V186 from PDZ to VNY with VOR/DME only

[Cyrus]

Hi. Me again...

Let's say I'm going to fly the ONTN16 TEC Route.

What is the correct way to navigate from PDZ to VNY along V186 with slant alpha equipment only?

Thanks to the PE Workshops , I noticed a changeover point at TIFNI, so I'm thinking that this is where you stop tracking outbound on PDZ and swtich to inbound on VNY - which would mean /A is all you need..... correctomundo?

Cheers.

P.S. Incidentally, I see from this example that you'll probably get vectors to join the VNY 095R soon after take off anyway, so perhaps my question may only be theoretical (but also valid in the case where I'm enroute from somewhere east of PDZ).

[Pieces]

I'm confused about what you are asking. Flying that route is no different than flying any other Victor route, which (I believe) you can fly with only one VOR. The workload would be brutal, but you could do it.

[Cyrus]

Thanks Reece. But let me ask it another way.... Is this section of V186 an exact straight line from PDZ to VNY? (because it doesn't seem to be when I join them up in SkyVector).

I see a lot of intersections and, so, I'm just wondering if one is really expected to navigate along those (if "V186" is the assigned route)? Or yet another way of asking the question, is "V186" (for this section) theoretically different from a route of "PDZ VNY"?

If I make TIFNI a waypoint on the chart, I do get the correct heading from PNY to TIFNI, as seen here.

However, it still shows up as hdg 278 from TIFNI to VNY, whereas the chart suggests it should be 180+95, i.e. 275. (see the "95" in the circle at VNY for V186).

I know 3 degrees isn't the end of the world on this relatively short run, but I'm just asking about the theoretical approach to navigating V186.

[Cyrus]

The workload would be brutal, but you could do it.

For me, this implies that one should navigate to all of the intersections, i.e. TIFNI, PIRRO, ITSME, ELMOO, PURMS, DARTS....??! Yes, that would be bonkers.

Yet V186 is what the TEC Route says (it doesn't say "PDZ VNY").

[Pieces]

Ah. No, V186 is not a straight line between PDZ and VNY. As you noted, it is the PDZ278R to TIFNI, VNY95R VNY and then on. The other waypoints are important as well. You could get an instruction such as "Cross PURMS at 5000" or whatever.

I think (and I may be wrong about this) that there is a slight discrepancy between how GPS calculates heading and the VOR headings. That's why there is difference between the courses that Skyvector shows and the charted courses. Someone please correct me if that is not the case. I'll try and find a source to back that up.

[Pieces]

Aha! Found it: AIM 1-1-18.I

There may be slight differences between the course information portrayed on navigational charts and a GPS navigation display when flying authorized GPS instrument procedures or along an airway. All magnetic tracks defined by any conventional navigation aids are determined by the application of the station magnetic variation. In contrast, GPS RNAV systems may use an algorithm, which applies the local magnetic variation and may produce small differences in the displayed course. However, both methods of navigation should produce the same desired ground track when using approved, IFR navigation system. Should significant differences between the approach chart and the GPS avionics' application of the navigation database arise, the published approach chart, supplemented by NOTAMs, holds precedence.

Due to the GPS avionics' computation of great circle courses, and the variations in magnetic variation, the bearing to the next waypoint and the course from the last waypoint (if available) may not be exactly 180° apart when long distances are involved. Variations in distances will occur since GPS distance-to-waypoint values are along-track distances (ATD) computed to the next waypoint and the DME values published on underlying procedures are slant-range distances measured to the station. This difference increases with aircraft altitude and proximity to the NAVAID.

[Cyrus]

it is the PDZ278R to TIFNI, VNY95R VNY and then on.

So then is DARTS to VNY (just 12nm) a heading of 278 or 180+95? If 278 (which Skyvector suggests) then what is the "095" on the chart supposed to be signifying (the one showing inside the VNY circle)? [EDIT: I think the "095" is stating the direction from VNY to PDZ direct... although Skyvector has this at 096... but maybe that's the error you refer to]

Good point about needing to know which fix you're at/near (using DME, I assume).

[Pieces]

If you're flying /A, you would not be flying a specific heading, but following a radial. The radial that defines the section of V186 between DARTS and VNY is the VNY 095 radial. The heading to fly to track that radial (assuming no wind, etc) would be very close to 095+180. See my last post with the quote from the AIM as to why those headings don't necessarily line up.

[Cyrus]

Thanks for the AIM ref.

Also, I think I just found what I'm looking for.

TIFNI to VNY shows a course of 278. However, VNY to TIFNI shows a course of 095.

So now I understand what you're saying about V186 essentially being PDZ278R to TIFNI then VNY95R VNY.

I do believe that the penny has dropped.

[Cyrus]

If you're flying /A, you would not be flying a specific heading, but following a radial. The radial that defines the section of V186 between DARTS and VNY is the VNY 095 radial. The heading to fly to track that radial (assuming no wind, etc) would be very close to 095+180. See my last post with the quote from the AIM as to why those headings don't necessarily line up.

Thanks, that helps (and sorry that we're cross-posting).....

But isn't the changeover point at TIFNI telling us that, for V186, we should follow the PDZ278R (until TIFNI) and then immediately switch to the VNY095R to VNY? (and not use DARTS at all, other than as a DME reference)?