Speed versus Visual Separation

derg

derg

Apparently a "terse" writer
Staff member
Rolling into DTW this afternoon, got cleared for the visual, maintain 170 until a 5 mile final.

We did just that.

The traffic behind us was instructed to maintain visual separation from us, 170 until a 5 mile final.

We're on short final and tower tells our following traffic that he has a 40 knot closure on us and they start bitching about how they were instructed to maintain 170 until 5 miles and tower shouldn't be barking at him about the closure rate.

My understanding if it's 170 to the marker, but maintain visual separation from the traffic fly 170 knots until either (a) the 5 mile point as directed or slow to maintain "safe" spacing from the traffic you're following.

Was this another "Captain Happy" moment or am I out to lunch?
 
Derg said:
Rolling into DTW this afternoon, got cleared for the visual, maintain 170 until a 5 mile final.

We did just that.

The traffic behind us was instructed to maintain visual separation from us, 170 until a 5 mile final.

We're on short final and tower tells our following traffic that he has a 40 knot closure on us and they start bitching about how they were instructed to maintain 170 until 5 miles and tower shouldn't be barking at him about the closure rate.

My understanding if it's 170 to the marker, but maintain visual separation from the traffic fly 170 knots until either (a) the 5 mile point as directed or slow to maintain "safe" spacing from the traffic you're following.

Was this another "Captain Happy" moment or am I out to lunch?
Click to expand...

yes.
 
Well first off the pilot shouldn't have been told to maintain visual separation, but instead to follow the traffic, cleared visual approach.

Secondly, if you're told 170 (ATL uses 180 for some idiotic reason that 17 years there still hasn't been a reasonable explanation given to me) then you fly 170 to the marker. The controller has, presumably, spaced you adequately so when the first aircraft slows the 3 or so miles will compress down to 2 or so, but give aircraft 1 time to exit the runway prior to #2's arrival. As always I recommend asking prior to just slowing on your own, that's when problems happen. Just yesterday I had to pull a trailing aircraft off of the final because the pilot of the leading aircraft thought 180 to the marker meant that at 8 DME he should/could slow to 150 without a word. This wasn't you Derg was it? ;)

Lastly, what did the tower controller expect to happen when acft 1 hits the marker and slows to final. Of course there's going to be an overtake. It always surprised me that this logic is lost. Certain Center controllers seem to miss this when they run 7 in trail, the lead is a B763, both doing 310 to the 40dme but then need to be at 250kts. Once the first one hits the 40 he's at 250kts and #2 is still doing 310:bang: with a massive wake overtake.
 
It's all in the presentation and wording by a local controller. You can sit on monitor all day and tell the difference between a quality local and a poor one based on what they say to pilots inside the TCP and on initial checkin.
 
Just wondering how the controller sounded, ive given plenty of " you have 60 knots on the traffic" call when running visuals with no speeds just to give the pilot a little more info. i could care less if they slow or not as long as he has the traffic in sight, but if you want to run up someones ass and get a go around be my guest !
 
queeno said:
Just wondering how the controller sounded, ive given plenty of " you have 60 knots on the traffic" call when running visuals with no speeds just to give the pilot a little more info. i could care less if they slow or not as long as he has the traffic in sight, but if you want to run up someones ass and get a go around be my guest !
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In my little time as a approach fella, I've already discovered this is how i run visuals and it works for me. I've never had a pilot push back, they are always "thanks for the info, going to tower"

I've been pushing myself to get the tower to ask for more space to get departures out. Keeps my trainer happy.
 
A80TRACON said:
Certain Center controllers seem to miss this when they run 7 in trail, the lead is a B763, both doing 310 to the 40dme but then need to be at 250kts. Once the first one hits the 40 he's at 250kts and #2 is still doing 310:bang: with a massive wake overtake.
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Hey as long as they're 7 at the boundary we're good right? But honestly I watch this on a daily basis and shake my head when they ask what approach is angry about. On the flip side some people don't know how to let physics work and overreact to groundspeed readouts that are well behind what the airplane is actually doing. If they're tight and still showing an overtake ill usually just confirm they've reached their speed before I switch them.
 
queeno said:
Just wondering how the controller sounded, ive given plenty of " you have 60 knots on the traffic" call when running visuals with no speeds just to give the pilot a little more info. i could care less if they slow or not as long as he has the traffic in sight, but if you want to run up someones ass and get a go around be my guest !
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"See that airplane? Don't hit him, and let him clear the runway."

"Roger, slowing to final approach speed."
 
Ozelot said:
In my little time as a approach fella, I've already discovered this is how i run visuals and it works for me. I've never had a pilot push back, they are always "thanks for the info, going to tower"

I've been pushing myself to get the tower to ask for more space to get departures out. Keeps my trainer happy.
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If tower ain't cryin', you ain't tryin'.

That's what I tell my trainees, at least.
 
Although not a factor in Derg's situation, one problem I've seen is the controller makes the assumption that you'll start to slow down after maintaining "170 to the marker".

If assigned, we regularly hold 170 to the marker, then speed up so we can get it to the ground quicker. Not at the cost of ramming up another plane's back end but we'll do it if the space is available.
 
dustoff17 said:
If assigned, we regularly hold 170 to the marker, then speed up so we can get it to the ground quicker. Not at the cost of ramming up another plane's back end but we'll do it if the space is available.
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I guess I've been doing it wrong all these years because I've never done that! :)

I'm assuming you have "stabilized approach criteria" at 1000 AFE?
 
Derg said:
I guess I've been doing it wrong all these years because I've never done that! :)

I'm assuming you have "stabilized approach criteria" at 1000 AFE?
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We meet the stabilized criteria but we bump the speed up after the marker until we have to stabilize.
AND we're part 91
 
dustoff17 said:
We meet the stabilized criteria but we bump the speed up after the marker until we have to stabilize.
AND we're part 91
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If typical FAF is at 5 miles, and you claim to be stabilized by 1000', which by my calculations is approximately 3nm to the 1000' markers, given a 3° glide path, I'm curious as to what advantages you gain from this?
 
dustoff17 said:
Although not a factor in Derg's situation, one problem I've seen is the controller makes the assumption that you'll start to slow down after maintaining "170 to the marker".

If assigned, we regularly hold 170 to the marker, then speed up so we can get it to the ground quicker. Not at the cost of ramming up another plane's back end but we'll do it if the space is available.
Click to expand...
What type of airplane?
 
dustoff17 said:
We meet the stabilized criteria but we bump the speed up after the marker until we have to stabilize.
AND we're part 91
Click to expand...

1303008086154.jpg


(I still can't wrap my head around the risk/reward of speeding up between the marker and 1000' AGL)
 
Derg said:
(I still can't wrap my head around the risk/reward of speeding up between the marker and 1000' AGL)
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Even using VMC criteria of 500' it just doesn't make sense. If you guys ( @dustoff17 ) have a safety officer or safety director I think you might wanna go have a chat with him/her about this practice. Seems to be the classic "At Risk Behavior."

If you're flying with a captain who is doing this I'd have the same conversation with him/her as to why this practice is the "norm" and evaluate why you guys do this and the risks involved versus any perceived reward. I think you would find that most of your peers will look at this practice like this: o_O:ooh:o_O:confused2:
 
dustoff17 said:
We meet the stabilized criteria but we bump the speed up after the marker until we have to stabilize.
AND we're part 91
Click to expand...

I mean.... Even when we're doing our job well as ATC, how are we supposed to account for that? It's sort of like saying "Well, a lot of the time the Earth will revolve around the Sun. But, OCCASIONALLY you'll see it happen the other way around."

Call me ahead of time and remind me not to put you close to anyone else please.

What space are you looking for exactly? Tell me exactly what mileage you consider optimal.

If there's a shear layer and ground speed increases at lower altitudes, then shame-on-me for not making the spacing work because I should have noticed that (at least after the first sequence of the day). But, to hear that pilots will take "Maintain 170 knots to the final approach fix" to mean: "go ahead and speed up after that, obviously, we don't much care for legal separation," kinda blows my mind.
 
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I've seen it happen on occasion, never really been an issue though if someone speeds up after they pass the FAF for me. If they're compressing on final, it's just a quick transmission to tell the plane to start slowing to approach speed. It's almost always turboprops when I see it happen, 1900s, 99s, some King Airs, Cheyennes, and the occasional smaller Falcon jets.
 
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