IFR descent through uncontrolled airspace

[ScandinavianFlyer 0]

Hi,

 

During one of my recent flights online with ATC, the ATC asked me if I wanted to descend through uncontrolled airspace so that I didn't have to level of for a while. I accepted this offer and nothing was unordinary, but my question is: What is the difference in this case since I was still on his frequency? The benefits of descending through uncontrolled was that I could keep descending constantly, but what are the consequences (because I assume there is some, because otherwise I don't see why ATC asked me if I wanted to do it or not)?

 

Also, please note, this was a flight in Europe and therefore I'm looking for an answer regarding ICAO standards.

 

Thanks in advance

[rototom 198]

I think, you would be responsible for terrain and traffic clearance and VFR minimums would apply.

[Dave_YVR 973]

 You are still IFR, there are no VFR minimums to apply. You may descend through cloud IMC but as Jim mentioned terrain and traffic separation is not guaranteed within uncontrolled airspace.

[ExNusquam 11]

Dave- you're also incorrect. The controller will never issue an altitude clearance below their Minimum Vectoring Altitude - which will assure terrain clearance. Uncontrolled airspace means that a controller may not provide IFR services. 2-way radio communication is also not required, even for IFR operations. See: https://en.wikipedia.org/wiki/Uncontrolled_airspace

[Dave_YVR 973]

 

 

The controller will never issue an altitude clearance below their Minimum Vectoring Altitude

 Neither I or the OP ever said anything about a minimum vectoring altitude. There aren't MVA's everywhere.

[ExNusquam 11]

 

Jim mentioned terrain and traffic separation is not guaranteed within uncontrolled airspace.

 

 Neither I or the OP ever said anything about a minimum vectoring altitude. There aren't MVA's everywhere.

 

You are correct there aren't MVAs everywhere - but a controller won't issue an altitude clearance that doesn't assure terrain/obstacle clearance. If you're being vectored for an approach, the minimum altitude will be MVA. Enroute it will be the MOCA for the segment you're on. 

[DavidP 1,410]

Dave- you're also incorrect. The controller will never issue an altitude clearance below their Minimum Vectoring Altitude - which will assure terrain clearance. Uncontrolled airspace means that a controller may not provide IFR services. 2-way radio communication is also not required, even for IFR operations. See: https://en.wikipedia.org/wiki/Uncontrolled_airspace

It's best not to make generalisations. As a RW IFR pilot, in my country, IFR in uncontrolled airspace requires continuous 2 way communications. Traffic separation advisories are required to be provided. You are not under direct control, so clearances / vectors are not routinely given, but intentions to change level / routing are - if you intend operating below the route or grid LSALT then you will be challenged to confirm that you have calculated a pilot LSALT.

 

In these things it is best to refer to a country's AIP rather than reference wikipedia.

[Dave_YVR 973]

 A MOCA by definition is the lowest published altitude in effect between fixes on VOR airways or route segments. Off airway etc has different min IFR altitudes named differently depending on the country which are similar, but those are still within controlled airspace.

 

 

but a controller won't issue an altitude clearance that doesn't assure terrain/obstacle clearance.

 This is true but is also applicable within controlled airspace. There are many areas where there is no controlled airspace below 12,500ASL and sometimes even much higher. Here ATC WILL include "While in controlled airspace" with the clearance.

 

 

 

 

In these things it is best to refer to a country's AIP rather than reference wikipedia.

  Exactly, just because you (not specifically) haven't seen it doesn't mean it doesn't exist. I've been an IFR controller since 94' and have used it many hundreds of times.

[skelsey 765]

The benefits of descending through uncontrolled was that I could keep descending constantly, but what are the consequences (because I assume there is some, because otherwise I don't see why ATC asked me if I wanted to do it or not)?

 

Essentially, once you are outside CAS you are in bandit country.

 

Controlled airspace exists to provide a known traffic environment -- in (most classes of) controlled airspace, two-way communication is mandatory and you cannot enter without a clearance. This means that the controller in theory knows about and is in contact with every aircraft in that area of controlled airspace. Therefore, ATC can provide guaranteed separation, or traffic information (airspace class dependent) about every aircraft that may come in to conflict with you.

 

Outside controlled airspace, there could (and probably will be) be aircraft flying around which are not in contact with ATC, not transponding, etc etc etc. Whilst the controller will endeavour to provide traffic information (in the UK you would, as an IFR flight, be offered a "Deconfliction Service") there is no guarantee that the controller will know about everything that you might come across. Fundamentally it becomes up to you to "see and avoid" -- whilst (in the UK) ATC will aim to achieve certain deconfliction minima (between 3 and 5NM laterally or 500-3000ft vertically depending on whether the other traffic is identified/in communication with the controller or not), there may be stuff flying around that ATC cannot see and/or do not know about and therefore you are on your own with those.

 

Ultimately it is up to you to judge the risk and accept or decline the offer as you see fit. The advantage, as you say, is usually to make your flight more efficient either by keeping you descending or by reducing the track miles by "cutting a corner" somewhere. In the UK at least, in most cases the chances of coming across a spamcan not in communication with ATC at much above 4000ft or so are very limited, and (counter-intuitively) if the weather is poor most recreational pilots will stay on the ground, further reducing the chances of hitting anything. Gliders may be more of a danger than powered aircraft if the weather is good -- they are small (and thus difficult to see) and generally less likely to be speaking to ATC or transponding. Note also that in the UK not all airfields served by commercial traffic have controlled airspace around them, and some of the smaller of those that do are not necessarily joined directly (or conveniently) to the rest of the airways system, so on occasion operating in to some of these places you may not really have much choice.