I think that Skydemon needs to be online for the wind.
Clearly it does (not having data from the pitot) which means that – unless SD supports a satellite phone connection – that feature is of very limited use in flight, for deciding which direction to glide. The wind at say 5000ft could easily be opposite to the surface wind, yet one needs to land into wind (at almost all costs) because even a 10kt wind dramatically reduces the energy to be dissipated.
Also, normally, the general wind direction is very obvious as soon as one gets airborne.
It would be possible to determine the probable wind vector if one was doing some significant heading changes and the software assumed a constant TAS.
My guess is that SD can grab the GFS wind data when on the surface.
Ok, excluding the dubious benefit of “online wind” I still think it’s a nice feature for peace of mind during the short hop to Borkum:
“GlideSafe takes altitude, wind speed and direction, as well as your configured aircraft glide ratio into account when depicting the glide safety radius around your aircraft, so a strong headwind would minimise your glide radius ahead, and a tailwind would have the opposite effect.”
When I was last at Borkum (a few years ago) they had bikes for rent at the airport. The town is certainly within a distance for an easy cycle.
Borkum is within an ecological area so you need to above 2000ft AGL if possible.
2000ft = 1/3 of a nautical mile.
A typical light aircraft has a glide ratio of around 9:1. So a glide from 2000ft in nil wind is about 3nm. So you’re unlikely to be out of gliding distance for your arrival to Borkum. Departure you will be (because light aircraft generally climb at a shallower angle than they glide at). But even then, it’s likely to be less than 2 minutes.
So the exposure is for a small time frame.
Having said, that I normally insist on life jackets being worn even for such a short distance. On some occasions in the past, I’ve removed my life jacket when the cross water part is finished. It’s incredibly difficult to remove in the confines of the cockpit, and impossible without someone else to ‘man’ the controls (or an autopilot). Even then, it’s a really manouver. There is no way that I’d manage to put it on in the event of an engine failure without a lot of spare time.
This might be (probably is) a bit stupid, and it’s a random guess, but could SD try and interpret the winds or glide safe distance by comparing the planned IAS for the profile plane (so 110 kts in my PA28) and comparing to GS, which it could calculate in flight? It sounds stilly, but with SD and others you have to take these things at face value…
But for 5nm I wouldn’t wear life jackets or take a raft. Even mid point you should be able to glide somewhere on and near land. And if the waters really cold, you’d probably be thinking immersion suits and that too would be overkill. If check the t’s and p’s, carb heat and just for for it.
Wouldn’t SD just calculate the wind from the last internet-connected data it got?
It seems to come up with pretty good en-route winds in the planning phase – the headings it derives and the GS it estimates tend to be pretty accurate in my experience. This makes me think it is pulling winds aloft data from somewhere rather than just surface wind from METARs and TAFs.
So when things go wrong the winds aloft data might be a couple of hours old, but I imagine better than nothing.
As someone else said it can also make a pretty good estimate of headwind/tailwind component by comparing GS to user-specified cruising IAS, assuming one entered it accurately or at all. It doesn’t know from which side it is coming though, because although it knows your track it doesn’t know what heading you’re steering. Perhaps it uses the last known winds aloft data that it pulled from the web and refines things in flight based on groundspeed, but this would be susceptible to a complete change of wind direction.
What would be nice would be an in-flight feature where one could input present magnetic heading and IAS, then press a ‘calculate current wind’ button.
You would need to feed in the magnetic heading and the TAS, and TAS needs IAS, pressure altitude, and temperature.
In principle this could be done but not in any certifiable way. You could collect the above parameters and emit them on a bluetooth link, for example.
It should be able to get close enough to be useful on most of those things.
Cruising IAS you told it when you planned (but would be nice to be able to update).
Pressure altitude – well it knows your height based on GPS and can calculate pressure altitude to a reasonable degree based on the QNH from the last weather information it got. Same with the OAT – again would be nice to be able to update.
I don’t think SD users are terribly interested in anything being certifiable – just useful. If it can do the above then that is certainly more useful to me that how I may have interpolated the winds from the 214 form a few hours ago.
Does SD take terrain into account in its glide distance computation?
I implemented such a function in my software. It uses GFS forecast wind data (if available, read if downloaded before flight), and uses SRTM terrain data and then shades the map slightly lighter in places where you could glide to. Over water terrain obviously does not matter, but in the alps it does… I have turned that feature mostly off however, because it requires quite a bit of processing power, and I have a Core i5, i.e. much more capable CPU than most tablets…
What would be nice would be an in-flight feature where one could input present magnetic heading and IAS, then press a ‘calculate current wind’ button.
We did this in the Windows CE (and Windows PC) versions of PocketFMS. Having said that, it wasn’t a feature that I often used. Firstly you have to maintain a very accurate heading and speed while entering the known info (let nose drop just a little or rise just a little as you look enter the data and your speed changes by 10mph fairly quickly making the results incorrect).
But still I don’t think that was the reason that I didn’t use it very much. I think it was more to do with the fact that the reason that I wanted to know about wind was because I wanted to know what it was going to do to my groundspeed. And that I could see very easily by comparing my planned ground speed to that shown on my GPS. If it was adding or subtracting 10 kts from me, I didn’t really care which direction or what speed the wind was. The effect on my ground speed was what I wanted to know.
Can i type in the wind, if i have it… ?
