LSGG <—> LSZH incorrect flight levels

IIRC this was fixed many years ago. Appears broken again. Possibly related to airway-specific flight level rules.

LSGG/04 N0302F150 MOLU4N MOLUS N871 BERSU BERS2G LSZH/14 (odd level, should be even)
LSZH/28 N0301F140 VEBI4W VEBIT T50 ROTOS Z669 ULMES ULME1N LSGG/04 (even level, should be odd

.

Regards,

Tim

Hadn’t realized the old forum was still up as read-only, here are the relevant discussions from almost 10 (!!!) years ago :astonished:

https://www.simbrief.com/forum/viewtopic.php?f=5&t=766 (first post)
and
Automatic cruise altitude gives different value for B763 - SimBrief Support Forum (but, in my tests yesterday, automatic step climbs were enabled, so the second topic is not actually applicable and only provided as additional reference re: airway-specific flight level rules)

Regards,

Tim

Hi Tim,

According to the AIRAC data this is correct. I’m not sure why the real flight plans are showing differently.

The AIRAC data shows both the LSAS FIR and the N871 airway as using an East-West rule below FL200 and North-South rule at or above FL200, as follows:

Bearing Levels
360-179M 1000, 3000, 5000, 7000, 9000, 11000, 13000, 15000, 17000, 19000
180-359M 2000, 4000, 6000, 8000, 10000, 12000, 14000, 16000, 18000
270-089M 20000, 22000, 24000, 26000, 28000, 30000, 32000, 34000, 36000, etc.
090-269M 21000, 23000, 25000, 27000, 29000, 31000, 33000, 35000, 37000, etc.

This is more complex than most airspaces, so normally I’d be inclined to trust it. In any case, there is no bug in SimBrief. Only potentially a bug in the AIRAC data from our provider.

Unfortunately I can’t cross-reference with the Switzerland AIP since it seems to be behind a paywall, unless you have access or know of a way we can check the AIP (specifically the cruising levels for the N871 airway)?

Cheers,

I do not. Are you able to bisect when it changed? As per the forum topic from 2016, the restrictions matched the IRL flown levels back then:

https://www.simbrief.com/forum/viewtopic.php?p=2491&sid=15130aba6d2a800cfe95903fcdfddb6a#p2491

For what it’s worth, the SimBrief database does contain the proper restrictions (airways T50, Z669, and N871 all use a reverse flight level assignment, so westbound should be odd levels and eastbound should be even, max level F195).

Regards,

Tim

Looks like cycle 2111 (04 Nov 2021). Cycle 2110 had the old (reverse east/west) levels, cycles 2111 and later have the new split levels.

Best regards,

Thanks!

Annoying but without more tangible data there doesn’t seem like much can be done.

Regards,

Tim

Wait, isn’t that it (from autorouter, AIP Browser, Switzerland, EN, AIP, ENR)?

LS_ENR_3_3_en.pdf (311.2 KB)

As far as I can tell (very limited experience reading airway charts), document doesn’t appear to specify east/west and north/south rules, but rather, in which direction you’re taking the airway, for example:

UL613, going from HOC to NATLI, even levels, going from NATLI to HOC, odd levels

N871, one-way airway, even levels from MOLUS to DITON, odd levels from DITON to GAMSA

T50, one-way airway (and also one-leg as far as Swiss airspace is concerned), always flown on odd levels

Interestingly, there’s no difference in the level parity whether you are above or below FL195.

Regards,

Tim

That appears to match table 5.3 on LS_ENR_1_7_en, FWIW (but is contradicted, as far as some airways are concerned, by LS_ENR_3_3_en and actual real-world flights).

I’m guessing, possibly, airways where FLs both above and below 195 are authorized use the same north/south rule for all flight levels for practical/operational purposes?

Regards,

Tim

In many instances published levels available on airways differ from the E/W N/S rvsm rule at least within Europe.

I would take the ENR_1_7 data as correct.

I would too, except I haven’t found any plan on edi-gla that flies odd levels on N871 even below FL195.

Might be worth contacting SkyGuide for clarification perhaps.

Regards,

Tim