B 737 800 RNAV APP and predicted satellite coverage

[slam dunk 4]

My OM-A says:

Dispatch based on RNAV Approach

For aerodromes where an RNAV approach is the only available approach a non-GNSS
based approach procedure must be available at the alternate aerodrome and satellite
coverage has to be verified for ETA +/- 15 minutes.
For aeroplanes using RAIM (B737): RAIM outages have to be checked regardless of number
of operational satellites.
If the predicted satellite coverage is insufficient the aerodrome is unusable except additional
fuel is carried according OM-A, 8.1.7.1.3 "Reserve Fuel".

How can I check on the FMS the predicted satellite coverage ....? RAIM Prediction where to find in the FMC??

On the ATR we were able to check the sat. coverage very easy by hitting some keys on the FMS progress page, it than showed us the number and availebilty of the satellites at our ETA ...but with the B738 I was not able find anything... any idea?

[ImbracableCrunk]

My company publishes the RAIM predictions on the same paperwork as the NOTAMs. We do RNP, and there's no procedure to look it up in the FMC.

[slam dunk 4]

ok thats the same procedure with my company except: the RAIM is not published with the briefing package! That was the reason why I asked....is there a trick where we could see it in the FMS? some people can even look up the density in the three different fuel tanks...I thought that their might be some experts who know how to manipulate the FMS to see the prediction.....

thanks for your quick answer!

[Denti]

As far as i know there is no possibility to check RAIM on the 737. All you need is an ANP less or equal to RNP. However to know in advance if that is given is something that puzzles me quite a bit.

In our OM A is no mention of RAIM, however the airbus fleet uses that quite a bit, the boeing fleet simply doesn't care. As long as the ANP is good enough we can do whatever we want, surprisingly i haven't seen an ANP of more than 0.05NM on the NG. On the classic we had approval to fly RNAV approaches with down to RNP 0.3, less wasn't possible as we had no GPS installed.

We are certified for RNP 0.1 approaches and CAT I approaches using GLS on the boeing, the airbus is certified for RNP 0.3 and no GLS.

[ImbracableCrunk]

I was just thumbing through out Standards Notes, and they made a point in the last two issues that RAIM prediction below the approach RNP is not required, but you might want to try a different approach, if you can.

But, most of my company's manuals are vague suggestions on possible ways of doing things.

[c100driver]

My airlines A320 are RNP AR certified to 0.10 and require a RAIM prediction prior to starting an RNP AR approach.

[V1... Ooops]

I have no idea how Predictive RAIM is viewed on complex aircraft such as Boeing and Airbus products, but on simple fixed-gear aircraft such as a Twin Otter, we just go to the PRAIM page and look.

The column on the left shows the RAIM prediction for 15 minutes before and after the expected approach time (this is taken from the FMS and is updated dynamically), and the column on the right is there to let you type in an alternate (CYVR is shown) and see if you will have adequate satellite coverage at the alternate.

It's not really necessary to look at this page, though, because if the RAIM prediction for the estimated approach time ever becomes unfavourable, the FMS will pop up a message advising the pilot.

Honeywell Primus Apex - Predictive RAIM Display

[Checkboard]

In our company the AUGUR GPS RAIM Prediction Tool, was used to look up the RAIM prediction at the briefing stage for 737 operations, when a GPS approach was to be planned.