Ceiling below DH
 

Hi, My question is, if the ceiling of an airport is OVC001, and the ATC clears you for a CAT 2 ILS approach, legaly can you commence the approach to CAT 1 minima, provided that the A/C is not certified for CAT 2 operations ?
I think than on a precision approach RVR is only a requirment.

Thanx in advance

Hello...

as you already know...the CAT 1 minima (MDA) is always 200 feet above the landing thresh-hold.

and the CAT 2 minima (DH) is always 100 based on radio altitude.

so if you commence the approach to cat 1 minima and having known that the cloud is overcast at 100feet...there is a big big chance that you might not see the runway.

legal or not....my insturctor told me once...if you will use precesion approach ..you can commence the approach if you have at least the required RVR.

if you are Non precesion approach...you should have cloud base not below your minimum decent altitude.

but this what my instructor told ...please don't judge on it.

Cloudbase assessment is regarded as vague and only poorly approximate, therefore the only limiting factor is the RVR requirement. Therefore you can ignore cloudbase. It changes so much and so rapidly it is not worth taking into consideration.

I agree with Rainboe - The science of recognizing and reporting a cloud base isn't all that great and "mother nature" doesn't often agree to make no changes. In the US, the requirement has been strictly RVR for quite some time - however, the US military had stubbornly maintained the DH/MDA and ceiling height issue for some time. Now they also recognize the futility of such a stance and use RVR.

The only thing I would point out is that there are a number of "new" instrument approach procedures being developed - and the ability of the pilot to see another aircraft involved in one of these newer procedures may come into play in a way that we may not be aware of at the moment.

The simple answer is "yes you can" as long as you have the required visibility for CAT 1.

It seems to me the question is about being cleared for a CAT 2 approach when you can't fly it. So you could ask for a CAT 1 approach and try that, no matter what the ceiling is. RVR or visiblity is the only requirement, and only at the final fix. Thereafter, it may drop (at least the touchdown zone value).

Regards Mike

I think it may drop only on an AWOPs approach. Isn't CAT I only to CAT I vis limits only?

A UK orientated answer but I think it's generally the same elsewhere...

ATC do not clear aircraft for a Cat I or Cat II approach. The pilot is made aware of the category of approach that the ground equipment can support and the aircraft will be cleared to use it in whatever way the Ops Manual says.

In practical terms, if the ILS can support Cat II or Cat III approaches, a pilot has assurance that it will be suitably protected for use in such conditions when LVPs are in force.

@K340.
Cat I minima is not allways 200 ft. - but it cannot be lower than 200 ft. (and its a DA(H) and not a MDA(H))
The same goes for the Cat II minima
And according to JAR OPS you can, once past outer marker or equivalent position, allways continue to minima.

Regards

Der_dk.

Thanks very much to bring this to my attention...i made a mistake.

well done.

Check your theatre guide
 

The purpose of this response is to point out that some countries requirements for beginning an approach are different than others. Jepp lists these in the theatre guide...chapter 11. I realize the original poster has ATH as the g-ref. Many on this forum will be from other hemispheres.
Brazil

Approach Ban

The final approach segment of any instrument approach procedure shall not be initiated, unless the controlling ceiling and controlling RVR, or if no RVR is
available, the visibility conditions are reported to be at or above the minimum
authorized for the approach being conducted.

NOTE: 5 Octas or greater (Broken or Overcast) constitutes a ceiling.

In the US, they will clear you only for the ILS. They do not know or care what your certification limits are.

As to whether or not you are legal, that depends on whether you are Part 91, Part 135 or Part 121 in the US.

Thank you all for the usefull infos and replies.
Actually the airport I was mentioning was in Germany (EDFH).

Cheers