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How does one determine DA(H) and MDA(H) using the ICAO charts found in the AIP in Europe?

bookworm wrote:

NCO.OP.111 is indeed the document you need. In general, system minimum tends to prevail for precision approaches (for which the PANS-OPS minimum margin using pressure altimetry is 130 ft above obstacles penetrating the obstacle assessment surfaces, and the system minimum is 200 ft), and OCH for non-precision approaches (for which the margin is usually 246 ft above any obstacles in the final approach segment).

What about that 50ft we add to 200ft for BARO error for ILS approaches?
Or is it only taught to IR(R) students?

EGTR

The 50 feet on an ILS is position error correction if PEC is not stated in the POH. Some GA types the PEC is stated 25 feet.

In CPL/IR the 50 feet added on an MDA non precision is buffer to ensure MDA is not breached. A CDFA non precision is technically a decision altitude and you can go below as long as the go around was initiated before the MDA, however on commercial non precision tolerance is treated as minus zero.

Oxford (EGTK), United Kingdom

This sort of thing is why a lot of pilots pay money for Jeppesen charts. Unfortunately these are much more expensive for Europe than for the US – in the US they have to compete with the free govt charts which are cockpit usable, unlike the AIP charts whose sole purpose is to discharge the ICAO data publication mandate, without regard for whether the result is usable in the cockpit.

This is also a big reason why Jepp are trying to move everything to the Ipad platform – they can cripple printing options which are the prime route for sharing Jepp charts

Administrator
Shoreham EGKA, United Kingdom

I think the main reason for people buying Jepp charts is not so much the DA/MDA calculation, but the better readability/layout.

OCA vs. DA/MDA differences are usually very small and more an academic thing rather than a practical relevance.

Mainz (EDFZ) & Egelsbach (EDFE), Germany

RobertL18C wrote:

The 50 feet on an ILS is position error correction if PEC is not stated in the POH. Some GA types the PEC is stated 25 feet.

There is no mention of it in PANS-OPS. I’ve read the full IR TK twice with no mention of it. I’ve taken the IR tests twice without any question mentioning it. I’ve taken an IR skill check twice without any mention of it. I must have taken something like 15 IR PCs without any mention of it.

Why is it that no one talks about it except in the UK…?

ESKC (Uppsala/Sundbro), Sweden

I believe the FAA AIM on precision minima calculation states it

1.19.2 all DA must be adjusted to determine an AOM which accounts for aircraft pressure error. Operators may apply aircraft Pressure Error Correction (PEC) or, alternatively, add at least 50FT to the published DA. Compensation for aircraft pressure error is not required when determining AOM for non-precision approaches.

Also NZ and Australia.

I mis named it position error, but this is distinct to the low temperature PEC calculation which am guessing Scandinavians apply by nature in the cold season :)

Oxford (EGTK), United Kingdom

I think the main reason for people buying Jepp charts is not so much the DA/MDA calculation, but the better readability/layout.

Yes, definitely. They were designed to be readable on the original 800×600 tablets… fonts and all.

The AIP charts are just meant to be printed on A4, which itself is too big for cockpit use and if you print them A5 you need reading glasses…

Why is it that no one talks about it except in the UK

My JAA IR examiner, who had an amazing eye for detail, was amazed that the TB20 POH contained no add-on. He had earlier asked me how far down I fly an ILS and I told him “to the minima on the plate”. I didn’t add “what else” because that would have sounded cocky But surely that is what you do. The minima is designed to give you sufficient obstacle clearance for a non sky god pilot.

Administrator
Shoreham EGKA, United Kingdom

I recall an enquiry being made in the UK about why the minima weren’t just on the AIP plate in a more straightforward manner, followed by a reply along the lines of it not being part of their remit to compete with commercial data providers.

So essentially the authorities deliberately publish poorly-presented information in order to subsidise an aviation-related industry that makes money from simplifying it. Disappointing but not surprising.

That said, the only types of instrument approach I fly are ILSes in the UK and I’ve never found it that difficult to look at the OCH on the AIP plate, decide whether it’s higher or lower than 200ft and then add the higher of those two numbers to the elevation. I’m certainly not going to pay Jepp for their ‘re-interpretation’ and I just use the AIP ones, printed A4 and folded in half when not in use. I am very familiar with the format and actually Jepp ones look odd to me – it’s just a question of familiarity. I will never go to electronic plates because as far as I can tell that is the one scenario where a tablet failure really could kill you.

The 500ft precision / 600ft non-precision absolute minima for IMCr (IR(R)) holders is advisory and has no legal status, as is the suggestion that they add 200ft earlier in the calculation process per the chart provided by @MattL. The chart is somewhat poorly designed anyway because it says “IMC absolute minima” where it ought to say “IMC rating absolute minima”, potentially leading to confusion about whether the minima might be different if one is actually in instrument conditions.

I’ve never known anyone actually use the 50ft PEC and it’s not surprising that it appears to be a UK-only thing. I would have thought that the system minima, being based on the equipment being used (part of which is the aircraft’s altimeter) would already have taken into account the fact that a pressure altimeter is only so accurate. I worry even less because I know that in our TB10 the altimeter actually under-reads by about 50ft.

It would be funny if it wasn’t so important.

Last Edited by Graham at 09 Jul 08:35
EGLM & EGTN

lionel wrote:

While I am relatively clear on the OCA/DH/MDH stuff, I get completely lost in the data necessary to determine the visibility/RVR minima. The app asks whether the lighting is BALS, IALS or FALS. The AIP doesn’t use these terms, and I don’t know how to convert. Some old sources acknowledge this is problematic and hard to determine for sure, and say the FAQ has some explanation. But the FAQ has been offline since I looked for it a year ago, and I have never seen it.

The free app is not updated now for years (it is my app) but the principle is the same after all these years. You need to determine the length of the approach lights from the ICAO aerodrome chart to determine if the lights are basic or high-intensity approach lights, thus giving you the BALS etc setting.

Full Approach Light System (FALS): It consists of 720m or more of High Intensity approach light system (HIALS), runway edge lights, threshold lights and runway end lights. Lights must be on.

An Intermediate Approach Light System (IALS): It consists of 420 – 719m of HIALS, runway edge lights, threshold lights and runway end lights. Lights must be on.

A Basic Approach Light System (BALS): It consists of any other Approach Light System (HIALS, MIALS or ALS 210m – 419m approach lights, runway edge lights, threshold lights and runway end lights). Lights must be on (MIALS is Medium Intensity ALS).

I could see if I can find some time after the summer to bring back the FAQ in the app. The app was meant as a contribution at that time to the GA flying community to get rid of the expensive Jeppesen charts.

Last Edited by AeroPlus at 09 Jul 09:23
EDLE, Netherlands

The PEC comes from AIPAD section:

4.6 Altimeter Error

4.6.1 When calculating Decision Height (DH), account must be taken of the errors of indicated height which occur when the aircraft is in the approach configuration. Details of the Pressure Error Correction (PEC) should be available from the aircraft Flight Manual or handbook. In the absence of this information a PEC of +50 FT has been found to be suitable for a wide range of light aircraft and should be used. This addition of 50 FT need only be applied to DH. The required RVR should be calculated prior to applying the PEC.

You should also add Temperature Error if required as well. Anything that drives the DH up a bit is a good thing for IR training and tests

Posts are personal views only.
Oxfordshire, United Kingdom
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