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Approach plates that show OCA/OCH - are they safe?

www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=6&Itemid=13.html

Instrument plates that are are available freely in the UK do not show MDA/MDH they show OCA/OCH. Why is this? Is this the case with all instruments plates supplied by national aviation authorities?

Doesn’t t publishing them in this format give a reduction in safety?

I think that the providers of such charts (CAA/NATS in this case) would argue that they are not designed for operational use, and that operators are responsible for calculating their own MDA/DA based on a combination of surveyed data, as shown in the plates, their own SOPs, legal minima, aircraft specific data etc.

This is neatly done by third parties, such as Jepp, and in some cases by the airlines themselves, such as Lufthansa.

Some countries do more of the calculations, including RVR minima, but that is not an ICAO requirement.

The French, ironically, publish a more usable plate, then make it very difficult to extract in a usable form from their eAIP.

EGKB Biggin Hill

the providers of such charts (CAA/NATS in this case) would argue that they are not designed for operational use

Indeed, they would claim it is published to discharge their ICAO obligations to depict the AIP data, as in e.g. the reported purpose of the French SIA chart even if the result is almost unusable.

Some years ago (amybe 10) I spoke to the then head of UK CAA charts asking why they don’t publish approach plates in a cockpit-usable form i.e. A5 and with the MDA/DA etc on them. He replied that they are not in the business of competing with commercial providers (Jeppesen, in the context of the conversation)! The discussion then moved to the topic of the Australian CAA’s legal action against Jeppesen (for alleged breach of copyright, republishing material owned by the CAA) and he said he was very familiar with that but would not say any more. My take is that, following the Australian action which was settled out of court confidentially, Jepp are paying a license fee to the various national CAAs for the use of the data and in return for that the CAAs are not allowed to compete with them. Obviously any such agreement would be confidential.

Administrator
Shoreham EGKA, United Kingdom

The ICAO requirement is only to publish OCA as the applicable aerodrome operating minima are supposed to differ depending on your type of operations, which in turn depend on the applicable national regulation.

I have seen OCAs on approach plates (I can’t remember off the top of my head for which airport) which are below 200 ft as the lack of higher terrain supported that, however for standard ILS CAT I operations the DA cannot be below 200 ft. The Jeppesen plates then still show a DA of 200 ft. There is a Jeppesen document somewhere (I will try to find it) that explains how Jeppesen converts OCA information into DA/MDA and RVR/CMV values.

Similar minimum rules are included in the the EASA Air Ops, e.g. Part-NCO, see here, local copy, page 1580 and following pages.

Wolfgang

EGTF, EGLK, United Kingdom

As an operator, we add all sorts of additional criteria to the published ‘minima’. Personally, I think third parties could be on a bit of a sticky wicket when they promulgate MDA/H DA/H etc. I would be more content with a figure that represented an absolute minima (based on higher of OCH and system minima) but, in the same breath, some operators are allowed to fly to 50ft below system minima!

Funny old world, but a good example of how instrument pilots need to thoroughly understand what they are looking at.

Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom

I vaguely recall somebody developing an app for converting the OCH to MDH etc. However (and this was quite some years ago) I think he did a CFIT and is no longer around. One can do it using a calculation.

A previous thread from 2012

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

My take is that, following the Australian action which was settled out of court confidentially, Jepp are paying a license fee to the various national CAAs for the use of the data and in return for that the CAAs are not allowed to compete with them.

I wouldn’t be so sure. I’ve seen a Jeppesen copyright notice which expressly says that data is used by permission of the Australian CAA, but doesn’t mention any other country.

Obviously any such agreement would be confidential.

Not at all “obviously”. It would depend on the legislation of each country. But it is an interesting question. I might check with my national CAA.

ESKC (Uppsala/Sundbro), Sweden

@wbardorf EGMC Southend 23 ILS has an OCA below system minima, for example.

EGKB Biggin Hill

Timothy wrote:

ILS has an OCA below system minima, for example

Not sure I fully understand – in Denmark every ILS except one has (Cat A) OCH below system minima. Isn’t that the norm for ILS’s all over?

huv
EKRK, Denmark

huv wrote:

Not sure I fully understand – in Denmark every ILS except one has (Cat A) OCH below system minima. Isn’t that the norm for ILS’s all over?

I know it’s hard to believe….but some countries actually have hills and mountains…

YPJT, United Arab Emirates
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