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Heathrow to Dublin

Question about VNAV descent and ATC vectors - slow descent problem.

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I was descending on a STAR with VNAV when p3d atc took me off it early and gave me initial vectors for approach.    I followed their altitude instructions and heading (heading select) by inputting them into the MCP with VNAV remaining on.  However, Vnav seems to descend very slowly at times doing this and I got the "expedited descent' message often.  I wonder why it doesn't get you down faster when I push altitude intervene on the MCP after an instruction by ATC. 

 

So, Is it usual procedure in this case to remain on Vnav even if you are not going to be near your STAR waypoints and their associate altitude restrictions?  Is this messing up the VNAV descent profile somehow?  Should I be using a different mode when ATC starts vectoring me off my STAR and giving different altitudes than my STAR has?

 

The final waypoint in the plan was of course the final approach fix for the runway, which was 2500 feet.  My cruise was around FL250.

 

Also, is there anyway to be able to fly most of the STAR using p3d?.  I had a flight plan loaded with the waypoints, but they took me off very early. 

 

Thanks

John Murphy

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I was descending on a STAR with VNAV when p3d atc took me off it early and gave me initial vectors for approach.    I followed their altitude instructions and heading (heading select) by inputting them into the MCP with VNAV remaining on.  However, Vnav seems to descend very slowly at times doing this and I got the "expedited descent' message often.  I wonder why it doesn't get you down faster when I push altitude intervene on the MCP after an instruction by ATC. 

 

The first issue here is the default ATC in sims today. The STARs you're using are from the real world. The ATC in the sim doesn't control according to real world procedures - specifically those STARs. Furthermore, it doesn't control with an understanding of the aircraft type. A controller has to control a Cessna differently than he or she would control a 747, or a 737. The sim control function does not do this.

 

There's only so fast that you're going to be able to descend. As mentioned in the Intro Manual, and many many times here on the forum, the 800 is a slippery plane, so it's a little tougher to get down. Keep in mind, as well, that if you have hardware throttles, you should make sure that they're at the IDLE stop to ensure that they don't interfere when the AT mode drops to HOLD.

 

 

 


So, Is it usual procedure in this case to remain on Vnav even if you are not going to be near your STAR waypoints and their associate altitude restrictions?  Is this messing up the VNAV descent profile somehow?  Should I be using a different mode when ATC starts vectoring me off my STAR and giving different altitudes than my STAR has?

 

As soon as you come off the magenta, I'd argue that you should be in FL CH or V/S.

 

 

 


Also, is there anyway to be able to fly most of the STAR using p3d?

 

Yes. Ignore the default ATC. It has no knowledge at all of the STAR.

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The best luck I've had with the default ATC is V/S @ 2300-2600 FPM to 10,000 feet (from cruise) and then FL CH at 220-240 until I'm 30 NM out and then I'll start slowing things down for approach. At least that's with the default FSX ATC. Otherwise they'll be barking at me to expedite descent or I'll hit the FAP waaaaaaay too high or too fast.

 

I've used Pro ATC/X which is pretty solid, uses real-world STAR/SID but it's still not perfect with approaches.

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When flying with the default ATC I almost always use VNAV to climb, then FLCH to follow descent instructions from ATC.   The exception is when I am using an RNAV approach (which the default ATC does ok at, as long as things haven't changed too much since 2006).   With an RNAV approach, you can often switch back to VNAV  when you are on the approach.

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Some other aircraft types automatically drop out of VNAV as soon as you come off the LNAV path -- Boeings will stay in VNAV as you have but it can problematic.

 

The issue with VNAV once you come off the LNAV path is that it has no idea what your actual track mileage to run is going to be, so its descent profile calculations are necessarily going to become pretty useless pretty quickly. It helps if you "tidy up" the map a little so that the distance to go figure in the FMC is a bit more in line with what you are actually going to fly and therefore gives VNAV some slightly better data to generate a profile with.

 

However, as Kyle says, once you're on vectors I'd be considering V/S/FLCH as appropriate.  

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Ok thanks all for the advice.  I'll definitely start to switch to FLCH or V/S to avoid this issue.  I'll check out some ATC add-ons that deal with STARS/SIDS properly too.  However, is there any way edit the default ATC to make it start vectoring you later so that that it allows you to fly more of the STAR?  I inputted the STAR waypoints into the IFR flight plan but the vectoring started after the second waypoint on the STAR was reached.  In real life, how much of a STAR does a typical flight follow before getting vectors?

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is there any way edit the default ATC to make it start vectoring you later so that that it allows you to fly more of the STAR?

 

Nope.

 

In real life, how much of a STAR does a typical flight follow before getting vectors?

 

Depends where you are. In the UK, you'll normally go all the way to the holding stacks and then be either put in the hold our vectored from there (so at Heathrow, LAM, BIG, OCK or BNN), though occasionally you might get a shortcut from further out if it's (very) quiet. Other places it depends a bit but usually you'll go to some sort of IAF (indicated on the charts).

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Do not be afraid to use the speedbrake on descent. Do not be afraid to start your descent earlier than the fmc tells you on the navigation display. Do not be afraid to plug in a higher number for descent than the vnav spits out that could be as low as 240 knots at altitude if you fly with a low cost index. Also a helpful addition to the fmc giving you a good planned descent is plugging in the winds on the legs page and winds on the descent forecast page. You have to do this manually in the ngx but the 777 grabs the info from active sky wx engine - David Lee

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I had a flight plan loaded with the waypoints, but they took me off very early.

I watched a video of a Virgin Atlantic 744 from EGLL to KSFO. Just after getting on the STAR which was GOLDEN GATE SIX, they were cleared direct to LOZIT which is about 25 miles from KSFO skipping 4 waypoints of the STAR. Instead of being in VNAV they had to go to V/S and use the green banana. It happens in real life also, not just P3D.

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I watched a video of a Virgin Atlantic 744 from EGLL to KSFO. Just after getting on the STAR which was GOLDEN GATE SIX, they were cleared direct to LOZIT which is about 25 miles from KSFO skipping 4 waypoints of the STAR. Instead of being in VNAV they had to go to V/S and use the green banana. It happens in real life also, not just P3D.

That's why I fly actual flights grabbed from flightaware. Ideally I'm about an hour behind actual time so I can see the ground tracks for departure and arrival. The other day, I saw traffic on the KIAD GIBBZ (tip the hat to NCIS) vectored direct to final at about LDN forming an extended base leg instead of to midfield via STAR and thence downwind.  Usually the traffic follows the STAR but I guess traffic was light.

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That's why I fly actual flights grabbed from flightaware. Ideally I'm about an hour behind actual time so I can see the ground tracks for departure and arrival. The other day, I saw traffic on the KIAD GIBBZ (tip the hat to NCIS) vectored direct to final at about LDN forming an extended base leg instead of to midfield via STAR and thence downwind.  Usually the traffic follows the STAR but I guess traffic was light.

I like to listen in on liveatc feeds in America or Australia almost every big airport has good coverage and Flightaware has all the real routes. I'll pick a flight scheduled within an hour or so and follow it in real time either in the ngx or 777, listening in from liveatc clearance feeds if available all the way to pulling up at the gate. Even setting the same squawk.

 

It can be a scramble to find en route feeds as the airplanes travel from frequency to frequency, many not covered with liveatc or sometimes part of a single center frequency feed but ground, tower, arrival and departure are well covered in the USA. Flightradar24 gives me the readouts I need if I can't hear the atc through liveatc and if you pay for the service, the current squawk codes. - David Lee

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KIAD GIBBZ (tip the hat to NCIS)

 

Never noticed that. It's a tip of the hat to Joe Gibbs, though, who was one of the former 'skins coaches. Note that the fixes are primarily football references.

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Never noticed that. It's a tip of the hat to Joe Gibbs, though, who was one of the former 'skins coaches. Note that the fixes are primarily football references.

Burst that bubble, didn't ya.  Well, good to know that it is a reference to a real and good person. Lots of football references in Houston too, and also a STAR named for a much loved Texas creamery Bluebell. Fiction does appear in procedures as in  Chicago's references to Star Trek.

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Burst that bubble, didn't ya.  Well, good to know that it is a reference to a real and good person. Lots of football references in Houston too, and also a STAR named for a much loved Texas creamery Bluebell. Fiction does appear in procedures as in  Chicago's references to Star Trek.

 

Bursting bubbles is apparently what I'm good at.  :P

 

Isn't there a STAR down that way with MLRRR and then LYYTE in the progression, too? Gotta love picking out references on STARs.

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Bursting bubbles is apparently what I'm good at.  :P

 

Isn't there a STAR down that way with MLRRR and then LYYTE in the progression, too? Gotta love picking out references on STARs.

Yup, the RIICE non-RNAV arrival with obvious reference to Rice University, not sure why the beer reference but arrival also has BAZBL BAATS so maybe it's the college baseball theme.

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Also in to Denver:

 

.facebook_1470590387021.jpg?raw=1

 

Came across that one during Wordflight last year. ZPLYN4 I think?

 

Made my mate who's a massive classic rock & blues fan smile!

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DOOBI2 or SKYND3 into KIAH or PAITN4,SSM into KORD. There used to be a BULLZ into KORD but it's been replaced. Seems to a lot of Rock or Sports in the STARS.

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