Real world ATC questions along with MCP modes and proper procedures

[anubhavs 66]

Hello,

 

I am a relatively recent owner of the NGX and it's a joy to fly (with FS2Crew). I have also read the manuals (to the best extent that I could comprehend) and done the NGX tutorials as well as Tom Risager's tutorial. In order to make sure I am mirroring the proper real-world procedures, I started watching the JustPlanes WestJet video and had a few questions about how to use MCP modes along with ATC instructions. Apologize if these questions seem basic in nature as I am trying to learn the aircraft plus proper SID/STAR procedures.

 

Climb questions (with SID):

1. I usually arm VNAV mode on the ground itself so that when I takeoff and select CMD A, the aircraft assumes VNAV responsibility after 400 ft or so, flies the SID and transitions all the way up to CRZ ALT. However, I noticed in the WestJet video that the Captain used LVL CHG to comply with ATC altitude instructions until about 9000ft and then switched to VNAV only after 9000 feet to climb under VNAV SPD. Is this normal? In a real-world SID departure, wouldn't the ATC controller basically be telling the pilot to fly the SID as per the chart and leave the pilot alone instead of giving altitude guidance?
   
2. If you are in LVL CHG climb, I am assuming you have to constantly be changing your CLB speed on the MCP. Is the CLB speed derived from optimal CLB SPD calculated in the CLB page in the FMC?
   
3. In the real-world, after the SID transition is over, what are typically the instructions from ATC? Do you normally hear "resume own navigation and " - at which point LNAV and VNAV SPD/PTH probably take you all the way upto CRZ or does ATC again start to give you altitude instructions all the way upto cruise?
   

 

Descent questions (with STAR):

1. Typically, when does ATC give you instructions to start descending from CRZ? I would guess this would be slightly before TOD as calculated by the FMC. Is the correct procedure then to use LVL CHG again to the new ATC cleared alttude and push DES NOW on the FMC as well? I am assuming the DES SPD calculated by the FMC would now be input on the MCP so that the aircraft follows the DES SPD in LVL CHG? Eventually with the LVL CHG mode we probably end up intercepting the vertical path and joining VNAV PTH again?
   
2. The NGX tutorial 1 recommends descend in ALT INTV (to get out of VNAV ALT). Is this more or less common than LVL CHG and which would be used when?
   
3. When does the pilot typically know from ATC which RWY and STAR to input in the FMC? Is this typically when the first descent is started or typically when you are handed over to approach?
   
4. Descending down on LNAV and VNAV, I assume the ATC clears you to a STAR as you approach the first waypoint on the STAR. ATC probably says to fly the STAR as per the chart - is this understanding correct?
   
5. If the STAR transitions into a FAF onto the RWY - I am guess ATC probably clears you straight in to land. However if the STAR ends some distance away from the FAF, ATC would give you vectors to the FAF - correct?
   
6. How common is it for ATC to disregard the STAR and start giving you vectors to the RWY while in descend or under STAR? I saw that they did this on the Air Canada 777 video into Tokyo. ATC took over (even though aircraft was flying a STAR) and just started vectoring them with speed, altitude and heading instructions onto the RWY.
   

I know these are a lot of questions and some of them may seem basic. Thanks again for your help!

[Spin737 102]

Hello,

 

I am a relatively recent owner of the NGX and it's a joy to fly (with FS2Crew). I have also read the manuals (to the best extent that I could comprehend) and done the NGX tutorials as well as Tom Risager's tutorial. In order to make sure I am mirroring the proper real-world procedures, I started watching the JustPlanes WestJet video and had a few questions about how to use MCP modes along with ATC instructions. Apologize if these questions seem basic in nature as I am trying to learn the aircraft plus proper SID/STAR procedures.

 

Climb questions (with SID):

1. I usually arm VNAV mode on the ground itself so that when I takeoff and select CMD A, the aircraft assumes VNAV responsibility after 400 ft or so, flies the SID and transitions all the way up to CRZ ALT. However, I noticed in the WestJet video that the Captain used LVL CHG to comply with ATC altitude instructions until about 9000ft and then switched to VNAV only after 9000 feet to climb under VNAV SPD. Is this normal? In a real-world SID departure, wouldn't the ATC controller basically be telling the pilot to fly the SID as per the chart and leave the pilot alone instead of giving altitude guidance?
   
   • Hard to say without seeing the video, but maybe the CA wanted to skip some climb restrictions or something along those lines. Some pilots prefer LVL CH.
     

[*]If you are in LVL CHG climb, I am assuming you have to constantly be changing your CLB speed on the MCP. Is the CLB speed derived from optimal CLB SPD calculated in the CLB page in the FMC?

• No, you would probably just set 250 until 10k, then something faster (eg. 280kias) until the changeover and then .78. You wouldn't try to follow every knot of change.
  

[*]In the real-world, after the SID transition is over, what are typically the instructions from ATC? Do you normally hear "resume own navigation and " - at which point LNAV and VNAV SPD/PTH probably take you all the way upto CRZ or does ATC again start to give you altitude instructions all the way upto cruise?

• At some point you'll be cleared to your cruise altitude. There isn't any communication required for you to exit the SID or anything. You might get a short-cut off the SID to some point down your route, in which case you'd just resume your route.
  

Descent questions (with STAR):

1. Typically, when does ATC give you instructions to start descending from CRZ? I would guess this would be slightly before TOD as calculated by the FMC. Is the correct procedure then to use LVL CHG again to the new ATC cleared alttude and push DES NOW on the FMC as well? I am assuming the DES SPD calculated by the FMC would now be input on the MCP so that the aircraft follows the DES SPD in LVL CHG? Eventually with the LVL CHG mode we probably end up intercepting the vertical path and joining VNAV PTH again?
   
   • ATC normally gives you a descent before the TOD, often it's a discretionary descent or "when ready." You could use ALT INT or DESC NOW. It's been a while since I've flown a jet with VNAV ALT, but I think if you use LVL CHG, you'd also need to jit ALT INT to tell the jet you're leaving CRZ. You can descent in any mode you like.
      
     

[*]The NGX tutorial 1 recommends descend in ALT INTV (to get out of VNAV ALT). Is this more or less common than LVL CHG and which would be used when?

• If you want to stay in VNAV, then you'd use ALT INT. That might be useful on a STAR with stepdowns. If not, then LVL CHG would be fine.
   
  

[*]When does the pilot typically know from ATC which RWY and STAR to input in the FMC? Is this typically when the first descent is started or typically when you are handed over to approach?

• You can get a good idea from the ATIS and personal experience as to what RWY you might get. Some STARs are specific to one runway, and you could assume that combination. Plan and brief your best guess before you start down. You could even brief more than one approach. Set your best guess in the box and then change as necessary. At most airports, Center will give you the STAR and Approach will give you the runway assignment.
   
  

[*]Descending down on LNAV and VNAV, I assume the ATC clears you to a STAR as you approach the first waypoint on the STAR. ATC probably says to fly the STAR as per the chart - is this understanding correct?

• Yes.
   
  

[*]If the STAR transitions into a FAF onto the RWY - I am guess ATC probably clears you straight in to land. However if the STAR ends some distance away from the FAF, ATC would give you vectors to the FAF - correct?

• That info is on the STAR. It will say something like, "expect vectors..." if it doesn't link up with the approach.
   
  

[*]How common is it for ATC to disregard the STAR and start giving you vectors to the RWY while in descend or under STAR? I saw that they did this on the Air Canada 777 video into Tokyo. ATC took over (even though aircraft was flying a STAR) and just started vectoring them with speed, altitude and heading instructions onto the RWY.

• Depends on the airport and how busy they are. Some places will have you follow the STAR and Approach as published. Some places will take you off of the STAR quite often. In China, I flew mostly STAR-FAF-APP except at some bigger airports (Pudong, Beijing). In the U.S. it's mostly vectors at some point.
  

I know these are a lot of questions and some of them may seem basic. Thanks again for your help!

[anubhavs 66]

Thank you so much for answering the above questions Spin737. Really appreciate it!

[Jeff_B 8]

Good question & answer post. Got a lot out of that myself. Cheers.

[acko52 13]

Gday

+i Matt, very informative, its always good to hear from real world jet pilots.

I have to admit when i first looked at your responce i didnt see your answers, but looking again i saw them.

Jeff

[jalexb88 7]

For the first question it may also be because it's in westjet SOP to takeoff and initial climb in LVL chg depending on type of sids (just a guess). SIDs are sometimes just an initial heading and altitude assignment and what do in case of communications failure. With this type of sid you don't really need LNAV/VNAV just heading mode and LVL chg is much more practical as ATC will give you headings and LVL chg will assure the best climb rate. An example of this is the o'hare six : It actually has no initial hdg, tower gives it before TO. It wants you at 5000 ft as quickly as possible.

 

http://dtpp.myairplane.com/pdfs/EC-3/00166OHARE_C.PDF

 

Then there's the RNAV SIDS with altitude restrictions for which LNAV/VNAV is better suited. Such as the STAAV 4 at KLAS:

 

http://dtpp.myairplane.com/pdfs/SW-4/00662STAAV_C.PDF

 

Hope this helps Alex Bart

[hs118 707]

Great thread. Thanks Matt C and Alex.

[Spin737 102]

With this type of sid you don't really need LNAV/VNAV just heading mode and LVL chg is much more practical as ATC will give you headings and LVL chg will assure the best climb rate. An example of this is the o'hare six : It actually has no initial hdg, tower gives it before TO. It wants you at 5000 ft as quickly as possible.

 

I don't think LVL CHG doesn't really have any advantage over VNAV and VNAV doesn't need to be "paired" with LNAV. For the ORD.6, we usually put DME rings on the FIX page to monitor the climb performance, just to get better situational awareness. The speeds are maybe not as important as having a full-power climb if you are really heavy. You could climb at BEST RATE or BEST CLIMB just by selecting that on the CLIMB page and still use VNAV. Whatever works. Different pilot, different technique.

 

VNAV definitely helps out of places like Vegas. Especially if you have ALT INT, since departure often deletes some of the restrictions.

[jalexb88 7]

I stand corrected :-)

 

Alex Bart

[FBC57 1]

I totally agree with the other guys, this is a great thread and one that I've learned from as well.

 

Good questions and great answers, guys.

 

 

 

Frank Cooper

[scandinavian13 5,192]

Matt's answer is awesome, but I want to address some of the ATC stuff (speaking from a US slant here).

 

Climb questions (with SID):

1. In a real-world SID departure, wouldn't the ATC controller basically be telling the pilot to fly the SID as per the chart and leave the pilot alone instead of giving altitude guidance?

 

Not really. Some SIDs do have altitude restrictions, and the FAA implemented "climb via" for those departures for about a day or so, and then cancelled the order citing safety/coordination concerns because pilots apparently wouldn't know what that means (despite having heard "descend via" for quite some time now - odd, I know).

 

As a controller, you generally clear the flight up to the top of your airspace ceiling, but that's all handled by how the facility writes their SOP. That being said, departing IAD right now towards ORD, you'll likely get 3000 initial, 12000 at most on initial contact with departure, 17000 after a frequency change within the TRACON, and two from center. This is all traffic-dependent, of course.

 

2. In the real-world, after the SID transition is over, what are typically the instructions from ATC? Do you normally hear "resume own navigation and " - at which point LNAV and VNAV SPD/PTH probably take you all the way upto CRZ or does ATC again start to give you altitude instructions all the way upto cruise?

 

The SID doesn't need to be over for you to get any special instructions. Often, you get "own nav" right at the beginning of the SID. Flying the TERPZ2 out of BWI, you'll hear:

"SWA3242, proceed direct TERPZ, join the TERPZ2 departure, resume own navigation."

...and that's almost immediately after calling up departure after takeoff.

As noted above, you'll get altitude assignments all the way up. To add to the above, however, a good controller who sees no conflict will give you the new altitude early, and ship you off to the next controller so that he or she can give you higher before you level off.

 

The very general rule of thumb is give the instructions and if there's nothing else to say, ship them to the next controller down the line.

 

Descent questions (with STAR):

1. Typically, when does ATC give you instructions to start descending from CRZ? I would guess this would be slightly before TOD as calculated by the FMC. Is the correct procedure then to use LVL CHG again to the new ATC cleared alttude and push DES NOW on the FMC as well?

 

Depends on the instruction, and there are two main versions of what you'll hear:

Version 1: The most common thing you'll hear is "cross [point] at [Altitude]."

If you're flying into DCA on the OJAAY1, you'll hear "AWE443, cross OJAAY at 1-0 thousand, 2-5-0 knots. Washington altimeter 29.87."

This means you may descend at your own discretion. The general controller rule of thumb is ( [altitude in hundreds] - [crossing altitude in hundreds] ) x 4. Note that this is slightly higher than the pilot's rule of thumb, which is x 3. That allows room for the communication to happen before the pilot expects to descend.

 

Version 2: "Descend and maintain."

This means do it now. The reason may be to get you below crossing traffic before your top of descent so that you don't need to delay it and make a steeper descent after the traffic. There are a number of reasons for the instruction, however.

This is one of the instances I would use DESC NOW, unless the controller says "expedite."

 

3. When does the pilot typically know from ATC which RWY and STAR to input in the FMC? Is this typically when the first descent is started or typically when you are handed over to approach?

 

As Matt noted, you get your runway assignment when checking in with approach. You can pick up the ATIS slightly farther out to get an idea of which direction beforehand, and you should tell approach that you have this information when you check in with them.

 

4. Descending down on LNAV and VNAV, I assume the ATC clears you to a STAR as you approach the first waypoint on the STAR. ATC probably says to fly the STAR as per the chart - is this understanding correct?

 

In the United States, you normally file the STAR as part of your flight plan. In Europe, you don't file it and they assign it as you get closer to the destination. When you call for clearance and ATC says "as filed," or specifies a STAR for you, you've been cleared for it even before taking off.

 

Here's a quick scenario into Dulles for you (you were cleared "as filed" before departure, which included the SHNON2 STAR):

Center: "UAL622, cross DOCCS at 1-1 thousand and 250 knots. Dulles altimeter 29.87."

[uAL622 reads back]

[Center sees you're getting closer to DOCCS]

Center: "UAL622, contact Potomac Approach on 120.45 - night."

UAL622 [reads back and calls Potomac]: "Potomac Approach, UAL622 1-7 thousand for 1-5 thousand with Bravo."

Approach: "UAL622, Potomac Approach, roger. Descend via the SHNON2 arrival, Runway 19C."

 

5. If the STAR transitions into a FAF onto the RWY - I am guess ATC probably clears you straight in to land. However if the STAR ends some distance away from the FAF, ATC would give you vectors to the FAF - correct?

 

In Europe, yes. In slow periods in the US, maybe. The predominant way to get people from the STAR to the runway at busy fields, however, is through vectors. It allows for a better flow of traffic because the controller can avoid speed adjustments with vectors if he or she does it right most of the time (depending on the amount of space and traffic).

 

If the STAR ends at a fix on an approach, you are correct in that ATC can clear you right onto the approach at that point.

 

If it doesn't, you're right that they'll vector you.

 

How common is it for ATC to disregard the STAR and start giving you vectors to the RWY while in descend or under STAR? I saw that they did this on the Air Canada 777 video into Tokyo. ATC took over (even though aircraft was flying a STAR) and just started vectoring them with speed, altitude and heading instructions onto the RWY.

 

It's really dependent on the airport ops (which runways they're using), the traffic levels, and somewhat of the controller. If you're flying from the NY area to IAD on the HYPER4 arrival, you'll actually get vectored off at MULRR when IAD is landing to the south. So, from then on, it's all vectors, "descend and maintain," and perhaps speed restrictions. In that case, about half of the STAR gets dropped (though there's another page for the HYPER4 that stretches all the way back to the NY Area). Everything after MULRR is there to bring you to the south of the field to land north, so it's useless when landing to the south.

 

 

 

Hope that helps answer some of the ATC side. I know it can be mysterious at times.

[anubhavs 66]

scandianavian13,

 

Thank you for your detailed answers!

 

This was my first post ever at avsim and I have learnt a lot from it - thanks again everyone!

[tazisdylan 2]

All usefull info guys. Many thanks.

[scandinavian13 5,192]

Thank you for your detailed answers!

 

This was my first post ever at avsim and I have learnt a lot from it - thanks again everyone!

 

You're welcome Anubhav. Glad we could help/

[JazzPilot 0]

Thought I'd throw in my recent experience on a 738.

 

So we were flying to Stuttgart (my local airport), CRZ at FL380 and T/D 10-15 NM ahead. While I was talking to the CPT (PF on that flight) he changed the altitude on the MCP to FL280 (so cleared to descend by 10.000ft, when ready..). We flew on FL380, with FL280 selected for a few minutes, when the captain used V/S mode, first -700ft, then -2400 - which I didn't quite understand because on the NGX when you start an early descend and select VNAV after a while, being let's say 2000ft below planned descend path, it will decrease the rate to -1000ft and keep it at that until the aircraft catches the desc. path. Anyway in our case the captain used -700ft V/S mode, after a few seconds -2400ft and right after that he selected VNAV mode. I can't clearly remember if the aircraft kept -2400 or -1000, so I can't really give you an information on that.

 

That's basically how we started our desc. Got a few cockpit shots, I enjoy looking at those pictures remembering how I sat in there, even on the F/O seat, gaining motivation with my studies to finally be in the flight deck in uniform

 

I hope that helps.