Lead Radial on chart but no DME arc

[uncreative]

The ILS or LOC RWY 29R into KSCK has a lead radial of 112 off of the ECA VOR. Why is this? It's not a DME arc. I'm guessing it's to give you a heads up that you're going to intercept the localizer if you're inbound from the MOD VOR IAF, but the 29 degree intercept angle isn't overly aggressive.

Here's the chart:

http://imageserver.fltplan.com/merge/merge1606/Single/00407IL29R.PDF

 

[luvflyin]

My guess is it is because you have to use 3 different NAV frequencies in a short period of time. You can get established on the MOD 323, hold that heading and then get ECA dialed in, ID'd and ready to twist to 080 to identify CUSEX. You could do this without the ECA 112 to lead the turn to the localizer but things could be happening pretty fast if you're struggling to get back on the localizer if fly through it while your trying to get CUSEX dialed in.

 

[MAKG1]

That's the highest workload approach I've ever seen. It's only worse if you enter from ECA and have to do the course reversal, too. It's quite close in to the FAF.

I think luvflyin is onto something. Most people do not have three nav radios. This approach cannot be flown with less than two, unless you substitute a GPS for one.

 

[BigBadLou]

I vaguely remember reading somewhere that if a feeder route from an IAF lets you intercept the localizer closer than 15 DME or the intercept angle is >30 degrees, the approach is required to provide a lead radial.
I believe it is due to the narrower LOC signal that close to the rwy and a natural tendency to blow through it, especially for cat C or D airplanes.
But I COULD be wrong so please do correct me if I am.

 

[MAKG1]

I'm not sure if it's legit for controllers to do so, but if there is an aircraft in the hold (and most people fly that approach from the west, which means using it for a HILPT at a minimum), you will be pointed head-on to him if you blow through the final approach course. If that were excluded, you would be at least a minute apart as you passed on the straight-in.

 

[Gucci Pilot]

Looks like it is for if you are coming from MOD. At that intercept angle, I'd just dial in the LOC and track that instead of the 112 off ECA.

That's the highest workload approach I've ever seen. It's only worse if you enter from ECA and have to do the course reversal, too. It's quite close in to the FAF.

I've seen worse. Take a look at the HI-ILS 21 KROW.

...This approach cannot be flown with less than two, unless you substitute a GPS for one.

That seems to be how almost all ILS/LOC approaches these days are that don't have marker beacons.

 

[luvflyin]

The more I thin

I vaguely remember reading somewhere that if a feeder route from an IAF lets you intercept the localizer closer than 15 DME or the intercept angle is >30 degrees, the approach is required to provide a lead radial.
I believe it is due to the narrower LOC signal that close to the rwy and a natural tendency to blow through it, especially for cat C or D airplanes.
But I COULD be wrong so please do correct me if I am.

I'd be willing to bet a beer you're right about those numbers but I haven't seen that written. The more I think about it, I think the intent of how that approach should be flown from MOD is start out with MOD and ECA dialed in. Start the turn to the final approach "heading" at the lead radial while changing NAV 1 from MOD to the localizer and twisting ECA on NAV 2 to the 080r for CUSEX

 

[Clark1961]

This approach cannot be flown with less than two, unless you substitute a GPS for one.

Nope, the ILS can be flown with one nav.

 

[luvflyin]

Nope, the ILS can be flown with one nav.

I suppose so, but you would be busier than a three legged cat covering up sheet. Of course there is Radar there. Ya can get vectored to final and they can call CUSEX for you. You can do the LOC also, not just the ILS. I don't think I would want to try it without Radar, single pilot and in a pretty fast airplane.

 

[aterpster]

The ILS or LOC RWY 29R into KSCK has a lead radial of 112 off of the ECA VOR. Why is this? It's not a DME arc. I'm guessing it's to give you a heads up that you're going to intercept the localizer if you're inbound from the MOD VOR IAF, but the 29 degree intercept angle isn't overly aggressive.

Here's the chart:

http://imageserver.fltplan.com/merge/merge1606/Single/00407IL29R.PDF

ILS IAPs have lead radials for three different reasons, only one of which involves a DME arc.

1. The intercept angle exceeds 90 degrees.
2. DME source for arc not collocated with the localizer.
3. Flight inspection unsuccessful for intercept fix and localizer.

#3 is the reason or perhaps flight inspection told the designers to add it because they didn't like the "flyability" of that transition without the LR.

 

[luvflyin]

ILS IAPs have lead radials for three different reasons, only one of which involves a DME arc.

1. The intercept angle exceeds 90 degrees.
2. DME source for arc not collocated with the localizer.
3. Flight inspection unsuccessful for intercept fix and localizer.

#3 is the reason or perhaps flight inspection told the designers to add it because they didn't like the "flyability" of that transition without the LR.

Makes sense. I could see them getting a little behind on that one. Some approaches have a Dual VOR's required note. Seems like this one should have

 

[aterpster]

Makes sense. I could see them getting a little behind on that one. Some approaches have a Dual VOR's required note. Seems like this one should have

Related, but a bit different. Dual VOR minimums are required when it would be too critical to be tuning back and forth, generally in the final approach segment.

 

[luvflyin]

Related, but a bit different. Dual VOR minimums are required when it would be too critical to be tuning back and forth, generally in the final approach segment.

Yeah. I haven't gone looking but it seems I recall Dual VOR notes mostly on approaches with step down fixes inside the FAF

 

[BillTIZ]

That's the highest workload approach I've ever seen. It's only worse if you enter from ECA and have to do the course reversal, too. It's quite close in to the FAF.

I think luvflyin is onto something. Most people do not have three nav radios. This approach cannot be flown with less than two, unless you substitute a GPS for one.

Look at Provo UT ILS Rwy 13 from the Fairfield IAF. Fairfield VOR, to PVU VOR Arc, to I-PVU for final, PVU VOR and then to Fairfield VOR for missed to holding. Two Nav receivers with flip flop Freqs. Plan your navaids well.

 

[aterpster]

Look at Provo UT ILS Rwy 13 from the Fairfield IAF. Fairfield VOR, to PVU VOR Arc, to I-PVU for final, PVU VOR and then to Fairfield VOR for missed to holding. Two Nav receivers with flip flop Freqs. Plan your navaids well.

That's a great example of the benefits of LPV over ILS.

 

[luvflyin]

Look at Provo UT ILS Rwy 13 from the Fairfield IAF. Fairfield VOR, to PVU VOR Arc, to I-PVU for final, PVU VOR and then to Fairfield VOR for missed to holding. Two Nav receivers with flip flop Freqs. Plan your navaids well.

Yeah. My Navaid plan would be having FFU and I-IPVU on Nav1. Nav2 and the DME on PVU. When crossing FFU Nav1 gets flipflopped to I-PVU right now. I'd waste no time trying to fly the FFU 313r, just turn roughly in that direction. It's only 4 miles to JETLI, by the time you get positive station passage indication you're even closer. PVU is on the 302r (122 on the OBS with a TO flag.) Start a right turn to about 030 at around 12-13 DME leaving 9000 for 8000. Start a turn to final when crossing the PVU 302r. Leave 8000 for 6300 when the LOC needle moves, shoot approach. Get PVU twisted to 130 preparing for a missed approach. If you miss, everything is pretty much ready to go with just a couple more easy things to do. NAV1 flipflopped back to FFU, plenty of time to do this. The arguments for having the OBS set to the final approach course when on the LOC aside, I may have twisted it to 290 a long time ago. You could change the DME to FFU after ZIPUT, but not necessary.