need help with GPS questions!!!

[ubernerd]

I am planning on writing the INRAT very soon, and need a few things clarified (hopefully someone can do this for me) I was under the impression that if you had a RAIM warning at any stage during a flight (enroute, approach), you had to discontinue using the GPS as your means of navigation (unless in an emergency) correct me if I am wrong??? I have also just been informed that a GPS with an out of date databank can be used in IFR flight, can someone please tell me in what situation it can be used, and where I can locate the information..... I cannot find an answer to either of these questions in any of my studying aids and would REALLY appreciate any help given!!!

[DHC3Rwannafly]

read the AIM.....

[ubernerd]

thanks, I have actually read the AIM many times. I have gone over and over the RAC and COM sections and can't still can't find the answers!

[CID]

From AIM:

In practice, pilots can use GNSS for guidance most of the time. If an integrity alert occurs while en route, the pilot can then continue by using traditional aids, diverting if necessary from the direct routing, notifying ATS of any changes to the flight and obtaining a new clearance, as required.

All approaches must be retrieved from the avionics database, and that database must be current. While it is sometimes acceptable to use pilot-generated waypoints en route, it is not permitted for approach procedures, as any database or waypoint coordinate errors could have serious consequences.

From a typical GPS Flight Manual Supplement:

Limitations:

IFR enroute and terminal navigation is prohibited unless the pilot verifies the currency of the data base or verifies waypoints for accuracy by reference to current publications.

Instrument approaches must be accomplished only in accordance with instrument approach procedures that are contained in the GPS navigation data base. The GPS must incorporate the current update cycle. The pilot must verify approach waypoints for accuracy by reference to current publications.

Abnormal Procedures for RAIM alerts from a typical GPS AFMS:

During approach operations:

Terminate IFR approach and execute a missed approach if required.

During enroute/terminal operations:

Continue to navigate using the GPS or revert to an alternate means of navigation. When continuing to use GPS navigation, position must be verified every 15 minutes using other IFR approved navigation systems

So generally speaking, for approach operations, you MUST have a current navigation database and no RAIM alerts. For enroute operations or terminal operations, you can use an outdated database if you can verify the accuracy of the waypoints. Furthermore you can fly enroute/terminal with a RAIM alert if you verify your position every 15 minutes using some other means.

The contents of GPS flight manual supplements vary a bit so don't treat this as gospel for all installations.

I hope that helped.

[ubernerd]

thanks CID, that helped!!! Although I have read those very paragraphs from the AIM, I was still a bit confused!

[husky]

edit...i just realized CID said pretty much the same thing I did.

[groundtoflightdeck]

If you loose RAIM you should revert to different nav aids. RAIM goes sometimes then comes back so you can plug along until it returns, but be prepared to use the traditional nav aids- as thats not really proper. If you loose RAIM on an approach you should execute a go around.

You can use the GPS with and expired database for En Route and Terminal Modes (Ie/ Everything but apporach) so long as you confirm your waypoint coordinates with the coordinates provided on a CURRENT chart.

Hope thats more clear than the AIM