Avionics Opinions

[nyoung]

The GPS offers lower minimums (I do not dispute that) but the real question... How often is that valuable?

For example, I am based @ 3ck. If you can get a local altimeter setting, VOR-26 minimums are 492ft AGL. LNAV minimums are 412 feet (rwy 26) and 392 feet (rwy 08) respectively.

The number of days where a pilot can get in with the extra 80-100 feet are minimal, probably a handful of times a year. In my ~7 years of flying instruments to 3CK, I have had to divert to DPA twice. In both cases, I flew the DPA ILS to 300 feet or lower. So the GPS approach at 3CK would not have helped, I would have ended up at DPA anyway.

I have never had to divert at my destination.

Regarding GPS vs VOR. True, the GPS is more accurate. But, I have never missed a VOR because of not being aligned with the runway. Typically approaches are missed b/c of the cloud base.

Why is a GPS approach easier to fly? With a VOR/DME approach, I open an approach plate, select the VOR frequency, dial the approach course on the OBS, verify the VOR (audio panel). I bet I can do that quicker than most people can program an approach on a 430 ! And as far as the in-flight portion. What's more difficult with VOR/DME than GPS? They both involve crossing a FAF, following an approach course, descending, and waiting for the MAP. Sans-GPS, it is not hard to bracket a VOR course, and if you have a handheld, it is easy to use to zero out the cross-track without bracketing, thereby nailing the heading.

Last, regarding your direct routing comment. That's the trick and it works >90% of the time. It is pretty rare when a controller won't let you fly a requested heading.

In my experience, for the cost, IFR GPS offers minimal extra capability.

Now, if we want to talk about a WAAS approved GPS with GPSS steering coupled to an STEC-55, then that's a different story. But that is also $25k of avionics, which in no way is relevant to the original post.

I beg to differ on the GPS vs VOR mins, which IME are often 100-200 ft lower. In addition a GPS is easier to fly AND more accurate plus it gives you the ability to fly VOR and LOC approaches that require DME or ADF.

And while those friendly controllers will indeed allow you to fly off airway, you are not legally entitled to accept a clearance to a distant waypoint that you cannot navigate to on your own without using your VFR GPS unless you use the subtefuge of requesting and getting a "vector".

 

[gismo]

I also used some Google-fu and it appears that there is not a single airport in the US that has an approach but that you can't get into with an approach-certified GPS. I know the FAA has been on a big kick about that, and it appears that they have been pretty successful.

While I agree on the general usefulness of an IFR GPS there are indeed still IFR airports with no GPS approach and some of those only have an NDB approach (no VOR/LOC). An example of that is KGYL (Glencoe MN) just west of me. They are slated to get a GPS approach next year though so I suspect that your claim will eventually be true (sometime in the next few years).

 

[dogman]

Okay, I had to geek out and figure this one out.

In the state of Wisconsin, there are 127 public-use land airports (as opposed to pure seaplane bases). 88 of those have instrument approaches.

I split the approaches into 6 categories: ILS, VOR (including SDF, LOC, VOR/DME, etc.), GPS (including some that were VOR/DME RNAV overlays), NDB, VOR + GPS overlay, and NDB + GPS overlay.

This table shows the total number of approaches of each type, and the total number of airports with each approach type:

[ROW][CELL]IAP type[/CELL][CELL]ILS[/CELL][CELL]GPS[/CELL][CELL]VOR, etc.[/CELL][CELL]NDB[/CELL][CELL]VOR + GPS overlay[/CELL][CELL]NDB + GPS overlay[/CELL][/ROW][ROW][CELL]IAP #[/CELL][CELL]26[/CELL][CELL]162[/CELL][CELL]66[/CELL][CELL]26[/CELL][CELL]30[/CELL][CELL]21[/CELL][/ROW][ROW][CELL]# airports[/CELL][CELL]16[/CELL][CELL]72[/CELL][CELL]37[/CELL][CELL]23[/CELL][CELL]25[/CELL][CELL]17[/CELL][/ROW]

Now, as far as what you can actually fly... Here's the number of airports you can get into, with just an approach certified GPS, just a VOR/LOC/GS, just an ADF, VOR/LOC/GS with approach GPS, and VOR/LOC/GS with ADF but no GPS, and not that anyone has this setup but ADF and GPS:

[ROW][CELL]GPS only[/CELL][CELL]VOR only[/CELL][CELL]NDB only[/CELL][CELL]VOR+GPS[/CELL][CELL]VOR+NDB[/CELL][CELL]GPS+NDB[/CELL][/ROW][ROW][CELL]88 (100%)[/CELL][CELL]54 (61%)[/CELL][CELL]38 (43%)[/CELL][CELL]100%[/CELL][CELL]85%[/CELL][CELL]100%[/CELL][/ROW]

Yes, you read that right. With only an approach certified GPS, you can get into every one of the airports that has any kind of approach in the state. 82% of the airports have a pure GPS approach, the rest have a GPS overlay on a VOR or NDB approach. The VOR/LOC/GS plus DME will get you into 61% of the airports, that plus ADF will get you into 85% but the GPS alone will do every one of 'em.

I also used some Google-fu and it appears that there is not a single airport in the US that has an approach but that you can't get into with an approach-certified GPS. I know the FAA has been on a big kick about that, and it appears that they have been pretty successful.

So, in closing - IMHO, any panel upgrade that is undertaken should result in an approach-certified GPS in the panel if you intend to fly IFR.

This is why I went with the KX155/GS and the GNC300xl KI208 annunciator.

The gnc300xl was Cheaper than the KLN-94 with install. I had to have the annunciator for both GPS installs because unit is mounted down low on the panel.

 

[gismo]

The GPS offers lower minimums (I do not dispute that) but the real question... How often is that valuable?

Often enough that it's made a difference to me at least twice in the last couple of years. I must admit though, this is more likely with a TSO C146a GPS (WAAS) which I have.

For example, I am based @ 3ck. If you can get a local altimeter setting, VOR-26 minimums are 492ft AGL. LNAV minimums are 412 feet (rwy 26) and 392 feet (rwy 08) respectively.

The number of days where a pilot can get in with the extra 80-100 feet are minimal, probably a handful of times a year. In my ~7 years of flying instruments to 3CK, I have had to divert to DPA twice. In both cases, I flew the DPA ILS to 300 feet or lower. So the GPS approach at 3CK would not have helped, I would have ended up at DPA anyway.

And if you happen to be the lucky one that arrives on one of those handful of times? Check out the approaches to KACB, an airport I frequent. The VOR approach mins are nearly 1000 AGL due to nearby terrain and the inaccuracy of a distant VOR. The LNAV mins are about 600 AGL and before I got WAAS I needed the lower mins at least twice. But with WAAS I can get under 300 AGL, something I've already needed once. The nearest airport with better mins is TVC which is 40-45 minutes from my house there vs 8-10 from ACB. So maybe there'd be little or no improvement for you at 3CK, but that's not true everywhere.

I have never had to divert at my destination.

FWIW, I've had to divert from my planned destination several times both on VOR approaches and GPS approaches (I don't think I've ever had to divert on an ILS but I've come very close a couple times).

Regarding GPS vs VOR. True, the GPS is more accurate. But, I have never missed a VOR because of not being aligned with the runway. Typically approaches are missed b/c of the cloud base.

Why is a GPS approach easier to fly? With a VOR/DME approach, I open an approach plate, select the VOR frequency, dial the approach course on the OBS, verify the VOR (audio panel). I bet I can do that quicker than most people can program an approach on a 430 ! And as far as the in-flight portion. What's more difficult with VOR/DME than GPS? They both involve crossing a FAF, following an approach course, descending, and waiting for the MAP. Sans-GPS, it is not hard to bracket a VOR course, and if you have a handheld, it is easy to use to zero out the cross-track without bracketing, thereby nailing the heading.

VOR is indeed accurate enough to get you to the runway in most cases but GPS is "easier" because they rarely require a PT and on the average are better aligned with the runway. Most VOR approaches bring you in at some angle to the runway which can make it more difficult to find the runway, especially if there are no approach lights. And WRT to the vis vs ceiling as a cause to miss, IME that's about 50/50 and BTW only the vis matters (kind of a moot point when the vis inside the low clouds is 500 ft though).

The fact that you find a handheld GPS makes it easier to fly a VOR approach kinda makes my point that GPS is easier.

Last, regarding your direct routing comment. That's the trick and it works >90% of the time. It is pretty rare when a controller won't let you fly a requested heading.

True, most controllers are pretty accommodating. Just keep in mind that ATC will often give clearances that cannot be legally flown without some sort of area nav and it's on the pilot to decline such a clearance.

In my experience, for the cost, IFR GPS offers minimal extra capability.

Well, given that there were a lot fewer GPS approaches available during the 9 years I flew with a non WAAS GPS than today, and that even then I found those GPSs to be quite useful, I must guess that my experience differes from yours (and that's OK).

Now, if we want to talk about a WAAS approved GPS with GPSS steering coupled to an STEC-55, then that's a different story. But that is also $25k of avionics, which in no way is relevant to the original post.

That's pretty much what I have now and I've been quite satisfied with this latest improvement. If I were Greg I'd seriously consider a WAAS IFR GPS in the 195. IIRC from when I flew it, it's stable enough that a coupled autopilot would be more of a convenience than a necessity.

 

[RMCN172RG]

Quote:
Now, if we want to talk about a WAAS approved GPS with GPSS steering coupled to an STEC-55, then that's a different story. But that is also $25k of avionics, which in no way is relevant to the original post.
That's pretty much what I have now and I've been quite satisfied with this latest improvement. If I were Greg I'd seriously consider a WAAS IFR GPS in the 195. IIRC from when I flew it, it's stable enough that a coupled autopilot would be more of a convenience than a necessity.

This is probably over $30K S-TEC raised their prices this year and the 430W isn't cheap either. That is 2/3 of what I paid for the plane last year and half's or more of it's current value since I've added the S-TEC 30.

I have not flown hard IMC to minimums with the auto-pilot but I have done some actual and a lot of simulated coupling the AP to the LOC and just monitoring and controlling the descent to know it is a vast improvement over a single pilot shooting the ILS.

Looking at my normal missions and common airports I can't justify the higher priced AP or the 430W over the S-TEC 30, Garmin 196 and basic IFR radio setup.

Will probably upgrade to a 496 for in cockpit weather but when I bought the 196 I was renting and thinking backup along with the Sporty's NAV/COM.

 

[rpadula]

Bump... 25 minutes to go on this auction Greg!

P.S. Found an Ebay auction for a GX60 + the annunciator I have!