Hello to Everyone Just a quick and curious question,hoping some would be kind enough to please help me. Last night I file a flight ONLINE with VATSIM network.-LIMC2025-N0440F180 AOSTA B4 BANKO-LSGG0030But the ATC told me that the minimum enroute altidude was FL200.I was wondering why being the highest mountain in the area is 12000 ft.Million thanksBest regardsB737

ATC was obviously wrong as the B4 only extends upto FL195 between AOSTA and BANKO.Cheers[br][/img]

Thanks a million OBK Very kind of you.I just took a look at the RADAR VECTORING AREA charts and saw around the waypoint AOSTA they have the minimum vectoring altitude of FL180.I think there could be a mis-interpretation by the ATC.And for my knowledge could you please explain the technical difference. Also if I am not asking too much what altitude do they file in real life for the LIMC-LSGG leg. Thanks very much in advance Best regards B737

Minimum Enroute Altitude is basically the lowest published altitude between two fixes that will allow safe terrain clearance for the whole width of the airway. It may also be the minimum altitude at which sufficient radio navigational signal coverage can be maintained, whichever is the highest.Minimum Vectoring Altitude, well that's pretty straight forward.There are many types of the "Minimums" in the aviation industry, took me a while to learn them but they are all pretty much similar whether it be MEA, MSA, MORA, MDA, MDH, MRA.Cheers[br][/img]

Thanks a Billion.Man you are quick. Well to be honest I am still a bit confuse.Maybe I word myself a bit badly.But my curiousity was how's it possible to have a Minimum Vectoring Altitude of FL180 and at the same time fly enroute at the same Altitude (FL180) or under (that's according to the B4 airways).But still I am not sure if in real life they file that low so maybe I am just confusing you and myself. Thanks a million Best regards B737

You probably do you need a real raw data to do comparisons. I am assuming the flightplan above is one you made? While it may be absolutley valid, you're right in saying it is posing more questions than I have answered lol! :)Cheers[br][/img]

Thanks a Million OBK For or your help,time and effort.But as I thought without the "real raw data" we are busted ;-((( I hoped that TOCART would have jump in to give us a hand but I guess he is super busy. Thanks very much All the BEST B737

Hi Terrence/B737, radar minima are established not only with consideration to obstacles clearance but with consideration for radar coverage as well. You certainly know that in the AOSTA area the highest obstacles are 15780' (Mt. Blanc). The B4 airway passes north of the Mt. Blanc so maybe the relevant obstacles are slightly lower, make it 14000'. So as far as obstacles are concerned we can certainly have MVA lower than FL195; MVA in Milano Area are established so that they can guarantee a separation of 1000' from highest obstacle within 5NM from the estimate position of the a/c when beyond 20NM from the radar antenna. So we could expect something like FL180 as MVA as well.If FL195 is established as radar minima near AOSTA it's certainly a radar coverage limitation that comes into play. Even if we consider the is expressed as FL and that when qnh drops to very low values the actual separation from obstacles reduces we see that the minima of FL195 is not justified by obstacle clearance . An aircraft maintaining FL195 (altimeter on 1013) right on the top of Mt.Blanc when qnh is 977 is actually separated from the terrain by 2658'. It's not the 3630' we have when the qnh is 1013, anyway is still a solid separation.So the airway minima can be lower than the MVA. You can fly on the airway (with MEL FL175 in the AOSTA BANKO) but the controller can't, for example, get you off the airway and start giving radar vectors as you are below his MVA. In fact maybe he could even not see you if you fly at FL180 in that area (due to radar coverage limitations; in real world of course)So FL180 on B4 AOSTA/BANKO is acceptable according to the MEL of the airway segment, just be aware that it places you below MVA; so no vectors and other radar goodies from the ATC etc until you are at 195 at least :-))Just to be complete the MORA (Minimum Off Route Altitude) in the area is 17700.So now we know everything we need to fly safe between AOSTA and BANKO :-)))CheersGian Paolo Codeb

Hello GPC "My hat off to you"I knew you was good but not this good.I must say I really did under-estimated your aviation knowledge.Never thought an avaition enthusiast could reach such level of sagacity in this field.If I knew this before I would have ask you directly instead of the real life experts in this forum. Anyway thanks a billon for clearing this haunting curiuosity about "MVA" "MEA".Never did understand why so much spacing from the obstacles.Still so much to learn ;-((( Thanks a lot Best regardsB737