Fuel Range Ring

cmgolden

I love flying!
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Apr 28, 2014
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I think it would be nice to have a wind-adjusted fuel-range ring on the map (similar to the new glide ring). I believe all the data is there. Just need to do calculations and draw it. Maybe two rings, one for specified fuel reserves and one where you run dry.
 

dynonsupport

Dynon Technical Support
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Would you want that based on some efficient power setting, a worst case power, or the current fuel flow?
 

GalinHdz

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Would you want that based on some efficient power setting, a worst case power, or the current fuel flow?

I vote for selectable on setup. Default to current fuel flow unless no fuel flow data is available then it defaults to worst case power.
:cool:
 
W

William_Ince

Guest
Would you want that based on some efficient power setting, a worst case power, or the current fuel flow?
I vote for selectable on setup. Default to current fuel flow unless no fuel flow data is available then it defaults to worst case power.
:cool:
Concur.
The fuel range ring is an excellent idea. Would be an invaluable tool for cross country flying, especially in a situation where the winds are stronger than forecasted.
I hope Dynon will take a close look at that.

What say you Dynon? :)
 

dynonsupport

Dynon Technical Support
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If you have a flight  plan, we already calculate fuel remaining at that point, dynamically calculated with the current winds and fuel flow.

If you're going cross country, I assume you'd have a flight plan. Is there a reason that a ring that could easily be 750 miles in diameter is better than a readout of "3.2 gallons at waypoint"?

We also have fuel range displayed , which is also based on current conditions. So if that says 427 NM and your waypoint is 500NM...

Just trying to figure out what advantage of the graphical depiction is over the current data set.
 
K

KRviator

Guest
I'm for this. Definitely based on current fuel flow though.

One reason for using it during cross-countries would be for either an alternate or diversion. The current setup gives fuel at waypoint/destination, and that is great in itself, but if you are planned to fly A-B-C and refuel at B, but you have better-than-forecast tailwinds, the endurance-ring would show you could actually make C and possibly D beyond.

A local flight is another possibility, loitering until your endurance ring (which should exclude your 45 min fixed endurance) touches your destination and you know you need to head for home now to keep your reserve intact.

OzRunways include an endurance ring based on a set cruise fuel flow, which I've always thought was a great idea.
 

dynonsupport

Dynon Technical Support
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The issue I see in using "live" data is that the ring will breathe in and out with every slight change to the plane. Whenever you do the following it will change dramatically:

1) Adjust throttle
2) Adjust mixture
3) Climb or descend
5) Turn
6) Go through updraft / downdraft while holding altitude

This is because the live data uses fuel flow and ground speed. Anything that changes either will change your range. You could easily see 100 NM when you're climbing out and 500 NM once in cruise.

So the question is how do you make it useful. If you can't trust it because anytime you look at it you have to consider if your TAS or fuel flow is representative of your cruise condition, then it's not super useful. I think there'd be a lot of questions about why the ring was always changing size.

If we used some fixed numbers, like we do for glide ring, then it would be a lot more stable. But of course if you're hammering along ROP when you have it programmed for a LOP flow, or if the airplane has more drag than normal, you won't make it where the ring says.

Kevin,
Personally, I use the FUEL RANGE and have my flight planned A-B-C-D. If when I'm enroute A-B and my range says XXX miles, if XXX is more than the distance to C or D, that's how I know I can get there.

--Ian @ Dynon
 

mmarien

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The fuel range ring is a nice idea but would it be useful? We have the Range Info item. Zooming out until the distance circle approximately equals the Range would be the same as the fuel range ring.

I went through my screen shots for 2014 and 2015. In most the distance circle is 12, 20 or 30nm and smaller when I approach an airport. I found one at 80nm. Given my average zoom I probably wouldn't see or use the fuel range ring with anything but a near empty tank. By that time I've probably done the calculations and are making an approach.

The glide ring will fit within my normal zoom and would be useful when the fuel range ring shrinks to a dot. ;)
 

cmgolden

I love flying!
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Wichita, KS
The always-changing issue is no big deal. Dynon already handles that problem for the top-of-climb indicator (blue arc) nicely. Ditto for fuel quantity and probably many other similar data. Just smooth it a bit over a short period of time. And I want it to change. Add power and see the impact to range.

To answer the question "what's better about a ring over the numerical data?" 1) a picture's worth a thousand words, 2) wind adjusted for all directions, and 3) what was Dynon's answer to that same question when posed about the glide-range ring--it too could have just been a data number.

P.S. I often have one map showing zoom scales greater than 80 on trips. But I also pan to my destination as well.
 

dynonsupport

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But I also pan to my destination as well.

This is why these discussions are so useful! It isn't a given that a ring like this on the map is available when panning. So knowing that is a use case is very helpful.

The math on the distances we are dealing with is useful to frame the discussion about when the ring will be shown though. If you are in a 150 knot airplane, a 30 minute fuel reserve is 75 NM. This will just show up on a 80NM zoom screen. By default, we turn off all the airports at 120NM, so just one more click and you don't have airports shown except the ones in your flight plan, yet you are almost out of fuel.

If you're in an RV at 170 knots ground speed, burning 9 GPH, and have 20 gallons on board, that ring is 378 NM in radius. So you need to zoom to 500NM to find it. Then, if you pan to your destination that is 300 NM away, you will hardly be able to see the fuel ring on the 80NM range, and it will be missing at the 50 and lower zooms. If your fuel flow rate changes by even 0.1 GPH, the ring moves 5 miles. If the wind changes by 1 knot it moves 3NM. When you're zoomed out to 80NM, an airport icon is about 5NM wide on the map.

Thus, the challenge for using it to plan long distance flights is that to actually see your ring you need to zoom way out, find it, then zoom in to an edge of it near where you are going and find the local airports that are inside it.

The glide ring doesn't really have this issue. Most piston powered aircraft have glide ratios of less than 15:1. Thus, at 12,000' AGL, they can glide less than 30 NM. This means a glide ring is visible at most commonly used zoom ranges. By the time your fuel ring shows up on this screen in the same airplane, you're deep into your VFR reserves (12 mins left at 150 knots). When your fuel ring gets inside your glide ring, you should probably start practicing the use of the glide ring....

So that's why we see the trade-off here. Glide rings are great for close-in use, and they show the offset of wind which can make a huge difference to where you can land in the next 6 minutes. For fuel though, if you're planning for your current winds for the next 3 hours and 500NM, and trying to decide on airports 50NM apart, you're fooling yourself.

Don't take any of this as push-back on doing it. Just trying to find out how we can make it most useful! Is there a more useful implementation like highlighting airports that are within your fuel range so that you can tell this even when zoomed in to an airport that is 300NM away while your fuel state is 500NM? What about showing fuel for all your points in the flight plan page? What about an option to shade the map or airports in areas that are outside your fuel range so it's clear your're looking outside your range?
 

TJRV8

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Mar 12, 2013
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It would still be useful to have a "Fuel at destination" option.
The fuel at waypoint is good for tracking your planned numbers, but with multiple waypoints it would be nice to see if the actual conditions are going to give you the required reserve at your final destination.
 
W

William_Ince

Guest
It would still be useful to have a  "Fuel at destination" option. 
The fuel at waypoint is good for tracking your planned numbers,  but with multiple waypoints it would be nice to see if the actual conditions are going to give you the required reserve at your final destination.
Correct me if I'm wrong, but isn't that already available on the Flight Plan page, if the last fix is the destination airport?
 

TJRV8

Thanks
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Mar 12, 2013
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I don't think so. Can only find track, distance, and time. If fuel is available please tell me how to get it. I was thinking primarily about making "fuel at destination" an info item to display on the EMS page, but if it's on the flight plan page that would also work. Thanks
 
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