi! I'm saving up for an avionics upgrade and really like the Dynon SkyView setup. I saw this feature and was curious what this looks like - does anybody have a video or pictures or even description of what this feature does?

Fuel Computer/Totalizer with Fuel Tank Gauge Crosscheck

This question is inspired by discussions on an email list about a recent Cirrus fuel exhaustion incident, where rank speculation about fuel leaks led to discussion about cross checking fuel gauges with totalizers, and I wondered what, if anything, Garmin might have on the stock Cirrus avionics, and saw this feature in Dynon that sounds awesome.

 

[dlloyd]

Are you talking about this, from page 6-6 or 6-7 of the User Guide: a FUEL MISMATCH message to indicate that the fuel measured by the in-tank fuel quantity sensors does not closely match the fuel computer’s fuel remaining value. Just a simple message to draw your attention to the fuel level in the tank not matching the fuel flow computer calculation of fuel in the tank. It might alert you to something out of order: entered the wrong amount of purchased fuel, a fuel flow transducer not working or not working properly, a huge fuel leak draining one tank while you aren't looking, etc.

I built an RV7 with Van's standard resistive fuel level senders. I was skeptical of their accuracy. Followed Dynon's instructions for calibration and found them to be extremely accurate. As the tank level would go from 10 to 9 gallons, the fuel flow would show going from 10 to 9.9. Over and over. The tank levels in flight were equally accurate as the flow calculated levels and that was impressive. Being a taildragger, I would sometimes get the fuel mismatch message on the ground, never in flight.

All certified airplanes I have ever owned had inaccurate fuel gauges, including the Mooney now owned. Actually, the Mooney is the worst of the lot. Still there is no excuse whatsoever for not knowing how much fuel you have on board.

 

[porterjames]

There is that feature (mentioned above) and another feature-when inflight, you can check the relationship between the computer calculation of fuel remaining and the airplanes fuel gauges.
The Skyview does not issue a warning, but I frequently use it. Select the "Engine" and then "Fuel". It will show the two totals. It also allows you to make changes.

 

[douglips]

Thanks, that helps!

 

[Raymo]

My RV-7A has capacitance senders in the tanks and almost always wrong. I've tweaked them in flight as fuel is burned and the totalizer (Red Cube) shows fuel used. They're much better than after calibration but I still only trust the totalizer.

 

[swatson999]

My RV-7A has capacitance senders in the tanks and almost always wrong. I've tweaked them in flight as fuel is burned and the totalizer (Red Cube) shows fuel used. They're much better than after calibration but I still only trust the totalizer.

Same set-up, same plane, and mine have been extremely accurate. I am using the Princeton 2-point C2V converters, though, not the stock Dynon transducers, as I couldn't get those to calibrate worth a s**t.

 

[Raymo]

Same set-up, same plane, and mine have been extremely accurate. I am using the Princeton 2-point C2V converters, though, not the stock Dynon transducers, as I couldn't get those to calibrate worth a s**t.

I need to switch to those transducers, I guess. Are you using the Vans capacitance plates or the Princeton units?

 

[speedbird1]

without washing to hijack this thread. Does anyone know why both side don't show the same level when totally full and calibration has just been complete? (see below).