Predictive RAIM

[Ian_J]

Is there a reference that tells me exactly what I need to check for predictive RAIM along the route of flight?

Each waypoint? Just the destination airport?

Also, the AIM is clear on what to do if you lose RAIM prior to the FAWP or after the FAWP... is there any guidance on if you lose RAIM enroute? I remember reading somewhere where RAIM was only critical during approaches but can't find a reference.

Background - this is a military 128D IFR certified GPS and I am building classes to teach aviators with no GPS + IFR experience. The "manual" is less than stellar. I'm pouring through the AIM, my operators manual, our AWR and enclosures, and a bunch of other material.

Thanks so much for pointing me in the right direction!

 

[Alchemy]

I may well be mistaken, but I believe RAIM needs to be verified at all points on your route for which GPS is the primary means of navigation to said point. The airline dispatchers have vendors which provide this service. One time, at brand X, the vendor went T.U. randomly and we all had to file/fly straight J-airways along with conventional nav arrivals and departures (because dispatch couldn't satisfy the requirment to verify RAIM without this vendor operating properly). For most of us it's all taken care of by dispatch as far as I know; I'm not sure how this applies to aircraft with full blown independent IRU's capable of B-RNAV or better, but in a previous life GPS was all we had so RAIM had to be verified.

 

[moxiepilot]

http://www.faa.gov/about/office_org...vice_units/techops/navservices/gnss/faq/waas/

answers questions about RAIM and WAAS

 

[Ian_J]

http://www.faa.gov/about/office_org...vice_units/techops/navservices/gnss/faq/waas/

answers questions about RAIM and WAAS

Thanks Moxie - I had actually already looked there and it basically regurgitates what the AIM says about RAIM. Appreciate the help though!

 

[Ian_J]

I may well be mistaken, but I believe RAIM needs to be verified at all points on your route for which GPS is the primary means of navigation to said point. The airline dispatchers have vendors which provide this service. One time, at brand X, the vendor went T.U. randomly and we all had to file/fly straight J-airways along with conventional nav arrivals and departures (because dispatch couldn't satisfy the requirment to verify RAIM without this vendor operating properly). For most of us it's all taken care of by dispatch as far as I know; I'm not sure how this applies to aircraft with full blown independent IRU's capable of B-RNAV or better, but in a previous life GPS was all we had so RAIM had to be verified.

Thanks - I wonder if that's specific to 121 ops?

 

[Ian_J]

Actually, I think I just found my answer in AC 90-100A:

(5) If TSO-C129 equipment is used to solely satisfy the RNAV requirement, GPS RAIM availability must be confirmed for the intended route of flight (route and time) using current GPS satellite information. The availability of SBAS or ABAS fault detection can be determined through NOTAMs (if available) or through prediction for the intended RNAV 1 or RNAV 2 operation. Operators may choose to monitor the status of each satellite in its plane/slot position, account for the latest GPS constellation NOTAMs, and compute RAIM availability using model-specific RAIM prediction software, or by using the FAA en route and terminal RAIM prediction website: www.raimprediction.net , or by contacting a Flight Service Station. Receiver RAIM prediction capability can also be used. In the event of a predicted, continuous loss of RAIM of more than five (5) minutes for any part of the intended flight, the flight should be delayed, canceled, or re-routed where RAIM requirements can be met. Pilots should assess their capability to navigate (potentially to an alternate destination) in case of failure of GPS navigation.

Edit: And research fail on my part - my specific AWR states basically the same as above - I just glossed over it.