Peter wrote:
I am not sure. I have seen a supposedly exact implementation (taking into account real wind from an airdata computer) and it wasn’t a circle if there was wind. It was an oval shape.
It depends on how uniform the wind is. If it blows everywhere within the circle the same and the terrain is not a factor (it’s flat), it should be a circle as every point is moved exactly the same. But if wind changes direction and/ or magnitude within the circle, it will be deformed.
Peter, I mostly agree with you. However, now that I think about it, even in flat terrain / no wind, you won’t have a circle: you can’t reach as far back as forward, as you lose non negligible time / distance / altitude / energy in the turn.
In these conditions, the furthest you’ll go is directly ahead, and conversely.
I am actually wondering how wind displaces the shape. I am not sure about the oval (stretching), I think it might just do a translation of the shape (considering flat terrain, if you get mountains it gets very complicated, as you being able to pass a ridge or not creates non linear issues).
It will, but only if you have preselected in Setup: Connectivity Options / Live Data when Planning and Flying.
Also the wind info will still be only forecast, and not actual.
2greens1red wrote:
Also the wind info will still be only forecast, and not actual.
Well, if you can just make a landing site if the actual momentary wind allows, then you have picked the wrong landing site anyway. And SkyDemon can’t know much about the glide performance of your plane either nor how precisely you are able to maintain best speed which means that the computed glide range is only an approximation.
And regarding the thread itself:
I have been taught and am teaching as first memory item and immediate action after losing an/the engine: “Lower the nose to maintain safe speed”. If you already know which direction to turn you can of course initiate your turn immediately while trimming for the best speed. Next set up your approach to the selected landing site. If you are happy with it and confident that you will make it, tell someone about your situation and intention. And only now, when altitude and remaining time permits, start troubleshooting your engine problem. Some theorists even say: Don’t try to restart your engine unless you positively know what the problem is (i.e. selection of a wrong tank). Because one of the worst things that can happen is a momentary engine restart, e.g. because of a partially blocked fuel line or filter which allowed just enough fuel through to feed the engine for a few seconds. This will make you overshoot your landing site with maybe insufficient time to set up for an alternate one. But honestly I doubt I would do that…
2greens1red wrote:
It will, but only if you have preselected in Setup: Connectivity Options / Live Data when Planning and Flying.
I second that. Not sure why the option is not enabled by default. Very useful to pick up updated METARs in the air (otherwise it doesn’t and isn’t super clear about it)
Maybe because it doesn’t usually work above say 2000ft. No coverage over Belgium for example.
Also easy to get partial or corrupted data. A recent thread on this?
Peter wrote:
Maybe because it doesn’t usually work above say 2000ft. No coverage over Belgium for example.Also easy to get partial or corrupted data. A recent thread on this?
Possibly, but in france i’ve had quite wonderful coverage at a few thousand feet. I get at least sporadic coverage at ~10k feet in france / germany. Enough to get the metars to update.
Partial / Corrupted data seems weird: I imagine there is some easy verification on this (not an expert on comms but I imagine you could have some hash key and both have to match. discard if no good).
Are there verified issues in using data in flight (other than increased battery consumption, which could be relatively high)
what_next wrote:
And SkyDemon can’t know much about the glide performance of your plane either nor how precisely you are able to maintain best speed which means that the computed glide range is only an approximation.
True, but you do input the glide ratio for your airplane….
And yes the winds are only forecasted but it’s a good start…. one thing I haven’t looked into is whether the range plot algorithm takes into account the varying wind strength/direction as you descend….again as What Next said you don’t really want to be cutting it that fine for it to matter…
In terms of immediately lowering the nose, I was taught to zoom climb decelerating to Vbg and then lower the nose….but in reality that may not be the best course of action if you already know where you are going….
what_next wrote:
I have been taught and am teaching as first memory item and immediate action after losing an/the engine: “Lower the nose to maintain safe speed”.
Huh?? Sorry, that makes no sense, unless you are in a climb and below Vbg. I was always taught to pitch up and climb until reaching Vbg, which will normally be well below your cruising speed. That gives you altitude and altitude = time = more options.
Agree however with the comment WRT restarting. Unless you are pretty damn sure why the engine has stopped (and can remedy it!), then it’s a distraction and a waste of valuable time.
172driver wrote:
Huh?? Sorry, that makes no sense, unless you are in a climb and below Vbg. I was always taught to pitch up and climb until reaching Vbg, which will normally be well below your cruising speed. That gives you altitude and altitude = time = more options.
If you don’t lower the nose during an engine failure in a climb you will get into trouble. If you initially lower the nose during an engine failure in the cruise you lose nothing, because the little extra speed can be converted back into altitude or glide range once you are satisfied that your speed is safe. Most accidents after engine problems (especially on twins!) are caused by aircraft getting too slow and falling out of the sky. Therefore lowering the nose as an instinctive reactions seems a smart thing to do for me.
