Question about descend

[Georgi Bonchin 1394205]

Hi,

I would like to mention first that I am relatively new to VATSIM and as long as I fly as many the questions are coming. Hope this is normal Here below I would like to ask some specific questions about flying my favorite A320. Please note that all values mentioned are for example only just to make my statements clearer. Second important is that I am not flying in US where some of the rules especially for application of SID and STAR are bit different.

Let's say I am flying a STAR approach to an airport and the controller had given me FL240 without changing the heading or speed. After some time he requests descending to FL110 again without changing the heading or the speed. My questions are how should I practically execute the requested and what are his expectations concerning the time frame? There are 3 options, at least as per my knowledge:

Option 1: Set the altitude and push the FCU button letting the AC decide the descending profile.

Option 2: Set the altitude and pull the FCU button in order to request the AC to come to requested altitude faster, but within reasonable limits.

Option 3: Switch off the AP and initiate fast descent using the joystick.

I personally think and prefer options 1 or 2, which are more related to the real world, or at least what I was told, but unfortunately the controller gets angry sometimes. It is obvious that there are some simple calculations, which can be made, however only the altitude difference is not enough for such.

Would appreciate any comments and sharing practical experience.

Thank you!

[Simon Kelsey]

Hi Georgi,

 

Could you be more specific about the controller "getting angry"?

 

If you are issued a climb or descent instruction then you are expected to comply with this in a timely manner. In other words, unless you have been specifically instructed to descend when ready, you should start descending essentially immediately and at a minimum of 500fpm (minimum rate of climb or descent in ICAO airspace).

 

However, beyond that it is up to you to manage your descent in such a way as is appropriate to meet any crossing restrictions you might have been issued or to be at an appropriate height to commence the approach. If the controller requires a particular rate of descent in order to resolve a traffic conflict for instance, then they should tell you that.

 

In any event you can use the three times table -- 3 x range = FL or FL/3 = range from touchdown (obviously you will need to take in to account airfield elevation if it is not near sea level!) - to judge what height you should be at at any particular moment.

[Dave Hodges]

I'm going to apply to more of a generic situation, because you're going to see this a lot.

 

First, let's talk about what STARs are designed for. They are created to maintain a steady, even and orderly flow of traffic into a large, busy airspace/airport. They are published so that everyone (controllers and pilots) know what to expect, thus they can plan for certain events. Otherwise it would be pure chaos with aircraft coming and going all sorts of directions at all types of speeds and altitudes. A secondary purpose of SIDs and STARs (particularity SIDs) is to keep aircraft away from noise or other types of sensitive areas (including wild life).

 

Complying with STAR crossing restrictions are mandatory for the pilot once they're on the arrival, but as you've learned a controller can take you off the arrival. Once he doesn't this, speed and altitude are for the most part his discretion (though you always have the responsibility to operate your aircraft in a safe manner) until the controller puts you back on an arrival, approach or other published procedure - at which time the responsibility transitions back to you unless the controller gives you another speed, heading or altitude change at which point it's back to being his responsibility. The only possible difference is the <250kt/10,000ft speed restriction, which a controller can waive for as well.

 

In a busy environment, you can expect to fly the majority of a STAR as published, especially the early parts of the STAR. As the operational tempo slows down, controllers (especially VATSIM controllers) might well take you off the STAR to give you short cuts to the approach. It's best if a controller asks you if you'd like a short cut, and it's also a good if a controller briefly tells you what his plan is if he's going to take you off a published arrival as this allows you to plan a bit in advance (really helpful to a new pilot) - particularly if you're not familiar with how the airspace routinely works, as it gives you time to take the change into consideration regarding how and when you will fly and configure the aircraft. But don't expect controllers on VATSIM to tell you what their plan for you is, it seems the first thing many VATSIM controllers do is forget what it's like for someone new on the network (yeah, I know guys, there are exceptions, you don't need to pipe in to tell us that).

 

Taking you off a STAR can save you and the controller a lot of time. Controllers are volunteers with real life schedules and considerations, and if possible they will often stay online longer than they had originally intended if they see an aircraft coming in. But they will also want to get you down as soon as possible so they can log off to take care of things or get some sleep before work the next day. It's extremely nice of them, and good for both of you.

 

When flying online it's extremely helpful to listen to all the ATC chatter as you'll know in advance how controllers are working the airspace and what they're asking pilots to do. Combine the audio this with a program like VATSPY that provides you with a near real time picture of what's happening and you'll be able to make a educated guess about what controller(s) will have you do. Maintaining the "big picture" is incredibly helpful, and it's something I wish more pilots would do - especially during events!

 

Controllers (and pilots for that matter) getting angry is nothing new, and as it occurs real world it also adds realism to the experience. I'm not saying it should happen, and we all wish it wouldn't, but at the end of the day we're all just people with our individual personalities, stresses, and real life matters that affect how we deal with others. Unless he calls you a name or is otherwise wayyyyyyyy over the line, I'd like it go.

 

I hope this has been helpful to you!

[Robert Shearman Jr]

Nearly all of my flying experience is in the US and with the 737-800, so take this with a grain of salt.

 

However, over here, if I am given a "descend pilot's discretion to {xxxxx}," that means I can start descending whenever I am ready, which means I'll set the MCP altitude but the plane won't start down until it arrives at my FMC's calculated top of descent point.

 

If however prior to T/D I'm given "descend and maintain {xxxxx}," I'm going to immediately put the aircraft into a 1000 ft per minute descent until the calculated VNAV path "catches up with me" (because although it starts later than where I did, it's coming down quicker than 1000fpm) -- at which point I'll return to VNAV mode and let the aircraft join it & descend at the rate it wants to per the programmed descent profile. Sort of like a radial intercept, but vertically rather than laterally.

 

Hope that helps,

[Georgi Bonchin 1394205]

Hi Guys,

Thank you for the information and shared opinions. Many things got much clear to me especially after reading what Dave wrote, but I feel that better give some more details in order to explain what exactly I was looking for. Following [Mod - Happy Thoughts]umptions will apply to my further statements in the post:

- we fly a route from Europe to OMDB using A320. Our cruising altitude was FL370;

- we were given instructions to descend to FL240 by the controller in Emirates center when reached TD;

- the controller from Dubai Approach had given us expected STAR VUTEB 1C and expected landing on runway 30L;

- I will be using the LIDO charts from AIRAC 1713 for explaining the further actions. Unfortunately I am unable to attach them here due to the forum restrictions realizing all the inconvenience for the same...

What I normally do when initiating descent and no other instructions were given, to adjust the altitude to IF flight level specific for landing runway, which in the particular case is 2000 ft. This normally works good and the computer calculates properly the descend in such way to follow all constrains on the STAR and especially to bring the plane at desired altitude at the final point where localiser and glide slope are available. However all this is when there are no other instructions given by the controllers...

In the particular case app. 15 NM before VUTEB I was given instructions to descend to FL110 obviously to meet the requirements for LOVOK, which unfortunately the plane could not achieve after adjusting the altitude and leaving the descend to its computer (pushed button). Actual situation was that it was above 11000 on LOVOK, above 8000 on DB529, which is as per the chart and reached PATID at 7000, which is again according to the chart. Speed was 230 KT, which is normal for this part of the leg.

The STAR was not flown fully because I was given a shortcut between RIDEV and DB504. A mistake, which I did at that point was that did not notice the speed restriction of 185KT and approached ULDOT with higher speed than necessary, which was corrected with speed brakes till IF.

What I meant in my first post mentioning that controller got angry was that he repeated several times (using caps) that I was not coming below FL110 at LOVOK. Another place was the final approach, but this is something, which I admit and said sorry.

The question was how fast to follow the instructions and what is considered as a reasonable time frame because this definitely depends and defers between different planes and their loaded condition.

Hope this makes the things a bit more clear.

[Andreas Fuchs]

Don't worry about this. If you realize that you kind of messed up your descent, please TELL the controller to give him a chance to provide you with extra space/miles to help you descend or even avoid a conflict with other traffic. Errors happen. When you realize that something went wrong and if you think that it will have an impact on the operation (e.g. vertical limit), then speak up: "unable to cross ABCDE at FLxxx". If you then get yelled at, complain to the ATC unit, as it would be unacceptable behaviour by the other member.

[Dace Nicmane]

You can increase your rate of descent if you see you're not going to make a restriction (but as far as I understand, no restriction was given). There's no need to dive like it's an emergency, though, if you're way too high. In that case just let the controller know, but as long as you're monitoring your descent properly, it shouldn't happen. Also, if the controller is giving you altitude instructions, you're not bound by the chart altitudes, indeed, you may not descend below your cleared level. You can just use them for reference, so that you know that you're at reasonable altitudes for that part of the STAR and the controller hasn't forgotten about you.

 

What I normally do when initiating descent and no other instructions were given, to adjust the altitude to IF flight level specific for landing runway, which in the particular case is 2000 ft. This normally works good and the computer calculates properly the descend in such way to follow all constrains on the STAR and especially to bring the plane at desired altitude at the final point where localiser and glide slope are available. However all this is when there are no other instructions given by the controllers...

In the particular case app. 15 NM before VUTEB I was given instructions to descend to FL110 obviously to meet the requirements for LOVOK, which unfortunately the plane could not achieve after adjusting the altitude and leaving the descend to its computer (pushed button). Actual situation was that it was above 11000 on LOVOK, above 8000 on DB529, which is as per the chart and reached PATID at 7000, which is again according to the chart. Speed was 230 KT, which is normal for this part of the leg.

Edited December 14, 2017 at 04:01 PM by Guest

[Christopher Liu]

Don't worry too much about altitude restrictions on most STARs as they're usually for pilot guidance only (although this does depend on the country), actual descent restrictions will normally be as issued by ATC over the radio. Generally ATC will say "Descend FLxxx level by XXXXX" if they need you to meet a restriction, and what they say may not always match what is published on the chart.

 

If ATC just say "descend" then you can do a normal "OP DES" in the Airbus (or use -1000 VS DES as mentioned above, until you catch your VNAV profile and go to a Managed Descent/VNAV), and if they say "descend when ready" you can immediately select the Managed Descent/VNAV.