julesmusician
Posts: 378
Joined: Sun Aug 28, 2005 3:25 am

Rnav Precision/implementation/GPS Use

Wed Dec 14, 2005 5:35 am

I have been reading a lot about RNAV, but it seems quite complex. Is GPS appropriate for what I have read is called "precision RNAV" and how is it being implemented across different places at the moment? A document says aircraft for some routes must be precision RNAV equipped - isn't that the same as GPS. Are there many routes this is now used on or is it still experimental stages?

J
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
usnseallt82
Posts: 4727
Joined: Tue Jan 06, 2004 4:49 pm

RE: Rnav Precision/implementation/GPS Use

Wed Dec 14, 2005 7:00 am

Quoting Julesmusician (Thread starter):
Is GPS appropriate for what I have read is called "precision RNAV" and how is it being implemented across different places at the moment?

Military uses it extensively.

Quoting Julesmusician (Thread starter):
Are there many routes this is now used on or is it still experimental stages?

Both. GPS is developing rapidly, but it isn't to the point where precision GPS/RNAV approaches can be made to a lot of locations. However, many are beginning to see the feasibility of it and are trying to implement the approaches. A lot of it has to do with what standard equipment the aircraft coming in have. If its a regional airport with mainly CE-172's as traffic, don't expect one too terribly soon. But, most of the busier airports are trying to get approaches made for this.
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xjramper
Posts: 2318
Joined: Wed Dec 10, 2003 1:10 am

RE: Rnav Precision/implementation/GPS Use

Wed Dec 14, 2005 12:23 pm

Quoting Usnseallt82 (Reply 1):
If its a regional airport with mainly CE-172's as traffic, don't expect one too terribly soon. But, most of the busier airports are trying to get approaches made for this.

Actually there are a lot of airports with this function that usually get small light aircraft.

Im guessing that you are talking about the RNAV/LNAV function. Its basically an ILS, but instead of radio waves, you are using satallite nav.

XJR
Look ma' no hands!
 
Woodreau
Posts: 1186
Joined: Mon Sep 24, 2001 6:44 am

RE: Rnav Precision/implementation/GPS Use

Wed Dec 14, 2005 1:04 pm

RNAV is just a form of area navigation - it's been around since the 1970's the earliest crudest form of RNAV was with the VOR/DME RNAV computers "VOR mover" (you might find these avionics, like the KNS-80 on some older aircraft)

In some aircraft, RNAV is implemented by the FMS. Most smaller general aviation aircraft don't have an FMS, so an appropriately certified GPS receiver alone does qualify as RNAV.

Our airline has FMS equipped CRJ-200's/700's but we're not authorized in our opspecs to fly RNAV(GPS) / RNAV(RNP) approaches, we still have to switch to green needles and fly instrument approaches using the old NAV receiver using ILS or VOR/VORDME.

However we are allowed to use the FMS to fly these new RNAV DPs that are starting to be implemented across the US in places like Las Vegas, Dallas, Atlanta.

At airports served by major air carriers, RNAV approaches are a kind of a waste because any ILS, even a Cat I ILS will have lower minimums than a RNAV approach, it's a no brainer to go with ILS - an ILS will just get you down lower.

The biggest beneficiary of RNAV approaches is general aviation (little Cessnas and corporate/business jets) who operate out of smaller airports that might not have spent the money to get an ILS installed. RNAV will probably have lower minimums than the non-precision VOR/NDB approaches.

There are newer RNAV approaches - Approaches with Vertical Guidance (APV) which provide vertical guidance - similiar to the glideslope of an ILS. You can tell those approaches from the older RNAV approaches by looking at the minimums criteria. You'll have LNAV minimums, LNAV/VNAV minimums, and LPV minimums. The LNAV minimums is like the LOC minimums of an ILS - you can use those minimums if your RNAV equipment isn't certified or is incapable of providing the vertical guidance, just like you can shoot an LOC only approach instead of a full ILS approach. The LNAV/VNAV and LPV minimums are available for you to use if you have the RNAV equipment which provides the vertical guidance.
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