View Full Version : Destination Alternate

21st Dec 2003, 00:39
My destination alternate has a CAT 1 ILS so for planning minima I need non-precision approach minima, can I use localiser approach minima for planning minima or should I use VOR/ADF minima for planning purposes



21st Dec 2003, 01:35
Are you telling that you are not equiped with ILS on your aircraft or you are only to use non-precision for alternate? Well go for the localizer approach if allowed in the plate (I don't see why not) and it should get you a lower MDA for your minima then the VOR/DME; and of course all this according to your expected wx and obeying the rules in Europe. Im new to the IFR world so please correct me if I'm wrong.

21st Dec 2003, 02:32
Aero D

May interpretation of the rules would suggest that you must use VOR or NDB or circling minima if all there is is a Cat 1 ILS.

I think the logic goes that you must consider any single plausible failure at the planning stage, which means that any component of the ILS installation of the ILS (LLZ or GS) could fail. This being the case you alternate weather should be good enough to allow you to successfully complete a non-precision approach.

If alternate only has say a non prec app, then in my company I would need wx of minima + 200ft ceiling and rvr + 1000m. (Ceiling defined as >50% coverage ie BKN or worse).

Does that make sense or not?

21st Dec 2003, 04:59
Aero, I understand your dilemma and of course legally a localiser only would be a non-precision approach, so here's another grey area. However, as it isn't going to be your day when all this happens I personally plan as topbunk suggests and use the non-precision minima assuming ILS is off the air completely.

Top Bunk it makes sense, and as far as I'm aware that isn't just your company but any company operating under JAA regulations that has additions.

Sanket, you don't understand the question. There are rules laid down under JAROPS for what minima you must PLAN on for a "destination alternate." Briefly, if my destination alternate is CAT 2 or 3 capable, my planning minima is CAT 1. If it is CAT1 capable, my planning minima is non-precision minima. If it is non-precision approach, my planning minima is non-precision plus 200ft/1000m. Circling approach, planning minima is circling minima.

22nd Dec 2003, 03:18
Wow FLEX42, thx for the clarification. Doesn't work like that here in Canada but it does have a good logic! :ok:

seat 0A
23rd Dec 2003, 00:38
In my opinion LLZ minima suffice. My company manuals say the same.

23rd Dec 2003, 01:24
LLZ is sufficient.
ILS can be unavailable for many other reasons. DME u/s if their is no other distance aid (OM etc), displaced threshold or G/P u/s to name but three.

25th Dec 2003, 07:32
As I see it (I may not be correct) It is enough with LLZ mins. The "One up" proceedure is to give you a weather margin.
As with CAT 2 or 3 you go to CAT 1 not to VOR,NDB. A failure of the ILS would not only degrade CAT2 or 3, it would fail the whole ILS.

28th Dec 2003, 04:43
Md driver (and others)

The ILS comprises 2 components, the LLZ and the G/S.

So take the scenario, on departure the ILS is working, and the wx would allow a LLZ minima approach.

So what do you need for your alternate? You are assuming that the G/S fails, in those circumstances, yes the wx is good enough for the LLZ approach. But what is the LLZ fails? You can't do a G/S only approach. That is the reason for downgrading from Cat 1 ILS to non precision and not LLZ only.

If your company or national requirements vary then fine, but I suspect that you either don't understand them or are ill-thought out for the above reasons.

28th Dec 2003, 10:09
Our (USA) OPS SPECS do not differentiate as to precision or non precision approach capabilities for filing of alternate airports. The only planning requirements are to add 200' to the ceiling of the approach minimums (HAT) and 1/2 SM to the visibility minimums...for alternate airports with two runways; or 400' and 1 SM for alternate airports with only one runway. Once airborne, these higher alternate minimums no longer apply; in other words, once you actually proceed to your alternate, regular minimums apply.