GPS vs VLOC approaches

[MooneyBob]

As I am getting ready to pick my J with brand new GTN750 and other gadgets I am studing and learning more about the GPS flying.

It looks like that if there is a ILS approach there is also LPV approach. Also many other airports have non precision VLOC and GPS approaches for same runways.

Q: What situation you would prefer one before the other? I mean, would you fly ILS for some reason if there is LPV, etc.

Thanks.

[rbridges]

Most of the time the controller seem to prefer ILS approaches. I guess you could request rrnav in those situations. It's weird but I've never been given an LPV approach when ILS was available.

[PTK]

Personally I prefer the LPV over an ILS. The LPV offers guaranteed WAAS vertical guidance while doing away with any potential loc/gs problems.

Garmin also offers the LNAV +V designation. This is widely available only when there is not an LNAV/VNAV approach available. +V is a cool advisory gs on a non prec. approach.

[Jerry 5TJ]

I prefer to fly the LPV approaches (1) all LPV approaches have the same "needle response" whereas ILS approach widths depend on the runway length (2) no "scalloping" of the needles (3) no false GS possible (4) stable operation below the DA with LPV, not that you'd descend below DA in IMC of course (5) most if not all LPV approaches are "the same" Tee shaped configuration (6) you know the distance to the waypoints ahead at all times during the approach (7) there are nearly four times as many WAAS approaches as ILS

[Marauder]

I find the LPV approaches simply divine... and really easy to fly. That said, I can't say that I have run into too many LPVs that go down to the ILS mins. As was mentioned above by my esteemed colleagues, the stability of the LPV is something to behold. You will also appreciate how the GTN applies a dummy factor telling you things like what heading to fly to make a smooth transition on some pretty aggressive turns and as well, how to enter a holding pattern. This is true of both a ILS/VOR or GPS approach (with the overlay turned on).

 

In addition, if you fly it coupled, you will be amazed at how smoothly it handles the approach. Not sure when our next NJ fly-in is, but it would be great to see your setup.

[jnisley]

I prefer LPV for all the above reasons.

I've never had controllers question me when I requested LPV in lieu of ILS

[M016576]

outages can occur on either ILS or LPV. My only concern with an LPV approach is losing the LPV and being forced to LNAV/RNAV mins. Never actually seen it happen, though. In practice, I have see no difference in performance between the two. I typically shoot the ILS these days, though, because it doesn't require hundreds of dollars in updates every year.

I've been shooting ILS approaches using pretty old equipment (and some newer equipment) on multiple types of jets and props for about 12 years now and never had a "false glide slope" or needles that weren't "stable"... Unless I was flying them in an unstable manner. I find that the only time that approaches aren't "smooth" it's because of some confounding factor... Typically it's because I'm not flying smoothly, or there's turbulence that's bouncing me all over. I still couple the mooney up to the gps approaches when I'm on a straight in at my home base in VMC- it hunts a little, but I attribute that more to the KFC-150 than anything else. Otherwise I see equal performance between the two. That's probably why they have same/similar mins typically. JMHO

The only reason I'd pick one over the other is if it was more convenient (the IAF was in a closer spot to my routing). Typically I solve that problem, though, by getting vectors to final, and that makes it easy.

[Bob - S50]

Assuming weather does not require one over the other due to minimum differences, I too prefer the LPV.

 

Do not be afraid to ask for something other than what they offer.  Going into EUG they told me it would be vectors for the ILS.  I asked for and was given the RNAV (LPV).

 

Bob

[M016576]

Assuming weather does not require one over the other due to minimum differences, I too prefer the LPV.

Do not be afraid to ask for something other than what they offer. Going into EUG they told me it would be vectors for the ILS. I asked for and was given the RNAV (LPV).

Bob

Ask and ye shall recieve!

I think the reason that the approach "default" is an ILS by most RAPCONS and centers is that more aircraft are equipped with them vs WAAS gps's- it's not a performance measure. Speculation on my part, though

[carusoam]

Is there an update to filing /G to include WAAS vertical nav?

I still don't have a WAAS box yet...

Best regards,

-a-

[M016576]

Is there an update to filing /G to include WAAS vertical nav?

I still don't have a WAAS box yet...

Best regards,

-a-

No requirement to have WAAS to file /G. You don't even need an updated nav database, so long as you've verified it's accuracy.

That might change, though, as we get more in line w/ ICAO

[M20F]

LPV approaches are much more precise but the main difference between an ILS and an LPV is lighting and runway markings. Both will impact the decision height of a LPV but even with no markings and lousy lights you can get really low on a LPV. The sight picture breaking out at 200' on a ILS at night with low RVR versus breaking out at say 300' with just REIL lights on a LPV can be a bit jarring.

Love LPV's but keep in mind that when you break out it isn't going to look like breaking out on an ILS (unless obviously it is a LPV and ILS supported runway).

[tony]

take the one that gives you a lower decision height.

[Hank]

Assuming weather does not require one over the other due to minimum differences, I too prefer the LPV.

Do not be afraid to ask for something other than what they offer. Going into EUG they told me it would be vectors for the ILS. I asked for and was given the RNAV (LPV).

Bob

Amen, brother! Going into FAY to visit the inlaws, I was vectored between some impressive build ups before descending into the soup. Approach told me to expect the ILS Back Course, which I had never even flown in training. I asked for and was immediately cleared for the GPS approach to the same runway. It was much simpler, and when I broke out, there was the runway in the windshield. Must have been about a year after my checkride.

If you don't have an approach GPS, you're in for a treat when you get one. Wish I had the panel space to debate upgrading GNS-->GTN . . .

[M016576]

Amen, brother! Going into FAY to visit the inlaws, I was vectored between some impressive build ups before descending into the soup. Approach told me to expect the ILS Back Course, which I had never even flown in training. I asked for and was immediately cleared for the GPS approach to the same runway. It was much simpler, and when I broke out, there was the runway in the windshield. Must have been about a year after my checkride.

If you don't have an approach GPS, you're in for a treat when you get one. Wish I had the panel space to debate upgrading GNS-->GTN . . .

ILS back course and back course localizers should be banned. Those approaches are trouble! Emergency procedure material at best!

[M016576]

Amen, brother! Going into FAY to visit the inlaws, I was vectored between some impressive build ups before descending into the soup. Approach told me to expect the ILS Back Course, which I had never even flown in training. I asked for and was immediately cleared for the GPS approach to the same runway. It was much simpler, and when I broke out, there was the runway in the windshield. Must have been about a year after my checkride.

If you don't have an approach GPS, you're in for a treat when you get one. Wish I had the panel space to debate upgrading GNS-->GTN . . .

Panel space? Wish I just had the spare 15k...

[Hank]

Panel space? Wish I just had the spare 15k...

Without panel space for mounting, there's no need for me to save money for it . . . Unless it's ADSB-Out compliant, which is also have no panel space for.

[carusoam]

M016576,

Why would the reverse course ILS be considered E level?

Because of the reverse sensing nature of the situation?

In this case, would an HSI/AP with the ability to properly display the reverse sensing be of use?

These are hypothetical questions out of interest.

Best regards,

-a-

[M016576]

M016576,

Why would the reverse course ILS be considered E level?

Because of the reverse sensing nature of the situation?

In this case, would an HSI/AP with the ability to properly display the reverse sensing be of use?

These are hypothetical questions out of interest.

Best regards,

-a-

Great questions- for me- and I know I've mentioned this before in a few other threads- I count proficiency as a huge part of my risk mitigation in actual IFR flight. I also plan on coupling my autopilot.., but always assume it won't work (so I do feel the need to be able to hand fly the approach).

Back course localizers and ILS approaches are pretty darned rare, and I've only shot two in my professional career outside the simulator. They are inherently confusing based on the reverse sensing nature. Of course, the systems you may or may not be flying with could mitigate this confusion (sa devices like iPads, handhelds and gps's make these things look easy). But try to shoot one just using the needles.... There is lots of potential for error. Compared to a standard tacan, VOR, or ILS approach, which are difficult enough for most as it is.

The things exist, people seem to shoot them... But for me, I avoid at all costs... Unless I absolutely have to.

Now would be a great time for me ta ask... How many on here have actually shot back course approaches in GA?

[Marauder]

Great questions- for me- and I know I've mentioned this before in a few other threads- I count proficiency as a huge part of my risk mitigation in actual IFR flight. I also plan on coupling my autopilot.., but always assume it won't work (so I do feel the need to be able to hand fly the approach).

Back course localizers and ILS approaches are pretty darned rare, and I've only shot two in my professional career outside the simulator. They are inherently confusing based on the reverse sensing nature. Of course, the systems you may or may not be flying with could mitigate this confusion (sa devices like iPads, handhelds and gps's make these things look easy). But try to shoot one just using the needles.... There is lots of potential for error. Compared to a standard tacan, VOR, or ILS approach, which are difficult enough for most as it is.

The things exist, people seem to shoot them... But for me, I avoid at all costs... Unless I absolutely have to.

Now would be a great time for me ta ask... How many on here have actually shot back course approaches in GA?

A couple of the WNY airports I flew to in the 90s had BCs on the ILS. And they were all replaced with RNAV approaches. I did practice them because they were fair game for my practical and like you, found them challenging.

Fast forward 20 some years and right after I had the new Aspen PFD installed. I was still learning the new hardware. I was intending on flying the ILS to a local airport and had the GPS in VLOC mode on the back course side. Interestingly, the Aspen knew I was on the BC side and displayed that on the HSI and converted the reverse sense to the correct orientation. The marvels of new technology.

Sent from my iPad using Tapatalk

[ArtVandelay]

Wish I had the panel space to debate upgrading GNS-->GTN . . .

Panel space? Wish I just had the spare 15k...

Sarasota avionics has a special: $5789 for a GNS To GTN upgrade.

Also, if upgrading I'm don't know why you need more panel space?

[Hank]

Because the 430 is pretty small, and adding traffic and weather to the screen will leave it pretty cluttered.

[Parker_Woodruff]

I just want to clarify that VLOC is describing if a radio within the GPS or if the GPS itself is providing input to the CDI/HSI.

A precision approach like the ILS is still flown in VLOC mode.

I'm sure the OP understands this, but I'm just clarifying...

Also, a great thing to add to your approach checklist is to verify you've selected the correct setting for the approach.

This has caused problems for expert and newbie IFR pilots alike.

[midlifeflyer]

Because the 430 is pretty small, and adding traffic and weather to the screen will leave it pretty cluttered.

I fly multiple A/C some with the GTN 650 (same space as the 430) and some with the 750. Obviously I love the big screen on the 750 but the full color makes the 650 easy enough to read even with the additional information.

[BorealOne]

I have fond(ish) memories of the ILS B/C for RW 25 at CYOW. It's where I learned to fly IMC. I used to do a lot of ILS B/C on RW 07 into CYMM too. Both are now gone, replaced by an RNAVs with LPV. I suspect that all the B/C approaches will go that way.