Well, the IRSs can drift, and FSX does model the decreased sensitivity of VORs at range. GPS might be accurate, but I'd imagine that PMDG took into account the actual precision of the GPS receivers on the real 737.

the Civa INS that comes with the FSlabs Concorde has a built in error accumulation when out of range of a VOR for updating. Also the Level-D 767 features this. I imagine aircraft fitted with proper itergrated GPS systems will be very accurate 99% of the time.

How exactly is ANP calculated fluidly/realistically when all nav sources are 100% accurate in FS?

They could set ANP to a fixed (typical) value and leave it like that, their simulation would not suffer.Or they could use some statistical data and modulate ANP, the only interesting event is when ANP exceeeds RNP and they could give you this once-in-a-lifetime-event- these are pretty rare events.But the biggest threat to RNP operations is not the lateral error - it is the special baro-VNAV that these aircraft use. This is the weakest link.

Aaaaa.. interesting, perhaps I was onto something after all, great to be of service. :(

Haha, still. Think we learned something. And it's still localizer deviation, and still the indication was weird and useless. Good to see it all made sense.

well the new AoA video shows the HGS to be utterly fantastic!. I cant wait. Its like when your a kid and its Christmas eve and you know whats coming so you cant sleep, but its like that 24hours aday 7 days a week. Maybe I just need to get out more. :(

How exactly is ANP calculated fluidly/realistically when all nav sources are 100% accurate in FS?

The ANP does vary, I've seen it do so, though not by a drastic amount. It's like any other indication in the NGX: it is dynamic and reactive, but unless you introduce a whole bag of failures or start switching off systems your ANP value is going to remain pretty low anyway!

It looks like the vertical lines point "where the nose of the aircraft is pointing", which would be a bit to the right due to crosswinds. My wild guess! :(

It looks like the vertical lines point "where the nose of the aircraft is pointing", which would be a bit to the right due to crosswinds. My wild guess! :(

No, it should have nothing to do with the wind.The vertical line should be roughly where the localizer beam is.

Will the NGX simulate RNP approaches like that of KEWR R29 where RNP values are set to less than .3 miles lowering the minimums.

Again, read Robert's statement ofn RNP, it is not difficult to find. I don't want to use my own words because someone will accuse me of not being faithful to the orginal statement.

I believe the MD11 will decellerate on VNAV pretty smooth also, but of course that's PMDG also.

Thats incredible! I am really excited to get my "hands" on this "plane". JaneRachel, please excuse this question if comes across rude or anything else! But my question is based off your screen name. Are you one of the very few female sim pilots ? If so, I think thats awesome and I hope to have more women flying FSX style in the future. If not, weird name dude :) Cheers!

How exactly is ANP calculated fluidly/realistically when all nav sources are 100% accurate in FS?

Remember that even in the real aircraft, the computers can't know how accurate the navigation solution is - the ANP is a representation of how confident the system is of its computed position. The system uses a lot of fancy algorithms to decide how much accuracy each navigation input is worth to come up with the ANP. The GPS input works a little bit differently because each of the two GPS actually know how accurate their 'position' is (based on the geometry of the satellites) and I would guess that this would have an impact on the ANP. Cheers, DZ

Ha, then it should be possible to replicate the Perm crash scenario (http://www.aaib.gov.uk/cms_resources.cfm?file=/VP-BKO_Report_en.pdf), when the crew erroneously entered IRS position (1nm off), the IRS error accumulated during the flight to over 2.7nm (the bigger error at start, the higher ratio of error accumulation during the flight), and due to lack of GPSes and other navigational aids, the FMS-computed position could not be corrected. cheers,Jakub

Remember that even in the real aircraft, the computers can't know how accurate the navigation solution is - the ANP is a representation of how confident the system is of its computed position. The system uses a lot of fancy algorithms to decide how much accuracy each navigation input is worth to come up with the ANP. The GPS input works a little bit differently because each of the two GPS actually know how accurate their 'position' is (based on the geometry of the satellites) and I would guess that this would have an impact on the ANP. Cheers, DZ

You make a good point on the GPS systems. By having the two GPS radios I would assume it makes it very diffiuclt then the get the ANP to rise significatly to where it challenges the RNP. In the PMDG, and of course this is more of a question to those on the beta, is it possible to fly a NGX that is not equiped with GPS and thus rely only on the IRS and the pilot entered initial position?