GPS Primary Lost during RNP-AR approach

[divinehover]

Hi All

This questions refers to Missed Approach actions in the event of a GPS Primary lost on both sides on A320/330 types during a RNP-AR approach WITHOUT a Nav Accuracy Downgrade.

In this case, can the Missed Approach be flown in Nav mode or will you need to pull Heading to execute the extraction maneuver?

Obviously the actual RNP will degrade without GPS sensor input, but can we rely on the Nav accuracy until the Nav Accuracy Downgrade alert?

[underfire]

Is the MA a coded RNP-AR procedure in the box?

[Stone_cold]

DH , you should defer to your organizations policies instead of relying on the opinions proffered here . . The replies don't seem to indicate a knowledge of the requirements / setup / or various missed approach criteria and techniques .

[divinehover]

Stone Cold

I couldn't agree more. I just wanted to see if there was a difference in the way other operators would handle the situation.

[divinehover]

Stone Cold

I couldn't agree more. I certainly won't be using this forum for for policy development. I just wanted to see if there was a difference in the way other operators would handle the situation.

[aterpster]

Stone Cold:

DH , you should defer to your organizations policies instead of relying on the opinions proffered here . . The replies don't seem to indicate a knowledge of the requirements / setup / or various missed approach criteria and techniques .

I would add that DH has obviously not been through an RNP AR training program.

Just as an overview for the lurkers: there are two levels of nav redundancy required for RNP AR.

"Entry level" also known as single string, does not require at least one IRU but is limited to RNP 0.30 for minimums, and RNP of 1.0 or greater for the missed approach. If GPS is lost extraction can be by whatever means is available, including DR.

For any minimum of less than 0.30, or missed approach of less than RNP 1.0, then at least one IRU is required (dual string) to provide stand-alone IRU position for extraction. Missed approach protected airspace for a missed approach of less than RNP 1.0 requires the missed approach laterally protected airspace expand at a rate greater than the presumed decrease in accuracy of a stand alone IRU.

[rudderrudderrat]

Hi aterpster,
then at least one IRU is required (dual string) to provide stand-alone IRU position for extraction.
Good job we have 3 IRUs plus all the rest of the equipment listed under Aircraft Equipment Requirements on page 6 of http://www.uasc.com/documents/whitepaper/UASC_RNAV_WhitePaper.pdf

[Microburst2002]

It looks like they need to clarify the RNAV RNP approach procedures a bit more:
To begin with, they need to clarify when to go around, when to extract and when to "fly the black"

[The bird]

Well depends. If you fly a GNSS/GPS app then 2x GPS primary is req so check GPS pred in both boxes. Once you started the app you are allowed to continue if you lose one GPS sensor. If you lose both you must go around. If accuracy is high I would consider flying the GA in nav and if possible back it up with raw data or just ask rv.

[safelife]

You may fly the missed approach in NAV, provided the nav accuracy doesn't drop below 1.0 NM.
If it does (likely only if no DME-DME update possible) you would have to go on heading and follow conventional navigation.

I don't think there is a GPS RNAV approach with only GPS based missed approach segment, that would leave you with no option in case GPS failes. Which is possible even with positive RAIM prediciton as it could be switched off or just fail.

[aterpster]

Micro:

It looks like they need to clarify the RNAV RNP approach procedures a bit more:
To begin with, they need to clarify when to go around, when to extract and when to "fly the black"

All of that is supposed to be covered in an RNP AR qualification training course.

[aterpster]

safelife:

You may fly the missed approach in NAV, provided the nav accuracy doesn't drop below 1.0 NM.
If it does (likely only if no DME-DME update possible) you would have to go on heading and follow conventional navigation.

That is correct only if the selected line of minimums is no less than RNP 0.30 and the missed approach does not require RNP of less than 1.0. Otherwise at least one IRU is required for the missed approach or extraction.

I don't think there is a GPS RNAV approach with only GPS based missed approach segment, that would leave you with no option in case GPS failes. Which is possible even with positive RAIM prediciton as it could be switched off or just fail.

Sure there are. But, the approach in such case does not require RNP of less than 0.30 and the missed approach doesn't require RNP of less than 1.0 In such case the missed approach will splay essentially like a conventional RNAV IAP. If you are in a remote area you have to DR the missed approach if the GPS signal fails. There are quite a few basic RNAV IAPs in remote areas that have no ground-base nav backup. Take a look at KBIH:

http://aeronav.faa.gov//d-tpp/1403/05737RR30.PDF

This approach does not require IRU redundancy and there is no requirement that the BIH VOR be operational to fly this approach.

[I-2021]

Hi All

This questions refers to Missed Approach actions in the event of a GPS Primary lost on both sides on A320/330 types during a RNP-AR approach WITHOUT a Nav Accuracy Downgrade.

In this case, can the Missed Approach be flown in Nav mode or will you need to pull Heading to execute the extraction maneuver?

Obviously the actual RNP will degrade without GPS sensor input, but can we rely on the Nav accuracy until the Nav Accuracy Downgrade alert?

Hi,

have a look at the Getting to grips with rap-ar. Just google it and you will find the link.

Cheers.

[aterpster]

202:

have a look at the Getting to grips with rap-ar. Just google it and you will find the link.

The loop can't really be closed without going through the training. And, that qualifies the pilot only one type of airframe/FMS combo.

[kopatuc]

Sorry to go off subject But,
What are the procedures for a Comm failure after T/O from a radar and Non radar airport.? (ETOPS)