Hi,
I would like to add the following comments:
Airbus aircraft (equipped with Litton/Northrop Grumman LTN-101) use AIME (Autonomous Integrity Monitored Extrapolation) in their Global Navigation Air Data Inertial Reference System (GNADIRS).
Quote from the manufacturer's website:
"If the data’s integrity is compromised, AIME® automatically uses the aircraft’s position history to maintain accuracy and integrity."
http://www.nsd.es.northropgrumman.co...ucts/AIME.html
That means RAIM is not required, for example when you're doing a RNAV (GNSS) approach (for example with RNP 0.3).
As part of the pre-planning the pilot should check that more than 22 satellites are available from the expected time of departure time until the expected time of arrival. Applies to a flight were GNSS is required.
The US Coast Guard and the European AUGUR-Website
http://augur.ecacnav.com/ provide prediction tools.
Even if GNSS and Radio Update are not available, the IRS provides the pilot with good accuracy. Here's an example for the reliabilty of modern IRS:
From FAA Order 8400.12A (applies to RNP-10 airspace).
In case of a flight through the RNP-10 airspace you can fly up to 6.2 hours after the IRS system has been placed in the NAV-mode. This time can be extended depending on the IRS installed and the last time a Radio Updated was done.
Cheers,
Nabla330