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VFR v. VMC v. IFR v. IMC and cloud spacing under VFR

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AirV wrote:

I think SVFR is not limited to control zone.

Not true, SVFR is limited to Control Zones in Europe per SERA.5010 and to the equivalent of it (controlled airspace to the surface around an airport) in the US per 14 CFR 91.157.

Friedrichshafen EDNY

AirV wrote:

I think SVFR is not limited to control zone. It is still VMC but just 1,5km ahead.

According to international rules and SERA, SVFR is limited to control zones. I don’t know about the US. And it is NOT VMC. The very definition of SVFR is visual flight in conditions “below VMC”, i.e. in IMC.

What may confuse people is that the minima for SVFR are similar to VMC minima in uncontrolled airspace. But SVFR can only happen in controlled airspace.

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

The very definition of SVFR is visual flight in conditions “below VMC”, i.e. in IMC

Nitpicking somewhat here, but this is not the common way these terms are being used: Imagine flying in bright sunshine 900 ft above an undercast in controlled airspace. You are not meeting VFR minima, but you are definitely not in IMC either.

Friedrichshafen EDNY

Well, here’s the definition of SVFR in SERA (ICAO may has…probably does have!….a different definition).

‘special VFR flight’ means a VFR flight cleared by air traffic control to operate within a control zone in meteorological conditions below VMC;

Here’s the SERA conditions for SVFR


‘Special VFR flights may be authorised to operate within a control zone, subject to an ATC clearance. Except when permitted by the competent authority for helicopters in special cases such as, but not limited to, police, medical, search and rescue operations and fire-fighting f lights, the following additional conditions shall be applied:

(a) such special VFR flights may be conducted during day only, unless otherwise permitted by the
competent authority;

(b) by the pilot:
(1) clear of cloud and with the surface in sight;
(2) the flight visibility is not less than 1 500 m or, for helicopters, not less than 800 m;

(3) fly at a speed of 140 kts IAS or less to give adequate opportunity to observe other traffic
and any obstacles in time to avoid a collision; and

(c) an air traffic control unit shall not issue a special VFR clearance to aircraft to take off or land at an aerodrome within a control zone, or enter the aerodrome traffic zone or aerodrome traffic circuit when the reported meteorological conditions at that aerodrome are below the following minima:

(1) the ground visibility is less than 1 500 m or, for helicopters, less than 800 m; (2) the
ceiling is less than 180 m (600 ft).’;

EIWT Weston, Ireland

tschnell wrote:

Nitpicking somewhat here, but this is not the common way these terms are being used: Imagine flying in bright sunshine 900 ft above an undercast in controlled airspace. You are not meeting VFR minima, but you are definitely not in IMC either.

Yes, you definitely are in IMC. Read SERA Definitions (Article 2, item 91): “’instrument meteorological conditions (IMC)’ mean meteoro­logical conditions expressed in terms of visibility, distance from cloud, and ceiling, less than the minima specified for visual meteorological conditions” (my emphasis).

I know that many people think that “VMC” = possible to fly visually and “IMC” = can’t fly without reference to instruments, but this is not what the terms mean. That sloppy way of using terms just makes it harder for people to understand what the regulations say, confuses communication with ATC as well as discussions such as this one.

If fact, if we look at the following three distinctions:

  • VFR – IFR
  • VMC – IMC
  • Visual flight – Instrument flight

you can find situations (legal, but not necessarily safe) corresponding to each of the possible eight combinations!

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

Yes, you definitely are in IMC.

I don’t really agree with this. According to the SERA/Icao Annex 2 definition then, technically, yes. But those are not definitions of what IMC actually is, they are just a definition of what is is not, by exclusion, i.e. “if it’s not VMC then it must be IMC”. But this dichotomy does not reflect the real-world reality that you can have conditions which are below technical VMC, but would not be considered “instrument conditions” by any real-world pilot or controller, in the sense that they can still easily be flown visually.

There really should be a definition in between, say MVMC (marginal VMC) to indicate below official VMC, but not yet requiring instrument flight, and not yet down to zero visibility, and not yet inside visible moisture. i.e. there should be a flight conditions definition that is the counterpart to the SVFR flight rules definition.

Would you seriously report “IMC” to a controller, if flying in bright sunshine 900ft above an undercast as per the example above, and would this be helpful? I would not use that phrase to the controller in that scenario as I think it would be misleading.

Last Edited by at 22 Jan 14:29

Would you seriously report “IMC” to a controller, if flying in bright sunshine 900ft above an undercast as per the example above, and would this be helpful? I would not use that phrase to the controller in that scenario as I think it would be misleading.

I couldn’t agree more. Most pilots would say IMC = in cloud. That is also what ATC want to know, i.e. whether feeding you traffic info is worth anything i.e. whether you are ever likely to come back with “visual”.

Also IMHO 99.3456% of pilots have no idea about the 900ft above cloud in CAS and even if they knew they couldn’t care less

Administrator
Shoreham EGKA, United Kingdom

@ortac, @peter, so what you are saying is that since there is no way of precisely knowing your distance to cloud (and I agree with that), then you don’t have to care about the distance to cloud at all? I disagree.

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

so what you are saying is that since there is no way of precisely knowing your distance to cloud (and I agree with that), then you don’t have to care about the distance to cloud at all

That is the only conclusion when reading the regulations. Things get a bit different when remembering why you should keep a distance to clouds, but then it would be a judgement call. A much better solution is to install ADS-B in/out IMO.

The elephant is the circulation
ENVA ENOP ENMO, Norway

Airborne_Again wrote:

so what you are saying is that since there is no way of precisely knowing your distance to cloud (and I agree with that), then you don’t have to care about the distance to cloud at all?

I’m not saying that at all. Even if I had a device in the cockpit that told me exactly the distance to the nearest cloud to within an inch, what I am saying is that I would never report “IMC”, which implies instrument conditions, if I was technically below VMC minima but actually in perfectly good visual flight conditions.

Let’s say it’s a perfect summer day, unlimited visibility, FEW030. Are we serious going to call flight conditions “IMC” if we get slighty too near to one of those clouds. I might even not have any instruments in my aircraft, so the term just doesn’t make any sense. I might call it “technically illegal VFR” or “unable to maintain VFR” or even “marginal VMC” but not “IMC”.

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