Approaches

[GravityHater]

What is the operational difference between these approaches?

1 GPS
2 GPS (RNAV)

 

[troy]

somebody correct me if i'm wrong, but you could use LORAN with RNAV?????

 

[dkelly]

Actually, I do not believe that there are any loran units certified for IFR approaches-my bad, just hadn't seen a Loran Runway 3 approach. I would have to look at a plate, but I think that it may be an overlay such as many GPS approaches overlay a VOR approach.

 

[MauleSkinner]

GPS approaches are generally overlaid on some other approach.

GPS (RNAV) approaches are designed as GPS approaches from scratch, and are generally in the "T" configuration rather than having a procedure turn.

Fly safe!

David

 

[mike1mc]

I think GPS was the old designator for GPS approaches and GPS overlays (i.e. VOR or GPS Rwy 13).

RNAV (GPS) now designates all the standalone GPS approaches. Other RVNAV approaches will remain the same (i.e. VOR/DME RNAV Rwy 13). There is some more info in the AIM 5-4-5 paragraph 3.

 

[BLing]

Correct me if I am wrong:

GPS approaches are GPS approaches (overlay or whatever)

GPS (RNAV) Approaches could be used as either a GPS or an RNAV approach depending on your a/c equipment.

 

[avbug]

Actually, I do not believe that there are any loran units certified for IFR operations.

Oh really? Wow, we've been doing it illegally all these years. There was life before GPS, you know.

RNAV has been around a long time, longer than GPS by a long shot. In many forms. VOR/DME (Rho-Theta), LoRaN-C, DME/DME, FMS (multi sensor), INS/IRS, Omega, and today we have GPS, and DGPS, to name a few.

GPS is Global Positioning System...RNAV is Area Navigation, and can take many forms of nav input, from GPS to DME/DME to INS/IRS, to multifunctional units that take input from all types of sources...and yes, even LORAN.

A GPS approach is a GPS approach. It requires GPS. An RNAV approach requires approach approved RNAV equipment, but doesn't necessarily require that GPS be the only or primary sensor in use while flying the approach. The GPS approach can only be flown by GPS equipment, while the RNAV approach can be flown by any area navigation system certified to the minimum RNP (required navigational performance) level assigned to the approach.

 

[GravityHater]

i guess I'm dumb as a rock, because I still don't know how they are different or what I need to do differently despite everyone's attempts to answer my Q

If the approach has the three letters G P S in it somewhere and I have an approach-cert'd GPS unit I somehow figure I can do it.

 

[MauleSkinner]

If the approach has the three letters G P S in it somewhere and I have an approach-cert'd GPS unit I somehow figure I can do it.

That's about the extent of it...

As Avbug said, there are other means of navigation that might qualify for RNAV (GPS) approaches, but if you don't have 'em, you don't need to worry about 'em

Fly safe!

David

 

[dkelly]

Oops

Oh really? Wow, we've been doing it illegally all these years. There was life before GPS, you know.

My bad, edited my post, just hadn't seen a Loran approach before.

 

[avbug]

i guess I'm dumb as a rock, because I still don't know how they are different or what I need to do differently despite everyone's attempts to answer my Q

If the approach has the three letters G P S in it somewhere and I have an approach-cert'd GPS unit I somehow figure I can do it.

Careful. Some of my best friends are rocks. Next time, do a little more research.

Seriously, you have the answer. In the case of both GPS and RNAV, you must first determine if your approach approved nav unit has the approach in it's database. In the case of the GPS approach, you must have GPS. This includes ensuring that you have adequate signal at the time, that you have it available, that your sensor is working. If you're using other types of area nav, you can't fly the GPS approach if you don't have GPS.

The RNAV approach, which encompasses all forms of RNAV that meet the RNP requirement, may also be flown by the GPS, so long as it meets the specified RNP requireent for the approach...so that would be step three...determining that your unit is certified to mee the required RNP capability requirement of the approach proceedure to be used (if specified). It may, or may not. You'll also need to make a RAIM determination to ensure that your unit can receive adequate signal at the arrival time and hold approach mode during the arrival.

You also need to ensure that your unit sequences to the necessary RNP selectivity during the approach. Some units do it automatically, some elementary ones and early ones do not.

Jedi Nein should reply to this thread, as she's written something like twenty or more books, brochures, pamphlets, and guides on the subject, many specific to each unit that's out there to be found. (Worth picking up if you own that unit or fly it, or are thinking of flying it).

As far as the operational requirement of flying them, it remains the same. You either show the waypoint as flyover or flyby, the latter enabling an early turn, and you fly according to the minimums listed on the proceedural chart. The real difference is in the equipment required to fly either one. Some proceedures may exclude certain sensors or types of RNAV...for example, a proceedure may be RNAV, but specifically disallow DME/DME. You must have available whatever the specific proceedure requires.

Eventually you'll be seeing all proceedures labled RNAV, as it's a rare thing any more to see any kind of RNAV unit that doesn't include GPS.

 

[mike1mc]

From the AIM:

WAAS (LPV and LNAV/VNAV), and GPS (LNAV) approach procedures will be charted as RNAV (GPS) RWY (Number); e.g., RNAV (GPS) RWY 21.

VOR/DME RNAV approaches will continue to be identified as VOR/DME RNAV RWY (Number); e.g., VOR/DME RNAV RWY 21.

VOR/DME RNAV procedures which can be flown by GPS will be annotated with "or GPS" e.g., VOR/DME RNAV or GPS RWY 31.

 

[cvtplt]

Thanks avbug. The way you describe it is much easier to understand than trying to read it out of the AIM. I may be a rock also. Oh well.

 

[GravityHater]

Next time, do a little more research.

Thats what I call this!

Hey. Can I reword what y'all have said in short form, to see if I got it?

GPS RWY 21
you need a GPS (with all the caveats you mentioned)
only a GPS can do this approach

GPS (RNAV) 21
you can do this with a GPS (with all the caveats you mentioned*)
but other units can do these as well.

*one of the caveats is: Because this one has RNAV in the title, your unit must be capable of the required RNP for this approach.

Rocks a-Rattling!

 

[avbug]

GPS RWY 21
you need a GPS (with all the caveats you mentioned)
only a GPS can do this approach

Any approach approved RNAV unit that has GPS capability can fly this approach. A FMS, for example, which may have sensor inputs from many sources, including GPS.