I thought this would be a good example of changing STARs while on an existing STAR. We were descending into LAX on the IRNMN2 BURGL transition. We were direct to DOUIT and already into the IRNMN2 with BURGL behind us.
On the first selection in DEP/ARR, I purposefully did not select the BURGL transition. I just selected the BAYST1 (00:35). As you can see, after DOUIT, there is no CROWEY, MUPTT, MDOTS, GRIPR, BIKING, RUNNN, IRNMN, and SYMON. That's most of the BAYST1 arrival. It just starts with BAYST after a DISCON.
The second time (01:22), I selected the BURGL transition. When we select the BURGL transition, we will have two DOUITs, so we have to find the second DOUIT on the LEGS page and put it in front of us. Selecting the BURGL transition will put BURGL in 1L, which was behind us at the time (01:26). Towards the end of the video (01:10) the FMC cycled over DOUIT and went to CROWEY as I was doing all this, so in this case we would have to put CROWEY in front of us.
This is where the "never execute on the DEP/ARR page" rule is important. With so many waypoints/constraints on these arrivals, it will be a rude awakening if you execute a new STAR without first selecting an appropriate transition and going to the LEGS page to tidy things up. If you screw it up, trying to get the waypoints in there before crossing the next waypoint (DOUIT in this case) will be a challenge. After DOUIT is a DISCON. Even if you do get it installed in time, it takes VNAV a minute or two to recalculate the fixes so you won't have a path during that time period and may very well bust an altitude.
https://youtu.be/R8IlOOCWUNA
(http://www.hoppie.nl/forum/var/bayst1(1).jpg)
Quote from: emerydc8 on Fri, 14 Jun 2019 16:11
Even if you do get it installed in time, it takes VNAV a minute or two to recalculate the fixes ...
It's really impressive that the real FMC takes so long for this recalculation. Maybe in this case there's not only a calculation process running but also some sort of validation and resynchronization in the background across the two FMCs, even though there is no extra RESYNC or STANDBY scratchpad message.
|-|ardy
Thank you for sharing this example.
So preferably you should have at least a couple of minutes to the next waypoint when you execute the modified route? In order to give the FMC time to do all the calculation and keep everything running smoothly.
When you consider how long your car nav system takes to recalculate, even when you pass a turn, and you are going a lot slower than an aircraft. I guess it seems OK to take a minute or two.. :)
AlexB
Accepting the clearance is the problem. You can't just tell SoCal I need a few minutes for the FMC to catch up, so don't hold us to the new constraints on the STAR. What do you expect from an FMC that is updated by these things!
(http://www.hoppie.nl/forum/var/img-20190614-00116(1).jpg)
QuoteWhat do you expect from an FMC that is updated by these things!
I expect brilliance. Aerowinx PS
1 was loaded using floppy disks ;D
These are 2HD, so they are really cutting edge.
I'm almost at the point that I can offer the replacement for production. Patience :-)
When you replace diskettes by over the air solutions, you need to produce a few hundred pages documentation on why the Russians/Iranians/North-Koreans/whatever are not going to hack it and replace everybody's FMC database with whatever. This takes a bit. But the end result is more secure than a few blokes walking around with floppies.
Hoppie
I guess this is what us home simmers don't really get to experience. ( And I'm not just talking about the floppy disks) :-p But a very busy airspace with this sort of sudden changes to arrival route or other requests from ATC, where you must make te right choices and have no room for errors or scratching your head on what to do.
Of course one can try to simulate this, but I bet it's a whole lot different thing when the real pressure is there.
This is just the kind of thing PSX is good for. You can set up and save a situ file on the IRNMN arrival just inside of BURGL and then practice switching to the BAYST arrival.
Quote
I'm almost at the point that I can offer the replacement for production
Probably at this point it's cheaper just to stick with the floppies, but this is coming from someone who still uses a Blackberry 9900.
For you in your 767 it's four (4) wires only... I bet that it's coming.
Hoppie