I-03 routing questions

Questions and comments about the PE Pilot Training Program
Turner
Posts: 134
Joined: Fri May 06, 2016 7:18 pm

I-03 routing questions

Post by Turner »

Hi everyone,

Sorry if this was covered (I imagine it has been)...

I'm reviewing the I-03 routing and found that when routing this in SkyVector, the course from POPPR to SMO is 308 (128 radial), but the description here notes a 125 radial.

311 SMO > SILEX looks ok.

How should this be interpreted?

2nd question - do we actually file radial values, or just nav points? It instructs us to file radials, but I'm not clear on why this is done if the flight is point-to-point betweeen airports, navaids, and fixes, which would imply radials/headings.

Thanks!
Andrew
wmburns
Posts: 474
Joined: Mon Jun 10, 2013 7:28 am

Re: I-03 routing questions

Post by wmburns »

Seems to me that if one is to understand some of the nuance of the TEC routing system there's some information missing here. Namely the aircraft type and equipment suffix.

The aircraft type is important because there are some TEC routes that only apply to certain aircraft.

The navigation equipment suffix is important because if flying /A going direct to a GPS way point just isn't possible.

As a well rounded pilot, you should be able to understand and execute a flight plan written using "old school" radials because they are valid. And while uncommon, it is possible to be given an instruction to fly a specific radial. It's an important skill to be able to fly one radial and then transition onto an intersecting radial.

As to the "reason" why the I-03 rating has specific instructions to file a radial, I suspect it's designed to prevent someone from just entering the flight plan into a GPS and hitting play. One has to actually set the navigation radios up and monitor for crossings. Then turning on a new heading and tracking a new radial. Thus forcing the pilot to "stay ahead" of the aircraft by thinking about and preparing for the "next" move. An important skill to learn.

Have you used the TEC route search function in Myflightroute.com?
Marcus Becker
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Joined: Fri Feb 08, 2013 5:12 pm

Re: I-03 routing questions

Post by Marcus Becker »

From Airnav.com
Information on fix POPPR

Identifier: POPPR
Name: POPPR
Location: 33-50-33.570N 118-17-17.900W
Navaid radial/DME: SLIr272.00/12.21
SMOr125.00
Fix use: Reporting point
Published: yes
Charts: ENROUTE LOW
Do you actually file the radials? Yes. File them as they are published. Shortcuts or simple instructions can be given to any point or radial at any given time. Remember the I-2 rating flight route? Depending on your aircraft, your routing was V23 OCN, right? Not much different than filing a radial if you think about it.
Last edited by Marcus Becker on Mon May 23, 2016 6:55 am, edited 1 time in total.
Image
Turner
Posts: 134
Joined: Fri May 06, 2016 7:18 pm

Re: I-03 routing questions

Post by Turner »

Hi wmburns,

Thanks for the note!

My main question was really about how to handle discrepancies between values found in instructions here on PE vs. those found in other planning resources, e.g. a 3 degree heading difference.

I looked through some random routings on myflightroute.com and it's pretty interesting. I am still curious about why radials are specified; from what I've seen, they're on the "actual" TEC routes as well, so I think maybe it implies specific courses vs. "direct-to" flight.

But I'm not sure. :)
Turner
Posts: 134
Joined: Fri May 06, 2016 7:18 pm

Re: I-03 routing questions

Post by Turner »

Interesting...

Haven't tried any other routing sources, but will.
Screen Shot 2016-05-23 at 9.55.06 AM.png
Screen Shot 2016-05-23 at 9.55.06 AM.png (282.06 KiB) Viewed 7343 times
Marcus Becker wrote:From Airnav.com
Information on fix POPPR

Identifier: POPPR
Name: POPPR
Location: 33-50-33.570N 118-17-17.900W
Navaid radial/DME: SLIr272.00/12.21
SMOr125.00
Fix use: Reporting point
Published: yes
Charts: ENROUTE LOW
Keith Smith
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Joined: Sat Oct 09, 2010 8:38 pm
Location: Pompton Plains, NJ
Contact:

Re: I-03 routing questions

Post by Keith Smith »

poppr.png
poppr.png (664.84 KiB) Viewed 7337 times
Swap to the LAX area chart and you'll see that it is indeed the SMO R-125, but the GPS-based course is 128. This is because of the difference between the magnetic variation that was used when SMO was last calibrated (back in 1975), versus the figures that are derived today by the GPS.

Here is the variation for the airport vs the VOR:
ksmo_variation.png
ksmo_variation.png (23.5 KiB) Viewed 7337 times
smo_variation.png
smo_variation.png (8.51 KiB) Viewed 7337 times
Note the 3 degree difference (12E for the airport, 15E for the VOR). That would explain the 125 vs 128.
wmburns
Posts: 474
Joined: Mon Jun 10, 2013 7:28 am

True course compared to VOR radials

Post by wmburns »

Turner wrote:My main question was really about how to handle discrepancies between values found in instructions here on PE vs. those found in other planning resources, e.g. a 3 degree heading difference.
Are you asking about why the VOR's and GPS disagree because the Earth's magnetic poles drift over time?

viewtopic.php?f=26&t=5308&p=34926&hilit ... ift#p34926
http://www.askacfi.com/3857/true-course ... adials.htm

Let's also talk about required navigation accuracy. What is the width of a Victor airway?

When VORs are less than 102 nautical miles (NM) from each other, the airway extends 4 NM on either side of the centerline
https://en.wikipedia.org/wiki/Victor_airways

For the distance involved, a setting difference of 3 degrees will still be within the width of a Victor airway.

Is it possible that you are over thinking this on some different levels? One of the goals of the lesson is not to hit the mark exactly but to learn the basics of how to set up two navigation devices (GPS and/or VOR) to track two intersecting radials.

Note, it's quite possible to use the GPS OBS mode to fly a radial much the same way as a regular VOR works.

Hope this helps.
Last edited by wmburns on Mon May 23, 2016 7:57 am, edited 2 times in total.
bbuckley
Posts: 232
Joined: Sun Mar 29, 2015 4:30 pm
Location: Jupiter, FL

Re: I-03 routing questions

Post by bbuckley »

If you look carefully at the IFR Low chart the 128 is the "T" route. The black line just below it indicates "125" radial to POPPR.
Edit: tried editing from iPhone but operator error... I originally said "radial" for "T" route when i should have said GPS course.
Last edited by bbuckley on Mon May 23, 2016 9:24 am, edited 4 times in total.
Commercial / Instrument / KMLB
Keith Smith
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Location: Pompton Plains, NJ
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Re: I-03 routing questions

Post by Keith Smith »

To be clear, there is no discrepancy between the route on PE vs the route that is issued or published in real life.

The issue is that you're equating a radial that was established in 1975 with a magnetic course to be flown today and that is incorrect (as counter intuitive as it seems). Sure, they're close, but due to how long ago most VORs were established, the Earth's magnetic field has moved around since then, hence the magnetic course you need to fly today no longer matches the courses implied by the radial numbers.

When you get to the I-4, you'll be looking up TEC routes yourself. At that point, if you haven't already, feel free to verify that the SNA to BUR route is as stated on the I-3 rating.
Keith Smith
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Location: Pompton Plains, NJ
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Re: I-03 routing questions

Post by Keith Smith »

wmburns, my concern with your post is that you're implying that the degree difference isn't going to exceed the width of the airway over such a short distance.

In fact, if you track the SMO R-125 perfectly, your TRK on the GPS will indicate 128. Despite the apparent difference between the 2 numbers, they refer to exactly the same true course over the ground.
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