Seychelles FIR - FSSS - RVSM Rule

SimBrief General
1

Hello,

I wanted to check if in the SimBrief dispatch system, the RVSM Semi-Circle rule for the Seychelles FIR/UIR is different than standard? I am looking at a couple of filed flight plans across the airspace on UM307 where the flights were stepped to an odd FL when entering FSSS and back to even when leaving FSSS whilst flying southwest bound. Can this be correct? Because my source material shows that FSSS has the standard East-West RVSM semi-circle rule.

Cheers,

Xander

2

Hi Xander,

Yes FSSS in general uses the standard East-West rule. But individual airways can also have their own rules that sometimes differ from the general FIR rule. These rules are normally contained in the AIP ENR section, but it seems I cannot find the Seychelles AIP freely available online.

In our source AIRAC data, however, the segment OTKIR UM307 NESAM (the portion of UM307 that crosses FSSS FIR) is specifically coded to use the RVSM-opposite rule. Which means odd altitudes for westbound flights. SimBrief is interpreting this correctly, so it isn’t a bug with SimBrief in any case.

Since the source data from Jeppesen has manually set this rule, I can only assume the official AIP also specifies odd levels when flying on UM307 westbound. But I can’t check this 100% with the real AIP unfortunately.

I also can’t say why Seychelles would use opposite levels for UM307, but I imagine they have a reason. It is actually quite common for airways to have custom cruise levels, so this is not particularly unusual in and of itself.

Best regards,

3

Oke, thanks. I’ll keep trying to find source material and/or IRL examples and post here. Thanks for that.

4

Here is an example of a current flight filed over UM307. Fortunately, FlightAware has the ATC route filing string. Notice it is currently Eastbound at an ODD flight level. The route string also does not have level changes to any even FL across its filed route.

I’m not saying the AIRAC is wrong. Only that this flight supports my findings that I cannot see any restrictions in LIDO CRAR or GEN or anywhere else.

CX748 (CPA748) Cathay Pacific Flight Tracking and History - FlightAware

5

I do not see the ATC route string in the link you sent. Can you send a screenshot of it?

In any case, normally FlightAware removes step climbs from their route strings. So the lack of a step climb isn’t really proof of anything when it comes to FlightAware unfortunately.

Best regards,

6

Untitled
Untitled1784×660 163 KB

Here it is. It also correlates to their last ADS-B FL of 390. In any case. It’s no big whoop. I was just curious and in no way a big issue.

Cheers,

7

Thanks, in that case, maybe the opposite levels for UM307 are indeed a mistake in the source data.

Normally when we report such issues, we need to be able to quote/provide the relevant AIP section to our provider. It’s unfortunate that we can’t find the Seychelles AIP online..

If you find anything in your searches let us know! I’ll keep looking as well.

Best regards,

8

I’ll see what I can find, and thanks for replying :wink: