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Garmin GNS430 & 530 versus 430W/530W (and approach coding)

Airborne_Again wrote:

Does the US publish DH? Most ICAO countries do not. They publish OCH and it is then up to the PIC to determine the DH.

No, that is a European thing. US, Australia and Canada all use DH/MDA in their government plates. European usage of OCH is just plain unhelpful to IFR pilots and actually makes commercial providers more attractive.

EGTK Oxford

Yes, really arrogant to publish minima which are not directly usable.

On a similar topic (why are UK AIP plates not readable in A5) the CAA head of charts told me that they are not in the business of competing with commercial providers!

Seems to be a pattern in Europe.

Shoreham EGKA, United Kingdom

Cobalt wrote:


Vertical Alarm Limit. It is the maximum permitted value for VPL which is the Vertical Protection Level. VPL is measured as the integrity parameter for vertical guidance on a vertically guided approach. It is dynamic and must not exceed the VAL value in order to not have the vertical guidance flagged. It is the vertical 5 sigma limit that encompases the actual vertical position.

KUZA, United States

huv wrote:

Eurocontrol document, LPV system minima is 200 ft AND the required VAL is 50 m.

I don’t see the two together. VAL for DH of 250 or greater is 50 meters. VAL for DH < 250 is 35 meters. The VAL is coded in the database for the specific approach. I don’t believe that Europe is less conservative than the US. No US procedures with a DH less than 250 feet have a VAL other than 35 meters.

KUZA, United States

NCYankee, the Eurocontrol document has the VAL = 50 m on page 5 and the system minimum of 200 ft on page 7. However, I suspect you are right. The document is obviously not a technical or authoritative paper, but only a presentation. But Part-NCO, which is the law for pilots, makes no mention of VAL or HAL. I think I will ask some of the gurus in PPLIR.

Last Edited by huv at 30 Oct 19:26
EKRK, Denmark

I’ve also wondered how a pilot in Europe is supposed to know whether a specific LPV approach was designed for LPV250 or LPV200.
What information does Jeppesen use when they calculate the DA?

One thing that I have heard that the EGNOS NOTAMs for LPV250 and LPV200 are different.


Anders wrote:

What information does Jeppesen use when they calculate the DA?

It looks as if Jeppesen has done exactly as you and I would have. Compared the OCH and the system minima and used the higher value. Since I referred to Part-NCO in an earlier post, I have checked Part-CAT also, and confirmed that system minima is lowered to 200 ft for commercial ops flying LPV also, and the way DH is established is identical. So Jeppesen would not have the problem of differentiating between commercial and non-commercial ops.

With system minima being 250 ft at the time of Jeppesen publishing an approach, that would have been the minimum value for the approach before lowering system minima.

Whether system minima was actually lowered with the final introduction of the new OPS rules on August 25th this year, or it happened before, I do not know.

It would be interesting to know if any LPV approaches have been commissioned i EASA-land since August 25th, and which DH Jeppesen in that case have put on their plates.

Last Edited by huv at 31 Oct 13:01
EKRK, Denmark

Jeppesen gets the FAS Data Block as part of the definition of the final approach definition. It includes fields for the HAL and VAL values. I also presume they get the DA in source data from the state. They certainly do from US TERPS.

KUZA, United States

Should not the HAL and VAL value be considered, among a myriad of other parameters, when designing the approach and establishing the OCA(H) ?
In which case those values must satisfy LPV200 conditions in order to result in a OCH below 250 ft.
That is the only way I can get the rules to make sense.

Last Edited by huv at 31 Oct 13:12
EKRK, Denmark

HAL and VAL are not considered, they are set to match the requirements of the approach.

HAL and VAL values for various types of approach procedures:

LPV DH >= 250 feet, HAL is set to 40 meters and VAL is set to 50 meters
LPV DH < 250 feet, HAL is set to 40 meters and VAL is set to 35 meters
LP, HAL is set to 40 meters and VAL is not set, but if advisory vertical guidance is provided (+V), then VPL must not exceed 50 meters
LNAV/VNAV HAL and VAL are not set, but HPL must not exceed 556 Meters and VPL must not exceed 50 meters
LNAV HAL and VAL are not set, but HPL must not exceed 556 Meters and if advisory vertical guidance is provided (+V), VPL must not exceed 50 meters

In the US, there are two LPV specifications, LPV and LPV200. The main difference is that LPV only provides for a DH to 250 feet, while the LPV200 provides for a DH down to 200 feet and a visibility as low as 1/2 SM. In order for a runway to qualify for the lowest LPV200 DH and visibility, the runway must be at least 4200 feet long, have precision markings, approach lights, and a parallel taxiway. There must not be any obstacles in the 34 to 1 slope as well.

KUZA, United States
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