paco1980
Topic Author
Posts: 13
Joined: Mon Jan 12, 2009 10:28 am

Mission Calculation Using RVSM

Thu Feb 19, 2009 10:46 am

Hi All,

Just wondering when calculating missions parameters (time, necessary fuel...), what is the impact of flying RVSM or not on the calculation ?

To my knowledge, flying RVSM is just having a relative height versus other Aircraft of 1000ft instead of 2000ft....
So, when calculating a mission, you focus on your aircraft with a typical mission profile but you shouldn't care of the others whether they are 2000ft or 1000ft above you during cruise....
So, why is it always precised RVSM ?

Second question I have is in term of results, how come RVSM represent a better view on the performance?

Thanks for any answer that could help.
Cheers,

Paco
 
CosmicCruiser
Posts: 2097
Joined: Tue Feb 22, 2005 3:01 am

Mission Calculation Using RVSM

Thu Feb 19, 2009 1:42 pm

Flying in RVSM airspace requires certain equip on the aircraft such as 2 independent alt., a/p w/ alt hold and xnpndr to name a few as well as crew trg. Without it you will not be allowed to fly in RVSM airspace without ATC approval. In most places RVSM airspace is FL290-FL410. If you are qualified then it is really tranparent and will not affect your "mission profile".
 
paco1980
Topic Author
Posts: 13
Joined: Mon Jan 12, 2009 10:28 am

Mission Calculation Using RVSM

Thu Feb 19, 2009 2:09 pm

Thanks CosmicCruiser, but what will be the impact on calculation of necessary fuel for the route if I fly RVSM or not ? Would you need less fuel if you fly RVSM ?
 
CosmicCruiser
Posts: 2097
Joined: Tue Feb 22, 2005 3:01 am

Mission Calculation Using RVSM

Thu Feb 19, 2009 2:27 pm

I can't see why you would. I'm not sure what you're thinking about here. You will have a few more alt to choose so you may be able to pick the most optimum but in the end ATC will give you the alt to fly. All RVSM provides is the ability to put more planes in the sky in a given space. I can't see it affecting your fuel planning at all unless of course you plan on dropping below the RVSM airspace in which case you would need more fuel but no one actually plans on that happening or you would be flying around with a bunch of extra gas all the time!!
 
OldAeroGuy
Posts: 3318
Joined: Sun Dec 05, 2004 6:50 am

RE: Mission Calculation Using Rvsm

Thu Feb 19, 2009 3:49 pm

Flying RVSM can result in an increase in range or decrease in mission fuel burn because the airplane can be operated in a manner closer to optimum.

Optimum performance would have the airplane doing a continuous cruise climb so it operates at the design lift coefficient (CL) for best cruise L/D. Without RVSM, in most cases, the airplane is limited to 4000' step climb increments. This means the airplane starts off at an altitude with a higher than design CL, flies through the optimum CL to a CL that is less than optimum until it is light enough to make a 4000' step climb to the next legal altitude.

With RVSM, the steps are reduced to 2000' so the time that the airplane is operating at CL's higher or lower than optimum is reduced. Operating closer to optimum means less fuel burn for a given mission or better overall range capability.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: Mission Calculation Using Rvsm

Thu Feb 19, 2009 4:23 pm



Quoting OldAeroGuy (Reply 4):
With RVSM, the steps are reduced to 2000'

Assuming the track you fly on is unidirectional, why can't you do 1000' steps?
Exceptions confirm the rule.
 
jgarrido
Posts: 258
Joined: Thu Mar 08, 2007 4:40 pm

RE: Mission Calculation Using Rvsm

Thu Feb 19, 2009 4:27 pm



Quoting Paco1980 (Reply 2):
Thanks CosmicCruiser, but what will be the impact on calculation of necessary fuel for the route if I fly RVSM or not ? Would you need less fuel if you fly RVSM ?

One major issue is that non-RVSM qualified a/c are generally not allowed to use the RVSM stratum. This means that you have to plan for not being able to climb above 280. There are exceptions that are allowed in ICAO rules, such as being a state operated a/c. Also "special" cases can be made, but only if each ATC sector is willing to accept the a/c. There are some FIR's I know that flat won't allow non-rvsm/non-state operated a/c above 280

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