VECTORS in the FMC

[pcubine 143]

It appears that VECTORS in FMC legs page cannot be selected to the scratchpad so VECTORS are essentially an immovable object in the FMC. It can be over written by subsequent waypoints but VECTORS cannot over write waypoints. I run across this quite frequently but I wanted to give this a specific example.

 

Here is the situation. FLIPR2 STAR landing ILS 8R at KMIA. The STAR finishes with LECIT, JODPO, VECTORS and the ILS starts with KROME. Now the deal is to get rid of JODPO which cannot be deleted and VECTORS cannot be copied over JODPO. Well you could do a Heading Select at LECIT for CHROME and once your lined up on KROME or were less that 3 miles from it, go to LNAV. Now my concern is the vertical profile has been calculated as if you were going to JODPO which is 20 miles from LECIT and do essentially a 180 degree turn back to KROME. I would guess there is an additional 35 miles to the route in the FMC which has been used in the descent calculation.

 

Does anyone have any thoughts on this or am I worrying about nothing?

[g_precentralis 191]

First, if you do all of route trimming while still in cruise, FMC will just recalculate profile and move T/D point. If you do it in descend the chances are you will slip out of profile.

 

You can do what you want in several different ways:

-Use lower level of automation

-Trim the arrival and approach in legs page to match what you want to do (not so wise thing to do, but in sim it's ok)

-Combination of these two

 

You can overwrite vectors with waypoint below it and then delete the waypoint that was above vectors:

1.Enter waypoint KROME between VECTORS and CORPA.

2. Select KROME and overwrite JODPO (that should kill VECTORS too as it's in between).

3. Close discontinuities and trim vertical profile as you wish.

 

This will result in very bad turn at KROME:

 

This is why it's not smart to trim arrival. You will short you route by 15-20nm, but that is really about 5 minutes and almost no fuel penalty (in descend at idle).

[scandinavian13 5,192]

 

 

Does anyone have any thoughts on this or am I worrying about nothing?

 

Worrying about nothing.

 

 

 

Here is the situation. FLIPR2 STAR landing ILS 8R at KMIA. The STAR finishes with LECIT, JODPO, VECTORS and the ILS starts with KROME. Now the deal is to get rid of JODPO which cannot be deleted and VECTORS cannot be copied over JODPO.

 

Why are you trying to get rid of JODPO?

 

 

 

Well you could do a Heading Select at LECIT for CHROME and once your lined up on KROME or were less that 3 miles from it, go to LNAV.

 

Bingo.  No need to add extra steps to something so simple.  VECTORS are going to be flown on HDG SEL.  You DO NOT NEED TO HAVE AN UNBROKEN MAGENTA LINE FROM DEP TO DEST.

 

Sorry...but that simism is one of the ones that drives me completely nuts.  People try to go so far out of their way to make the line "work" that they add in so much unnecessary work...

 

 

 

Now my concern is the vertical profile has been calculated as if you were going to JODPO which is 20 miles from LECIT and do essentially a 180 degree turn back to KROME. I would guess there is an additional 35 miles to the route in the FMC which has been used in the descent calculation.

 

By this point, ATC is commanding descents anyway, which means your VNAV profile is essentially worthless.

 

 

 

 

 

 

As always:

The FMC is a tool to ASSIST you in doing your job.  It is not there to add extra work.  If you're doing extra work to make the FMC "work," then you're not using it right.  If I need to turn a screw into a board, I'm not going to use a hammer...

[pcubine 143]

Why are you trying to get rid of JODPO?

I am not going to JODPO. Therefore I don't want it in the descent profile calculation.

Bingo. No need to add extra steps to something so simple. VECTORS are going to be flown on HDG SEL. You DO NOT NEED TO HAVE AN UNBROKEN MAGENTA LINE FROM DEP TO DEST.

I am not trying to get an unbroken line from TNCM to KMIA. I am trying to get rid of JODPO. You must be looking at the route in post #2 which has no vector in it.

You can overwrite vectors with waypoint below it and then delete the waypoint that was above vectors:

 

1.Enter waypoint KROME between VECTORS and CORPA.

 

2. Select KROME and overwrite JODPO (that should kill VECTORS too as it's in between).

 

3. Close discontinuities and trim vertical profile as you wish.

 

This will result in very bad turn at KROME:

I don't want to over the VECTORS. I just want them after LECIT and JODPO gone from the route.

[scandinavian13 5,192]

I am not going to JODPO. Therefore I don't want it in the descent profile calculation.

 

Since VECTORS exists in the STAR, the descent profile is essentially worthless.  VECTORS is ambiguous in length, so the FMC doesn't have a clue what to do with it.  Again, ATC assigns altitudes when you're on the "downwind" leg of that STAR.

 

If you're really concerned about the alt profile (which, again, is getting worked up over something pretty minor), then force an altitude of 3000 at JODPO on the LEGS page.  From there, it's HDG SEL, FLCH / V/S, and APP to the final approach course (or just hand fly it).

 

Don't be a slave to the idiot box...

[pcubine 143]

Worrying about nothing.

That's probably true. But you know I like to count the angels on the head of a pin.

[g_precentralis 191]

I am not going to JODPO. Therefore I don't want it in the descent profile calculation.

I am not trying to get an unbroken line from TNCM to KMIA. I am trying to get rid of JODPO. You must be looking at the route in post #2 which has no vector in it.

I don't want to over the VECTORS. I just want them after LECIT and JODPO gone from the route.

You cannot do that. The closes thing you can do is to enter LECIT272/30nm (for example), an that would give you straight line from LECIT at 272. I know it's not the same as vector, but that's the only way I can think of.

[scandinavian13 5,192]

That's probably true. But you know I like to count the angels on the head of a pin.

 

haha - yeah, thus why I'm offering the alternatives.

 

For the record, I came up with the 3000 value because it's the initial altitude on the chart for the ILS to 9 at MIA.

 

Just a reminder: trying to get too detailed is going to be like a laser sight on a buckshot shotgun...it's really not worth all of the extra effort.  I understand the obsessive compulsions (I used to be the same way), but in the end, you'll discover that the art of aviation is in the pilot interaction and decision-making, not the overly obsessive details about the numbers and paths.

[pcubine 143]

For the record, I came up with the 3000 value

Before I read the complete sentence I thought you were writing about the number of angels on the head of a pin. The word value rather than altitude must have confused me.

[Spin737 102]

I think the FMC considers a vector to be "direct" to the next fix for descent purposes. I imagine MIA gives out very specific instructions for crossings.

 

If you're really wanting some guidance, you could simply plan to follow a 3:1 descent. That would be at 10,000 about 30 from LAWNN.

 

My experience with Florida is they start you down very early, so you end up dragging it in anyways.

 

You're getting to the point where maybe you need to be concentrating on techniques to handle being too high or too low, even if you had the best planning.

[scandinavian13 5,192]

 

 

I think the FMC considers a vector to be "direct" to the next fix for descent purposes.

 

I think it does.  As an example, on the LENDY into JFK, the FMC will constantly flip out about being at FL190 over LGA, and needing to be down at 20ish only 20nm beyond it.  My earlier statement wasn't exactly phrased well to that end.  Basically, with a vector leg, the thing has to assume direct, but at the same time, a vector is ambiguous, so trying to force it to plan a VNAV path isn't entirely the best choice of action.  Unless you're flying the LNAV path, the VNAV path isn't going to be of much use.

 

 

 

I imagine MIA gives out very specific instructions for crossings.

 

From my own experience (in the sim / VATSIM), and working with them on the RW side on procedures development (and general research into facility practices), I think you hit the nail on the head.  The usually give the expected crossings on the chart, and beyond those, simply "descend and maintain" instructions (usually from about 10-15 and below).

 

 

 

You're getting to the point where maybe you need to be concentrating on techniques to handle being too high or too low, even if you had the best planning.

 

Bingo.

[pcubine 143]

I would like to thank Kyle, Matt and g_precentralis for their answers. I guess the deal is you can't get there from here and if you could it makes no difference anyway.. Deal with it.

[scandinavian13 5,192]

 

 

I guess the deal is you can't get there from here and if you could it makes no difference anyway.. Deal with it.

 

haha - pretty much.  Vectors are a big deal over here in the United States.  It allows controllers to sequence and space aircraft effectively.

 

Magenta lining in removes that opportunity.  Sure it's more along the lines of "first come, first served," but if that first arrival is a prop doing 170...?  Have fun trying to explain that delay to the airlines, or explaining to the poor prop driver why he or she is being kept at a super high speed until short final.

[Cristi_Neagu 134]

 

 

Have fun trying to explain that delay to the airlines, or explaining to the poor prop driver why he or she is being kept at a super high speed until short final.

 

Which reminds me of:

 

 

 

Cont: "AF1733, You are on an eight mile final for 27R. You have a UH-1 three miles ahead of you on final; reduce speed to 130 knots." 
Pilot: "Rogo', Frankfurt. We're bringing this big bird back to one-hundred and thirty knots fer ya." 
Cont: (a few moments later): "AF33, helicopter traffic at 90 knots now 1 1/2 miles ahead of you; reduce speed further to 110 knots." 
Pilot: "AF thirty-three reining this here bird back further to 110 knots"
Cont: "AF33, you are three miles to touchdown, helicopter traffic now 1 mile ahead of you; reduce speed to 90 knots" 
Pilot (a little miffed): "Sir, do you know what the stall speed of this here C-130 is?"
Cont: "No, but if you ask your co-pilot, he can probably tell you."