Lateral Offsets (SLOP)
 

ICAO Doc 4444; §16.5.3
Almost everywhere in the world where SLOP is authorized, this seems to be the case where it is talked about in the respective AIP (or the Jeppesen Airway Manuals). Now, I know from experience that SLOP is permissible in the Pacific on the NOPAC and PACOTS routes, but I can’t find a single official source that states SLOP is permissible in Japanese oceanic airspace. Not in any Jeppesen document, not in the Japanese AIP…

Is there a circular I’m missing or something else I’m completely missing? Someone asked me how do you know where you can apply SLOP, and just giving a blanket statement of “non-radar, remote or oceanic airspace” isn’t always true. There has to be guidance and I’m not finding any. Any help?

Thanks

No help but just a comment; In the days before improved IRSs with GPS; aircraft were "scattered" either side of oceanic airways, owing to poorer navigational accuracy - resulting in random lateral offsets. It is the improved accuracy and reliability of laser ring gyro IRSs coupled with GPS that makes track keeping so much more accurate and therefore SLOP sometimes desirable.

If you unofficially applied SLOP of just 1 or 2 nm over the Ocean, who is going to either notice or care? (as long as you remember to cancel the SLOP after the crossing).

I found this from Japan's country RAR's in Lido:

3.94.7.3. Strategic Lateral Offset Procedure (SLOP)SLOP shall only be applied in the oceanic control area over the Pacific Ocean within the Fukuoka FIR.

For one, ATC will be aware you are offset !

This. Surveillance is much more accurate now and they see everything.

If you’re only a tenth of a mile or a few tenths right, how would they know you’re doing SLOP or maybe you’re just … sloppy?

I had to say it.

ATC will notice and will certainly care. If in surveillance coverage, e.g. ADS-B, ATC will see you off track on their screens and challenge you. Even out of surveillance, the periodic automatically downlinked ADS-C position reports (which will report the aircraft is somewhere other than its filed/cleared route) will generate route conformance warnings to ATC, who again will challenge what you are doing. Being off route can stuff up lateral separation very quickly, given the larger lateral tolerances applied to tracks in oceanic airspace.

Regarding improved navigational accuracy - true. This has flowed through to non-surveillance ATC separation standards so that reduced tolerances can be applied to suitably equipped aircraft with commensurately qualified crew.

Got pounced on by ATC in the middle of Australia once for deviating half a mile right of the centreline to avoid a CB without permission!

Yes correct, because, although there is not much there, that is not oceanic. You're under radar control CTA. Aussie AIP ENR 3 refers.
Once in Oceanic Control Area, slop away, up to 2 miles right.

Ah yes, "ATC in the middle of Australia", part of the second best ATC system in the world.

But if you're in the middle of nowhere over the ocean - as I specified. That was my point.

I'm not defending AirServices, but if I deviated half a mile right of route over Germany, Lyon or Stanstead without clearance, I'd expect I'd be pounced on.

Flying between NZAA-RKSI a small deviation ( less than one mile) around a developing CB near Noumea had Brisbane ATC send a CPDLC message, "Report back on track", Big brother is watching you!

Likely because China often assigns a SLOP, so they accommodate incoming traffic from China. Once I had China assign me a 30 mi offset!

Along with a lot of other aircraft in the same middle. You can't just go rogue and help yourself to manoeuvring off your cleared route in Class A type airspace. That's consciously and deliberately taking away one of those layers of risk management for you and impacting all the others.

Think of it more as ATC doing their job and looking after you. If an off-route deviation developed into something serious (for whatever reason) and ATC did not query it, the subsequent investigation report would (quite rightly) castigate ATC for detecting something unusual and doing nothing about it. In the particular example you mention, the big brother was probably your own aircraft - it likely dobbed you in when it automatically downlinked the periodic ADS-C position report showing you off route, which in turn triggers an alert generated by the ATC equipment to the controller.

Yeah, and that's basically the kind of reference I'm looking for Japanese Oceanic Airspace. :(

I'm not familiar with Lido? What is that?

Point taken but I don't think flying in the congested airspace over Europe can be compared with crossing the GAFA on an airway 8 miles wide and no other aircraft with a thousand miles of you.