A320 Radio Nav disable
Joined: Aug 2007
Posts: 289
Likes: 2
From: The Netherlands
Setting Priorities
O(riginal) P(oster), do you mean that for an approach, where GPS is a requirement, you think that you should disable DME/DME updates, in order to be legal?
Isn't the priority sequence for updating, first GPS position, then DM/DME position, then VOR/DME position, which last mentined mode could be fighting for priotity with raw average INS position depending on time in NAV mode?
If GPS is available, IT will be the primary position source, so it wil not be necessary to DISABLE DME/DME updates. If DME/DME updating happens to be the primary mode, it means that GPS is not available, and if that is the case, a GPS REQUIRED approach cannot legally be performed.
Don't start your reasoning process from the back-end of the solution.
Isn't the priority sequence for updating, first GPS position, then DM/DME position, then VOR/DME position, which last mentined mode could be fighting for priotity with raw average INS position depending on time in NAV mode?
If GPS is available, IT will be the primary position source, so it wil not be necessary to DISABLE DME/DME updates. If DME/DME updating happens to be the primary mode, it means that GPS is not available, and if that is the case, a GPS REQUIRED approach cannot legally be performed.
Don't start your reasoning process from the back-end of the solution.
Joined: Mar 2007
Posts: 2,766
Likes: 4
From: Here and there
Would you please provide a link to GTG with RNP AR. My airline requires a RAIM prediction before departure if a crew can expect to fly a gnss approach.
How are you disabling Radio Nav updating?
How are you disabling Radio Nav updating?
Joined: Mar 2007
Posts: 2,766
Likes: 4
From: Here and there
Not all fmgs have the predictive GPS page and this requires a crew to access a RAIM forecasting website AUGUR GPS RAIM Prediction Tool - GPS Status
Joined: Apr 2006
Posts: 274
Likes: 0
From: Front right seat
For RNP-AR only. It's meant to protect the Nav accuracy (in case of corrupt ground station signal) in the case of GPS Primary failure to allow for a safe extraction procedure on IRS Nav. Nav accuracy should remain HIGH until a safe extraction in completed. A corrupt ground based signal will worsen the Nav accuracy.
Joined: Mar 2007
Posts: 2,766
Likes: 4
From: Here and there
Have a look at this FAA AC and in particular appendix 2.
http://www.faa.gov/documentLibrary/m...%2090-101A.pdf
I think that your procedure only applies to RNP AR, as the normal requirement for a standard go around is an accuracy of 1.0 nm.
I would still like to know what GTG is.
http://www.faa.gov/documentLibrary/m...%2090-101A.pdf
I think that your procedure only applies to RNP AR, as the normal requirement for a standard go around is an accuracy of 1.0 nm.
I would still like to know what GTG is.
Joined: Sep 2017
Posts: 1
Likes: 0
From: Colombia
For RNP-AR only. It's meant to protect the Nav accuracy (in case of corrupt ground station signal) in the case of GPS Primary failure to allow for a safe extraction procedure on IRS Nav. Nav accuracy should remain HIGH until a safe extraction in completed. A corrupt ground based signal will worsen the Nav accuracy.
