Gps as DME for non published waypoint during ILS

[elmanzah]

Hello

I am currently working on my IFR rating and wanted to hear comments on the ILS approach for runway 24 out KABE. Here are two ways to program the avionics to complete the approach.

Method 1:
1- Load and activate the g1000 ils 24 procedure (using vectors)
2- Get vectored and intercept the glide slope and land.

Method 2:
1- Manually tune in the localizer frequency into Nav 1
2- Set gps “direct to IGUW”
3- Get vectored (switch the CDI manually) and intercept the glide slope then land.

I am told method 2 is safer because in the event the ils fails, I can use the distance to IGUW for to execute a localizer approach. The G1000 doesn’t have IGUW as a waypoint in either the ils or loc approaches.

I’m bummed because Method 1 affords me the go around capabilities and the pathways of a synthetic vision. My plane doesn’t have DME equipment and even though I get distances to a vor, I don’t get any distances (outside of using gps) to this localizer even though it is capable of transmitting that information ( because the frequency is underlined in the plate)

Thoughts?

[jb642DA]

As far as method 2 goes, I question the "safer" part -

While GPS can be used "in lieu of DME", to shoot the LOC/DME to 24, my question is why are you plannning this? Is the Glide Slope notamed out of service?

If the glide slope is "out of service", I would shoot the RNAV (GPS) RWY 24 instead of the LOC/DME. If your plane is capable of flying to lower minimums for LPV or LNAV/VNAV to a DA, this approach is "better", minimums-wise, than the LOC/DME.

If the glide slope goes out during your PLANNED ILS to 24, I would execute a miss and reset for the RNAV (GPS) RWY 24.

Back to Method 2: If you want to be able to transition to the LOC/DME, in the event that the glide slope goes out, method 2 will "allow" you to do that....... However, assuming you're still IFR, what are you going to do if the GS "dies" when you are at 780' MSL? How about 820' MSL? Or 600' MSL? How long is it going to take you to recognize that the GS has failed? Where are you going to go if you get to 800' MSL using method #2 and the runway is NOT IN SIGHT? You had better have your "ducks in a row"!

I'd try to keep it simple as a new (or seasoned!) IFR pilot. I would recommend method 1, planning on the ILS. That approach will really aid your positional (situation) awareness (there are 3 named fixes on the approach versus trying to keep track of what "DME" you are currently at and what you need to do at those "DME numbers"). If the Glide Slope fails, go "missed approach" and figure out what you're going to do next.

[elmanzah]

As far as method 2 goes, I question the "safer" part -

While GPS can be used "in lieu of DME", to shoot the LOC/DME to 24, my question is why are you plannning this? Is the Glide Slope notamed out of service?

If the glide slope is "out of service", I would shoot the RNAV (GPS) RWY 24 instead of the LOC/DME. If your plane is capable of flying to lower minimums for LPV or LNAV/VNAV to a DA, this approach is "better", minimums-wise, than the LOC/DME.

If the glide slope goes out during your PLANNED ILS to 24, I would execute a miss and reset for the RNAV (GPS) RWY 24.

Back to Method 2: If you want to be able to transition to the LOC/DME, in the event that the glide slope goes out, method 2 will "allow" you to do that....... However, assuming you're still IFR, what are you going to do if the GS "dies" when you are at 780' MSL? How about 820' MSL? Or 600' MSL? How long is it going to take you to recognize that the GS has failed? Where are you going to go if you get to 800' MSL using method #2 and the runway is NOT IN SIGHT? You had better have your "ducks in a row"!

I'd try to keep it simple as a new (or seasoned!) IFR pilot. I would recommend method 1, planning on the ILS. That approach will really aid your positional (situation) awareness (there are 3 named fixes on the approach versus trying to keep track of what "DME" you are currently at and what you need to do at those "DME numbers"). If the Glide Slope fails, go "missed approach" and figure out what you're going to do next.

What you are saying makes sense to me and that is also what I thought. Go missed at any sign of trouble and try again using another method. I posted this here to validate my gut feel that method 1 is better and wanted to develop a deeper understanding. Your response helps jb642DA.

[jb642DA]

Glad to help - hopefully others will "chime in " also.

[smoss]

To be clear, the sensitivity of the CDI is different in simple tuned to ILS mode vs in approach mode (after hitting the APR button)--it is more precise (each lateral dot represents a smaller course deviation) in APP mode then if you just manually tune to it. Per the manual, if I recall correctly, an approach is only officially authorized in APP mode.

[Wall-e]

I would always choose to load the approach with all the guidance that it gives. If you have to do a LOC approach instead of the ILS w/GS, take a look at the distance depicted between fixes on the plan view of the approach plate. You can use those distances to calculate the location of the fixes that may not be displayed on the PFD or in the FLP. The approach will show distance to the MAP (usually end of RW on NP approach). I would always recommend a MA if you have passed the FAF & you lose the GS. Setup again to fly without the GS or use RNAV.

[TimS]

Why use ILS to begin with? Assuming this is a WAAS enabled G1000.
Once I had WAAS, I only used ILS in training.
Given the choices above, I would like others follow the KISS concept. Keep it simple stupid.
Fly the ILS in method one; something goes wrong fly the missed and come in with a new approach.

Tim

[Wall-e]

I agree with Tim that given a WAAS airplane, RNAV is preferred, if you have that choice.

[ultraturtle]

Most places I fly, the ILS gets you lower minimums than the RNAV LPV to the same runway... but not always (KFFC LPV to RWY 31 gets you a whole foot lower than the ILS to RWY 31).

[TimS]

Most places I fly, the ILS gets you lower minimums than the RNAV LPV to the same runway... but not always (KFFC LPV to RWY 31 gets you a whole foot lower than the ILS to RWY 31).

Curious, where? And if possible what TERPS aspect allows the lower altitude,

Tim