Source? Timothy, you ought to know that I have better things to do that say I have an email from Avidyne when I haven’t actually got one.
The chances of Avidyne themselves drafting all the +V virtual glideslopes for the almost irrelevant European market, given their evidently cash-strapped situation, is somewhere south of minus zero. Presumably one of the European IFR540 users can confirm the +V functionality?
When the Jeppesen approach plate has a straight line, the navigator will offer a +V.
I think that you are misinterpreting.
Jepp do not publish a FAS Datablock for an LNAV approach, only for LPV approaches.
However, they do publish a FAF at an altitude and a MAP at another altitude.
What both Garmin and Avidyne do is the rather simple mathematics/geometry of drawing a straight line between the two. That line is not approved, nor is it coded by Jepp, it is provided by Garmin and Avidyne (and, I imagine others, but I don’t know) as a courtesy to their customers. Neither Garmin nor Avidyne is creating any NavData, just using it in an unapproved manner.
This makes it a very different matter to the glidepaths of LNVA/VNAV and LPV approaches, which are approved and part of NavData.
Oh Dang! I have given an answer to one of the 17 questions!
Thanks Timothy. My PBN instructor was correct after all !?
How can a straight line which is above the surveyed glideslope be approved or unapproved? There are no rocks hanging down from the sky. Both Jepp and the box maker have to conform to some QA standards for the databases. For the most part the databases are bought from Jepp but any add-ons (and Garmin do a lot of add-ons for e.g. VFR) are under the box maker’s QA process.
Inside the GPS, the control loop implementing the +V glideslope is the same as the control loop implementing the LPV glideslope.
This is just getting silly. It is something the pilot doesn’t need to worry about.
All paths (other than curved paths) are coded as endpoints. An airway segment e.g. SFD-LYD is just a line, at the MEA.
What about the GPS-ILS app for which (according to its developer) you Timothy generated the glidepaths. It’s the same idea, and there is no “approval” there either, but if done right that glidepath should also be above the real glideslope and thus obstacle-safe (well, for airports with a real ILS).
Timothy wrote:
What both Garmin and Avidyne do is the rather simple mathematics/geometry of drawing a straight line between the two.
By the way, just to show that this stuff can get worse, there is a discussion taking place on the PPL/IR forum as to whether it truly is a straight line in Euclidian Space, or if it follows the curvature of the Earth 
Entirely relevant. At 5NM, the height you have when following a straight line and the height when following the curvature of the Earth, differ by around 22ft. The knowledge of this is critical, and I am sure part of the EASA approved syllabus.
Also, it is crucial to understand that on an east-west final approach, you have to constantly adjust your heading since the signal is following a great circle, while north-south approaches and those flying near the equator do not have to worry about that complication. Timothy can attest to the difficulty of flying straight around the North Pole, this is extremely hard, and if you not careful you end up on the north pole turning at an infinite rate!
Standby while I calculate the effect of Gravity on the ILS signal. While the GPS signal compensates for that, the ILS beam gets bent down by gravity a little a little, which means the altitude differs by something around 0.00002"….
PS – while we look down on our ancient ancestors, who until around 2500 years ago thought the earth was flat, this was a perfectly reasonable approximation for all practical applications at the time.
Then long-distance navigation made the understanding of the spherical nature of the world necessary, which for all practical purposes is all a pilot or ship’s navigator has to understand.
Only when you are a surveyor, or building your own satellite navigation system, you need to understand the geoid, undulations, and for the GPS, the effects of gravity on time according to general relativity.
So – when flying an ILS, it is perfectly reasonable to assume the Earth is flat.
Sarcasm travels poorly on the internet but in this case its path has been very well lubricated 
Cobalt, I do expect you to calculate the curvature of the glideslope due to relativistic effects. I can’t do it (I failed every maths exam at univ but they couldn’t chuck me out because I always got 100% in electronics) but I know you can.
I reckon the # of people on any forum debating this usefully is a positive integer between 0 and 2 (after adjusting for the £75 fee), but it will likely be implementation dependent. The GPS constant-altitude line is of course a curve, but you could implement some funny stuff on the LPV glideslope. I reckon it must be curved… I mean straight. Must get off the Ouzo… this is real stuff from Lesbos, unlike the fake stuff we got at Dresden.
Cobalt wrote:
Timothy can attest to the difficulty of flying straight around the North Pole
I claim the record for the fastest round the world trip, having flown a Rate 2 turn around the North Pole, so round the world in one minute…eat that, 80 days
