Peter wrote:
I accept that the bit about the leg track coding is stuff which nobody needs to know, ever
I would say that knowing the leg track coding is on about the same level as knowing that the ILS works by transmitting, on two carriers, one for the LLZ and one for the GP two different signals and that their relative strength tells you where you are in relation to the nominal track/glide path.
Would you consider that also be stuff that nobody needs to know, ever?
Timothy,
I only now had the time to look through it and would like to say thanks a lot for sharing this. It has made some stuff clear to me which I should have known or read up on a while ago but never bothered (as I am not IR rated right now, I still need to explain to my pilots what the airplane can actually do (RNAV5, 1, RNP APCH LNAV/VNAV, RNP APCH LP/LPV). And obviously I will have to pass the endorsement for this stuff when I reactivate my IR.
I think at the moment, this is the one document which really has all the necessary information you need to know or at least have read about in a structured way if you want to play in the RNAV league.
There is a lot of background information which is valuable insight in things we usually do not look at but shows (e.g. the procedures descriptions of SID/RNAV SID) what our navigators really do. Magenta line can be deceiving in such cases. For me, that is very valuable stuff to know.
I would not weigh too much on those who went a tad tiddly with their comments here, as probably there were some who never imagined it could involve some serious change in what they learnt doing their IR decades back… and people tend to get grumpy when they see that they don’t know it all after all… 
Peter wrote:
My take on the discussion was mainly that a lot of the subject matter nobody needs to know, ever, while others bits one does, sometimes. I accept that the bit about the leg track coding is stuff which nobody needs to know, ever (although I would like to see an example of it so I can see if the KLN94 has it in its database, as a matter of curiosity).
Coming from you who likes to get to the bottom of stuff, sometimes even below, I can only say I am astonished at this comments.
Most of what I read will help me understand how the things work and why they are as they are. Mind, I have worked with ARINC databases extensively for my flight sim work, but there is still a lot of stuff which make me re-think some things I took as “given”.
Maybe digest the whole thing properly before deciding what you really want to know.
I quite like the document – it is thorough. I would question the relevance of some parts from an operating perspective (for example, elements of the section on how GPS works) as I’m cognisant of the fact that we in GA generally tend to think that training syllabi are too comprehensive. I suppose the acid test would be trying to understand how much classroom time it would take to deliver the entirety of the manual.
I’ve saved the document to my ForeFlight App, a location I reserve for important stuff.
Peter, FYI the reason most TSO C129 systems are not certified for RNAV 1 SID/STAR procedures has to do with the fact that these early designs don’t support the CF leg terminator in the database. The CF leg terminator is used as the first leg on some RNAV SIDs.
Timothy, nice job. This link AC 90-100A Compliance lists which early GPS navigators are approved for RNAV ! SID/STAR. It was developed to identify which aircraft systems were approved, particularly those that had an AFMS that predated the issuance of AC 90-100A. Recent AFMS have an explicit statement of compliance, but the early systems AFMS writers were not psychic, so this document handles the early systems.
One comment on pdf page 124, there is this statement:
RNP approach procedures to LPV minima
Vertical guidance provided by SBAS-GPS. Procedure may ‘downgrade’ to LNAV/VNAV minima if satellite signal or runway environment/lighting does not meet LPV criteria
I don’t think this is accurate, at least on the Garmin units. When the integrity is below that required for LPV, prior to reaching a point one minute before the PFAF, LPV is annunciated in an amber color, sort of warning you to expect a downgrade. If the integrity still does not meet the criteria at the “one minute to go point”, the procedure downgrades to LNAV without any vertical guidance provided.
