View Full Version : NAT Random Route

9th Oct 2018, 13:57
Two Questions on Random Routes

1. Is there any real benefit of flying offset since it's a random route?

2. In the event of an Emergency is there really any need to deviate from flight track by 15NM?

It seems to be that Random Routings basically nullify the need to do either of the above. But if anyone with more experience can shed some more light on the matter I would appreciate it.

9th Oct 2018, 14:59
1. I normally SLOP if it puts me closer to any desired alternate airport, or to get me out of any wake vortex from a preceding aircraft (admittedly rare).
OTOH, I would consider no SLOP if it puts me significantly closer to a published track.

2. Probably a good idea anyway but I take the point that the 15nm offset may put you closer to another random route. TCAS is your friend!

Bear in mind that some random routes are quite busy, as they may be published tracks which have only just expired, or consist partly of a published track with a random segment at some point.

9th Oct 2018, 15:18
Bear in mind that some random routes are quite busy, as they may be published tracks which have only just expired, or consist partly of a published track with a random segment at some point.

Very much agree. Iíve met vertically separated but opposite direction traffic on a random track (defined as such because the timings expired) as we approached Shannon FIR eastbound and encountered the start of the early westbound wave..Personally I SLOP on a random track unless I have a compelling reason not to do so.

9th Oct 2018, 17:38
1 usually I slop depending on known/tcas traffic and always when itís a just-expired track.

2 the 15nm offset for a contingency will be very important close to particular longitude or latitude points (like at multiples of 10 degrees or Fir changes). thatís where the probability of encountering anothef random track will be maximum.

9th Oct 2018, 18:47
Last month I followed a non company 787 the whole way across the Atlantic to Canada before he disappeared off our track. I figured afterwards that his company flight planning software might be trying to emulate what ours had done too... Hence a random route may be freely planned, but may follow similar paths to others as everybody tries to conserve fuel! So yes, I’d use the techniques in you question regardless...

9th Oct 2018, 20:26
We do use offsets on RNP procedures, for wake sep.

9th Oct 2018, 21:23
NATS OTS recommendation is that SLOP should be standard procedure and not just a wake considerations.

However random routes are just as likely to have a traffic flow, off course it could be that offsetting put you in a wake blown down wind, personally given just how accurate mordern systems are I can see a very compelling argument for always offsetting on any airway seeing a jet closing at 1500+ km/ph with no lateral offset can be a bit scary

10th Oct 2018, 10:43
Follow NATS OTS guidance, use SLOP.
An acute awareness if any published routes are in your proximity is the other requirement.

10th Oct 2018, 12:06
From SKYbrary (https://www.skybrary.aero/index.php/Strategic_Lateral_Offset):
NATS ... has been routinely collecting data on offsets on behalf of ICAO since 2005, and its most recent data showed that 60% of traffic at longitude 30 degrees West was on the track centreline, 30% was offset at 1nm and the remaining 10% was offset at 2nm.

So much for random selection of the offset value.

11th Oct 2018, 08:57
I agree, it is important to SLOP on random routes as well. They can also be quite busy and they’re probably being used in the opposite direction.

In my opinion SLOPS should be used on all Airways to reduce collisions/wake encounters. Our industry is being ridiculously slow in promoting a SLOP procedure worldwide. Let’s hope it doesn’t take another ‘midair’ before a change is made

11th Oct 2018, 17:34
Ok so how exactly does SLOP benefit?

1. With regard to wake turbulence, yes it is a big help.

2. With regard to avoiding potential collisions I simply don't see how this really plays out over the Atlantic. If you're on the OTS then opposite direction traffic simply isn't a factor. As for random routes they are chosen to take advantage of or to minimize effect of wind. Therefore flying the same route in the opposite direction is the worst possible choice.

I feel SLOP would be far more advantageous on traditional bidirectional airways. But then again how many times have planes collided head on on the same airway?

Ian W
11th Oct 2018, 18:03
If aircraft are truly flying their business trajectory developed entirely for their particular weight and cost index against the weather winds and temperatures to make a particular approach time, it is extremely unlikely that they will be closely following another aircraft in the way they can in the current North Atlantic organized Ocean Track Structure. SLOP has just as much chance of putting you behind another aircraft as flying your business trajectory. It is expected that there will be possibly significant dispersion of ocean tracks add in the use of ADS-B (possibly satellite sensed by the controllers) and the unstructured 'free routing' of the FABs will continue out over the oceanic airspace at least the European and Canadian controlled airspace possibly with almost en-route levels of separation.

With everyone 'following the favorable winds' there will not be opposite direction traffic, there could be crossing traffic but that will be separated by its trajectory from your trajectory. Sitting in the continual chop from an aircraft ahead will no longer be an issue. Emergency descents similarly should just be straight ahead as offsetting is as likely to find another 'user preferred trajectory' below you. TCAS, CDTI and controllers with ADS-B surveillance will become important in cases like that..

11th Oct 2018, 19:33
On your 2nd point, I have passed opposite direction traffic many times on random tracks.
On your 3rd point quote “how many times have planes collided head on on the same airway?” I think there have already been 2......Learjet/B737 over Brazil, also B737/HS125 over Senegal. If we don’t do something now it’s only a matter of time before hundreds more die needlessly.

We now have GPS and RVSM, these have both conspired to increase the risk of collisions. You won’t find me on any busy centreline.

11th Oct 2018, 20:01
The solution is simple. Everyone offset 1 mile right of track. Everywhere in the world, all the time. Use airway centerline's as just that, centerline's.

Una Due Tfc
11th Oct 2018, 20:04
Itís also to protect you from an aircraft above or below you busting your level.

12th Oct 2018, 07:11
I have passed opposite direction traffic many times on random tracks.

Likewise, most frequently on a time expired eastbound track as you approach the Shanwick/Shannon boundary