Libretto wrote on May 27^th, 2011 at 8:44pm:


Librettto

I don't think there ia anyway to get rid of MON01 name and start again. Sometimes when I have been adding a waypoint for one reason or another and the first three were incorrect, the correct one would be named DHP04. MON01 and DHP01, DHP02, and DHP03 will have no effect on your or my route.

I started off with 010 degrees and decreased by 10 degress per waypoint. I think that at 13 miles or 20 miles which I used for the arc the decrease should be 5 degrees per waypoint for a smoother arc. At 10 degrees the plane was turning left, wings level, turning left, wings level as it went around the arc.

Michael Cubine

Libretto

Several items I would like to cover.

1. On the HSI you will notice a green circle and straight line. The circle is at 20 miles from the airport and the line represents a straight line thru DTMB at the runway headings for both 7 and 25. This line runs through the center of the airport and not the MON VOR. The purpose of this circle and line is as reference point in case something goes wrong on the approach and I need to do a 180 degree turn, head out 17-20 miles, do another 180 degree turn and try another appproach. I do this at all airports at which I am landing. It is just conicidence that both the arc and the circle are at 20 miles. This circle and line are entered on the FIX INFO page.

2. On the HSI you will notice the last waypoint in the arc is DTM02. This is enterted on the scrachpad as DTMB253/20 and then line selected to RINOS. RINOS does not disappear but a disco develops that you must remove. DTM02 is now part of the approach to 7. So this has exteneded the apprroach out to 20 miles and should give you plenty of time to capture the LOC and setup a stablised approach. On do this on any approach that has a sharp turn onto final in the 10-15 mile range.

Michael Cubine

Libretto

That's great that everything worked from 13 miles out. A lot do in not much time.

Michael Cubine

That's great work from Michael there.

But before some misconceptions take place (especially those with 'I hope they fix this in 4.5'), lets explain something.
First thing, those DME arc procedures suffer the same fate as e. g. the ones with a procedure turn in it. They all are based on some real world data format for FMC devices, called ARINC 424-19 protocol specification.
Now, our Navigraph based FMC data (which not only includes Captain Sim planes but all current addon ones, even the ones with the L and the D or the big P) shortens this detailed data format and cuts it down do "simple" descriptions of a waypoint.
This happens because the FMCs can't handle rw data but need a simpler format there. Again, all of them, not only Captain Sim.

Normally, every procedure at an airport is stored within the FMC database and if e. g. a DME Arc is included, they store the waypoint or fix which is at the center of this arc and they then attach 'draw arc at 13DME' to it, giving you infinite waypoints describing that arc, leading to high accuracy.
That's a thing a rw FMC can and will follow, it is also allowed to do so.
You can't manually enter an arc there, the procedure has to come from the FMC database.

Now, in the sim, we don't have that description 'draw an arc' available (for guidance), we only can describe waypoints, their location and their height, together with some speed restriction.
That's what you are seeing at every FMC plane in the sim (not only CS ones), those arcs and also procedure turns get reduced to some initial waypoints only, leading to this square-like appearance.
That's a simulator based factitiousness, so to speak.

In the real world, you wouldn't be allowed to use such data for any FMC guidance. You would be rendered "unable" to follow that approach if the FMC would be your only source of guidance there. Choose another approach then (if available) or, depending on the plane, use the basic VOR instruments to fly that arc. It's much fun to go with the needles only.
Also, Michael points that out correctly, those drawn arcs with the "Fix" feature are for situational awareness only.
Real guidance does not come from pixels on a CRT (and following them with the pilot's eye via HDG select), it comes from "raw" data in the FMC, so what we are doing with those manually entered waypoints is to create such data, within in the limits of FSX.
As I've pointed out, the real unit would have infinite "waypoints" there, ours only has few. So don't compare the approach with the waypoints on that arc with any rw operation, it's a (nice and clever) workaround only.


To prevent the FMC to see some waypoints as "fly by" only, most Boeing planes can only workaround by adding a manually entered waypoint close or even at the location of the current "fly by" one.
The Airbus people have an extra button to define every given waypoint as "flyover", the Boeing guys have to trick a bit since the manual stuff usually doesn't get cut to enable a nice curve.

So the trick is, as the other guys already pointed out, to add a manual waypoint there, forcing the FMC to really overfly it.
Again, this isn't a Captain Sim limitation but a Boeing one.
Every Boeing sim unit I know suffers from this more or less shortened route when some predefined waypoints are close to each other. This may be another downside of the current sim data format since rw procedure data on a real FMC won't be "shortened" for the sake of nice curves since you would lose (lateral) accuracy then.

Edited:

And, not only praise Michael but also recognize that the FMC manuals of the CS planes describe all methods and formats of adding waypoints too. Always worth a look.  
For the 757, this would be cs757_manual5.pdf.


And additionally, you won't come across this lack of realistic data if you just look at the procedures a sim FMC draws. Those edged lines may therefore look normal to you, unless somebody shows you some charts with real DME arcs or procedure turns.
You may google those phrases (DME Arc + Procedure Turn) to catch a view (on rw data) and you may also follow Michael's tip to run some "real" pdf charts besides your sim, to catch a glimpse on how it is supposed to be.
And please don't think that those two things aren't commonly used. They are! You may just have formed up a bad habit to believe that the edged sim display is the real thing, that's all.  

You mean that approach description? I don't know, but you can set up your own.

Just use the charts here. http://hk.vatsea.net/charts.php?show=charts.php
Those are no rw charts but they'll give you all the information you need to set up the waypoints by entering them manually.

(that's only a partial view on the chart for IGS13, download it for full details, it's free)

Starting the approach from the hold at CH (Cheung Chau VOR) which is available in the sim and the FMC.
On a radial of 270 until 7DME, you would enter that waypoint as CH070/7, setting you up abeam SL (Sha Lo Wan NDB). For that abeam point, you can also use the "FIX" page of the FMC to actually calculate the exact location.
Now, depending on your speed which itself is depending on your plane (category), turn towards that NDB and prepare to intercept the Localizer while leaving the NDB at a heading of 045. The Localizer course is 088.
The Localizer will lead the (lateral) way to the famous Checker Board (which you will pass, not overfly), therefore leading to a right turn (no FMC guidance there, just plain visual) to rw13.
When you can see the Checker Board but no rw, your visuals aren't suitable for continuing the approach.

Use the radial 315 from TH (Tathong VOR) for some rough guidance when looking for the centerline of that runway. This will also define your go-around way to fly, so setting it up is a good idea.
While using the FMC or the LOC to guide you, the vertical planning is fully up to you, watch the diagram on the chart and mind the minimums.

When setting up the STAR for that airport/approach you can also use those charts. They all lead the way to the mentioned holding at CH, using some normal intersection names which should be present in the FMC database, so setting them up is easy.
If not, the coordinates are also given on that chart, so you can enter them, just in case.

Of course, as tough sim pilots as we are, we kick out all that sissy tech and take the 707 to get into the old Kai Tak.
If you ever wondered what "workload" may describe, set up some not so nice weather (at least no smooth air) and fly the hold, configure your plane and follow the precise track to get safely to that Checker Board, descending, slowing down, bringing the flaps and gear down and also running the checklists while watching your systems.

Now the rw guys may correct me there but I think that Mike Ray describes a sim only procedure there, using the wrong self-build LNAV waypoints for arcs.
The use of raw data is true, but the real world fellows in a 757 or 767 would either have a FMC database to describe that arc in full detail or they are unable to use FMC guidance there, at that procedure, using a DME arc.
Of course, this statement may well depend on the actual tolerance allowed for that special procedure, in that country, at that airport. If you're allowed to deviate more, the edged "arc description" may well be ok for this.

Needs some Lourification I think.  

Mike Ray may describe the stuff for the same reason why e. g. Michael does. It's the only way to "cheat" your sim FMC to fly close to an arc.
A real FMC would have this for example.
Quote:

Since no current sim FMC can understand such descriptions, the 'describe an arc with lots of waypoints' method is indeed common.
You can spot the advantage of the FMC based approach too, it doesn't actually need an installed navaid on the ground while still being able to precisely track the way as given in the approach description.

Regarding the shortening of routes, I've seen other dev's FMCs doing this too, more or less severe, so even if they are using an "overfly flag" (which is a good point by the way), they seem to struggle from some logical problems there.
Now I can't measure the actual "rounding capability" at my addons, but, so far, they all need some precaution from the user's side to avoid funny looking approaches when not using easy "straight in" all the time.

Here is an interesting situation that happened about a year ago. In February and March 2010 I set up flights between various Florida airports that were ready to takeoff and saved the flights prior to takeoff. When the flights were loaded at a later date they were set to go. Verify position in the FMC thru the CDU, press the thrust button, rotate, and away you go. Weather, STARS, route, SIDS, season, time of day, payload, amout of fuel were already in the saved flight. Several months later, I started to update the AIRAC cycles monthly. So waypoints especially in SIDS and STARS were starting to disappear from the procedures but this made no difference in LNAV or flying to waypoints which no longer exsisted. This led to the conclussion that LNAV was not navigating from name to name but from coordinate to coordinate.The name of a waypoint was shorthand for the coordinate. If I wanted to I could make a flightplan that consisted of nothing but coordinates. Am I thinking correctly or is this just all screwed up?

Thank you
Michael Cubine