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Descend via mach number until intrcptng 280

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Descend via mach number until intrcptng 280

Old 03-07-2021, 10:13 AM
  #11  
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From a controller friend of mine.
The expectation is if cleared for the STAR (not to descend via, just lateral) and then told to “descend and maintain” an altitude where in the descent you’d intercept 280k then that’s what they expect you to do unless other instructions have been received. No matter where you are on the route, even outside of KOZAR. At a minimum the speed note applies to the entire STAR.

Makes since since the speeds and altitudes are separate parts of the procedure, speed is ultimately more important for separation.

Personally, I just verify if they want us to slow as published or just to make the first fix restriction.

If anyone finds a legal interpretation that contradicts this, let me know.
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Old 03-07-2021, 01:51 PM
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That's a given, and not in question, though the speed restriction does NOT apply outside the STAR and a flight is NOT expected to maintain 270 outside the STAR, unless specifically cleared to do so.

That is not the question, however.

The question regards a flight at the initial fix (KOZAR( listed on the STAR, at FL240, at 300 knots. If the cruise altitude is 300 knots and the airplane arrives at the STAR at 300 knots, the first fix showing a speed restriction is not KOZAR, but EEEZI.

If ATC intends that the flight maintain 280 knots prior to that point, specifically in this case the aircraft arriving at KOZAR in cruise at 300 knots, then ATC will need to include that speed restriction in the clearance, because it's not found on the chart.

A wise pilot will still ask if it's needed.
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Old 03-07-2021, 03:01 PM
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Originally Posted by JohnBurke View Post
That's a given, and not in question, though the speed restriction does NOT apply outside the STAR and a flight is NOT expected to maintain 270 outside the STAR, unless specifically cleared to do so.

That is not the question, however.

The question regards a flight at the initial fix (KOZAR( listed on the STAR, at FL240, at 300 knots. If the cruise altitude is 300 knots and the airplane arrives at the STAR at 300 knots, the first fix showing a speed restriction is not KOZAR, but EEEZI.

If ATC intends that the flight maintain 280 knots prior to that point, specifically in this case the aircraft arriving at KOZAR in cruise at 300 knots, then ATC will need to include that speed restriction in the clearance, because it's not found on the chart.

A wise pilot will still ask if it's needed.
That situation is exactly what I was trying to answer, by asking a controller what they were taught to expect. And I passed along what he said.
Here’s another caveat. What if you are given, from FL450, a “descend via” clearance, and your 3 degree descent has you intercepting 280kts outside of KOZAR? What then? It may never happen due to design, but I haven’t delved into the TERPS to find out yet.

I know how the FAA describes speeds, but the OPs specific question isn’t published anywhere I have been able to find yet. If anyone has a reference to this specific explanation, I’d love to read it.
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Old 03-07-2021, 08:32 PM
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Originally Posted by EMAW View Post
Here’s another caveat. What if you are given, from FL450, a “descend via” clearance, and your 3 degree descent has you intercepting 280kts outside of KOZAR? What then? It may never happen due to design, but I haven’t delved into the TERPS to find out yet.
If I'm filed/cleared KLYNK 3...I'm going to program my FMS with a transition decent speed of 280 kts (probably while setting up for the approach during cruise) regardless of what FL I'm cruising at. On the arrival descent (either descend via or descend and maintain) I'll just let the FMS lock onto the transition speed of 280 without concern for where we are over the ground. Just looking at the STAR quickly though, it looks like you'd be well inside of Kozar. Hopefully I understood your question correctly? Also - everything Burke wrote is spot on as far as I can tell.

One other thing - above you talk about speed being more important than altitude....I'd go the other way particularly if I'm going to have to break one, I'll chose to bust the speed
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Old 03-08-2021, 02:40 AM
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Originally Posted by Gordie H View Post
If I'm filed/cleared KLYNK 3...I'm going to program my FMS with a transition decent speed of 280 kts (probably while setting up for the approach during cruise) regardless of what FL I'm cruising at. On the arrival descent (either descend via or descend and maintain) I'll just let the FMS lock onto the transition speed of 280 without concern for where we are over the ground. Just looking at the STAR quickly though, it looks like you'd be well inside of Kozar. Hopefully I understood your question correctly? Also - everything Burke wrote is spot on as far as I can tell.

One other thing - above you talk about speed being more important than altitude....I'd go the other way particularly if I'm going to have to break one, I'll chose to bust the speed
I agree with you on programming the FMS. But the original question was what if you are given an early descent, well outside of the arrival? Do you transition to 280 when you intercept it? Once you are on the arrival? Or by the first fix with a restriction? I have yet to have them leave me above where I transition to 280 until getting on the arrival.

Just thought of something else. Going along with what you said you would normally be on the STAR descending if on the optimized profile descent, and you wouldn’t be able to maintain 280 at the top of descent. My theory is that that is why the first fix, in this case KOZAR isn’t speed restricted, even though it really is via a floating restriction.
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Old 03-08-2021, 05:41 AM
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I think the proper answer to that clearance would be "I am currently indicating 300 KIAS, what speed would you like now?"

Joe
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Old 03-08-2021, 06:41 AM
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Originally Posted by joepilot View Post
I think the proper answer to that clearance would be "I am currently indicating 300 KIAS, what speed would you like now?"

Joe
I hear you on that.. But I'm looking for the technical / book answer to this scenario. Is that note considered a speed restriction once you hit a published segment?
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Old 03-08-2021, 08:30 AM
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Originally Posted by EMAW View Post
I agree with you on programming the FMS. But the original question was what if you are given an early descent, well outside of the arrival? Do you transition to 280 when you intercept it? Once you are on the arrival? Or by the first fix with a restriction? I have yet to have them leave me above where I transition to 280 until getting on the arrival.

Just thought of something else. Going along with what you said you would normally be on the STAR descending if on the optimized profile descent, and you wouldn’t be able to maintain 280 at the top of descent. My theory is that that is why the first fix, in this case KOZAR isn’t speed restricted, even though it really is via a floating restriction.
​​​​​​So lets say you're a 1000 miles out and given a descent to FL200 because it's the only smooth ride. I wouldn't be concerned at all about the transition airspeed / STAR at this point. So you get down to FL200 and decide to go 310. Unless told otherwise by atc, you can hold that 310 inside of Kozar and then slow to 280 for EEZI, is how i read it... but because this is unusual I'm probably going to ask what speed they want (as I'm approaching Kozar).

Re your second paragraph - yes / agreed, the intention of the note is to restrict your speed a bit.
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Old 03-08-2021, 11:36 AM
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Originally Posted by EMAW View Post
But the original question was what if you are given an early descent, well outside of the arrival?
The original question doesn't ask that.

In fact, the original question states that the example aircraft is arriving in cruise at 300 knots, and has not yet begun a descent.

The first published speed restriction is at EEEZI.

Again, the wise pilot will query ATC, and in fact, if any question exists, is required to query ATC.

If ATC desires a speed restriction prior to EEEZI, ATC is responsible to issue that restriction. In lieu of an ATC clearance to the contrary, the pilot is not responsible for a speed reduction prior to EEEZI.
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Old 03-08-2021, 01:38 PM
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Originally Posted by JohnBurke View Post
The original question doesn't ask that.

In fact, the original question states that the example aircraft is arriving in cruise at 300 knots, and has not yet begun a descent.

The first published speed restriction is at EEEZI.

Again, the wise pilot will query ATC, and in fact, if any question exists, is required to query ATC.

If ATC desires a speed restriction prior to EEEZI, ATC is responsible to issue that restriction. In lieu of an ATC clearance to the contrary, the pilot is not responsible for a speed reduction prior to EEEZI.
OK. So I assumed and early descent because it’s happened to me before that way. Either way the question and answer is the same, whether you were cruising lower at 300 kts or given “descend and mantain” a lower altitude earlier that would allow you to maintain 300 KTS. My situation has happened twice to me going into LAX and I have always just queried ATC on specifically what they want or expect in the particular setting.
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