Fuel used -needs to be for the flight not leg

[cbfraser]

Dynon fuel computer resets on engine start which makes it awkward to know how much fuel you have used since last refueling. 
Here's my submission to Dynon - if you agree please email 'support@dynonavionics.com'

EMS Background:
Currently fuel used is reset on engine start. 
Impact on safety:
This means that the pilot only knows the fuel used on the  current leg
but not since last refueling.  Since running out of fuel is still a significant cause of accidents it is important
to know fuel used since last refueling. With current Dynon setup pilot must record manually fuel used on each leg
and constantly add to current fuel used display # to know total fuel used. This is awkward and prone to error.
Requested feature:
When pilot adds fuel to EMS fuel remaining automatically clear fuel used.
Keep 2nd value – trip fuel used which is cleared manually. 
This is consistent with flight & trip timers that record time for current leg – and allows manual clearing at end of “trip”.
Competition:
Both JPI  and EI fuel computers clear fuel used when fuel is added – NOT when engine is started.

 

[dabear]

CB,

I think you will find that the SV does do what you want. Fuel used since start is there as you mention. However, total fuel on board is also there. If you filled up when started, flew to a location and stopped the engine. Then started again without re-fueling you'll find: fuel used since start (as you mentioned), but also total fuel on board being the total fuel (minus) fuel on first leg, and current fuel used.

 

[Dynon]

So that's been our thinking - that the fuel remaining is the authoritative "how much do you have left" number, which only ever changes when you set it. So when you fill up, you whap the full button, and if you take a partial fill, you add that many gallons via the interface. Isn't the fuel remaining the number that you're really after?

 

[dynonsupport]

Also, have you looked at all the things you can put on the EMS page? We have a lot of possible things to display and you may have the one you want turned off.

 

[mmarien]

I agree that fuel errors are a significant but avoidable cause of accidents and spent a lot of time tuning my fuel system to be simple and accurate. I've never used a fuel computer prior to Skyview but after trying a few of the functions and having limited space I settled on RANGE as the most important function. RANGE tells me if I'm going to make my next waypoint and I can keep my eyes outside and my mind on flying the plane. I believe RANGE is a function calculated from how much fuel you initial told SV that you had at last fill minus your fuel flow and time flying converted to distance remaining. It changes dynamically with fuel burn, time and ground speed - and faster than I can calculate.

In the screen below, the cross check is fuel in the tanks (~45 litres) divided by the fuel flow (~30 litre/hour) multiplied by the ground speed (~140 kts) = ~210 nm. So in my mind SV thinks the fuel remaining is about the same as what the fuel gauges show. A comforting feeling even though the next waypoint is only 30 nm away.

There are a lot of fuel functions available on SV all designed to reduce the pilots tasks. It's worth the time to try a few on the Engine Page to see which one fits your comfort level. Another great function is TIME REMaining if you're keeping an eye on that 30 min reserve and it's easy to compare with ETE. I prefer RANGE as the NEAREST function gives distance and direction.

 

[purlee]

I know I am inviting you to "howl me down" here, but while it is wonderful to have all of these computerised systems, and for Dynon to make them as accurate and reliable as they do, they do not and should not ever replace basic airmanship.

I know that things have changed a lot since I learned to fly on an old Piper Colt, some half a century ago, but back then we were taught "never trust a fuel gauge".

I firmly believe that to still be true, if you really need to know how much fuel you have left, and, trust me, you REALLY do, then nothing beats opening the tank cap and shoving a dipstick into the tank.

That way you know how accurate your readings are, you know how much you have burnt and you know that you are going to commit aviation with enough fuel to keep you safe.

I am sure that modern gauges are much better than what Piper were using in 1964, but they are still nowhere near as good as a Mk1 eyeball and a well calibrated dipstick!

 

[dynonsupport]

The fuel computer being discussed is something that is set by the pilot based on how much fuel they measured to be in the plane when they last fueled it.

It isn't the float sensors. It's something that you tell you have X gallons before you take off, and it says how much you have left some time into flight. It's a bit easier than climbing out on the wing 3 hours into your flight and using a dipstick

With a modern configuration where you have both very accurate floats in the tanks as well as a fuel computer, you have two independent measurements of fuel at all times which generally makes for a more comfortable flight than just trusting one measurement before you departed 400 miles ago.

 

[mmarien]

I am sure that modern gauges are much better than what Piper were using in 1964, but they are still nowhere near as good as a Mk1 eyeball and a well calibrated dipstick!

... fuel computer... It's a bit easier than climbing out on the wing 3 hours into your flight and using a dipstick

;D ;D Only in the movies.

Before I bought my Glasair I read as many accident reports I could so as to get a feel if it was a reliable aircraft. One accident report reported that the pilot looked in the tank and figured he had enough fuel but as the report stated he was forced to land off airport from fuel exhaustion. On the other hand you can dip my tank and may think it is empty but I can fly at least and hour plus on the apparent fumes in there. The dihedral on my wing makes it impossible to reliably dip the tank. The gauge is very accurate though.

With a modern configuration where you have both very accurate floats in the tanks as well as a fuel computer, you have two independent measurements of fuel at all times which generally makes for a more comfortable flight than just trusting one measurement before you departed 400 miles ago.

Another accident report just a couple of years ago described how the owner flying home from Oshkosk in a new LSA insisted that they had enough fuel to make the destination based on the fuel computer while the passenger pointed out the sight gauges showed the tank was empty. The fuel cap had fallen off and the fuel siphoned out. The passenger survived by swimming ashore after ditching. Unfortunately the pilot didn't make it.

While I prefer accurate gauges and fuel computers, I suspect that either method is only as good as the person using it.

 

[purlee]

Look, don't get me wrong, an accurate fuel computer is a great aid to flight safety and my new aircraft will certainly have everything it can have to make this work properly, I am not knocking it in the slightest.

But, the original question lamented the fact that the pilot did not know, from the computer, how much gas has been used, by reference to the computer, and thus could be caught by errors in calculation and run out of gas.

The point I am making is that the best way of being absolutely sure that you have enough fuel is to take the lid off the tank and look. It should be SOP before every flight.

I agree that the shape of some tanks does not allow you to dip all of the fuel in the tank, but the end result of this is that you finish up with more fuel than you think you have, that is never a bad thing in the quantities we are discussing