2 questions:
1. It is often NOTAM'd the GPS accuracy in NE. Italy is/maybe compromised. Why is this so?
2. Accuracy for NPA's. (nevermind PA's.) I see students fly autopilot LNAV approaches with no regard for checking the raw data lateral navigation. They should, but they don't. Now VNAV approaches are also in use it is also vital to check raw data for vertical. Again not so methodicaly done. They've checked RNP v ANP and all seems hunky dory, so they allow George to lead them to terra firma, hopefully in the correct place.
I heard that in Gulf War 1, (or was ir 2) before Bill, there was a error inputed into the civilian received GPS signal. I don't know how much. If it was deemed necessary - for national security - I presume the USA could do this again. What warning would us civvies be given about this. If the map shift was 0.5nm, and pilots blindly follow George as they do now, Ouch! Would such an inputed error trigger the message "Unable Reqd Nav Perf-RNP" during the initial approach? I assume that any such error would be acceptable at CRZ levels, but only become unsafe during terminal operations. In the CRZ would the ANP be much closer RNP value than normal thus indictaiong that there could be a problem at lower levels? (IRS + VOR/DME cross checking at lower levels would likely be within what non-GPS a/c call map shift parameters. On the B733 that was often > 0.5nm overland and often >1.0mn after seas crossings.)
Given all the NOTAM guff we have to study during the very very short flight planning phase at the start of the day I would hope there would be a very conspicuous method to alert us to any deficiencies in the system.