RNAV: Can anyone tell me how to get it to work all the way to final approach?

I've been trying all afternoon. According to the YouTube tutorials I've watched repeatedly, on autopilot RNAV is supposed to follow the "glide path" ("glide slope" in an ILS approach), and bring you down to within a few hundred feet off the runway before you have to do anything--a near "look ma, no hands" procedure. I could not get RNAV to work that way in repeated attempts to fly an RNAV course from Watsonville to Monterey this afternoon. The AP would not initiate a descent. I set up the RNAV flight plan in the "world" map. Before I take off, I go to the Garmin and confirm it's loaded, including the approach waypoints. I take off, turn on the AP on my Logitech panel, push the NAV button, and the plane follows the magenta line. But when I arrive at the first waypoint on the approach plate, at the assigned altitude or below it--nada. The plane doesn't begin to descend. I've tried doing nothing; I've tried pre-loading the approach and activating the approach mode in the Logitech panel and the Garmin, and still no reaction. So what am I missing? Anybody?

https://forums.flightsimulator.com/t/rnav-no-glideslope-on-approach/236741

https://forums.flightsimulator.com/t/rnav-no-glideslope-on-approach/236741

So, based on this thread, I need to fly to the start of the landing approach on RNAV and then, having loaded the approach into the Garmin, switch to the localizer for an ILS-guided final. Too bad it doesn't seem to work as advertised, but that doesn't explain YouTube demonstrations I've seen like this one:

So, based on this thread, I need to fly to the start of the landing approach on RNAV and then, having loaded the approach into the Garmin, switch to the localizer for an ILS-guided final. Too bad it doesn't seem to work as advertised, but that doesn't explain YouTube demonstrations I've seen like this one:

 

In an RNAV you do not need a Localizer. it is LNAV VNAV based and strictly GPS driven. you usually have to set the next altitude on the MCP panel for the Autopilot to descend, unlike an ILS where the GS is captured and the Altitude window is not used after setting the Missed app alt.

 

There is an approach which uses VNAV with an ILS Localizer, called an LPV.

What aircraft are you flying?

a question always wished to ask

 

if RNAV is a poor way of landing compared to ILS, why its so widely used?

 

Any airport that has RNAV also has ILS, when Im planning my flight, i see tons of option for RNAV in arrivals but when I see the ILS I say, to hell with rnav, im going with ILS...simple, gliding cue

 

Other than if the ILS equipment in the ground is INOP, what make airline companies policies, or captains, towers, or better..who determines what landing approach? tower control approach? or rather, when the pilot is programming his FMC at departure, he makes a choice of the star and approach, what makes him prefer a RNAV over an ILS?

a question always wished to ask

 

if RNAV is a poor way of landing compared to ILS, why its so widely used?

 

Any airport that has RNAV also has ILS, when Im planning my flight, i see tons of option for RNAV in arrivals but when I see the ILS I say, to hell with rnav, im going with ILS...simple, gliding cue

 

Other than if the ILS equipment in the ground is INOP, what make airline companies policies, or captains, towers, or better..who determines what landing approach? tower control approach? or rather, when the pilot is programming his FMC at departure, he makes a choice of the star and approach, what makes him prefer a RNAV over an ILS?

 

the reason is because many airports do not have ILS. RNAVS don't need expensive ground based equipment, and are far more common. They are almost as good as an ILS (LPV is better), and the needles stay more constant. ILS is a radio frequency, so the needles can sway slightly like a VOR.

the reason is because many airports do not have ILS. RNAVS don't need expensive ground based equipment, and are far more common. They are almost as good as an ILS (LPV is better), and the needles stay more constant. ILS is a radio frequency, so the needles can sway slightly like a VOR.

 

thanks, i understand now

 

the needle factor must be a main factor, specially in bad weather, to avoid last minute corrections with a heavy jet full of passengers

RNAVS don't need expensive ground based equipment, and are far more common.

 

I don't have this new sim, but everyone keeps talking about RNAVs as if they are one specific type of equipment -- is that something the sim does? Granted that there are RNAV approaches, but all of those that I've seen (for the U.S. anyway) require GPS, and used to be called GPS approaches, if memory serves me right. In 1991 they had RNAV approaches but there was no such thing as GPS. VOR/DME and a course line computer were needed. In 1999 they had "VOR or GPS" approaches and "NDB or GPS" approaches, and VOR/DME RNAV approaches, among other things.

 

But in the real world, most of the discussion I've seen in this thread would be discussing GPSs, which are one of several types of devices that provide aRea NAVigation (RNAV), including a course line computer that uses VORs and DMEs, and LORAN, neither of which is common today but were in moderate use well before GPS was available. And these devices DID (do) need expensive ground equipment.

 

I'm not trying to quibble about terminology, but I am trying to get a handle on why everyone in this thread says RNAV instead of GPS when talking about the specific device known as a GPS -- I'm puzzled. I suppose it must be something in this new sim. So why RNAVs, which are not devices at all?

thanks, i understand now

 

the needle factor must be a main factor, specially in bad weather, to avoid last minute corrections with a heavy jet full of passengers

 

The ILS (or VOR) "wobbles" are not THAT bad. They're nothing more than a mild annoyance, when they do show up, and they don't require INSTANT correction, just gentle correction, usually very small.

 

And it's not nearly as bad as the occasional GPS jamming that the U.S. military sometimes conducts which means no GPS reception at all, or major errors, which may be worse.

I don't have this new sim, but everyone keeps talking about RNAVs as if they are one specific type of equipment -- is that something the sim does? Granted that there are RNAV approaches, but all of those that I've seen (for the U.S. anyway) require GPS, and used to be called GPS approaches, if memory serves me right. In 1991 they had RNAV approaches but there was no such thing as GPS. VOR/DME and a course line computer were needed. In 1999 they had "VOR or GPS" approaches and "NDB or GPS" approaches, and VOR/DME RNAV approaches, among other things.

 

But in the real world, most of the discussion I've seen in this thread would be discussing GPSs, which are one of several types of devices that provide aRea NAVigation (RNAV), including a course line computer that uses VORs and DMEs, and LORAN, neither of which is common today but were in moderate use well before GPS was available. And these devices DID (do) need expensive ground equipment.

 

I'm not trying to quibble about terminology, but I am trying to get a handle on why everyone in this thread says RNAV instead of GPS when talking about the specific device known as a GPS -- I'm puzzled. I suppose it must be something in this new sim. So why RNAVs, which are not devices at all?

 

Larry, I think you're asking the right questions. And the point you're making is valid and actually sheds light on the problem. From our simmer-only perspective, these different systems are features of a video game. Just like any feature of any video game, you expect it to work in a certain way when you push the right buttons on your joystick, keyboard or mouse. We experienced simmers have gotten used to the sim feature known as "ILS," but only simmers who are real pilots know how ILS works in real life. The rest of us? It's just an abstract thing where you push a few buttons, and then auto-magically your plane locks in to the correct pitch and glide scope, and then voila, you land.

 

RNAV is viewed similarly, I think. We simmers have the disadvantage of not getting any real training to explain to us what RNAV actually is, what it means, how it works, and what it looks like in real conditions. We just know that it's another thing where we should be able to push a few buttons, move the plane into a particular space, and then events occur that are very similar to ILS.

 

I say all this as someone who is still pretty confused about RNAV (I have not gotten to it in real-life ground school yet), and is following this discussion closely. Sooner or later I'm going to have to figure this out.

Edited March 20, 2021 by neilends
typos

But in the real world, most of the discussion I've seen in this thread would be discussing GPSs, which are one of several types of devices that provide aRea NAVigation (RNAV), including a course line computer that uses VORs and DMEs, and LORAN, neither of which is common today but were in moderate use well before GPS was available. And these devices DID (do) need expensive ground equipment.

 

I'm not trying to quibble about terminology, but I am trying to get a handle on why everyone in this thread says RNAV instead of GPS when talking about the specific device known as a GPS -- I'm puzzled. I suppose it must be something in this new sim. So why RNAVs, which are not devices at all?

 

I just shot an RNAV today in real life about 5 hours ago. The terms GPS and RNAV are pretty much used interchangeably at this point. We called it a GPS approach on the Unicom, the ATC called an RNAV, and the Jepp Chart and TCP called it an RNAV. They are pretty much strictly GPS approaches now with imaginary waypoints and altitude restrictions the GPS (or MFD computer) computes into a path that is fed to the HSI, CDI, or what we fly with, the PFD.

 

when RNAVs first showed up in the 1970s, they were based off of a VOR, NDB, and an INS or IRS, so you are right there, but now they are mostly just GPS approaches, with some aircraft, including ours not having NDB capability.

In an RNAV you do not need a Localizer. it is LNAV VNAV based and strictly GPS driven. you usually have to set the next altitude on the MCP panel for the Autopilot to descend, unlike an ILS where the GS is captured and the Altitude window is not used after setting the Missed app alt.

 

There is an approach which uses VNAV with an ILS Localizer, called an LPV.

 

Today, I finally got RNAV to work (more or less) the way it's advertised on a flight from Watsonville to Monterey in the Cessna 172. First, I "filed" a flight plan on the MSFS World page, selecting low-altitude IFR and then departure and approach options that gave me a straight-in approach over the Monterey Peninsula to RWY 10R at Monterey (KMRY). Once in the cockpit, I clicked on the Garmin's "Proc" button, selected a final approach to the runway, beginning at "ZBED" on the approach chart, or "plate," and loaded it into the Garmin. I set the autopilot for a 2,600 foot cruise altitude--the minimum altitude at ZBED.

 

Taking off from RWY 20 at Watsonville, I was already lined up with the Garmin's "magenta line." I climbed out, staying on that course, and then engaged the AP from my Logitech flight multi-panel, pushed the panel's NAV and Alt., and VS buttons (I'd set a climb rate before takeoff), and watched the AP do its job. When I got to ZBED, I reset the altitude for 1,700 ft., the arrival altitude at MINK, per the approach plate. At MINK (marked with an "x" on the plate), I pushed the APR (approach) button on the Logitech panel, at which point the AP followed the glide path (slope?) down to the runway. At a few hundred feet AGL, I disengaged the AP and managed a reasonably smooth landing (for me), clearing the runway at the first available exit.

 

In my experience with sim's G1000 so far, RNAV works well laterally (LNAV), but needs serious intervention vertically (VNAV). In my previous attempts to RNAV my way to a landing on RWY 10R at Monterey, I arrived perfectly lined up for a final approach but way too high, and either had to shed altitude really, really fast to make the runway or go around. It seems that RNAV won't bring you down to the tarmac on final unless you preload the final approach sequence into the Garmin and then actively manage your descent on final until you reach the waypoint where you can activate the preloaded approach, which I've learned is the one marked with an "x"--in this case, MINK on final approach to RWY 10R.

 

Now I'm off to try this routine from Watsonville to Mineta-San Jose International Airport in a Beech Baron.

I just shot an RNAV today in real life about 5 hours ago.

 

Yes, you shot an RNAV approach, with which terminology I've had no problem. After going back over this thread several times, I can finally see that if I read "approach" after every "RNAV" it would make more sense (maybe the afternoon nap helped).

 

When referring to ILS, VOR and NDB approaches without the word approach it can make sense more easily because each is the name of a piece of equipment used to make the approach, in addition to being the name of an approach type, while reading about "an RNAV" without the word approach it sounded as if there was a piece of equipment named RNAV being referred to, though there is no such thing, of course, which I thought should have been a GPS reference instead.

 

Of course it didn't help that the first reference I saw was "on autopilot RNAV is supposed to follow the "glide path" " where GPS would be more appropriate (perhaps skewed my "thinking").

 

So I follow the terminology usage much better now that I've mentally put "approach" after each "RNAV." Perhaps I can eventually get used to thinking of that expression the same way as I do "ILS (approach)" or "VOR (approach)."

 

Thanks.

When referring to ILS, VOR and NDB approaches without the word approach it can make sense more easily because each is the name of a piece of equipment used to make the approach, in addition to being the name of an approach type, while reading about "an RNAV" without the word approach it sounded as if there was a piece of equipment named RNAV being referred to, though there is no such thing, of course, which I thought should have been a GPS reference instead.

 

Of course it didn't help that the first reference I saw was "on autopilot RNAV is supposed to follow the "glide path" " where GPS would be more appropriate (perhaps skewed my "thinking").

 

So I follow the terminology usage much better now that I've mentally put "approach" after each "RNAV." Perhaps I can eventually get used to thinking of that expression the same way as I do "ILS (approach)" or "VOR (approach)."

 

Thanks.

 

Ahh ok. makes sense! yeah I hardly ever say Approach after. Its a habit :p

This Wikipedia article gives a good background to RNAV.

https://en.wikipedia.org/wiki/Area_navigation

The explanation of the origin of the acronym from 'Random Navigation' is interesting.

What I took away from it is that RNAV is a generic term covering many ways to achieve the same aim. Just as there are many ways to skin a cat, there are many ways to achieve RNAV.

GPS is just one of the methods of achieving RNAV; another is inertial navigation and so on. Because GPS is almost the only method for RNAV used today, the acronym GPS has become, perhaps incorrectly, synonymous with RNAV.

the acronym GPS has become, perhaps incorrectly, synonymous with RNAV.

Which is why I was puzzled -- I go back to the early days of RNAV, have even used LORAN. But adding the word approach helps me understand most of the references.