Precision v. Non-Precision approach....
 

....and the effect on the relevant respective DH and MDA.

O.K., take the case of a runway with both precision, and non-precision approaches to the same runway end. Now, say a NOTAM has been issued, due to works in progress, raising the MDA of the Non-Precision approach. Common enough, I'm sure you'd agree.

Now, the question.... should one expect a similar NOTAM raising the DH for the Precision approach, to the same runway?

I ask this because I have seen both cases in recent NOTAMS, ie. one airport (LEBL, NOTAM 1A7481/08), raised the OCA(from which MDA is derived), for the ILS 25L, whereas all other similar cases left the Precision DH unchanged.

Is this a mistake on the part of the issuing authority?

:confused::confused:

My first thought is that it is possible that with more precise tracking on a precision approach that the obstacle may not be included in the splay therefore not affect the minima.

Hope that helps.

the raised oca(eg from 159 to 178agl) is then probably still below the 200 feet agl which is normally required minimum for that ils cat1 approach so the DA remain the same.

Or the OCA that is changed is only for the Non presision approach because this one is less precise and the new obstacle (eg a crane) is not in the ILS area because this is more precise.

Thanks for the replies folks.
I've just done a bit of digging through the Jeppesen Text manual, and the JAR publications, and it appears that the definitive answer is that:-

IF OCH/OCL IS INCREASED, THEN MINIMA MUST BE INCREASED FOR BOTH PRECISION, AND NON-PRECISION APPROACHES,TO THAT RUNWAY.

So, that NOTAM was'nt a mistake, at all........

Thought - inducing stuff, eh?:8

Could you provide a link, or reference to the Jepp? That's an interesting point, i've flown to a couple of places and didn't realise ILS also had to be changed. Might be worth pointing out to the big man next to me if it happens again.

Horgy

It is also common for the crane's to be lowered or removed when weather conditions require it - i.e. the ILS is being used to minima. Perhaps the NOTAM means that when the weather is reasonable, the crane's are up, so you only need know about it if you are conducting the non-precision approach (for practice or training), if the weather actually requires an ILS approach, the crane's are lowered/removed so the ILS minima is not affected?

Certainly, MrHorgy.

It's in the JAA Aerodrome Operating Minimums (AOM), SERIES 600,

Jepp. text, Air Traffic Control Section,(between RNAV and "Regional Proceedures", and in my Jepp. text, it's page 603.

"DH for Cat 1 operations........

"DH must not be lower than........

"The OCH/OCL for the category of the aircraft.........

as Michael Caine says "not a lot of people know that" !!!

at last, a definitive answer....or does anyone have anything to add to it?:ok: