View Full Version : Ceiling vs. Vertical Visibility

25th Feb 2010, 09:19
Airport EXXX has an ILS (DH 200') and an VOR (MDH 450') available. The TAF for our arrival gives us VRB01KT 7000 BR VV003=

Can we use EXXX as an alternate during planning?

I'd say definitely no, but some people in my company say we can. It doesn't make any sense to me but I can't find any reference in EU-OPS. OPS 1.297 doesn't mention VV it only states "the ceiling at or above MDH".

Can anyone point me in the right direction?


25th Feb 2010, 12:23
I would say yes. If the horizontal vis is 7000 m, then the mist is pretty thin. The vertical vis stops at 300 feet and that figure is so far below the 7000m figure it must indicate an effective ceiling at 300 feet, just without a definite base (as it fades into mist.)

In any event, as a European operator, you only have to account for visibility for ILS approaches, so the ceiling is irrevelant.

EU-OPS 1.297
Planning minima for IFR flights

(a) Planning minima for a take-off alternate aerodrome. An operator shall only select an aerodrome as a take-off alternate aerodrome when the appropriate weather reports or forecasts or any combination thereof indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival at the aerodrome, the weather conditions will be at or above the applicable landing minima specified in accordance with OPS 1.225. The ceiling must be taken into account when the only approaches available are non-precision and/or circling approaches. Any limitation related to one-engine-inoperative operations must be taken into account.

(b) Planning minima for a destination aerodrome (except isolated destination aerodromes). An operator shall only select the destination aerodrome and when:

1. the appropriate weather reports or forecasts, or any combination thereof, indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival at the aerodrome, the weather conditions will be at or above the applicable planning minima as follows:

(i) RVR/visibility specified in accordance with OPS 1.225; and

(ii) For a non-precision approach or a circling approach, the ceiling at or above MDH; or

[emphasis mine]

25th Feb 2010, 13:16
Well I would say NO.

From my recollection (stopped flying a few months ago!), the destination allternate minima used at the Planning stage assuming that the best approach minima is not available.

So if the airfield has Cat 3 ILS, use Cat 1 minima; ditto (in this case) Cat 1 available, use best non-precision minima (VOR 450ft MDH and about 1000m vis).

In this case it boils down to the surface vis of 7k versus the vv of 300ft. and the MDH of 450ft. I would suggest that you would have little chance of picking up any visual reference at 450ft given the vv (which is effectively the cloudbase) and must be considered.

Now, in flight it is different, as you can then use the ILS minima and nominate it as your alternate.

25th Feb 2010, 16:06
That's right

For Alternate, you cannot nominate that airport. If we consider VV as the ceiling.

But when is VV reported? If there are no clouds, but there is vis less than 9999, SKC will be reported. If there are clouds but above MSA, NSC (or this one is only in TAFs?).

25th Feb 2010, 16:11
TopBunk, that is correct! At planning stage you're not allowed to use the lowest approach minima. You have to ensure you'll make it down on the second best, in this case the non-precision VOR approach.

As far as I'm concerned the TAF should say VRB01KT 7000 BR BKN000 VV003 since the "ceiling" is actually at 0'. The VV is only there as a nice-to-know piece of information which tells you you can expect to get some visual reference at 300'.

I guess it all comes down to, do we consider VV as ceiling?

26th Feb 2010, 09:28

vv003 also means that maybe there is clouds somewhere, but there is no way to tell for the reporter as he can only see 300 ft up.
In the mentioned case there can very well be a ceiling at 400 ft, in which case you cannot use it as alternate.


26th Feb 2010, 12:10
Not much to add here except that the next best approach would most probably be the LOC-only approach in case of a CAT1 app. Ceiling does apply here for the planning stage since it is an NPA. VV003 just might be enough for a LOC approach; MDH250 is the absolute minimum, check Jepp for actual minimum.


26th Feb 2010, 13:31
For nominating EXXX as your alternate, you have to go one-up from the best avaliable approach. Ie, you say CAT1 is avaliable, you then have to have localiser minima (which is cieling+vis/rvr) or better to nominate. (If you had CATII you would have to have cat1 minima (which is vis/rvr ONLY, not the difference))

At least where I work, cieling is considered to be BKN, OVC or VV. Do note, again, that this is only relevant for non-precision approaches, but that IS relevant in this case, because of the requirement to one-up your alternate :ok:

Edit: so to answer your question; unless localiser minima is lower than 349'/7000m vis, you cannot use EXXX as an alternate. And while we're at it: what are your policies on TEMPO, BECMG, PROB30, PROB40 and TEMPO SH for destination/alternate planning, gentlemen?

26th Feb 2010, 15:22
Ooops - my bad! Should have read the question! :ugh:

26th Feb 2010, 17:14
I'm not convinced that you can go from Cat 1ILS down to LLZ only. Surely the reason for using the next level is in case there has been a failure in the better facility.

In the case of a Cat 1 ILS you could have lost the LLZ, hence imho you must go to a non-ILS based approach aid, so to a VOR/DME, NDB/DME, PAR etc.

26th Feb 2010, 18:03
Hi Topbunk,

I understand your point. But it's definitely LLZ only you'd plan for your alternate with CAT1. Ofcourse this is the legal minimum, I appreciate that any commander may decide to decide on a more conservative planning.


Port Strobe
26th Feb 2010, 20:13
I believe a large airline that likes to write their own manuals has written that for planning purposes they'll consider a VOR/NDB/SRA etc and not a LLZ only approach to a runway which is served by a Cat I ILS at best. Makes perfect sense to me, however as others said I think the legal interpretation does allow you to use LLZ only, seems to me like a 50/50 chance whether it's the LLZ or GP that will fail if there is a failure so I'd rather have my plan B based on a totally separate aid thanks.