RNAV: fly-by and a fly-over waypoint

[zubillagajose 2]

Hi guys, there are RNAV procedures where there are fly-by and fly-over waypoints., Looking at the charts for SKBO, the arrival TOLIM2E the waypoints are fly-by, when I do that procedure and I load it in the FMC of the 737 PMDG the waypoint NOR05 does fly-over. Is it an airac error?

[sloppysmusic 189]

I looked in my Navigraph cloud app and that STAR is not even there. Are you looking at the actual chart or loading it from FMC database. 

[Headley 26]

In the Navigraph Charts Desktop app TOLIM2E is present.

But sorry Jose, can not answer your question, not enough knowledge😕

[BlueStar 323]

17 hours ago, zubillagajose said:

the waypoint NOR05 does fly-over. Is it an airac error?

Any time there is a turn involved on an RNAV procedure the waypoint is a fly-by.  FMCs are programed to make the most efficient turn.   

To make this simple VOR/DME/ADF fixes are fly-over fixes, FMC fixes are fly-by fixes.  

Grace and Peace, 

Edited February 11, 2019 by Bluestar
type

[downscc 1,327]

TOLIM2E took a minute to find, it is part of the 2E 2W RNAV ARRIVALS sheet.  NOR05 is not indicated to be a flyover waypoint, it is indicated as a flyby and the FMS is correct.  True, the chart seems to indicate that the track from NOR04 goes all the way to NOR05 and then there is a 'instant' heading change at NOR05 to PULDI but of course this is not how it is flown.  If the waypoint were a flyover then it would be a symbol with a circle around it.  See the DANSA VASIL RNAV departures in the initial climb inset where there are waypoints designated as flyover.  Different symbols.

Examples of flyover would be something like track 149 until ABCd2 then turn right...etc.  The change in heading is after passing d2 from ABC so this is an example of an FMC flyover.

Edited February 11, 2019 by downscc

[JoeDiamond 67]

4 hours ago, Bluestar said:

Any time there is a turn involved on an RNAV procedure the waypoint is a fly-by

Not necessarily.  RNP approaches for example.

[sloppysmusic 189]

Approaches clearly show by the type of icons that a waypoint uses whether it is a mandatory fly OVER or fly BY can be used. Will edit this post and put the example if I can remember where I read it.

[zubillagajose 2]

 

Hi guys, thanks for your comments, I know the difference between both concepts fly by and fly over, I ask concrete is in the fmc of pmdg does a fly over, I do not know if it is correct or is a calculation that the fmc does to make the turn, for example in the airbus mcdu does fly by something wrong but does not fly over. thank you guys for your opinions

[sloppysmusic 189]

40 minutes ago, zubillagajose said:

 

Hi guys, thanks for your comments, I know the difference between both concepts fly by and fly over, I ask concrete is in the fmc of pmdg does a fly over, I do not know if it is correct or is a calculation that the fmc does to make the turn, for example in the airbus mcdu does fly by something wrong but does not fly over. thank you guys for your opinions

IF the waypoint is a fly OVER the FMC will definitely respect that and widen the turn to pass through it, otherwise will bypass. So it will be coded into the official approach and you do not need to change anything, which you should NOT do with any published approach, as this can be very dangerous and also illegal.

I think you might find the following link helpful from a Pro Pilot forum:

https://www.pprune.org/tech-log/490079-737-fmc-can-you-force-fly-over.html

This link informs about government requirements for FMC/RNAV nav gear so it can adhere to fly overs as well as fly bys,

http://tfmlearning.faa.gov/publications/atpubs/AIM/Chap1/aim0102.html

Edited February 12, 2019 by sloppysmusic

[zubillagajose 2]

 

hi russell the pmdg does fly over, I do not change anything

[downscc 1,327]

17 hours ago, zubillagajose said:

 

Hi guys, thanks for your comments, I know the difference between both concepts fly by and fly over, I ask concrete is in the fmc of pmdg does a fly over, I do not know if it is correct or is a calculation that the fmc does to make the turn, for example in the airbus mcdu does fly by something wrong but does not fly over. thank you guys for your opinions

I just flew the companion arrival (I was landing to the North instead of the South) in the 747-8 and the aircraft correctly flew by all the flyby waypoints.  The navdata for this arrival does not use the keyword FLYBY for the fix NOR5 so I didn't expect the NGX to flyover that fix until I looked at the Navigraph interpretation of the navdata:

STAR TOLI2E FIX TOLIM AT OR ABOVE 19000 FIX BO862 AT OR ABOVE 19000 FIX IRUPU 17000 SPEED 250 FIX NOR01 FIX NOR02 FIX NOR03 FIX NOR04 FIX NOR05 17000 TURN RIGHT DIRECT FIX PULDI FIX AMVES 13000 SPEED 215
  RNW 13R RNW 13L

Maybe the 'TURN RIGHT DIRECT' to the next waypoint PULDI is causing this problem in the NGX?  This rings a bell, I've had this discussion with Stefan at Navigraph in the past and I argue that without 'TURN RIGHT DIRECT' statement, the aircraft will turn right at NOR05 and proceed to fix PULDI, in other words the additional phrase is redundant.  In this case, it could be assigning in error a flyover method to NOR05.

If I were coding this I would not use 'TURN RIGHT DIRECT.'   Try it without that phrase and that segment becomes, "FIX NOR05 17000 FIX PULDI."

OMG I cannot wait for PMDG to finally update to 2005 standards and start using ARINC 424 navdata.  It is way overdue.

Edited February 12, 2019 by downscc

[zubillagajose 2]

 

hello Dan, you are absolutely right I wrote to navigraph and they sent me to the pmdg forum, saying that the airac was fine, edit the procedure directly in the file and made the flight perfectly calculating the anticipated turn without doing fly over, I do not know why in the file it says to turn to the right to the waypoint, I do not think navigraph makes that correction I am going to write again, thank you very much for your comments, can you explain me what is ARINC 424? regards

[downscc 1,327]

17 hours ago, zubillagajose said:

can you explain me what is ARINC 424? regards

Best to use Wikipedia, it is a specification for navigation data used by the real world.  PMDG is using a very old script format, more like a macro language, to define terminal procedures and the enroute structure.  Today one can get navdata from the FAA for their jurisdiction free as a download from their web site.  The data is highly structured or typed and is very efficient way to convey to the FMS or other device (even your GA Garmin units use ARINC 424) navigation data.

The problem for PMDG is that they need to rewrite the code behind the FMS they have in the 737/747/777 products and it will not be backward compatible.  They have indicated this is on their to do list.  Soon^TM

[zubillagajose 2]

hello Dan, thanks