Implement an engine-out glide distance indicator (ring, blob, whatever)

[Hook]

Per Brian's request, I am posting this as an official feature request. This has been requested by me and others many, many times, for a few years now. But he'd like to get a measure of the demand. So if you would like to see an option available that turns on some kind of airborne indicator of how far you could glide if your engine quit then please "upvote" it (use the up-arrow to the right of this post). Feel free to post a supportive reply also, but what's going to count is the count to the right.

What I think we're all envisioning is some kind of indicator around the aircraft icon while in flight. A (sort-of-circular) line, or translucent "blob". But post any other ideas you have for what would be a good indicator.

In a good model of glide distance, that ring/blob would not be perfectly circular. Besides using the glide ratio you entered in your aircraft profile, it would take into account that you will lose altitude (and therefore glide distance) if you turned left or right or 180 degrees, and also use the forecasted (or computed?) winds aloft to figure how far you could go in various directions. It could even take into account terrain. Personally, a rough first cut would be satisfactory to me just for the sake of getting this off the drawing board. Even as simple as a perfect circle around the plane based on just the glide ratio. Improvements can be made over time. If you agree with that sentiment you might also want to mention that in a post.

Brian: besides making this a optional always-on indicator, I'd also like to see it as an option for when you hit the emergency icon (red triangle) in the NRST (nearest) popup window. That is, I would like an option that says "Turn on glide ring in emergency". That way, if I happen to not be flying with it on at this moment, it will come up when I most want it.

 

[mark.medic]

Hook, thanks for pushing this feature request back towards the top - and we really like your suggestion regarding the emergency icon popup.

 

[Tony Bolstad]

Upvoted.

Another possible option would be if the Pressure Airspeed option is enabled the glide ring algorithm could include a calculation on the difference between IAS and Ground Speed along with forecasted winds aloft and nearest metar(s). In my seaplane I'm always paying attention to wind direction via visual indicators and the delta between IAS and GS. Usually the streaks on the water make it easy to pick up the wind direction (and I know what it is when I take off) but I always feel better when I confirm with the IAS/GS delta check especially when flying low or landing. I generally don't fly below 300' when flying downwind but am comfortable cruising along at 100' heading in to the wind.

Also, thinking about winds aloft I've encountered 90 degrees difference between wind on the water and wind at 1,500 feet around here. Not sure how to factor that in to the calculation of the glide ring. I even had one time where the AWOS and windsock were indicating to use runway 13 but on the downwind leg for it I had a headwind of about 5 mph at pattern altitude, and on final went to zero around 400' and back to about 7 or 8 mph headwind in the last 100'. My plane Challenger is pretty slow so lots of time to note the GPS groundspeed in Ifly.

Tony

 

[Hook]

I will guess that Brian will try to factor in winds, and that's great, but it will still be luck if reality turns out to match prediction (whether computed or taken from a forecast). Terrain though... that should definitely be factored in at some point. Obviously you can't glide as far if the top of some hill intersects your glide slope. This would be helpful for me because of the many hills and mountains in my general area.

[Edit: but I imagine the biggest factor in the initial glide ring prediction will be how well you estimated your aircraft's glide ratio. After that: assuming the glide distance gets frequent updates on the way down, these things will determine how fast and in what way the predicted line/blob is changing: how fast you got your aircraft to its best-glide speed, how well you keep it there, did you make a turn and in which direction, your actual glide ratio (I would hope that the computation would start using that instead of the glide ratio in the profile), the actual wind direction & speed you're experiencing at this moment, any change in terrain issues due to your actual glide versus the initial predicted one. So... in other words, the prediction will get more and more accurate on the way down -- should be perfect just before touchdown!]

 

[Hook]

[P.S. This is a trick I read somewhere: if you're flying a certified plane, like my Cherokee for instance, if you immediately go to full-up trim (when at idle or engine off) your aircraft should settle at right about best-glide speed and then you can turn your attention to other things. According to what I read, this was (still is?) a requirement for certification. I can say that in my plane it works. The CFI in my last flight review was pleasantly surprised to learn of it.]

 

[mark.medic]

And the full trim up works well for our Cessna Cardinal as well.

 

[bobw75087]

Per Brian's request, I am posting this as an official feature request. This has been requested by me and others many, many times, for a few years now. But he'd like to get a measure of the demand. So if you would like to see an option available that turns on some kind of airborne indicator of how far you could glide if your engine quit then please "upvote" it (use the up-arrow to the right of this post). Feel free to post a supportive reply also, but what's going to count is the count to the right.

What I think we're all envisioning is some kind of indicator around the aircraft icon while in flight. A (sort-of-circular) line, or translucent "blob". But post any other ideas you have for what would be a good indicator.

In a good model of glide distance, that ring/blob would not be perfectly circular. Besides using the glide ratio you entered in your aircraft profile, it would take into account that you will lose altitude (and therefore glide distance) if you turned left or right or 180 degrees, and also use the forecasted (or computed?) winds aloft to figure how far you could go in various directions. It could even take into account terrain. Personally, a rough first cut would be satisfactory to me just for the sake of getting this off the drawing board. Even as simple as a perfect circle around the plane based on just the glide ratio. Improvements can be made over time. If you agree with that sentiment you might also want to mention that in a post.

Brian: besides making this a optional always-on indicator, I'd also like to see it as an option for when you hit the emergency icon (red triangle) in the NRST (nearest) popup window. That is, I would like an option that says "Turn on glide ring in emergency". That way, if I happen to not be flying with it on at this moment, it will come up when I most want it.

This would be great, and I think is already working in ForeFlight. They continue to "add" things iFly already has; let's return the favor

 

[Chad]

I have had mixed feelings about the FF glide ring. With that said, I do have it on, but I have found it is accurate in some situations. Specifically with constant winds aloft and if you are generally gliding in the direction of travel. Where it really falls apart is when you have a shearing boundary below you and you select an airport 90*+ off your heading. I tested my glide ratio a few different ways a year ago and dialed in my Vg at different common weights. (Solo, Full Up, Normal config). Found that my Vg changed by +/- 5 KT and the slope was predictable from 10k to SL. 0 wind days, it was spot on 11.7 to 1. I do have it set to 11.0 to 1 as a fudge factor, basically .1 NM per 1000 difference.

True at 10k, I am going to spiral down over the closest airport beneath me, but I have seen how airports that were in my glide ring quickly moved out as I turned in that direction.

 

[Don Maxwell]

I will guess that Brian will try to factor in winds, and that's great, but it will still be luck if reality turns out to match prediction (whether computed or taken from a forecast). Terrain though... that should definitely be factored in at some point. Obviously you can't glide as far if the top of some hill intersects your glide slope. This would be helpful for me because of the many hills and mountains in my general area.

[Edit: but I imagine the biggest factor in the initial glide ring prediction will be how well you estimated your aircraft's glide ratio. After that: assuming the glide distance gets frequent updates on the way down, these things will determine how fast and in what way the predicted line/blob is changing: how fast you got your aircraft to its best-glide speed, how well you keep it there, did you make a turn and in which direction, your actual glide ratio (I would hope that the computation would start using that instead of the glide ratio in the profile), the actual wind direction & speed you're experiencing at this moment, any change in terrain issues due to your actual glide versus the initial predicted one. So... in other words, the prediction will get more and more accurate on the way down -- should be perfect just before touchdown!]

Accounting for wind seems like a no-brainer. But it's actually more complicated because--as we know--winds aloft often blow counter to the surface wind. So if your engine quits at, say, 10,000 feet you first need to know the wind aloft. iFly already knows the forecast, so that's possible. Then below 1,000 or maybe even 200 feet you need to know the surface wind. iFly also has this forecast and if there's a station nearby, it has the METAR. So that should be possible, too. Garmin Pilot seems to take those two wind conditions into account in its glide ring--so it seems to me that that's the standard for iFly to meet or beat.

Accounting for the wind low over water--for seaplanes--is much trickier because it's almost always a local condition that iFly can't know about. But it's also usually easy for the pilot to compare the GPS ground speed with indicated airspeed, even down to a few feet above the water. But by that time you've already made your landing site, so it's not a glide ring problem anyway.