Lead Radial

[midlifeflyer]

That’s what I was wondering about. Would it start the turn at the LR, before being on the inbound course and what the effect would be. How close to NIKEE would it put you on the Localizer. Looks like about 2.5 or 3 miles out. You shouldn’t leave 5000 until on the Localizer. Were you able to intercept the Glideslope from below? Or did you have to get it from above?
What I meant was let the Navigator do its thing which probably would have been turn anticipation approaching DRIBB from TUS and rolling out on the holding course outbound. Not a ‘true’ parallel entry, but it seems to be how all Navigators do it. I wanted you to also do it crossing DRIBB and then turn to a paralleling heading outbound. Go for a minute and the turn back inbound. That would have you crossing the LR a little further West and subsequently the Localizer a little farther out from NIKEE.

At that speed, 20 kts faster than approach category D, the glideslope came in and the AP began descending on localizer case break. And, of course, the localizer needle came in really fast given the angle.

I dunno about "true" parallel entry. Yeah, the AIM entry suggestions describe it as "a heading to parallel the holding course outbound on the nonholding side." But so what?

 

[luvflyin]

At that speed, 20 kts faster than approach category D, the glideslope came in and the AP began descending on localizer case break. And, of course, the localizer needle came in really fast given the angle.

I dunno about "true" parallel entry. Yeah, the AIM entry suggestions describe it as "a heading to parallel the holding course outbound on the nonholding side." But so what?

What’s case break?

 

[midlifeflyer]

What’s case break?

The needle just begins to move from full deflection; the first indication of positive course guidance. Not an official term but I've seen it and "off the peg" used quite a bit in discussions and picked it up as a pretty good description.

 

[luvflyin]

The needle just begins to move from full deflection; the first indication of positive course guidance. Not an official term but I've seen it and "off the peg" used quite a bit in discussions and picked it up as a pretty good description.

Ok, I learned something new. When you got case break, were you still at 5000, and if so, above or below the Glideslope or roll out right on it?

 

[luvflyin]

I ran it 200 KTS. I'm not sure what you mean by the juxtaposition of the two things I bolded in your post.

Parallel entry for the HILO as expected. The interesting part is, at that speed, the airplane never returned to the inbound course or to DRIBB. Instead, turn anticipation turned to intercept the FAC directly from the holding side of the HILO (the magenta line).

View attachment 116005

What Navigator was this? Did you see this over on Beechtalk. It flew right through the LR to intercept the Inbound Course. Barely made it before DRIBB. I asked how fast he was going. No answer yet. He said it was a GTN Xi simulator.

 

[midlifeflyer]

Ok, I learned something new. When you got case break, were you still at 5000, and if so, above or below the Glideslope or roll out right on it?

Keep in mind we are 20 KTS faster than the highest aircraft category speed. Case break, GS intercept, and descent all happened about the same time. I snapped this a moment after I saw the needle move - at 200 KTS, it moved fast - but it should give you some idea. I didn't record the screen, so no video.
(It's a GTX750Xi)

 

[luvflyin]

Keep in mind we are 20 KTS faster than the highest aircraft category speed. Case break, GS intercept, and descent all happened about the same time. I snapped this a moment after I saw the needle move - at 200 KTS, it moved fast - but it should give you some idea. I didn't record the screen, so no video.
(It's a GTX750Xi)

View attachment 116011

Looks like it isn't a big deal like I had thought it might be. Thanks for taking the time

 

[MauleSkinner]

Looks like it isn't a big deal like I had thought it might be. Thanks for taking the time

And if all else fails, coordinate to take another lap in the hold to get better oriented. That’s what my nav system is programmed to do already.

Which is yet another reason I never do parallel entries.

 

[asicer]

Yes, it will anticipate the turn inbound to meet the FAC and, if set for auto switch, will switch nav sources to the LOC once inbound to the FAF.

But there are pilots who treat all that as a backup when switching from pink to green needles.

I figured it was one of the prompts to switch to green.

 

[midlifeflyer]

And if all else fails, coordinate to take another lap in the hold to get better oriented. That’s what my nav system is programmed to do already.

Which is yet another reason I never do parallel entries.

I don't say "never." I don't like them mostly because the standard 1 minute hold generally doesn't provide enough time to get established inbound (the standard RNAV 4 nm hold gives more than enough time).

So, I fudge in favor of teardrop as SOP. But the 1 minute protected area is based on 200 knots with a bad wind, I would fly a hold at half that and would also have no qualms informing ATC I would continue outbound longer.

 

[luvflyin]

Keep in mind we are 20 KTS faster than the highest aircraft category speed. Case break, GS intercept, and descent all happened about the same time. I snapped this a moment after I saw the needle move - at 200 KTS, it moved fast - but it should give you some idea. I didn't record the screen, so no video.
(It's a GTX750Xi)

View attachment 116011

Here’s the Jepp chart. Gov chart doesn’t have the circled note. As you know from the Beechtalk thread it is being said, because of that, the LR only applies to the JIPSY Transition. I believe that to be wrong. Hoping @RussR can jump in here when he has time. Anyway, If you could, run this established on the 125 Course To RBJ. Start at JIPSY or from being established in Hold, doesn’t matter. Do it at 200 knots, the Hold speed limit. Wait for case break to start the turn. How far is the overshoot? Does it ‘break case’ on the other side?

 

[Clip4]

The needle just begins to move from full deflection; the first indication of positive course guidance. Not an official term but I've seen it and "off the peg" used quite a bit in discussions and picked it up as a pretty good description.

Case break is when you brake the glass on the VSI for an obstructed static port in an aircraft without a alternate static port.

 

[luvflyin]

I don't say "never." I don't like them mostly because the standard 1 minute hold generally doesn't provide enough time to get established inbound (the standard RNAV 4 nm hold gives more than enough time).

So, I fudge in favor of teardrop as SOP. But the 1 minute protected area is based on 200 knots with a bad wind, I would fly a hold at half that and would also have no qualms informing ATC I would continue outbound longer.

You could fly out bound fast for a minute and then bleed off airspeed in the turn back. That’d help some. I always cross the fix and fly a heading outbound, RNAV or not. Compensate for wind. Usually have a real good idea of what it is from paying attention to what the wind has been doing in the minutes before reaching the fix.

 

[Clip4]

I'm not completely sure about that. Grab a VOR approach with a DME arc. Do you see a lead radial? I think you only see them when the arc and the FAC use different navaids.
View attachment 115985

I don’t know the TERPS requirements for a lead radial, but on the chart you provided there is no operational need for a LR. At 27 DME on a VOR approach the final approach course is 9 nm wide; the needle will be live 4.5 nm before intercept of the final course.

When there is an Arc to intercept an LOC, the maximum LOC service volume is 18 NM. At 15 nm from an LOC the course is only 5 nm wide.

 

[midlifeflyer]

I don’t know the TERPS requirements for a lead radial, but on the chart you provided there is no operational need for a LR. At 27 DME on a VOR approach the final approach course is 9 nm wide; the needle will be live 4.5 nm before intercept of the final course.

When there is an Arc to intercept an LOC, the maximum LOC service volume is 18 NM. At 15 nm from an LOC the course is only 5 nm wide.

The TERPS requirement is based on two things. Either an angle greater than 90 degrees or the DME and the inbound course being different VLOC frequencies as a reminder to switch in time to intercept when you have only one NAV radio. An earlier post led me to look it up.

 

[RussR]

I don't think that it's different Navaids in and of itself. It's that the Final Approach Course is a Localizer. It's the narrow range of signal. Time to rattle @RussR 's cage. When ya have time can you give us the skinny on this?

From FAA Order 8260.19H, Ch8, Section 8-2-5

Here’s the Jepp chart. Gov chart doesn’t have the circled note. As you know from the Beechtalk thread it is being said, because of that, the LR only applies to the JIPSY Transition. I believe that to be wrong. Hoping @RussR can jump in here when he has time. Anyway, If you could, run this established on the 125 Course To RBJ. Start at JIPSY or from being established in Hold, doesn’t matter. Do it at 200 knots, the Hold speed limit. Wait for case break to start the turn. How far is the overshoot? Does it ‘break case’ on the other side?

Thanks guys, I felt the cage-rattling but was out on a trip and didn't have all my resources with me to provide a full answer. @TCABM already quoted one of the pertinent regulations about Lead Radials.

There are three cases requiring lead radials:
1. More than 90 degrees of turn onto final.
2. On an ARC but the DME source is not the same as the source for final approach guidance.
3. If an initial segment starts outside of the Localizer service volume, in order to make sure a false localizer course isn't followed, but only if the flight check is unsuccessful.

The first two are simply a "heads-up" to let the pilot of a single-VOR receiver-equipped airplane know that it's time to switch it over. It is NOT a calculated turn point. It does NOT change anything in the obstacle evaluation. In fact, it really is simply added as an afterthought, meaning all the design work is done, a lead radial is necessary, so (math math math, 2 nm, math), boom, there it is. No evaluation took place in the selection of a "good" lead radial, or accounting for aircraft speed, or anything like that. It's pure math for a 2nm lead. It means NOTHING to the design of the procedure. And I'll repeat - it is NOT an indication of where a turn should begin. That's up to you, the pilot, to determine via whatever means you like (or letting the GPS/FMS do it for you). It's literally just a "hey, you're getting close..."

I believe that the RYN procedure falls into the third scenario. The fix JIPSY is about 32 degrees off centerline, meaning it would be outside of the localizer service volume since it's past 10 nm away. I have no evidence to support that this IS the reason right now, but since it isn't an arc and isn't greater than 90 degrees, it's all that's left, and it seems to fit. HOWEVER, this lead radial was established in 1985, so I have no idea what the rules were back then or if they were any different.

HOWEVER again, according to the old source documents for this, the lead radial was simply added in 1985 due to "pilot requests". Whether they were having problems with a false localizer course, or something else, I cannot determine.

The reason the note applying the LR to JIPSY and is on the Jepp chart and not the FAA chart is one of charting convention. The question really is "how does Jepp know it just applies to that segment?" The answer is that on the source document, the lead radial is specified on the line with the route it applies to.



There is nothing on the source document (and there is nothing in the TERPS regulations) saying to "Chart this note", so it's not on the FAA chart. Jeppesen took it on themselves to chart it based on the information on the source document. I can't argue with that, it definitely makes it clearer.

 

[midlifeflyer]

3. If an initial segment starts outside of the Localizer service volume, in order to make sure a false localizer course isn't followed, but only if the flight check is unsuccessful.

Russ, I found references to the first two (Unless you are saying that #2 is only applicable to arcs, #2 applies because you may have TUS used it to identify JIPSY and may be continuing to monitor it to track progress From JIPSY to the localizer intercept.

But that aside, what's the TERPS reference for #3 so I can add it to my notes?

 

[RussR]

Russ, I found references to the first two (Unless you are saying that #2 is only applicable to arcs, #2 applies because you may have TUS used it to identify JIPSY and may be continuing to monitor it to track progress From JIPSY to the localizer intercept.

But that aside, what's the TERPS reference for #3 so I can add it to my notes?

I knew I shouldn't have closed that document, now I have to look it back up. It was in an obscure place.

8260.19I, para 7-5-2a(5). It's a heading that talks about when Compass Locators are required.

 

[midlifeflyer]

I knew I shouldn't have closed that document, now I have to look it back up. It was in an obscure place.

8260.19I, para 7-5-2a(5). It's a heading that talks about when Compass Locators are required.

Got it! Thanks.

 

[luvflyin]

Thanks guys, I felt the cage-rattling but was out on a trip and didn't have all my resources with me to provide a full answer. @TCABM already quoted one of the pertinent regulations about Lead Radials.

There are three cases requiring lead radials:
1. More than 90 degrees of turn onto final.
2. On an ARC but the DME source is not the same as the source for final approach guidance.
3. If an initial segment starts outside of the Localizer service volume, in order to make sure a false localizer course isn't followed, but only if the flight check is unsuccessful.

The first two are simply a "heads-up" to let the pilot of a single-VOR receiver-equipped airplane know that it's time to switch it over. It is NOT a calculated turn point. It does NOT change anything in the obstacle evaluation. In fact, it really is simply added as an afterthought, meaning all the design work is done, a lead radial is necessary, so (math math math, 2 nm, math), boom, there it is. No evaluation took place in the selection of a "good" lead radial, or accounting for aircraft speed, or anything like that. It's pure math for a 2nm lead. It means NOTHING to the design of the procedure. And I'll repeat - it is NOT an indication of where a turn should begin. That's up to you, the pilot, to determine via whatever means you like (or letting the GPS/FMS do it for you). It's literally just a "hey, you're getting close..."

I believe that the RYN procedure falls into the third scenario. The fix JIPSY is about 32 degrees off centerline, meaning it would be outside of the localizer service volume since it's past 10 nm away. I have no evidence to support that this IS the reason right now, but since it isn't an arc and isn't greater than 90 degrees, it's all that's left, and it seems to fit. HOWEVER, this lead radial was established in 1985, so I have no idea what the rules were back then or if they were any different.

HOWEVER again, according to the old source documents for this, the lead radial was simply added in 1985 due to "pilot requests". Whether they were having problems with a false localizer course, or something else, I cannot determine.

The reason the note applying the LR to JIPSY and is on the Jepp chart and not the FAA chart is one of charting convention. The question really is "how does Jepp know it just applies to that segment?" The answer is that on the source document, the lead radial is specified on the line with the route it applies to.

View attachment 116051

There is nothing on the source document (and there is nothing in the TERPS regulations) saying to "Chart this note", so it's not on the FAA chart. Jeppesen took it on themselves to chart it based on the information on the source document. I can't argue with that, it definitely makes it clearer.

Thanks for checkin in. The source document in the IFP Gateway was from 1985. I don't recall ever seeing the Source Document being that old in my searches in the IFP Gateway. It showed just 5 Amendments since then. All via Notam. An altimeter setting thing, remove MM, MDA/DA changes, add circling icon and move ADF from Planview to Equipment Required box. I was looking for an 8260-10, or other 8260 with 'Chart' instructions in Notes. Like "Chart Planview Note: lead radial for JIPSY approach transition." From looking at the JEPP Chart it seemed there may have been that there.

 

[luvflyin]

I ran it 200 KTS. I'm not sure what you mean by the juxtaposition of the two things I bolded in your post.

Parallel entry for the HILO as expected. The interesting part is, at that speed, the airplane never returned to the inbound course or to DRIBB. Instead, turn anticipation turned to intercept the FAC directly from the holding side of the HILO (the magenta line).

View attachment 116005

What Navigator was this? And I'm wondering about something else now. Which data Base did it use? Garmins or Jepps

 

[midlifeflyer]

What Navigator was this? And I'm wondering about something else now. Which data Base did it use? Garmins or Jepps

GTN750.In this case it was with the Jepp database. I wouldn't expect anything different from a GNS with a Garmin database. Why would there be? As Russ said, it's mostly a heads up for situational awareness, not a mandatory operative instruction. If a GPS is flying it, it will use turn anticipation, not a lead radial, to intercept the localizer.

 

[luvflyin]

GTN750.In this case it was with the Jepp database. I wouldn't expect anything different from a GNS with a Garmin database. Why would there be? As Russ said, it's mostly a heads up for situational awareness, not a mandatory operative instruction. If a GPS is flying it, it will use turn anticipation, not a lead radial, to intercept the localizer.

I was thinking that because Jepp had the note on the Chart, their Data Base made the Navigator fly it some how differently than others. My thinking was obviously wrong. I get it now. I was pretty much wrong about the whole thing at the beginning. Been an educational, thought provoking thread. Thank you all for playing.