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Posted: Thu Oct 12, 2017 9:30 am
by Peter Armstrong

I have had a couple of departures to join V4 and J20 recently. Just realised that these two departures conflict with the CHINS2 arrival at RADDY.

Is this a common occurrence in the real world? I thought that all departures were configured not to conflict with arrivals?

And, I understand that these two airways travel S/E via YKM and PDT – where they then diverge.


Re: STARs v SIDs

Posted: Thu Oct 12, 2017 2:49 pm
by Frank Miller
Not sure about real world, but the conflict doesn't seem likely to be an issue. CHINS2 arrivals need to be at or above 16,000 (if Sea is landing south), so the departures on V4 or J20 can be at 15,000 until they are past RADDY. If Sea is landing north, or the inbound is for KBFI, they need to be at 11,000 or 12,000, so the departure will be above them already. Props should be at 10,000, but an outbound prop can be at 9,000 on V4, so again, no conflict.

Seems to work ok to me!


Re: STARs v SIDs

Posted: Fri Oct 13, 2017 7:31 am
by Owen Catherwood
S46 works on the concept of 'Gates', where aircraft are either allowed to enter or exit the sector boundary; J20/V4 is an arrival gate.

In the real world this would be worked around by using SEA.V298.YKM, SEA.J90.MWH.DNJ, or SUMMA.BKE.DNJ to allow aircraft to reach their final cruising altitudes at a distance that arriving aircraft are either not descending yet or are still above FL180 in the case of the V4.

Re: STARs v SIDs

Posted: Fri Oct 13, 2017 9:03 am
by Peter Armstrong
Raddy is about 40nm from SEA and is outside the Tracon. Some of my A/C are at or above 16000 when departing the Tracon (arrival jets at or above 16000). And even if lower – say between 10000 – 16000, then they could still conflict with T/Props arriving at 10000, and BFI arrivals at 11000

Between 10000 – 16000

PROP – 10000
JET – (North) – 12000
(South) – not below 16000
BFI – 11000

This would be a sensible answer for Deps = SEA.V298(Bandr).YKM, SEA.J90 (Normy).MWH.DNJ, or SUMMA.BKE.DNJ

Re: STARs v SIDs

Posted: Sun Oct 15, 2017 3:33 am
by Peter Armstrong
Although in real terms, this scenario may never happen (thank God) but, my concern here is the theory behind such a design of routing being allowed. Over the past few years I have watched TV programmes which have highlighted Air Traffic incidences - even disasters. And, the one certain thing that has evolved after investigations, has been the improvement of the world of air travel, planes, piloting, techniques, procedures and air traffic control systems.

My point is this. We should not look at the alternatives just to get around the problem, we should face the problem - investigate it - and resolve it. I was under the distinct understanding that departure routes and arrival routes were designed NEVER to conflict - that's why they are designated departure and arrival routes. If that is not the case, then why not just call them ROUTES?

One of the most recent events shown on a TV programme was the collision in the 1950s of two aircraft over the Grand Canyon. About 175 persons killed in that accident. After extreme investigations it was revealed that everyone and everything was to blame. The pilots, the system, the planes and ATC. There was a type of IFR/VFR System in place called "look and avoid". Both A/C departed from KLAX and followed different departure routes ( within minutes of each other). One at 19000 and the other at 21000 (cruise alts). No Radar - something similar to cross the pond reporting fixes enroute. On those routes - both A/C planned to cross the same Fix - above the Grand Canyon - at different heights. However, during the flights one A/C captain decided to give his passengers some nice scenery to look at by making slight course corrections and the other Captain requested a climb from 19000 to 21000. This request was not approved. However, the Captain then requesedt to fly VFR on top. His request was granted, and guess what - he ended up on top at 21000 (the same level as the other plane) And you can guess what happened after that!!!

Anyway, my point is, air travel has evolved since then and is still evolving and no matter how miniscule a point is made about systems - or whatever - the attitude should be investigate and resolve, not accept and use alternatives, because one day, the alternative may not be utilised.