Procedure NA for radials…

D

DaveInPA

Pre-Flight
Joined
Sep 21, 2019
Messages
54
Display Name
Display name:
Dave
I know it’s minutiae but I’m reading approach charts carefully that are probable for my upcoming checkride and want to fully understand how radials are referenced.

On the LNS RNAV 31 it states…procedure Na for arrivals on LRP radials 054 CW 223. LRP vor is located at the airport btw. So do I think about this as a sector of space defined by the 54 radial on one side clockwise to the 223 radial and if my plane is In that section of space I can’t fly the procedure?

OR are they saying if I’m on any radial from 54 to 223 TO to Vor then it’s not available?

they aren’t the same because if I’m TO the vor on the 54 then I’m southwest of the vor on the reciprocal 234 radial pointed towards the VOR and for the 223 I’d be north east on reciprocal 43 radial.

it’s not much of a difference and in real life I’d be vectored but curious if other IFR chart nerds know the exact answer to this?
 
DaveInPA said:
I know it’s minutiae but I’m reading approach charts carefully that are probable for my upcoming checkride and want to fully understand how radials are referenced.

On the LNS RNAV 31 it states…procedure Na for arrivals on LRP radials 054 CW 223. LRP vor is located at the airport btw. So do I think about this as a sector of space defined by the 54 radial on one side clockwise to the 223 radial and if my plane is In that section of space I can’t fly the procedure?

OR are they saying if I’m on any radial from 54 to 223 TO to Vor then it’s not available?

they aren’t the same because if I’m TO the vor on the 54 then I’m southwest of the vor on the reciprocal 234 radial pointed towards the VOR and for the 223 I’d be north east on reciprocal 43 radial.

it’s not much of a difference and in real life I’d be vectored but curious if other IFR chart nerds know the exact answer to this?
Click to expand...

Those radials represent airways leading to the VOR, so it's essentially saying that you can't use the procedure approaching the IAF from those airways...the turn to the outbound portion of the procedure is too great of an angle. Typically there's a more appropriate route, and it only really is an issue when you're in a non-radar environment.
 
DaveInPA said:
I know it’s minutiae but I’m reading approach charts carefully that are probable for my upcoming checkride and want to fully understand how radials are referenced.

On the LNS RNAV 31 it states…procedure Na for arrivals on LRP radials 054 CW 223. LRP vor is located at the airport btw. So do I think about this as a sector of space defined by the 54 radial on one side clockwise to the 223 radial and if my plane is In that section of space I can’t fly the procedure?

OR are they saying if I’m on any radial from 54 to 223 TO to Vor then it’s not available?

they aren’t the same because if I’m TO the vor on the 54 then I’m southwest of the vor on the reciprocal 234 radial pointed towards the VOR and for the 223 I’d be north east on reciprocal 43 radial.

it’s not much of a difference and in real life I’d be vectored but curious if other IFR chart nerds know the exact answer to this?
Click to expand...

Radial is measured out from the VOR. If you are inbound towards the VOR, your track will be the reciprocal of the radial.
Basically, it looks like the procedure is NA if you are coming from the northeast, east or south (V39 through V93), probably because you will have to turn quite a bit to establish on the outbound.
 
Ahhh…if I look at the low IFR chart see the victor airways on these radials. But is it saying when I hit the vor I can’t turn outbound? Or is it saying if I’m tracking toward the VOR on any radials between these 2 airways then I can’t enter the hold in lieu of procedure turn?

upload_2021-10-21_21-40-0.png
 
The note actually refers to airways:

“Procedure NA for arrivals on LRP VOR/DME airway radials 054 CW 223.”

If you look at the IFR chart you’ll see about a dozen airways connect at that VOR.

I’ll take a stab at this, not sure if it’s right: Suppose you are NE of the field and you fly SW toward its VOR, not just in any random direction but exactly on the V39 radial to LRP because that’s your clearance to fly V39. You look at the Low IFR chart and see that NE of the VOR the airway V39 happens to be on the 054 radial of LRP. Well then, the note says that because you’re arriving at the VOR specifically on an airway and that airway is on the 054 radial, you cannot then get a clearance to fly the approach starting at the VOR.

Hope I got that right.
 
If your route of flight includes navigation to LRP then any arrival between radials 054-224 would not allow turning to AYOSA to fly the approach along the depicted transition, the reason being that the outbound turn would be regarded as too acute to fly within the designated safety bounds. In practice, you would never be cleared from LRP to the IAF if arriving on any of the prohibited radials if flying this approach, but rather you would at some point be cleared direct AYOSA. LRP is not an IAF, but there is a depicted transition from LRP to AYOSA, provided you are not arriving from the prohibited sector.
 
Last edited:
This ultimately comes down to understanding that radials emit outward from the VOR. The 060 radial DOES NOT EXIST southwest of the VOR. Sure, you can be inbound to the VOR on a 060 course, with your OBS set to 060, but make no mistake, you are inbound on the 240 radial in that case (placing you SSW of the VOR).

You can also use a process of elimination when thinking through the possibilities for your question. In the correct interpretation, the procedure is not authorized if you'll need to completely turn around once reaching LRP to continue the procedure. In the incorrect (reversed) interpretation, you can ONLY fly the procedure from LRP if you're arriving from the 'wrong' way.

So, if you have a brain fart regarding the nuances of radial terminology, a quick sanity check can help to confirm.
 
DaveInPA said:
Ahhh…if I look at the low IFR chart see the victor airways on these radials. But is it saying when I hit the vor I can’t turn outbound? Or is it saying if I’m tracking toward the VOR on any radials between these 2 airways then I can’t enter the hold in lieu of procedure turn?

View attachment 101164
Click to expand...

I think it’s all about airways.

The issue of airways is overlooked by half the posts in this thread. Maybe because few pilots use them anymore, and maybe because the word “airway” wasn’t mentioned in the OP, even though it’s in the actual note on the plate.

Many of the posts here focus on something else: the directionality of VOR radials, but that isn’t relevant because this note is all about airways, and an airway isn’t directional, it’s just there. The airway is like a line segment, defined at one end by a specific radial of a VOR, yes, but without an inherent direction.

The note in the plate is relevant I believe only if your clearance is to fly on a specific airway to that VOR. If that’s your clearance, on an airway in the range defined by the note, you cannot thence get a clearance to fly the outbound leg from the VOR to the IAF.

If your clearance is not on an airway, but instead flying direct, then presumably ATC would clear you direct to the IAF, where you could then do a course reversal in the hold, or just turn into the final approach course, depending on where you’re coming from.

So what about the airways? If you were given a clearance to fly one to the VOR, I think it’s likely that before you get to the VOR, assuming you haven’t lost communication, you would be given new instructions, either vectors to the final approach course or direct to the IAF where you could use the hold for a course reversal if needed. In those cases, the note wouldn’t matter.

It seems so unlikely that this note would have any effect that I’m guessing it is there mainly in case of lost communication, so that if you were cleared to the VOR on the airway, and then lost comm, you’ll not be tempted to choose that particular approach to complete your flight.
 
Here's what's is going on. Arrivals at LNS for the IAP turn southeast on a 129° course. Looking at the approach in the context of the enroute chart tells us why. Inbound to LNS on the 054° radial will require a 105° turn which exceeds the current 90 maximum for a turn on an RNAV approach. At the opposite end, inbound on the R223 will require a 166° turn (and yes, my math could be off, but you get the point). So we can't use those specific radials to arrive at LNS and use it ad the transition for the approach.

That's all it means. It does not mean ATC can't send you direct AYOSA for the approach. It doesn't mean ATC can't give you vectors to final. It doesn't mean ATC can't vector you off one of the airways and then give you a better angle to LNS (although that would be silly). In theory, the note doesn't even mean ATC can give you direct LNS from the "bad sector," but, separate from the note, ATC has similar rules about maximum angles (sort of like the way the IFR hemispheric rule works).


upload_2021-10-22_16-1-35.png
 
Wow this forum is awesome. I get it now…

- the “sector” the note refers to is defined my the victor airways. The chart refers to them by the radials for some reason but that doesn’t matter it’s the airways.

- this note is saying when on any of the airways within these 2 you can’t turn towards the IAF with the hold-proc turn. That thinner arrow tells me it’s a transition leg to the approach.

- this is only here and relevant in case I lose comms and was cleared to the airport as my clearance limit.

makes sense now….
 
DaveInPA said:
Wow this forum is awesome. I get it now…

- the “sector” the note refers to is defined my the victor airways. The chart refers to them by the radials for some reason but that doesn’t matter it’s the airways.

- this note is saying when on any of the airways within these 2 you can’t turn towards the IAF with the hold-proc turn. That thinner arrow tells me it’s a transition leg to the approach.

- this is only here and relevant in case I lose comms and was cleared to the airport as my clearance limit.

makes sense now….
Click to expand...
Yes!

But not necessarily lost com. Could be any situation which requires "own nav." Approaches are designed to be "own nav" unless the plate says "radar required."

In fact, lost com, I wouldn't give a hoot about the note.

BTW, if it makes you feel better, I was once asked about this note (on another approach) by a CFII who didn't understand it.
 
I always liked this discussion by the GOVERNMENT/INDUSTRY AERONAUTICAL CHARTING FORUM


“.Subject: Airway "NoPT" Notes on Instrument Approach Procedures

Background/Discussion: Some of the "NoPT" notes on IAP charts are confusing and allow two different interpretations of intent. For example, The note on the Chester, CT (SNC) VOR-A approach states "NoPT for arrival on MAD VOR/DME airway radials 235 CW 317". The note specifies airway radials and Air Traffic expects that aircraft arriving on V-34, V-475, or V-1 from the west comply with the NoPT note and execute a straight in approach.

However, the note results in about half of the pilots thinking that it applies to all radials from 235 clockwise to 317. This misinterpretation has been noted in both newly rated and highly experienced pilots.

Recommendations: On the Chester approach note and any other location where ATC wants to apply NoPT only to specific airways, the note must list the specific airway(s) and direction of flight; e.g., "NoPT for arrival at MAD VOR/DME on V-1 northeast bound, V475 northeast bound, and V-34 southeast bound." Additionally enhanced guidance should be placed in the AIM and IPH.”
 
Last edited:
Clip4 said:
I always liked this discussion by the GOVERNMENT/INDUSTRY AERONAUTICAL CHARTING FORUM


“.Subject: Airway "NoPT" Notes on Instrument Approach Procedures

Background/Discussion: Some of the "NoPT" notes on IAP charts are confusing and allow two different interpretations of intent. For example, The note on the Chester, CT (SNC) VOR-A approach states "NoPT for arrival on MAD VOR/DME airway radials 235 CW 317". The note specifies airway radials and Air Traffic expects that aircraft arriving on V-34, V-475, or V-1 from the west comply with the NoPT note and execute a straight in approach.

However, the note results in about half of the pilots thinking that it applies to all radials from 235 clockwise to 317. This misinterpretation has been noted in both newly rated and highly experienced pilots.

Recommendations: On the Chester approach note and any other location where ATC wants to apply NoPT only to specific airways, the note must list the specific airway(s) and direction of flight; e.g., "NoPT for arrival at MAD VOR/DME on V-1 northeast bound, V475 northeast bound, and V-34 southeast bound." Additionally enhanced guidance should be placed in the AIM and IPH.”
Click to expand...
I does show a sense of humor.
 
As NoHeat points out, the note only applies to arrivals on AIRWAYS using the radials! "Procedure NA for arrivals on LRP VOR/DME airway radials 054 CW 323". The procedure IAF is at AYOSA, but from LRP there is a feeder route that connects airways to the IAF. This feeder route can't be used if you are arriving on an airway using a LRP radial between 054 CW to 323 degrees. The procedure is an RNAV procedure, so there is no restriction on navigating to the IAF at AYOSA and using the required HILPT to join the procedure. The "airways" is part of the note and means what it says. If you are fling on one of the airways to LRP along one of the radials, you will either need vectors or a clearance direct to AYOSA, hopefully before you reach LRP.
 
You must log in or register to reply here.
Back
Top