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Trimeresurus
Topic Author
Posts: 119
Joined: Fri Jun 02, 2017 6:06 pm

### How does the ATC keep such precise seperations between aircraft during approach?

In some airports, most notably the IST, you can see several aircraft lined up to the same runway to land, seperated by maybe only 5-8NM and 1000-1300 feet in altitude. How does ATC balance the arrivals so close within each other? If say, the aircraft behind gets too close to one in front, is it instructed to go around? Is the localizer and glide slope not disturbed for the aircraft behind? And, why don't they give approaches to parallel runways in this case, rather than lining up the aircraft? And in this case, would the aircraft be following a STAR on their FMDs, or heading vectors by the ATC?

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

How does ATC space arrivals? Practice practice practice. Controller learn how to manage arrivals, assigning speeds and vectors for more or fewer track miles. The interview process for ATC at a large airport often involves a simulated approach sequence. Candidates are rated on how little "wasted" extra separation they have in total. So you want to get as close to minimum separation as possible, but not bust the minimum distance between any two aircraft.

What happens if the aircraft behind gets too close? It is instructed to go around. Not an uncommon occurrence. The occasional go-around is an acceptable price to pay for maximising arrivals per hour.

Is the localiser or glideslope disturbed by the aircraft ahead? Never seen it. It can happen if there are aircraft waiting at the hold point.

Why don't we get an approach to a parallel runway? In some cases you do. In other cases not. Depends on the airport.
- In some cases, one runway is dedicated for departures and one for arrivals, e.g. HKG. Approach may sometimes slot in an aircraft on the departure runway for a shorter taxi that won't involve crossing an active, (e.g. cargo aircraft getting the southern runway in HK), but in general they will segregate.
- In some cases, there are two arrival runways, e.g. LAX. Controllers will space you and assign runways based on various criteria, but you typically know which runway you'll get from pretty far out..
- In some cases, runways run "mixed mode", meaning arrivals and departures both use both runways, e.g. SYD. Again here, controllers use various criteria, and in the case of SYD expected terminal and the runway length itself are relevant.
- In some places you might get multiple runway changes on descent, e.g. PEK.
- In some cases, you can be offered a parallel runway quite late, e.g. FRA and CDG. The controller is trying to give you a shorter taxi, but it is pilot's discretion if you want to take it. It is often prudent to just stay on the original, especially if you're not pretty familiar with the airport.

Do we follow a STAR? Typically you'd follow a STAR initially, but at busy airports it would be inefficient spacing wise to keep everyone on the procedural path, so you'll get vectors. Approach controllers, and director controllers in some cases, are constantly fine-tuning.

Suggestion: Use bullet points for clarity.

CosmicCruiser
Posts: 2529
Joined: Tue Feb 22, 2005 3:01 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

How funny Starlionblue, before I ever opened the thread to comment my first thoughts were practice, practice, practice!

gloom
Posts: 580
Joined: Thu Jun 30, 2016 4:24 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Generally, as an ATC, you are able to do separations within a 1nm (for example, if you have 5nm as minimum, most ATC will be able to maintain between 5 and 6 nm as a rule).

Sometimes, if the runway is arrival/departure parallel, sometimes you will see 3nm extra for departure to fit in.

As to where this comes from - practice as mentioned above. Plenty of tools to help (transitions, distance tools, speeds etc), but at a time, you learn to trust your own predictions.

On the highest level, you get to know a person that's able to assess speed required to fit into arrival procedures 200nm further. Just by practice.

Cheers,

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Funny, no one mentioned the pilot’s role, we can adjust spacing somewhat, mostly visually when in the clear. I’ve been “cleared for the visual behind the xxx” and put the plane on about a mile final as the landing traffic cleared the runway. ATC sometimes asks to slow or speed up, s-turns on final to make it work. Up to us to accept, decline or make it work.

Woodreau
Posts: 2175
Joined: Mon Sep 24, 2001 6:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

ATC also issues speed instructions so that where there are multiple aircraft lined up on final to land on the same runway they are travelling at roughly the same speed...

Kind of like on the highway if everyone is driving the same speed, say like the 80mph speed limit, then in theory no one should pass anyone. But because no one drives the same speed people are always jockeying around all the slow drivers in the passing lane.

But on final everyone is flying around 170-180kts. Especially the poor caravan who is told to fly their approach at maximum forward speed.

atcsundevil
Moderator
Posts: 4656
Joined: Sat Mar 20, 2010 12:22 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Trimeresurus wrote:
seperated by maybe only 5-8NM

Large airports can and often do run aircraft significantly closer than this. A succession of "large" aircraft (referring to weight class, like the 737 or A320) with a Runway Occupancy Time waiver and visual separation means arriving aircraft can be as close as 2.5nm. They will shoot for as close to that 2.5nm as possible. Diverging departures only require 6,000ft. of runway separation and the preceding aircraft rotating. If you think about it, that's pretty dang close, but busy airports like ATL have it down to a science.

I don't work approach, but I do work in a center. While our separation standards are larger, we do still need to hit similar in-trail targets. If aircraft going to EWR require 10 miles in-trail for flow spacing, the idea is to get as close to 10.0 as possible. Anything less and you're screwing the next guy (which means you will be forced to hold your airplanes as punishment), anything more and you're screwing yourself because it's wasted space.

But like others have said, we can do this because "practice practice practice". Keeping the dots from touching is generally the easy part, it's keeping the exact amount of separation for sequencing that's tricky. Winds/weather affects the ability for you to hit your target, as does aircraft performance, as well as the assumption that the pilots are maintaining the exact speed you've assigned (which is not always the case), and in my environment, altitudes have a significant impact as well (less air resistance at higher altitudes, different winds aloft, etc.).

Knowing how to judge required vectors, when to turn aircraft back on course, getting a feel for speed assignments, and how the performance of different aircraft affects all of those things (e.g. a 737 at cruise has significantly better turn performance than an A320) is what's required to become proficient at the job. And of course we don't work in a vacuum, so there is other traffic to dodge, and we may be sequencing for several airports/flows (one of my sectors regularly sequences with in-trail requirements for five to six airports at the same time). Just like pro athletes train and practice for years to operate at the highest level, so too do pilots and controllers...we just get paid less and usually aren't in as good of shape

GalaxyFlyer wrote:
Funny, no one mentioned the pilot’s role, we can adjust spacing somewhat, mostly visually when in the clear. I’ve been “cleared for the visual behind the xxx” and put the plane on about a mile final as the landing traffic cleared the runway. ATC sometimes asks to slow or speed up, s-turns on final to make it work. Up to us to accept, decline or make it work.

No doubt. The skill (and/or level of cooperation) of the crew can either help us or hurt us. The vast majority of pilots are more than willing to oblige, because they know we have a job to do. Similarly, I think the best controllers are the ones who have a better understanding that pilots also have a job to do. A small number of pilots tend to take things like speed assignments as suggestions (I had a couple of those yesterday...I promise I'm not bitter), and that's when we get a little upset because it's hard to work precisely when there are unknown factors. I always appreciate when pilots keep a good attitude when when I need to slow them down or vector for spacing — of course I don't want to delay them, but we've all got a job to do. We're all trying to accomplish the same thing, so as you point out, you can't mention one without mentioning the other. I can tell you from experience that sequencing helpful, professional pilots is infinitely easier than trying to sequence pilots who clearly don't care enough to do you any favors.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Wow, what a pile of questions all of which are good questions. As a now retired controller who worked at a HUB airport when we did both tower and approach control back in the 80's and 90's to later ending my career as just an approach controller when the tower moved across the airport I'll attempt to respond to them all in hopes of giving answers that were valid prior to my retirement eight years ago and will use my experience at a larger/busier airport. Gosh so many variables.

How do we separate aircraft on approach? Well, using speed control. Sounds simple and it actually is though with the wind being different at different altitudes it can get tricky especially around fronts and thunderstorms. Many of the new arrival routes or Standard Terminal Arrival Route (STAR) have assigned speeds and altitude crossing restrictions, some altitude windows for the crew to make (cross ZZZXY below 14,000' above 17,000' at 280 KIAS). That starts the sequence we would get over say the northeast arrival route from the center. They hand off the arrival to approach control arrival controller who will take the aircraft off the STAR if there is no runway transition charted and vector/sequencing the single stream of arrivals they are giving to the final controller who provides the actual landing sequence to the tower. The arrival controller is very aware (or better be) of what the final controller has for traffic inbound from the other arrival controllers (we had four different arrival controllers, one from each corner post ie., NE, NW, SE and SW) and will assign speeds and vectors to give the final controller a chance of fitting in downwind traffic between the more straight-in coming from the east side arrivals if landing west as example or vice/versa if landing east. The final controller will issue the approach clearance and assign speeds such as "maintain 170 KIAS until the final approach fix" using the name or a distance from the runway. Depending on the runway in use and aircraft type for separation (wake turbulence issues) we'd use 2.5 NM inside a 10 mile final (hopefully that has no been moved out to 20 mile final), 3 NM if the runway did not qualify for the reduce separation on final (the term) 4 NM, 5 NM, 6 NM or 10 NM (for a Super). All of that is inside the controllers head depending on the leading aircraft type and following aircraft type. Altitudes issued ideally where the aircraft intercepts the ILS, GLS, RNAV, RNP final approach course at or below the glidepath altitude. Vertical separation is used at 1,000' increments (should be used to avoid any separation issues) when filling a hole as we call it on final with base leg or downwind traffic. So I'm working final and make a six mile hole to put downwind traffic in, I've used speed control to slow the following aircraft, given myself at least 1,000' of vertical separation when I turn the downwind traffic on to final and issue a speed to that aircraft to ensure I keep my required 3 NM separation (considering like type aircraft categories) between the lead and trailing aircraft.

Go Around as previously mentioned are not all that common. ATC would define a "go around" as when the arrival is close to the runway and for whatever reason has to as the phrase indicates has to go around for another approach. That makes the approach controller very unhappy as they have to sequence them again. If the arrival aircraft is still on the approach controller or final controller frequency and separation is decreasing we would cancel the approach clearance, issue a heading and altitude to re-sequence calling that a "pull out". Also, a headache we don't want to have. The object is to land and the arrival rate numbers for a runway/airport are not counting those type of operations, so during a big arrival bank it can get out of hand fast.

Localizer/Glide Slope disturbance During certain weather conditions the ground controller must protect the localizer and glide slope critical areas on the airport so arriving aircraft to not get disturbed signals. Numerous times we'd get reports of loc/GS fluctuations when an aircraft would cross the arrival runway when the arriving aircraft is following the ILS. GLS, RNAV and RNP approaches do not use the ground based signals of a loc/GS which does not create those fluctuations or at least that is what I was told by airline flight tech folks I used to work with and a reason we pushed for those type approaches to be charted and used among many other reasons.

Parallel Runways Not all airports have the luxury of having parallel runways or parallel runways that are capable of all aircraft type landing on them. They could be to short or narrow for an A320 to use, the approach could be in instrument conditions and not have a procedure on the chart called side-step maneuver to that the parallel runway in which case legally as a controller needed to clear the arrival for that "cleared ILS Runway 13R side-step Runway 13L". Remember I put "legally" so it does happen and if the fit hits the shan [img][/img] then questions get asked and that is never good. At airports with two or three parallel runways that are separated by the required distance between runway centerlines then we'd operate in what was called "independent simultaneous approaches, dual or triple" and there would be two or three separate final controllers sequencing aircraft only to their specific runway (of course you can do anything when they coordinate between each other like swap runways with one another, but that does create numerous workload issues for the crews at not a good time) using specific procedures and applying vertical separation when turning onto their runway final approach course. When using visual approaches it does help using he pilot eyes to follow the preceding arrival (thanks all you pilots for helping us out so often) and once they acknowledge the visual approach clearance they are responsible for the separation behind the folks they're following. WHEW!! Should a parallel runway be available and useable for a decreasing separation then it is certainly preferred over having to re-sequence the aircraft. Parallel runway are often used off of a STAR and contained within the FMS of the aircraft and or the crew is issued vectors or a "cleared direct ZZZYZ" to establish them on the final approach course to a parallel runway. Again, so many variables and much more info than needs to be put down here.

Take a look at this site and put in any major U.S. airport such as DEN, DFW, LAX, IAH, ATL, CLT, SEA, ORD, etc., and check out the STAR charts as well as approach charts to get an idea of how arrivals get from the enroute to terminal environments.

https://www.faa.gov/air_traffic/flight_ ... pp/search/

Hope this information helps and thank to Starlionblue, CosmicCrusier, gloom and GalaxyFlyer for their input, and yes the pilots incredible help has saved my bacon a great number of times back in the day. Thanks guys/gals.

Great questions.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

atcsundevil wrote:
The skill (and/or level of cooperation) of the crew can either help us or hurt us. The vast majority of pilots are more than willing to oblige, because they know we have a job to do. Similarly, I think the best controllers are the ones who have a better understanding that pilots also have a job to do. A small number of pilots tend to take things like speed assignments as suggestions (I had a couple of those yesterday...I promise I'm not bitter), and that's when we get a little upset because it's hard to work precisely when there are unknown factors. I always appreciate when pilots keep a good attitude when when I need to slow them down or vector for spacing — of course I don't want to delay them, but we've all got a job to do. We're all trying to accomplish the same thing, so as you point out, you can't mention one without mentioning the other. I can tell you from experience that sequencing helpful, professional pilots is infinitely easier than trying to sequence pilots who clearly don't care enough to do you any favors.

Outstanding comment. I know for a fact my flying hours and aircraft knowledge helped my every day do my job. Each developmental I trained it was my attempt to make the aircraft type smart while telling them to "stay out of the flight deck" as that does create a not so good working situation, similar to when the pilot has the "big picture" only not have the entire frame around it and then it can get chippy on the radio which none of us want to happen nor have time for to deal with, that' what a telephone is for after the fact and let the supervisor deal with it. Just don't do it and always thank the pilot for their help.

atcsundevil
Moderator
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Joined: Sat Mar 20, 2010 12:22 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

IAHFLYR wrote:
Outstanding comment. I know for a fact my flying hours and aircraft knowledge helped my every day do my job. Each developmental I trained it was my attempt to make the aircraft type smart while telling them to "stay out of the flight deck" as that does create a not so good working situation, similar to when the pilot has the "big picture" only not have the entire frame around it and then it can get chippy on the radio which none of us want to happen nor have time for to deal with, that' what a telephone is for after the fact and let the supervisor deal with it. Just don't do it and always thank the pilot for their help.

Massively agree, especially with that last part. I never have a problem owning up when I screw up, admitting that I need to change plans, or thanking them for helping me out. I've never understood the resistance some controllers have when it comes to giving pilots insight into what's going on. Little stuff like, "Can you keep your speed up for company behind?" can work wonders. Despite everything I mentioned in my last post, sounding good on freq and giving pilots a reason to want to work for you is the real difference between sinking or swimming!

JayinKitsap
Posts: 2699
Joined: Sat Nov 26, 2005 9:55 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

I recall back when the A380 was going thru certification it was found to have high wake turbulence, forcing larger distances for the plane following, with more distance to the smaller planes. Just recalling it is 3 nm typically for a NB and most WB's, but the A380 needed 5 nm behind it. ATC is the key performer in the art of maximizing arrivals while staying safe.

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

atcsundevil wrote:

GalaxyFlyer wrote:
Funny, no one mentioned the pilot’s role, we can adjust spacing somewhat, mostly visually when in the clear. I’ve been “cleared for the visual behind the xxx” and put the plane on about a mile final as the landing traffic cleared the runway. ATC sometimes asks to slow or speed up, s-turns on final to make it work. Up to us to accept, decline or make it work.

No doubt. The skill (and/or level of cooperation) of the crew can either help us or hurt us. The vast majority of pilots are more than willing to oblige, because they know we have a job to do. Similarly, I think the best controllers are the ones who have a better understanding that pilots also have a job to do. A small number of pilots tend to take things like speed assignments as suggestions (I had a couple of those yesterday...I promise I'm not bitter), and that's when we get a little upset because it's hard to work precisely when there are unknown factors. I always appreciate when pilots keep a good attitude when when I need to slow them down or vector for spacing — of course I don't want to delay them, but we've all got a job to do. We're all trying to accomplish the same thing, so as you point out, you can't mention one without mentioning the other. I can tell you from experience that sequencing helpful, professional pilots is infinitely easier than trying to sequence pilots who clearly don't care enough to do you any favors.

In this context, it is important as a pilot to tell ATC whether you are unable to comply. Don't just change your speed if you've been told something else. ATC is more than happy to help but they have to be aware of your situation.

For example, say tower wants you to keep 150 knots to five miles on final but you have a 12 knot tailwind. Clearly you want to start slowing down a few miles earlier, or you are unlikely to be stabilised by 1000 feet, meaning you have to go around. The key thing is to tell tower something like, "unable, 12 knot tailwind, slowing to final approach speed at seven miles". That way tower (and approach) can slow down the aircraft behind you, and also perhaps adjust that speed requirement due to prevailing conditions. If you just slow down early of your own accord, tower might have to tell the aircraft behind you to go around.

atcsundevil
Moderator
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Joined: Sat Mar 20, 2010 12:22 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Starlionblue wrote:
In this context, it is important as a pilot to tell ATC whether you are unable to comply. Don't just change your speed if you've been told something else. ATC is more than happy to help but they have to be aware of your situation.

For example, say tower wants you to keep 150 knots to five miles on final but you have a 12 knot tailwind. Clearly you want to start slowing down a few miles earlier, or you are unlikely to be stabilised by 1000 feet, meaning you have to go around. The key thing is to tell tower something like, "unable, 12 knot tailwind, slowing to final approach speed at seven miles". That way tower (and approach) can slow down the aircraft behind you, and also perhaps adjust that speed requirement due to prevailing conditions. If you just slow down early of your own accord, tower might have to tell the aircraft behind you to go around.

Abso-freakin-lutely. If you can't do it, then you can't do it! If you tell us, we'll work it out. We get upset when we have assigned speeds on numerous aircraft, but someone clearly isn't doing what they're supposed to be doing. I'm liable to spin somebody doing that, because if I can't trust them to comply with my instructions, then I can't reliably sequence behind them. If pilots need to pull speed back for the ride — cool! I'm more than happy to oblige, I just need to know. Fortunately it's an extremely small minority of pilots who will do that, but they won't be able to get away with it after we integrate ADS-B data with our systems.

gloom
Posts: 580
Joined: Thu Jun 30, 2016 4:24 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Yeah, pilot's crucial at those occasions. ATC would never know how much - and how well - pilot is able to increase/reduce. Two most important cases I see here are on approach position - maintain XXX knots as long as possible/until Y miles, and expedite climb. Those are two where pilots communication and plane capabilities mean so much. If you get clean until 5 miles DME on approach, will you be able to reconfigure and land? And stay on safe side? It's up to pilot to answer this question, especially considering there's someone behind coming. And say "unable" if there's any doubt. It's way better to have someone break out from landing queue, than to go around from touchdown zone.

Cheers,

KingOrGod
Posts: 194
Joined: Mon Jan 16, 2017 3:19 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

atcsundevil wrote:
Starlionblue wrote:
In this context, it is important as a pilot to tell ATC whether you are unable to comply. Don't just change your speed if you've been told something else. ATC is more than happy to help but they have to be aware of your situation.

For example, say tower wants you to keep 150 knots to five miles on final but you have a 12 knot tailwind. Clearly you want to start slowing down a few miles earlier, or you are unlikely to be stabilised by 1000 feet, meaning you have to go around. The key thing is to tell tower something like, "unable, 12 knot tailwind, slowing to final approach speed at seven miles". That way tower (and approach) can slow down the aircraft behind you, and also perhaps adjust that speed requirement due to prevailing conditions. If you just slow down early of your own accord, tower might have to tell the aircraft behind you to go around.

Abso-freakin-lutely. If you can't do it, then you can't do it! If you tell us, we'll work it out. We get upset when we have assigned speeds on numerous aircraft, but someone clearly isn't doing what they're supposed to be doing. I'm liable to spin somebody doing that, because if I can't trust them to comply with my instructions, then I can't reliably sequence behind them. If pilots need to pull speed back for the ride — cool! I'm more than happy to oblige, I just need to know. Fortunately it's an extremely small minority of pilots who will do that, but they won't be able to get away with it after we integrate ADS-B data with our systems.

Hey... We've had Mode S enhanced surveillance for at least half a decade in Europe. It's friggen awesome. No more "report heading" or "report speed". It's on our screens. No more lying from the flight deck about speed adherance!!!

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

KingOrGod wrote:
atcsundevil wrote:
Starlionblue wrote:
In this context, it is important as a pilot to tell ATC whether you are unable to comply. Don't just change your speed if you've been told something else. ATC is more than happy to help but they have to be aware of your situation.

For example, say tower wants you to keep 150 knots to five miles on final but you have a 12 knot tailwind. Clearly you want to start slowing down a few miles earlier, or you are unlikely to be stabilised by 1000 feet, meaning you have to go around. The key thing is to tell tower something like, "unable, 12 knot tailwind, slowing to final approach speed at seven miles". That way tower (and approach) can slow down the aircraft behind you, and also perhaps adjust that speed requirement due to prevailing conditions. If you just slow down early of your own accord, tower might have to tell the aircraft behind you to go around.

Abso-freakin-lutely. If you can't do it, then you can't do it! If you tell us, we'll work it out. We get upset when we have assigned speeds on numerous aircraft, but someone clearly isn't doing what they're supposed to be doing. I'm liable to spin somebody doing that, because if I can't trust them to comply with my instructions, then I can't reliably sequence behind them. If pilots need to pull speed back for the ride — cool! I'm more than happy to oblige, I just need to know. Fortunately it's an extremely small minority of pilots who will do that, but they won't be able to get away with it after we integrate ADS-B data with our systems.

Hey... We've had Mode S enhanced surveillance for at least half a decade in Europe. It's friggen awesome. No more "report heading" or "report speed". It's on our screens. No more lying from the flight deck about speed adherance!!!

Indeed. Large parts of East Asia too. However, as a pilot you can still make trouble by doing something unexpected. By the time ATC sees it, the fecal matter has already impacted the rotary air impeller, and they might not have time to fix the problem before someone has to go around. Better to tell ATC ahead of time so they can plan, than for them to find out after the fact.

atcsundevil
Moderator
Posts: 4656
Joined: Sat Mar 20, 2010 12:22 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

KingOrGod wrote:
Hey... We've had Mode S enhanced surveillance for at least half a decade in Europe. It's friggen awesome. No more "report heading" or "report speed". It's on our screens. No more lying from the flight deck about speed adherance!!!

I know, we're...working on it

I think we were supposed to get it within the next two years or so, but covid has delayed everything of course. All centers were supposed to be up and running for CPDLC months ago, but only a few managed to finish trials before they were halted in March. We had a couple of other big milestones and major airspace redesigns that were supposed to happen this year that are obviously delayed now. It's tricky trying to roll out big upgrades when there are so many facilities involved.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

My former facility was one of the first if not the first to implement ADS-B and Fusion piping multiple RADAR sensors into our STARS automation and that was about 10 years back. We have ONE second updates with it as opposed to the normal terminal updates from the RADAR sites at 4.8 seconds. Amazing how much easier it was to turn final with aircraft once you got used to it. Luckily I was on the test team at ACY Tech Center for years so was very accustomed to it when we went live with it.

rfields5421
Posts: 6374
Joined: Thu Jul 19, 2007 12:45 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Woodreau wrote:
But on final everyone is flying around 170-180kts. Especially the poor caravan who is told to fly their approach at maximum forward speed.

Been to many a youth sports game in Lewisville, TX - less than 4 km from touchdown at DFW - suddenly a very loud noise as a turbo-prop passes over head trying to keep enough speed to say even with the jet traffic ahead and behind.

Once while doing TNG in a C-182 at KTKI, I was told "Do not slow after touchdown and immediately clear the runway. Lear behind you at 3 miles."

Woodreau
Posts: 2175
Joined: Mon Sep 24, 2001 6:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Well there was that one time I was told that southwest 10 miles ahead on short final was doing a touch and go and I had a 100knot overtake on Southwest but I was cleared to land speed my discretion.

TTailedTiger
Posts: 2953
Joined: Sun Aug 26, 2018 5:19 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Yes, pilots play a part in it as well. I'm just a GA pilot but I've never given ATC any grief and always glad to do whatever the need me to. I don't understand pilots with the attitude "I'm flying the plane, not ATC". It's a dangerous mindset in my opinion. ATC has never instructed me to do anything that would jeopardize the safety of the flight. And why would they?

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

TTailedTiger wrote:
Yes, pilots play a part in it as well. I'm just a GA pilot but I've never given ATC any grief and always glad to do whatever the need me to. I don't understand pilots with the attitude "I'm flying the plane, not ATC". It's a dangerous mindset in my opinion. ATC has never instructed me to do anything that would jeopardize the safety of the flight. And why would they?

I think you're misunderstanding the expression "I'm flying the plane, not ATC".

It doesn't indicate a desire to go against ATC instructions or ignore them. It indicates that the pilot is not simply taking instructions on faith. This is a crucial part of the safety mindset for a pilot.

ATC won't intentionally give you unsafe instructions. But they are also human. Humans make mistakes. And the controller is not aware of your exact operating speeds, local flight conditions, or even company policies such as stabilised approach criteria. The pilot's job is to operate the aircraft safely. If ATC instructions don't allow this, for example an instruction that would likely result in an unstable approach, the pilot should not just blindly follow. That's what is meant by "the pilot flies the plane, not ATC".

I'll add that while I don't know where you fly, I'm guessing somewhere like North America or Europe. Controllers in such places tend to have up to date equipment, a high level of proficiency, plus they are handling a level of traffic that is not excessive. In contrast, controllers in many countries around South Asia, Africa and Southeast Asia often have obsolete equipment, are handling much more traffic than they should, and often don't have the level of proficiency that might be desired. In some places, controllers are so overworked that if you don't start talking on frequency before the guy before you is finished, you'll never get a word in.

If you get a vectoring instruction that takes you towards rising terrain and you can't get a word in edgewise on an overloaded frequency, you don't wait for ATC. You fly the airplane and you take whatever action you need to remain safe.

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

You might look up the C-141 descended into the Cascades many years ago. Wrong call sign was used by the controller and the crew didn’t question it. You don’t merely accept their guidance, it’s a two-way deal. I was once given a landing ckearance, noted a vehicle working near the threshold, asked the tower, what the deal was. ATCO didn’t see it, I said, “low approach”. The Pilot is ultimately responsible.

Woodreau
Posts: 2175
Joined: Mon Sep 24, 2001 6:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

TTailedTiger wrote:
Yes, pilots play a part in it as well. I'm just a GA pilot but I've never given ATC any grief and always glad to do whatever the need me to. I don't understand pilots with the attitude "I'm flying the plane, not ATC". It's a dangerous mindset in my opinion. ATC has never instructed me to do anything that would jeopardize the safety of the flight. And why would they?

From the pilot side, it’s knowing what your airplane is capable of and also knowing what it’s not capable of.

For example going into LAX, a typical instruction on the approach is to maintain 250kts. I’d have to reference where I am on the glideslope (and current altitude) and how far away from the runway I am to make a judgement on whether I can accept the 250kt speed assignment or not.

Every pilot learns there is a specific speed and configuration for the approach, and that’s what you do in the simulator, for a narrow body Airbus, it’s 180kts, Flaps 2. But as you get on the line and fly the aircraft you learn the capabilities of your aircraft.

A twin engine turboprop can be one of the faster airplanes in the terminal area below 10000ft. STL controllers knew how to sequence turboprops and turbojets and frequently you could be abeam the numbers at 11000ft on the downwind leg, and the controller would clear you for the visual approach, but ask you to keep it tight because there’s a md-80 on final to the same runway. A crew with an inexperienced FO wouldn’t be able to accomplish the maneuver and we’d have to decline and ask to go behind the MD-80. But a more experienced crew could get down, land and still give the tower time to launch a departure before the MD-80 landed.

In the end it’s teamwork between the controllers and the pilots, and you can pick up on the cues from the controller. In ORD, you start off at 11,000 on the downwind, then you’re stepped down to 7,000 and 4,000. If that’s all I hear, then I descend normally in open descent. But if the controller adds, “short final”, then that is my cue to get down - open descent with half speed brakes, or if I want to get down faster, autopilot off, full speed brakes. Or not. The controller is just waiting for the plane to get to an altitude to where he can turn the plane base and final. he’s just waiting for the plane. It doesn’t matter to him.

Or if the controller issues 250 or greater, 210 or greater, 170 or greater on the approach, it’s your cue that you’re #1 for the runway. And don’t slow to 180kts flaps 2 15 miles out, you’ll screw up the plan the controllers has for the planes behind you. But if 210 or greater isn’t going to work and you need to slow below 210, then you need to let the controller know.

It’s more common in cruise when they’ll assign a specific speed for sequencing. “unable .74, but I can do .74 if I go down 4000ft or .76 is my minimum speed at current altitude.”

mxaxai
Posts: 2811
Joined: Sat Jun 18, 2016 7:29 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

atcsundevil wrote:
Trimeresurus wrote:
seperated by maybe only 5-8NM

Large airports can and often do run aircraft significantly closer than this. A succession of "large" aircraft (referring to weight class, like the 737 or A320) with a Runway Occupancy Time waiver and visual separation means arriving aircraft can be as close as 2.5nm. They will shoot for as close to that 2.5nm as possible. Diverging departures only require 6,000ft. of runway separation and the preceding aircraft rotating. If you think about it, that's pretty dang close, but busy airports like ATL have it down to a science.

I don't work approach, but I do work in a center. While our separation standards are larger, we do still need to hit similar in-trail targets. If aircraft going to EWR require 10 miles in-trail for flow spacing, the idea is to get as close to 10.0 as possible. Anything less and you're screwing the next guy (which means you will be forced to hold your airplanes as punishment), anything more and you're screwing yourself because it's wasted space.

Would it help you if the aircraft had an autopilot that could maintain a certain separation to the leading aircraft? For example, the pilot could select another aircraft on their displays, set the separation target to 2.5nm, and then the autopilot uses the ADS-B information to adjust speed so that the target is reached as close as possible (but not exceeded).

We've seen Airbus talk about formation flying before; this could be a first step. The way it's been described in this thread, maintaining separation seems to create significant workload for both pilots and ATC.

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

mxaxai wrote:
atcsundevil wrote:
Trimeresurus wrote:
seperated by maybe only 5-8NM

Large airports can and often do run aircraft significantly closer than this. A succession of "large" aircraft (referring to weight class, like the 737 or A320) with a Runway Occupancy Time waiver and visual separation means arriving aircraft can be as close as 2.5nm. They will shoot for as close to that 2.5nm as possible. Diverging departures only require 6,000ft. of runway separation and the preceding aircraft rotating. If you think about it, that's pretty dang close, but busy airports like ATL have it down to a science.

I don't work approach, but I do work in a center. While our separation standards are larger, we do still need to hit similar in-trail targets. If aircraft going to EWR require 10 miles in-trail for flow spacing, the idea is to get as close to 10.0 as possible. Anything less and you're screwing the next guy (which means you will be forced to hold your airplanes as punishment), anything more and you're screwing yourself because it's wasted space.

Would it help you if the aircraft had an autopilot that could maintain a certain separation to the leading aircraft? For example, the pilot could select another aircraft on their displays, set the separation target to 2.5nm, and then the autopilot uses the ADS-B information to adjust speed so that the target is reached as close as possible (but not exceeded).

We've seen Airbus talk about formation flying before; this could be a first step. The way it's been described in this thread, maintaining separation seems to create significant workload for both pilots and ATC.

We're a long way away from that. All aircraft have different speeds they can operate at. Even the same aircraft will have different speeds depending on configuration and weight. What if the aircraft in front of you slows below your current configuration and weight's manoeuvring speed?

Formation flying is a different story because the aircraft involved would hold a reasonably constant speed. On approach speed and configuration are changing, as is direction and thus relative wind.

atcsundevil
Moderator
Posts: 4656
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### Re: How does the ATC keep such precise seperations between aircraft during approach?

IAHFLYR wrote:
My former facility was one of the first if not the first to implement ADS-B and Fusion piping multiple RADAR sensors into our STARS automation and that was about 10 years back. We have ONE second updates with it as opposed to the normal terminal updates from the RADAR sites at 4.8 seconds. Amazing how much easier it was to turn final with aircraft once you got used to it. Luckily I was on the test team at ACY Tech Center for years so was very accustomed to it when we went live with it.

I went to PCT a few years ago and the one second updates blew my mind. Our 12 second updates do us some favors sometimes (you know what I mean), but one second updates would definitely make sequencing easier once you get used to it. I can imagine it would be a big adjustment though...your experience is developed with that lag built in. I'd probably be turning planes back on course 30 seconds too early!

mxaxai wrote:
Would it help you if the aircraft had an autopilot that could maintain a certain separation to the leading aircraft? For example, the pilot could select another aircraft on their displays, set the separation target to 2.5nm, and then the autopilot uses the ADS-B information to adjust speed so that the target is reached as close as possible (but not exceeded).

We've seen Airbus talk about formation flying before; this could be a first step. The way it's been described in this thread, maintaining separation seems to create significant workload for both pilots and ATC.

Sure it would help, but that's many, many years off in the future. The idea is that eventually air traffic controllers will become air traffic managers. It goes along with the theory of free flight. It's not something any of us will ever see in our careers. It's all super cool stuff, but it would require billions in investment, years of development, and years of testing.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

atcsundevil wrote:
Our 12 second updates do us some favors sometimes (you know what I mean),

Oh yes I do know what you mean!!

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

mxaxai wrote:
The way it's been described in this thread, maintaining separation seems to create significant workload for both pilots and ATC.

That's what we signed up for being pilot/controller!

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

IAHFLYR wrote:
mxaxai wrote:
The way it's been described in this thread, maintaining separation seems to create significant workload for both pilots and ATC.

That's what we signed up for being pilot/controller!

Having been in a mid-air, maintaining separation is pretty important and a key task as pilot or controller.

The C-130 has had Station Keeping Equipment (SKE) for airdrop for decades, but it won’t ever be civil certified, too many scary failure modes, too expensive for marginal gains.

IFlyVeryLittle
Posts: 216
Joined: Mon Jan 29, 2018 7:31 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Are controllers' instructions informed by computer assistance such as speed and vectors. i listen to Tampa Bay area approach and departure control and Im flabbergasted by the speed and amount of information being put out by a single controller.

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

IFlyVeryLittle wrote:
Are controllers' instructions informed by computer assistance such as speed and vectors. i listen to Tampa Bay area approach and departure control and Im flabbergasted by the speed and amount of information being put out by a single controller.

Think that’s busy, try London Control! It makes just about anything in the US look like Des Moines, IA.

gloom
Posts: 580
Joined: Thu Jun 30, 2016 4:24 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

GalaxyFlyer wrote:
Think that’s busy, try London Control! It makes just about anything in the US look like Des Moines, IA.

How about New York approach? I guess it would be just next to London in terms of throughput, with JFK, EWR and LGA next to each other.

There's a sample somewhere in the net available, that helped me a lot to learn reading accelerated sequences. I have it somewhere on my HDD, with Korean 91 failing to answer properly quick...

Cheers,

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

gloom wrote:
GalaxyFlyer wrote:
Think that’s busy, try London Control! It makes just about anything in the US look like Des Moines, IA.

How about New York approach? I guess it would be just next to London in terms of throughput, with JFK, EWR and LGA next to each other.

There's a sample somewhere in the net available, that helped me a lot to learn reading accelerated sequences. I have it somewhere on my HDD, with Korean 91 failing to answer properly quick...

Cheers,

New York is indeed also very busy. However, IMHO London is way easier to deal with. Because instead of talking fast like New York, they always seem unhurried. Plus they are masters of standard praseology.
.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

[quote="IFlyVeryLittle"][Are controllers' instructions informed by computer assistance such as speed and vectors./quote]

Not certain I understand your question, but if I'm on the right track the answer is yes, there are some keyboard entries one can make to give the exact distance you have between airplanes though it won't help you assign a speed when following another on final or on departure traffic when you need to give the center the three miles increasing to five mile separation standard. That's all on you as the controller.

As for vectors, yes another keyboard entry can be made to give you an idea of what heading for a point in space or an airport as example. But making excessive keyboard entries just creates unnecessary workload in my mind, it is the experience you rely on for issuing these type of control instructions.

Woodreau
Posts: 2175
Joined: Mon Sep 24, 2001 6:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Our stations had the ability to compute vectors to cause two contacts to merge. It was for conducting intercepts... I remember the sailor who was doing the air intercept controller position making a remark about getting a job with the FAA when he got out... "I'm going to work for the FAA as an air traffic controller when I get out..."

I said he's working in the wrong shack - he needed to be an AC to be working in CATCC upstairs if he wanted an FAA job afterwards... not an OS working in CIC - you've spent your entire career making contacts merge, the FAA doesn't take too kindly to that kind of work experience... lol

KingOrGod
Posts: 194
Joined: Mon Jan 16, 2017 3:19 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

IAHFLYR wrote:
IFlyVeryLittle wrote:
[Are controllers' instructions informed by computer assistance such as speed and vectors./quote]

Not certain I understand your question, but if I'm on the right track the answer is yes, there are some keyboard entries one can make to give the exact distance you have between airplanes though it won't help you assign a speed when following another on final or on departure traffic when you need to give the center the three miles increasing to five mile separation standard. That's all on you as the controller.

As for vectors, yes another keyboard entry can be made to give you an idea of what heading for a point in space or an airport as example. But making excessive keyboard entries just creates unnecessary workload in my mind, it is the experience you rely on for issuing these type of control instructions.

I think he's asking if there is controller assistance software which gives us or suggests to us the speeds and vectors to issue.

To this the answer is no. We dream this stuff up in our heads and turn it into a manageable patch of airspace.

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

KingOrGod wrote:
IAHFLYR wrote:
IFlyVeryLittle wrote:
[Are controllers' instructions informed by computer assistance such as speed and vectors./quote]

Not certain I understand your question, but if I'm on the right track the answer is yes, there are some keyboard entries one can make to give the exact distance you have between airplanes though it won't help you assign a speed when following another on final or on departure traffic when you need to give the center the three miles increasing to five mile separation standard. That's all on you as the controller.

As for vectors, yes another keyboard entry can be made to give you an idea of what heading for a point in space or an airport as example. But making excessive keyboard entries just creates unnecessary workload in my mind, it is the experience you rely on for issuing these type of control instructions.

I think he's asking if there is controller assistance software which gives us or suggests to us the speeds and vectors to issue.

To this the answer is no. We dream this stuff up in our heads and turn it into a manageable patch of airspace.

I was once told by another pilot that Director has software to help them out with separation. No idea if that is actually true.

BOACJrJet
Posts: 9
Joined: Sat Feb 06, 2016 10:55 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

On the subject of localizer interruption and the A380 – I frequently listen to JFK Tower, and pilots often report losing the localizer while on approach. The cause is the previously arriving A380. Evidently, when it turns off the runway, it is massive enough to interrupt the localizer. The tower will say, don’t worry, it will come back!

KingOrGod
Posts: 194
Joined: Mon Jan 16, 2017 3:19 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Starlionblue wrote:
KingOrGod wrote:
IAHFLYR wrote:

I think he's asking if there is controller assistance software which gives us or suggests to us the speeds and vectors to issue.

To this the answer is no. We dream this stuff up in our heads and turn it into a manageable patch of airspace.

I was once told by another pilot that Director has software to help them out with separation. No idea if that is actually true.

IIRC LHR director has some fancy gimmickry to help sequence with time based separation and not distance based, using the transmitted wind data from each arrival via Mode S, they can ascertain exactly which way the wake will dissipate and adjust the spacing on final accordingly. A 30 knot 45 degree crosswind will get rid of wake faster than a calm day and so spacing can be reduced accordingly.

However, the headings and assigned speeds to achieve that spacing are still up to us I reckon. And as for a regular approach control sector, same this is stuff we have to make up on the fly

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

KingOrGod wrote:
IIRC LHR director has some fancy gimmickry to help sequence with time based separation and not distance based, using the transmitted wind data from each arrival via Mode S, they can ascertain exactly which way the wake will dissipate and adjust the spacing on final accordingly. A 30 knot 45 degree crosswind will get rid of wake faster than a calm day and so spacing can be reduced accordingly.

However, the headings and assigned speeds to achieve that spacing are still up to us I reckon. And as for a regular approach control sector, same this is stuff we have to make up on the fly

I remember a NASA study years ago on wake turbulence and an effort to reduce the separation standard with certain wind conditions. They came to our facility to pitch the feasibility of it and it sure made sense to this person though never heard anything else out of it before I retired in 2012. They may have implemented it at a few airports and hope they have it providing reduced wake separation.

https://www.dailypress.com/news/dp-xpm- ... story.html

Posts: 144
Joined: Thu Nov 05, 2015 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Starlionblue wrote:
- In some places you might get multiple runway changes on descent, e.g. PEK.

Any reason why PEK switches it multiple times? It's a very busy airport, so I'd assume they'd keep directional traffic flow to specific runways for efficiency's sake. Any other examples of airports that do that?

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

Starlionblue wrote:
- In some places you might get multiple runway changes on descent, e.g. PEK.

Any reason why PEK switches it multiple times? It's a very busy airport, so I'd assume they'd keep directional traffic flow to specific runways for efficiency's sake. Any other examples of airports that do that?

PVG, Shanghai, is similar.

Anecdotal, but Mainland Chinese controllers are notorious for this kind of thing. Always expect the unexpected. There seems to be a lot of fine-tuning by the controllers, leading to a quite a bit of re-clearing of aircraft. I'm not a controller but I can't really see this "method" making things more efficient. It does increase our workload quite a bit, and I imagine it increases controller workload as well.

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

I came across Burma once 2,000’ above an QR plane entering China. QR had been asking for a climb for quite awhile but we were “blocking” him and I couldn’t go up. China controller gives me the standard, “offset Romeo 5 miles”. I’m thinking he offsets QR 5 miles Lima and he can climb and we would soon be separating to different destinations, so it’d work. Nope, “QR, offset 5 Romeo miles, unable climb”.

Starlionblue
Posts: 20868
Joined: Fri Feb 27, 2004 9:54 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

GalaxyFlyer wrote:
I came across Burma once 2,000’ above an QR plane entering China. QR had been asking for a climb for quite awhile but we were “blocking” him and I couldn’t go up. China controller gives me the standard, “offset Romeo 5 miles”. I’m thinking he offsets QR 5 miles Lima and he can climb and we would soon be separating to different destinations, so it’d work. Nope, “QR, offset 5 Romeo miles, unable climb”.

Welcome to my life.

N47
Posts: 123
Joined: Tue Sep 26, 2017 7:38 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

BOACJrJet wrote:
On the subject of localizer interruption and the A380 – I frequently listen to JFK Tower, and pilots often report losing the localizer while on approach. The cause is the previously arriving A380. Evidently, when it turns off the runway, it is massive enough to interrupt the localizer. The tower will say, don’t worry, it will come back!

Its the massive 380 tail that causes that. The closer to the localizer the 380 exist the runway the worst the impact is. Flight inspection at the FAA had to change procedures when flight checking LOCs behind 380s. Fight check aircraft have to now be placed 30 nmi behind 380s when inspecting LOCs to make sure the LOC doesnt fail flight check because of the 380.

IAHFLYR wrote:
the test team at ACY Tech Center

atcsundevil wrote:
I know, we're...working on it

I work at the ACY tech center, albeit in navigation. They have a yearly conference at the tech center where they showcase various projects and developments. One really cool thing that i saw a couple of years back was showcased by Harris and it was a system which allowed controllers to “vector” or route aircraft by creating a path for the aircraft to follow on the controllers screen, the route would then be send to that particular aircraft via CPDLC and the pilot can accept (or decline) the re-route and it would be autmatically be loaded in their FMS. This was mostly targeted for centers for the purpose of re-routing for weather etc. i thought it was a very interesting concept. I can see that being applied at TRACONs as well to define more percise approach “vectors”.

atcsundevil
Moderator
Posts: 4656
Joined: Sat Mar 20, 2010 12:22 pm

### Re: How does the ATC keep such precise seperations between aircraft during approach?

N47 wrote:
I work at the ACY tech center, albeit in navigation. They have a yearly conference at the tech center where they showcase various projects and developments. One really cool thing that i saw a couple of years back was showcased by Harris and it was a system which allowed controllers to “vector” or route aircraft by creating a path for the aircraft to follow on the controllers screen, the route would then be send to that particular aircraft via CPDLC and the pilot can accept (or decline) the re-route and it would be autmatically be loaded in their FMS. This was mostly targeted for centers for the purpose of re-routing for weather etc. i thought it was a very interesting concept. I can see that being applied at TRACONs as well to define more percise approach “vectors”.

Nice. We've more or less been doing that on a limited basis with CPDLC equipped aircraft. We can do route key, track pick to one or multiple points, then tie back in to the route. It sends them fix radial distances, so I've had a couple of pilots reject it thinking it's gibberish. I got into a habit of explaining myself first, and the reaction from a lot of pilots has definitely been positive. In practice, a lot of us were already doing this anyway to keep ERAM probing so they don't free track...sort of estimating where they were likely to go. Now that we're able to actually send it to pilots if we know the way is clear, it can make everyone's life a little easier. It is a little bit tedious, but I had a few times this past summer where it helped me out. I'm sure it's something that will be refined in the future, because it's definitely a useful tool.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

N47 wrote:
I work at the ACY tech center, albeit in navigation.

I should have guessed you were a Fed by the screen name, an ole FLC bird that I think was a CV580 based at ACY! Hey stop by "Cristi's and have a cold one for the holidays, if Jill is still there tell her that her friends in Houston miss her.

In the terminal airspace it would seem to only help the weak sticks using those tools plus quite a few of the new RNAV arrival routes put the aircraft on a precise track on the downwind with some runway transitions even using RNP with RF Legs to turn final. IAH has two such transitions that work great from a north downwind to RWY 26R and a south downwind for RWY9 so vectoring not required. Believe ATL has some as well they use to the outboard runways.

https://aeronav.faa.gov/d-tpp/2012/0546 ... ddest=(IAH)

https://aeronav.faa.gov/d-tpp/2012/0546 ... ddest=(IAH)

https://aeronav.faa.gov/d-tpp/2012/0002 ... ddest=(ATL)

GalaxyFlyer
Posts: 8602
Joined: Fri Jan 01, 2016 4:44 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

IAHFLYR wrote:
N47 wrote:
I work at the ACY tech center, albeit in navigation.

I should have guessed you were a Fed by the screen name, an ole FLC bird that I think was a CV580 based at ACY! Hey stop by "Cristi's and have a cold one for the holidays, if Jill is still there tell her that her friends in Houston miss her.

In the terminal airspace it would seem to only help the weak sticks using those tools plus quite a few of the new RNAV arrival routes put the aircraft on a precise track on the downwind with some runway transitions even using RNP with RF Legs to turn final. IAH has two such transitions that work great from a north downwind to RWY 26R and a south downwind for RWY9 so vectoring not required. Believe ATL has some as well they use to the outboard runways.

https://aeronav.faa.gov/d-tpp/2012/0546 ... ddest=(IAH)

https://aeronav.faa.gov/d-tpp/2012/0546 ... ddest=(IAH)

https://aeronav.faa.gov/d-tpp/2012/0002 ... ddest=(ATL)

As a corporate pilot, G6500 and 7500, the FAA has made the AR process prohibitively difficult for GA. Allthe equipment is installed, but it’s near impossible to get approval unless you very frequently use an airport where RNP AR approaches are the norm.

IAHFLYR
Posts: 4425
Joined: Sat Jun 25, 2005 12:56 am

### Re: How does the ATC keep such precise seperations between aircraft during approach?

GalaxyFlyer wrote:
As a corporate pilot, G6500 and 7500, the FAA has made the AR process prohibitively difficult for GA. Allthe equipment is installed, but it’s near impossible to get approval unless you very frequently use an airport where RNP AR approaches are the norm.

That is crazy, though totally FAA like to do something silly as that. I'm checking with a G550 guy I know to see if they are qualified since they fly into IAH all the time.
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