RNP ANP

[dano291]

What does the RNP and ANP mean on the ND? This only showed up when I started flying the 900, also Ive read alot about greasing in the landings but as of yet no luck. If im at the recomened speed with full flaps the slight back pressure its like the ground effect is unreal i have to break the rule on pushing the nose down which is a no no as you know but to slow i smack the ground to fast my master caution flicks on and off and my teeth rattle. Ive been a pilot sense 1969 but this is tough to get it just right.Thomas Thompson

[wisefox7524]

First off, read the manuals/use the forum search function...they are your best friends. RNP = Required Navigation Performance. ANP = Actual Navigation Performance. You can choose to display them or not by using the FMC's built-in options feature.

Edited March 4, 2012 by rnathe

[Tabs]

Required Navigation Performance & Actual Navigation Performance. This is a huge subject that I don't really have time at this minute to type up. It has to do with the precision of the FMC's calculated position. It's what allows procedures to be flown with the FMC as the primary navigation source (ie no raw data from a ground-based navaid)

[Fabo]

Basically, any published routing has a number that is published somewhere, that states how precise you need to be to be able to fly that routing. Numbers vary, the least precise are some airways, usually non-rnav, where you can deviate up to 10 miles from the actual routing. The requirements will tighten when you want to fly on RNAV airways, then on SID/STAR procedures or RNAV transitions - you might sometimes see wording such as "P-RNAV capability required" for a certain SID or STAR on this or that airport.The biggest precision is required for so-called RNP approaches, down to 0.03 or maybe even less.The airplane knows what precision it can provide at the specific moment - it calculates its position from various sources, ranging from inertial reference system to GPS. Usually, the precision will be very high, but it can go to the drain, if your GPS fails, and you are over the ocean, for example...NPS, or Navigation Performance Scales will then let you monitor your navigation performance, or precision, in real time, which can be useful.