Simviation Forums

What is it, and how do I do it?  I've noticed that some airports have it as an option... I couldn't find a thread that already discussed it!

I might be wrong here, but dont GPS approaches use RNAV?

In that case, you would really need a FMC.

 

You select the proper approach and make SURE you have the NAV/GPS switch to GPS!
Since I'm not familiar with the garmin's (hey you don't find those in the 737's ) I cannot offer you any further advice other than YES, if it's a GPS approach you should be able to fly the approach by using the GPS as the only nav. source.

Billerator (this is long, sorry!) RNAV and GPS is not the same thing. RNAV has to comply with some strict navigation standards.

You don't need a GPS to fly in RNAV, just make sure radio updating is available.
The GPS is not needed because the FMC doesn't only use GPS for position updating, but also DME-DME, VOR-DME or even the IRS of course...

RNAV allows for a more tightly controlled airspace, some as narrow just some nautical miles. RNAV capable aircrafts will have better treatment in both cruising altitude and routing, but the price is quite high. We're talking about expensive gear here

To fly RNAV departures/approaches the aircrafts must meet a criteria called RNP. RNP is short for Required Navigation Performance. RNP is the navigation capability which is necessary for the aircraft to fly in a certain airspace segment.
RNP is expressed in nautical miles so if it says:
RNP 1.0
it simply means your navigation has to be more precise than a 1nm error from your true position

Different air segment has different RNP values. Oceanic airspace where accuracy is not that important allows for a 12nm error margin (RNP 12) but in busy airspace such as during an approach the RNP is 0,5!

the following is from another post by me a while back that explains a GPS approach. please tell me if you have any questions.

this involves programming a GPS approach, so youre gonna have to be somewhat familiar with the GPS module.

hit PROC on the module. in there, if the airport is significant enough, it should have pre-programmed GPS approaches to given runways at your destination airport. know which runway you are going to land on, and use the arrows to select that approach. on the next screen, if you are already on approach and no longer have NAV hold engaged, select "Activate vectors-to-final". if NAV hold is still on, then select "Load vectors to final". then, when NAV hold is no longer engaged, activate it. now, when its activated, MAKE SURE THE NAV/GPS SWITCH IS SET TO GPS. then, engage NAV hold and ur plane will stay centered on the runway. once your plane is lined up with the runway, set the heading hold to your current heading and engage heading hold. turn the GPS/Nav switch to Nav, because only on Nav can you see the ILS (except for B737). DO NOT TRY TO ENGAGE APPR WHILE THE NAV/GPS MODE SWITCH IS STILL SET TO GPS! this will result in disaster! anyway, the GPS approach for large jets is mainly a way to get your plane lined up on the runway earlier than need be, and to make sure you dont have to manually guess at headings before the ILS intercept. for smaller planes (or for runways without an ILS glideslope), what it does is allows you to concentrate on your altitude and not worry about staying lined up with the runway. ok, i know that may have been a bit fuzzy, so if theres anything you need me to clear up tell me.

Yeah I knew that RNAV was waaaaaay beyond my size of aircraft, so Ive never really payed any attention to it ( though I have the charts for RNAV ) .

Nice explanation there though  8) .

I have ambiitons to fly larger aircrafts than the Caravans so I'm doing my homework now just to get a head start  :)

If one has the DEST airport in the default FS9, GPS500 (or 295) and clicks on the PROCedure button, any GPS APProaches will be listed. Using the GPS/NAV combination the plane will then fly it. Altitude must be controlled by the crew.

as a general rule, realworld GPS APProaches are not approved for primary nav and often show a disclaimer: "GPS guidance not for navigation but monitoring only"
Bill