Fmc questions

[estri]

could anybody help me ?

How could i link GUITR to ZOMEX ? How does it work in real life with rnav waypoints ?

thank you so much.

[+TSRA]

Well, it depends. Which FMC are you trying to use?

[estri]

Originally Posted by +TSRA

Well, it depends. Which FMC are you trying to use?

it,s an UNS1, the site does not allow me to add a picture 😔

[+TSRA]

Depending on the clearance, there are three primary methods with the UNS-1 that you can use.

1. Waypoint Deletion

This simply involves deleting all waypoints or NO LINKs between the two way points you've mentioned in the FPL Page. However, this can be very time consuming as you have to verify each deletion. If you're flying something that has the UNS-1 in it, you likely are going to fast for this to be a realistic option unless you're on the ground or in cruise with lots of time. Also, another disadvantage is that if ATC changes their mind and wants you to go to a waypoint between GUITR and ZOMEX, you'll have lost that data and will have to quickly reload the arrival and/or approach.

2. Folding / Sandwiching

Each waypoint in the FPL page has a sequential number up to 99. Assume GUITR is in position 15 and ZOMEX is in position 20. What you would do is press the line select key for the waypoint that fills position 16 - the one immediately below GUITR. This highlights the waypoint in position 16. Type in 20 and hit enter. This will "fold" ZOMEX from position 20 to position 16.

This is considered the primary method for most airlines for accomplishing this task and is the way Universal wants us doing things when closing up a STAR or similar procedure. The same disadvantage as I described in point 1 exists for this method too.

3. Manual Leg Change

This method only works if you are already direct GUITR and ATC issues the clearance "After GUITR, proceed to ZOMEX..." You could use either of the above methods, or from the NAV Page select the line select key beside the TO waypoint. This will bring up a subsequent page that will allow you to type the position number for ZOMEX in the NEXT field. Once you hit ENTER, the TO waypoint would indicate GUITR and the NEXT waypoint would indicate ZOMEX.

This is a roundabout way though, and I can only remember maybe a dozen times where I've done it this way, but it can be done. This has the advantage of keeping the waypoints between GUITR and ZOMEX in place should ATC change their minds, but because of the limited application of this method, you'll likely not do it too often.

[estri]

That was great. Thank you so much for your help !

I tried with the second option you mentionned (folding ) but the waypoint was not on the list ( i asume there must be something wrong with my software ) Tried with the third one too but couldn’t ( possibly because i was on ground)

I have another question. Sorry if they seem very silly but i think it,s the only way i can understand how it works in a real flight. Even if i am working on manuals and trying to practise on the lapt have doubts.

I see there are many SIDs ending with an Rnav waypoint not linked to any airway. In case i was cleared by Atc for one of those SIDs how would i link that waypoint to my Route ?

I cannot do it selecting an airway so should i wait till i get to that rnav way point and then go to the NAV page and select a waypoint in the next key ?

Thank you so much for your help.

[+TSRA]

These methods only work with the FMS or with Universal approved emulators. If you’re trying to do this in flight sim or some other program, the functionality will not be the same - or will be reduced.

The manual leg change (#3) only works when you are direct to the waypoint you want to go FROM. So, if you’re trying to do this on the ground for a waypoint that is still down the line, it won’t work. It won’t work in flight either if you’re not already to that first waypoint.

As for RNAV SIDs or Vector SIDs that are loaded, you’ll notice a NO LINK is programmed at the end of the SID. This indicates the FMS does not know how to link the SID to the enroute network. With these SIDs, you’ll typically read “for vectors” somewhere on the chart. That is, ATC will provide radar vectors to intercept the flight planned track or will send you direct a waypoint on your flight plan.

For example, leaving CYYZ on the BOMET SID. You’d load it to get some of the turns to display immediately off the runway, but then ATC would have to send you direct to one of the waypoints further along for you to fly the balance of the SID profile. This may, or may not be immediate and may result in multiple vectors before being sent on your way.

The same principle applies when connecting to the enroute network.

[estri]

Hello TSRA,

Thanks a lot again.

Once I have set the flight secuence on the Fmc and I am on route, will I have to rotate my CDI every time the course changes using the AP in nav mode or won’t it be necessary since the UNS is working? I think I may do it just for the approach, setting the final approach course , is that correct ?

[+TSRA]

Once I have set the flight secuence on the Fmc and I am on route, will I have to rotate my CDI every time the course changes using the AP in nav mode or won’t it be necessary since the UNS is working?

It shouldn't be necessary to adjust the CDI at all as the FMS updates this for you on most equipment as it ties directly into an RMI. If you were flying an aircraft where you had to manually adjust the CDI, then having an FMS is overkill.

With that said, a limitation of the UNS-1 is that you cannot use it for final approach track guidance when flying a ground-based precision approach (i.e., ILS). So my previous statement about not adjusting the CDI is correct for all UNS FMS operations, except for final approach tracking of an ILS.

In that case, there are two options:

1) Without the UNS Enhanced Navigation package (typically up to the UNS-1C or D IIRC), you would have to change your nav source over to traditional methods when intercepting the final approach track. This would require that you change the CDI track to the inbound localizer. Setting the inbound track like this would normally be done in cruise and before or during the approach briefing. It depends on the installed equipment for just how you would do this.

I've flown aircraft where you had to change the flight director from LNAV to HDG SEL, then change the navigation source from FMS to LOC, and then input the inbound localizer track. You'd then change your navigation source back to FMS and reselect LNAV until such time you were ready to commence the approach where you'd do the same technique, just without inputting the track.

I've also flown aircraft where you did not need to modify the flight director, but you still had to change the navigation source in order to program the inbound localizer track.


2) With the UNS Enhanced Navigation package (typically UNS-1e and after), you have the option of having the FMS autotune the localizer for you, after which it will "ghost" the localizer until interception where it will automatically swap for you with no additional inputs. This is, by far, the easiest option, but it also requires a lot of integration with the aircraft radios, so I've only seen it where the FMS came as stock standard equipment from the aircraft manufacturer - think, Q400.