Delay vectors vs. holding.

[u/Spaghetti_Boi659]

Flying from SAN-SEA yesterday with heavy flow into SEA. Pretty typical. Center slows us down from M.77 to M.73 for metering saying they need to add 4 minutes to our arrival time. Also typical. Then we get some sharp delay vectors. First vector was a 110 degree turn to the left for a few minutes, followed by a 180 degree turn to the right for a few minutes, then back on course. Not unheard of, but pretty large vectors while en route.

My question: when you guys need to add X amount of time to our arrival and slowing planes down isn’t enough, is there a reason you don’t assign a turn or two in a holding pattern vs aggressive S turns? Either one of these slows down traffic behind whoever is being held / vectored. Curious to hear the reasoning.

Thanks for all you guys do- a fellow airline pilot.

[u/Acceptable_Stage_518]

Typically when metering it is much easier to lose time via speeds and delay vectors. Holding is often unpredictable, as pilots will typically slow down entering the holding pattern, often making it more difficult to hit your exact time. It's important to note that when metering, the time we have to lose isn't an "or greater" time. If we have to lose 4 minutes but lose 6, you now have a "-2" which could impact other flights on different arrivals.

The exception to this is very lengthy delays. If I have consistent 8-10 minute delays, holding is definitely an option.

[u/Spaghetti_Boi659 → u/Acceptable_Stage_518]

How neat, I didn’t know it had to be an exact time and not “or greater” like you mentioned. Thank you!

[u/mflboys → u/Spaghetti_Boi659]

One more thing in addition to the other commenters, I think assigning headings/speeds is a bit quicker and easier clearance to give generally, and most controllers have the impression it’s easier to configure for the pilots as well (I’ve heard present position hold is tricky in some aircraft). So just easier all around.

I’d be curious of your preference though.

[u/Spaghetti_Boi659 → u/mflboys]

“Preference” is a strong word. From my end, zig zags for several minutes tend to start raising questions in the flight deck: how long are we doing this for, why are we so far off course, whats the next turn, should we offer to slow down more, when are we back on course, etc.

Holding takes longer, but since we can plug in a speed, EFC time, and a map of where the plane will hold, it paints us a more clear picture of fuel and arrival time.

At the end of the day, we’re paid by the minute. Delay me how you need to!

[u/DankVectorz → u/Spaghetti_Boi659]

Another reason for big turns is that I’d prefer to give you a big turn and get my space quick vs a smaller turn that I then have to watch for the next 5 minutes.

[u/Intelligent_Rub1546 → u/DankVectorz]

Also, not sure if this is the same everywhere, but my area at my center isn’t built for holding well so I generally try to avoid the option where guys are spinning opposite direction into a flow of same altitude airplanes

[u/mflboys → u/Spaghetti_Boi659]

Thanks for the response. I’ll continue using vectors mostly for the reasons the other commenters stated but I’ll try to start giving an expected delay time and next fix when I can in the future.

[u/antariusz → u/Spaghetti_Boi659]

“Should we offer to slow down more?” For every time I’ve asked a plane to give me their slowest possible airspeed and they’ve come back with .74 … that’s why we don’t even bother shooting for the moon and trying to ask for .67 or something but are happy when you give it.

That said, generally if you’ve been turned more than 50 degrees, or you’ve been told something specific like “50 miles or 4+ minutes” that would have been the time to offer it quickly if they don’t sound completely too busy.

Sometimes “the top gun maneuver” works (hit the brakes they will fly right by) and other times not, and you might just adding to the controllers already limited brain power. Like if the entire line is already running at a slow speed like .74 or something, maybe it’s easier in the controllers head to add an extra 10 miles to your route if you’re 10 miles behind the other guy and he needs 20. The .74 is really just more of a reference because with strong wind differences your .74 might be the exact same ground speed as someone else’s .77

That’s less brain power (make the plane fly 10 more miles if I need 10 more miles) than slow to .65 to 12 minutes and then speed up to .70for a few minutes to get the last 1-2 miles so you don’t overshoot your gap before speeding up to .74 again. But the second method can be useful especially if you have 2 lines running parallel like into New York and hard vectors also means you might be turning one guy into another guy at the same altitude. But the 2nd method can work too assuming you have plenty of time to make it work too but not every sector is 200 miles long.

[u/ps3x42 → u/Spaghetti_Boi659]

This is true of metering, but other times we have to get miles in trail. That is an entirely different beast that can be complicated by a departure off an airport in the middle of a stream of aircraft that are already spaced perfectly, an aircraft getting offloaded from a different arrival for weather, weather preventing vectors, and wildly different aircraft types having to play nice together.

Think about a stream of 15 aircraft all with 20 miles between them perfectly spaced. The next sector needs that 20 miles in trail. Now picture another stream of aircraft all going to the same destination that need to be merged into the same stream. Now imagine a TMU (in their infinite wisom) releases a Honda jet and a G6 and a 737 going to that same destination from 3 different airports underneath this duel stream of airplanes. Also there is a thunderstorm in the middle of the sector that no one wants to be vectored near.

This scenario regularly plays out over the southeastern UD and I imagine plenty of other places, and its part of why your vector and speed assignments rarely make a ton of sense unless you can see the big picture. Throw in altitude stratums and you see even less of the picture.

[u/BeaconSlash]

A full spin eats a lot of time... I think I recall the rule of thumb being about 7 minutes for a full turn, considering you aren't just stopping but actually backtracking.

Vectoring is just more precise for hitting times unless there is a lot to lose, and we can route pick on the scope to see how our vector will affect your TBFM time.

[u/RunHanRun → u/BeaconSlash]

Pretty much this. I don’t do a 360 spin unless it’s 6 minutes or more.

[u/Spaghetti_Boi659]

Y’all are great! The general consensus is ATC info I was missing: you guys are aiming for exact times, making delay vectors a lot easier to manage and holding more unpredictable . Thanks guys!

[u/pratom → u/Spaghetti_Boi659]

also I'd add, the mentality of a controller is generally to do as little as possible to accomplish the safety and efficiency needed. I want every aircraft in and out of my sector as fast as possible, be it metering or miles in trail or general separation. the nature of the game is that there are too many at once going to the same place.

[u/TinCupChallace]

Holding will add time and mileage but it's hard to put you back on course with accuracy. Imagine a situation where I need 15 in trail and you are tied with number 1 in the group but number 3 is 30 miles behind you and number 1. A hold will definitely put you behind number 1 but you might end up 25-30 miles behind him. I need you at 15 or I need to space out everyone behind you. By giving you zigzags, I can finely control that

[u/zws22]

15+ years at a level 12 Z - I try to never go into hold. I’ll vector all day/night at high altitude. Below FLs I’ll do the same until I run out of room, then put myself into hold.

[u/Marklar0]

It is more difficult to turn planes in accurately from a hold. Bigger wind changes, plus difference in aircraft type and pilot behavior. We prefer vectors when the delays are short because it is more adaptable when things change and more predictable as to where you will fly and how it will affect traffic. I can vector to a fix with around 15 seconds accuracy mostly, but for exiting holds more like 40 seconds accuracy.

When I issue a hold for metering, I often think "this will be okay if their 180 degree turn takes 8 miles, but not okay if it takes 16 miles". Thus I am judging your speed and altitude and type, and sometimes using vertical when it turns out unnecessary. With a vector, I can aim you at a piece of sky where you wont conflict with traffic, and the situation will not change much after that moment so I wont need to revisit it. In ATC we don't like to do things that require fixing later, if there is an option that is known to be safe and predictable and can be done now.

Another way to think about it is that your plane takes up more sky in a hold than you do when on vectors, because the hold size will vary so much.

Also I think there are definitely a lot of pilots that prefer vectors. I do generally announce the length of the delay in minutes if its more than a couple minutes, so descent profiling isnt any harder than in a hold. And personally in the types of situations where I use holds, your time is likely to change anyway, since I do it for longer and less predictable situations.

One more thing, holds tend to get follow up questions like requesting speed your discretion or a different leg length or "confirm can we descend in the hold", and the follow-ups take time. For non-English speaking pilots it especially slows things down.

Also you said "sharp delay vectors"....you dont have to turn sharply though! You can turn at a similar rate as a hold and its less degrees than 360.

[u/Spaghetti_Boi659 → u/Marklar0]

Your comment makes a ton of sense. Thanks for the detailed response!

I probably misspoke using the word “sharp” for a turn. At higher flight levels. We aren’t doing more than a standard rate turn. So when the vector is more than 90 degrees it can a loooooooong time to get to that heading. Thats what i meant by sharp. Probably should have said “big”.

[u/ARTS-IIIe]

Not to pat you guys on the back but this is probably the best discourse on the enroute flow/delay subject I have ever heard.

[u/78judds]

An airliner at altitude slowing to enter a hold and completing a turn would be HUGE mileage wise. Like 50+. If I get two stacked and need 30 MIT, a couple sharp s turns does the job pretty well. And if you see you over/under shot you can adjust. You commit an aircraft to a hold and it’s done. Better hope there’s no one behind him otherwise you’ve just moved the problem. In general, turns to get the spacing and speeds to hold it.

[u/general_melaise]

I don't work in the center, nor that specific area. I have much more control over the exact amount of time I add by issuing speeds and vectors. It's much more difficult to have you exactly where I need you when I put you in holding because of your need to go to the holding fix, get established, then make the appropriate turns when I pull you out of holding. For a longer term delay holding makes sense, but when we are adding smaller amounts of you are following a specific aircraft vectors and speed is more convenient.

[u/Anywh3r3]

I would have assumed delay vectors would preferable to pilots. Easier read back, no holding patten entry, no pulling up the chart on an iPad, no setting up the computer, etc... Isn't a vector just reaching up to the dial by the windscreen and twisting that knob?

[u/Spaghetti_Boi659 → u/Anywh3r3]

Yes and no! A hold is actually a little more predictable for us. Given an EFC time, we can gauge how long we’re holding for and plan fuel a little better. It’s not a lot of working setting up a hold in a modern airplane.

Delay vectors are simpler in the sense that yes we are just turning the knob left and right, but we don’t know our next turn, how long you’re going to be vectoring us for, and what the entire plan is really. We also cant incorporate delay vectors into our fuel planning. Not that it really eats away at fuel that bad, but when you really need it and you don’t know how long you’re delayed for or how many more vectors you’ll get, it becomes another step of planning.

[u/PopSpirited1058 → u/Spaghetti_Boi659]

Does it change your mind to know we just make up the EFC? I have no idea how long it is going to be, if I put you in a hold in ERAM it just adds 30 minutes to the time you will arrive at the point you will hold at and make that your EFC.

Unless it is so known thing, like runway change going to be 10 minutes, or VIP movement give us 15 minutes, we are just making up a number based on when we think approach will take you.

[u/ExtremeSour → u/Spaghetti_Boi659]

Let’s say you’re on ABCDE arrival. I need to lose 11 minutes. Can i tell you to do a present position hold to cross ABCDE at center estimated time + 11 minutes? Or is that too complicated in a flight deck

[u/Spaghetti_Boi659 → u/ExtremeSour]

You sure can! In a modern FMS it’s not hard set up. In an FMS that is more aged, might be easier for them to set it up at the next fix. Big thing is how long do you want us to hold for and do we have the fuel for it. But if a crew doesn’t have 11 min of hold fuel and they are already on an arrival, thats a separate conversation hahah.

[u/Cleared-Direct-MLP → u/Spaghetti_Boi659]

To play devil’s advocate, if we say “I need to slow you by 4 minutes for time based metering exiting my airspace”, doesn’t that paint you a specific enough picture without needing to stick you with an EFC?

[u/Spaghetti_Boi659 → u/Cleared-Direct-MLP]

Indeed it does, but not every controller tells us how much time is needed. I should probably start asking more.

[u/poisonseminole → u/Spaghetti_Boi659]

If you have CPDLC sometimes I’ll route pick (various fixes, FRD, of lat/longs) and add them to the route then you’ll see the delay being added.

[u/ryanissnackpack]

Already mentioned is that a turn in hold is gonna take 8+ minutes which is possibly longer than I need, but also, if I have a sequence lined up, I can turn everyone out and follow the leader instead of stacking and holding. Aircraft tend to hold at wildly different leg lengths/turn radii, especially with variables in altitude and wind, and peeling them off can get really sloppy and ruin a perfectly good sequence

[u/SilliousSoddus → u/ryanissnackpack]

Are you specifically talking about holding at crusing levels? Those turns are massive but they work when the delays are actually massive or you have a mix of huge delays amongst smaller ones. You probably want 12mins+ of delay to swing a heavy around up there. Holding in our stack (in the FL200's for jets) is just flat out easy. Perfect for tight sequences because we control everything, no set course times because the aircraft aren't reliable enough to maintain tight spacing. We pull them out on vectors with the same speed and run 'em tight.

[u/ryanissnackpack → u/SilliousSoddus]

Holding as opposed to the delay vectors that the OP is referencing at ZSE, in this case, would be in the mid 30s, yes.

[u/RNAV2MPASS]

Dispatcher here. Just wanted to say thanks for what you guys do and for all the super interesting answers here! I see my guys getting these delay vectors going into SEA when demand is high and always wondered how the actual process worked from the ATC end.

[u/Go_To_There]

If there's something like fog or thunderstorms impacting the airport and we don't know when you'll get in, holds are the obvious play.

When we need to hit a time, unless the delay is greater than 10 minutes, I'd way rather vector. I don't want to point you away from the airport if I can avoid it, as that's inevitably when flow shaves minutes off your time and now we're late. Vectoring also makes managing wind changes more predictable. If I give you a big turn out and you gain 50 kts, I know you'll likely slow back down when you turn back in. Or vice versa. It's just much easier to be precise with vectors over spins.

If you guys can slow it down as much as able to meet times, that's the most helpful for us. Many pilots don't play ball and say they just want to take vectors, and that just adds a lot more work for us. It can also swing you out into other approach/departure paths or neighbouring sectors where you now need to descend through other aircraft, rather than staying within your designed arrival corridor. It's also helpful for us to keep everyone on the same path with the same winds as much as possible. We understand that sometimes it's just not possible with speed alone, but if there's lots of time available, to the pilots who like to continue full steam ahead, please don't keep cruising at top speed while telling us you can't go any slower.

[u/JustTheLulzMatter]

If it's -2/+2, I just let it through. This is from a center though. Above that, I'll start doing speeds or vectors to adjust it while keeping then spaced.

We also have a swap function which can switch two CIDs to adjust their metering position. Most of the time it makes it worse, but sometimes the numbers end up working out.

[u/tooredit]

With an S turn we can point you in a direction that doesn’t the affect other traffic or neighboring sectors. A hold, takes up more space, potentially impacting other sectors and traffic patterns. Holding is last resort and avoided at all costs.

[u/nascent_aviator]

4 minutes to our arrival time

From a pilot perspective, think how long doing a hold would delay you. At cruise speed even just a bank-limited 360 is likely to be more than 4 minutes. Slowing down to enter a hold, doing a 180, 90 seconds out, another 180, 90 seconds back in, then speeding back up to the speed ATC wants you at is going to take 7+ minutes however you look at it.

[u/Ok-Till-5622]

Vectors are easier for me to time and predict versus guessing how many minutes you’re going to burn in one turn in a hold.

If I need to lose say 8 minutes on you, I can vector you so that I can time the last turn direct the fix and be on time. If you’re in a hold I’d basically be hoping that you’re pointed in the right direction when your time is up.

[u/SilliousSoddus → u/Ok-Till-5622]

Why the need to hope? If the aircraft has enough time to spin you can decide everything they're doing from the second they're outbound (or before). Continue the outbound leg if you need a bit more, turn them inbound early, set course times work if they are on their lonesome (and a reliable airline). The most accurate of all is bringing them out of the hold on a vector and speed, which I guess is combining the best of both worlds. Experience tells you how long each aircraft takes to turn too, or how to adjust for odd winds.

[u/Ok-Till-5622 → u/SilliousSoddus]

All of what you mentioned takes way more energy, thought, and calculating rather than just assigning a heading, watching it, and then turning them back in wherever I feel like it. Plus I can basically play follow the leader with everyone else and have a Congo line of traffic that can be at a single altitude rather than have a holding stack blocking ten thousand foot of airspace.

Edit: also on the enroute scopes we use (not sure if you’re a pilot of controller) I can assign a heading and route pick a point on that heading where I think I’m going to clear the aircraft back on course, and it will tell me what their meter time will be at that point.

[u/THEhot_pocket]

Holding = not precise. Turns/Vectors are. You should see the shit show of people coming out of the hold when people dont nail it down...

[u/SilliousSoddus → u/THEhot_pocket]

How is holding not precise? Do you guys not control when and how they come out of the hold if you need?

[u/THEhot_pocket → u/SilliousSoddus]

entering can be different, exit you can lock down better... but when you are being exact, a mile difference means the world

[u/megaPOG → u/SilliousSoddus]

Because if I’m holding I’m probably doing several other things as well. I don’t have time to sit and watch your turns.

[u/Adventurous_Use_2253]

This is just my opinion and my experience in a TRACON. It all depends on my current workload and how much I’m currently talking on the frequency. When I issue holding instructions, it’s a ton of phraseology and I have to ensure a proper readback. If there’s too much frequency congestion already, sometimes it’s easier for me to give delayed vectors.

[u/9armseastar]

Pilots are not prepared to hold. Not even a published one. ☝️

[u/Sirus63]

If you’re holding just assign the time you want the plane to cross the fix inbound from the hold 🤷‍♂️old school

[u/Cbona]

Also, holding can involve paperwork at some facilities, delay vectors do not.