Lol! You are quite right of course. The correct answer should be to commence your decent 12 mile out. I divided when I should have multiplied! It just goes to show – never do anything in a hurry and check your figures!

Mike
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Just catching up on the the forum and note Sky Painter's remarks on calculating the descent. In the scenario above the calculation made is that 5 miles out will do it but if one is travelling at 1.5 miles per minute as described that means a time of 3.3 minutes is all one would have to lose 4000 feet and therefore 500 ft/min would never work. Perhaps a SkyDemon feature might be helpful after all as obviously even in an armchair this is proving a challenge though I agree it is not rocket science.

We could do that, but generally we do not implement features until we judge we can implement them perfectly. We do plan to include more circuit information in future, and your suggested feature would be a natural extension of that work.

Tim, You make it more complex than the solution I had in mind :-). I thought about a standard setting “prefer joining altitude above destination airport”  (+500ft, +600ft, +700ft etc.). Ton

C'mon guys! We're VFR pilots and SD is an aid to VFR flight, NOT a Flight Management System (FMS).

We all learnt to fly by reference to a line drawn on a chart, a stopwatch attached to our clipboard, and some fairly rudimentary calculations, using either a 'wizz wheel' or the 'max drift' method and forecast winds aloft to establish an approximate magnetic heading to steer and ground speed (GS).

So, in this scenario, you're approaching your destination at 5,000 feet, so you have 4,000 feet to lose to get down to circuit height which, at a descent rate of 500fpm is 8 minutes. Your aircraft cruises at 100kts, but you have a headwind component of 10kts, so your GS is 90kts (1.5 miles per minute). 8 divided by 1.5 (or 16 divided by 3 makes the mental arithmetic a little easier) indicates that you need to commence your descent at a little over 5 miles out. It's not rocket science!

I don't mean to sound patronising, and if I have upset anyone, then here and now I apologise unreservedly, but as VFR pilots, by relying too much on GPS, we are in danger of neglecting our responsibilities as airspace users and losing those precious skills learnt early on in our flying. Don't misunderstand me, I think GPS is a modern day miracle and an absolute godsend, especially if the weather turns against you. However, if we neglect those basic skills by which we all learnt to fly, we do so out our peril, because the day will surely come when we need to fall back on those skills to get us out of trouble.

Even as an avid SD user, my primary means of navigation is still a stopwatch and a chart, on which I have a course line drawn, annotated with magnetic heading, distance and an approximate a wind arrow. I also use all available radio navaids if appropriate. SD is my backup, especially if the weather turns bad, but if SD should fail (it never has, but could so easily do so through no fault if its own), I know where I am, how far and how long to my destination.

SD is a tool, and a very good one at that, NOT a replacement for basic flying/navigation skills. End of rant!

Mike
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We may implement this at a point in the future where you are nominating the runway, circuit and join you are performing. At the moment since SkyDemon does not know whether you're going for long finals, and it doesn't even know the circuit height either in most cases, it doesn't make sense for us to make this alteration yet.

I agree, a descent to 1000ft circuit height is more realistic. You may or may not get s straight-in. There are many places where you would get hurt if you blindly follow the descent to 0ft.

Good idea, but what if you plan a straight in?

Eric

Currently SD sugest to start decending from my flying altitude towards the aerdrome at 0ft sugesting I make a straight inn. Might it be possible to change that to circuit altitude? That more realistic as I have to fly the circuit before landing.
Thanks Ton