Flight level (even/odd) change from LIRR to LIBB

LIRF OKUNO ATRUP VAPUP LDSP

Simbrief plans an even level until ATRUP then switches to an odd level despite the same direction of flight on OKUNO → VATRUP and VATRUP → VAPUP. That’s regardless of the takeoff runway and selected departure procedure, as far as I can tell.

When you plan a low-level flight (OKUNO L5 VAPUP) an odd flight level is used throughout.

I am not sure which ENR document or other chart specifies the Flight Level Orientation System for the UIRs in question but I am confused as to why it would differ between LIRR and LIBB given they are both in Italy?

Flight level selection is also a bit confusing if I mix and match airways and directs:

LIRF/16L N0317F190 OKU5R OKUNO L5 ATRUP/N0315F180 DCT VAPUP VAPU1Y LDSP/23
LIRF/16L N0317F190 OKU5R OKUNO L5 SUTOB/N0315F180 DCT VAPUP VAPU1Y LDSP/23
but
LIRF/16L N0317F190 OKU5R OKUNO L5 VAPUP DCT SPL SPL2B LDSP/23
LIRF/16L N0317F190 OKU5R OKUNO L5 TINIX/N0315F180 DCT ATRUP/N0311F170 L5 VAPUP VAPU1Y LDSP/23

Regards,

Tim

Hi Tim, specific airways can have their own altitude rules that differ from the containing FIR.

As far as I can tell, eastbound traffic on L5 between OKUNO and VAPUP must use odd altitudes. However the LIRR and LIBB FIR use a north-south rule which results in the opposite structure (northbound flights should be even).

So if you alternate between the airway and DCT, it’ll switch from odd to even altitudes each time you do so.

Best regards,

The airway tests at the end was merely my experimenting, I guess it detracted from the main issue:

Then on the direct route, why does it switch to odd levels when reaching LIBB at ATRUP instead of staying even throughout?

LIRF/25 N0403F340 OKU6A OKUNO DCT ATRUP/N0398F330 DCT VAPUP VAPU1Y LDSP/23

Regards,

Tim

Right, sorry got distracted with the airway stuff.

I think I’ve tracked down the issue, should be fixed now.

Best regards,

Now I get:

LIRF/25 N0408F350 OKU6A OKUNO DCT ATRUP/N0404F340 DCT VAPUP VAPU1Y LDSP/23

…shouldn’t it be even to start with?

Regards,

Tim

Actually I don’t get the odd/even change if I e.g. set a specific ZFW, it doesn’t make much sense :confused:

https://dispatch.simbrief.com/options/custom?airline=&fltnum=&orig=LIRF&dest=LDSP&altn=LDZA&date=27%20Jan%202025%20-%2002%3A45&basetype=A319&ac_order=registration&type=16458_1724110720469&climb=250%2F300%2F78&cruisemode=CI&cruisesub=0&descent=78%2F300%2F250&fuelfactor=1&callsign=&reg=3A-MAA&fin=789&selcal=&planformat=ber&pounds=0&maps=0.5&taxiout=20&taxiin=10&flightrules=i&flighttype=s&altncount=1&navlog=1&etops=1&stepclimbs=1&tlr=0&notams=0&firnot=0&stehour=3600&stemin=600&origrwy=25&destrwy=23&fl=&pax=0&cargo=&manualpayload=&manualzfw=&contpct=0.03%2F5&resvrule=auto&taxifuel=0.2&minfob=0&minfob_units=wgt&minfod=0&minfod_units=wgt&melfuel=&melfuel_units=min&atcfuel=&atcfuel_units=min&wxxfuel=&wxxfuel_units=min&addedfuel_label=extra&addedfuel=&addedfuel_units=min&tankering=&tankering_units=min&pid=16458&cpt=Tim%20W&fo=C%20SULLENBERGER&dxname=TIM%20W&manualrmk=&route=OKU6A%20OKUNO%20ATRUP%20VAPUP%20VAPU1Y&route_type=&targetfl=28000&targettas=466&disable_tracks=1&force_track=&avoid_airways=&include_fixes=&altnsadv_number=1&altnsadv_radius=150&altnsadv_cig=600&altnsadv_units_vis=m&altnsadv_vis=3000&altnsadv_units_rwy=m&altnsadv_rwy=1600&altnsadv_exclude=&altnsadv_tsfgfz=1&altn_1_id=LDZA&altn_1_rwy=22&altn_1_fl=&altn_1_route=SIRM1V%20SIRMI%20M725%20RUDIK%20RUDI2Y&altn_2_id=&altn_2_rwy=auto&altn_2_fl=&altn_2_route=&altn_3_id=&altn_3_rwy=auto&altn_3_fl=&altn_3_route=&altn_4_id=&altn_4_rwy=auto&altn_4_fl=&altn_4_route=&toaltn_id=&eualtn_id=&etopsthreshold=60&etopsruleselector=&etops_exclude=&etopsentry=&etopsexit=&etopsaltn1=&etopsaltn2=&etopsaltn3=&etopsaltn4=&etopsaltn5=&etopsaltn6=&asp4_snapshot=disabled&debug_zerowind=0&static_id=&manual_acdata=


vs


https://dispatch.simbrief.com/options/custom?airline=&fltnum=&orig=LIRF&dest=LDSP&altn=LDZA&date=27%20Jan%202025%20-%2002%3A45&basetype=A319&ac_order=registration&type=16458_1724110720469&climb=250%2F300%2F78&cruisemode=CI&cruisesub=0&descent=78%2F300%2F250&fuelfactor=1&callsign=&reg=3A-MAA&fin=789&selcal=&planformat=ber&pounds=0&maps=0.5&taxiout=20&taxiin=10&flightrules=i&flighttype=s&altncount=1&navlog=1&etops=1&stepclimbs=1&tlr=0&notams=0&firnot=0&stehour=3600&stemin=600&origrwy=25&destrwy=23&fl=&pax=0&cargo=&manualpayload=&manualzfw=50&contpct=0.03%2F5&resvrule=auto&taxifuel=0.2&minfob=0&minfob_units=wgt&minfod=0&minfod_units=wgt&melfuel=&melfuel_units=min&atcfuel=&atcfuel_units=min&wxxfuel=&wxxfuel_units=min&addedfuel_label=extra&addedfuel=&addedfuel_units=min&tankering=&tankering_units=min&pid=16458&cpt=Tim%20W&fo=C%20SULLENBERGER&dxname=TIM%20W&manualrmk=&route=OKU6A%20OKUNO%20ATRUP%20VAPUP%20VAPU1Y&route_type=&targetfl=28000&targettas=466&disable_tracks=1&force_track=&avoid_airways=&include_fixes=&altnsadv_number=1&altnsadv_radius=150&altnsadv_cig=600&altnsadv_units_vis=m&altnsadv_vis=3000&altnsadv_units_rwy=m&altnsadv_rwy=1600&altnsadv_exclude=&altnsadv_tsfgfz=1&altn_1_id=LDZA&altn_1_rwy=22&altn_1_fl=&altn_1_route=SIRM1V%20SIRMI%20M725%20RUDIK%20RUDI2Y&altn_2_id=&altn_2_rwy=auto&altn_2_fl=&altn_2_route=&altn_3_id=&altn_3_rwy=auto&altn_3_fl=&altn_3_route=&altn_4_id=&altn_4_rwy=auto&altn_4_fl=&altn_4_route=&toaltn_id=&eualtn_id=&etopsthreshold=60&etopsruleselector=&etops_exclude=&etopsentry=&etopsexit=&etopsaltn1=&etopsaltn2=&etopsaltn3=&etopsaltn4=&etopsaltn5=&etopsaltn6=&asp4_snapshot=disabled&debug_zerowind=0&static_id=&manual_acdata=

…note that I am using a custom airframe with an altitude offset (IIRC -2000), not that it should matter in theory.

Regards,

Tim

It’s just very dependent on TOC and TOD location along the route, due to the nature of the bug.

Think I’ve got it fixed this time, let me know if you can still reproduce at all.

Cheers,

Better now, I tried a bunch of settings and airframes without reproducing an unexpected altitude change.

Thanks!

Tim

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