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Old 03-06-2021, 10:26 AM   #1  
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Default Descend via mach number until intrcptng 280

I get nothing but conflicting viewpoints on this one...
Look at the KLYNK arrival into DTW... (https://www.airnav.com/airport/KDTW)

Reference the 'descend via mach until 280' note...

Let's say you are just about to pass KOZAR and you are at fl240 indicating 300kts (your cruise speed).

My opinion is that you slow to 280 before passing KOZAR.. Some people agree with me, others say "we aren't descending yet and we don't have a published speed until EEEZI." Either way my viewpoint is more conservative. I know the intent of the note is to intercept 280 from the mach number when you were at a higher cruise altitude and descending.. But what about this scenario when you are starting out lower and faster (indicated)? Also would like to see a reference to a rule or guidance in writing if you have a strong opinion.

Cheers
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Old 03-06-2021, 10:33 AM   #2  
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Quote:
Originally Posted by ClearPr0p View Post
I get nothing but conflicting viewpoints on this one...
Look at the KLYNK arrival into DTW... (https://www.airnav.com/airport/KDTW)

Reference the 'descend via mach until 280' note...

Let's say you are just about to pass KOZAR and you are at fl240 indicating 300kts (your cruise speed).

My opinion is that you slow to 280 before passing KOZAR.. Some people agree with me, others say "we aren't descending yet and we don't have a published speed until EEEZI." Either way my viewpoint is more conservative. I know the intent of the note is to intercept 280 from the mach number when you were at a higher cruise altitude and descending.. But what about this scenario when you are starting out lower and faster (indicated)? Also would like to see a reference to a rule or guidance in writing if you have a strong opinion.

Cheers
If Iím on a published segment of the arrival Iím at 280 if Iím low, the way I look at it, 300 vs 280 doesnít save or ďmake upĒ time thatís garbage. So Iíd slow to 280 but legally I guess as long as you at 280 by the waypoint your ok.
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Old 03-06-2021, 10:35 AM   #3  
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Pretty obvious to me that the intent is that once on any part of the arrival (inside KOZAR or JAMOX) you're EITHER doing 280 OR descending at mach to transition to 280 when you get there.

If the guy ahead of you is higher and descending he will slow to 280 but you get to keep cruising along level at 300 until you catch him? Makes no sense.

The AIM might reinforce that.
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Old 03-06-2021, 10:39 AM   #4  
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Originally Posted by rickair7777 View Post
Pretty obvious to me that the intent is that once on any part of the arrival (inside KOZAR or JAMOX) you're EITHER doing 280 OR descending at mach to transition to 280 when you get there.

If the guy ahead of you is higher and descending he will slow to 280 but you get to keep cruising along level at 300 until you catch him? Makes no sense.

The AIM might reinforce that.
I agree.. but I've even had check airmen question why am I slowing down..
Would be nice to show people this in writing...
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Old 03-06-2021, 12:57 PM   #5  
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Quote:
Originally Posted by ClearPr0p View Post
I agree.. but I've even had check airmen question why am I slowing down..
Would be nice to show people this in writing...
I agree your viewpoint is conservative, but the way the AIM reads(4-4-12), it says you comply with the altitudes/speeds after you get a “descend via” clearance. I’m with you though; I’ve always started complying at the first point on the arrival.
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Old 03-06-2021, 04:27 PM   #6  
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I don't think this is necessarily a descend via clearance. They just want you to maintain current Mach till that Mach number exceeds 280 while you are descending. ATC figures you will transition from Mach to airspeed around FL 240. In the OP's example 300 knots is some Mach number so I would maintain current speed at KOZAR. The bottom altitude at EEEZI is FL 240 so there's no descent involved but there is a hard 280 knots at EEEZI so start slowing a few miles prior.
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Old 03-06-2021, 04:54 PM   #7  
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A good rule of thumb is FL310 = .76 / 280 KIAS crossover occurs.
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Old 03-06-2021, 05:32 PM   #8  
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Looking at one of the climb via/descend via publications on faasafety, the altitudes and speeds on an arrival are separate. You are required to comply with the speeds, unless told otherwise. You are to comply with the altitudes once directed, I.e. descend via.
If you are assigned a star that has “descend via until intercepting ___knots,” then once you are on a published portion of the arrival you comply with all speeds unless you are told otherwise even if you aren’t “descending via” yet. This includes if you are subsequently vectored off the arrival. Continue with the speed as published or assigned. Same applies if you are given descend and maintain.
Once you are given descend via the you comply with speeds AND altitudes until told otherwise.

On a related but separate subject, if the arrival only has “expected” altitudes you SHALL NOT be given a descend via. However, a lot of those arrivals have published speeds that do not include “expect”. Those are hard speeds and must be complied with unless otherwise instructed.

https://www.faasafety.gov/files/noti...1-20140220.pdf
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Old 03-06-2021, 08:59 PM   #9  
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Always comply with published speeds, whether youíre climbing, descending or straight and level. Unless ATC states otherwise.

In the above scenario the 280kts would only expected after youíve begun descent from cruise and transitioned.
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Old 03-06-2021, 10:11 PM   #10  
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Quote:
Originally Posted by ClearPr0p View Post
Let's say you are just about to pass KOZAR and you are at fl240 indicating 300kts (your cruise speed).
The first published speed restriction on the arrival occurs at EEEZI. 280 knots. If descending via mach number, upon airspeed reaching 280 in the descent, then the restriction is 280 at that point. Otherwise, the restriction of 280 knots begins at EEEZI. Exactly as the chart states.

If you are already at FL240, you are not flying a mach number. You are flying an airspeed. There is not a 280 knot restriction at KOZAR; were there one, it would be shown on the chart. It is not.

ATC can assign speeds or modify speeds at any point, via clearance. If you are cruising 300 knots to KOZAR at FL240 and have not received a speed restriction from ATC, your first speed restriction as published occurs at EEEZI.

The altitude range as published at EEEZI is FL240-FL270. For aircraft descending to EEEZI, the transition to 280 knots takes place from mach in the descent. Because nothing else is published prior to EEEZI, the reduction to 280 knots begins at EEEZI for aircraft not descending via mach number, because that's what's published. If the procedure were to slow to 280 knots at KOZAR, the procedure would reflect that, but it does not.

In either case, aircraft descending, or aircraft in cruise, will arrive at EEEZI at 280 knots and maintain that until BONZZ (260 knots), KLYNK (10,000'/250 knots), and BRDER (210 knots).
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