AUS_ATC

I went into work today and received a "stand up briefing" relating to new MEM RNAV STARS procedures that went into effect on the last chart change. After spending some time reviewing the new procedures and comparing them to the existing STARS for non-RNAV and turboprops, I discovered the following:

1. When I compared the RNAV STARS with the existing STARS for non-RNAV and turboprops, I discovered that there were numerous NAVAID radials that differed by as much as three degrees. This may not sound like much, but take a look at some of the transitions and do the math.

2. When I compared the new RNAV STARS with the existing STARS for non-RNAV and turboprop aircraft, I disovered that some FIXES were as much as ten (10) miles apart from one chart to another. Will this be YOUR error? Or will the error be charted to ATC? A ten mile error could place you in another ATC Sector, MOA or TFR.

3. The point at which you will be told to "Expect vectors to final approach course passing XXXXX" varies from one chart to the next. The charts for non-RNAV and turboprop aircraft indicate a fix that is outside of my airspace, and I am not allowed to issue a vector until you are within the lateral confines of my airspace. What will you do if you don't receive the vector? Start pestering ATC? Or continue inbound on the STAR?

4. MEM TRACON does not utilize Flight Progress Strips for arrivals, so we will have no idea which STAR you are flying. There are now two STARS from each corner post, each with slightly different radials and instructions.

5. The STARS for non-RNAV and turboprop aircraft utlize a heading at the "pivot point" (BOWEN, CLARK, OLIVV and TWIKL). The new RNAV STARS utlize tracks from the pivot point to two new fixes on the downwind. These downwind fixes are not depicted on our RADAR video maps, and the tracks to these fixes do not coincide with the headings off of the pivot point.

If someone can enlighten me as to why there are differences between these two types of STARS, I'd be most thankful. Otherwise, we should all start complaining to someone about the STAR irregularities at MEM.

MEM_ATC

TonyC

In my estimation, the differences are not worth mentioning. At FedEx we have just transitioned from Jeppesen products to LIDO products. In the process we discovered that the numbers printed on the charts can vary based on who is doing the measuring, and how they're measuring, and how long ago they did it. It's not unusual to find differences of several degrees. But guess what? When it comes to airways and such, the courses aren't as important as the pionts. J42 is defined as the line between MEM and BNA, not the XXX degree radial outbound and the YYY course inbound. Just point to point.


We've got the new Arrivals in a NOTAM-like format. Let me compare, for example, the WLDER 4 arrival with the RNAV arrival for the same quadrant, the LTOWN 1.

From SPKER we go to WLDER then LTOWN, MRCEL, and CLARK. That's the same for both arrivals. The Feeder Routes are the same, as well. Pocket City (PXV), Bowling Green (BWG), Nashville (BNA), McKellar-Sipes (MKL), and Jacks Creek (JKS) are all Feeder Routes for the WLDER 4. The LTOWN 1 (RNAV) only uses Bowling Green (BWG), Pocket City (PXV) and Nashville (BNA). While the published courses are, as you mentioned, up to 3 degrees different, the fact of the matter is the RNAV airplanes will be flying a straight line between the points, which have not changed. (Reviewing your post, I see you've said you noticed a difference in points of up to ten miles. I don't see that. I see the same points as before. What discrepancies do you see, specifically? Could there be an error in your charts?)

I'm a bit puzzled why the holding patterns are different, though. On the WLDER 4, the inbound course for the published holding pattern at SPKER is 225 degrees. On the corresponding RNAV arrival, the LTOWN 1, the inbound course is 226 degrees. I don't understand why these would differ. The holding pattern at MRCEL is the same on the WLDER 4 and the LTOWN 1 (RNAV). Oh, there's one more thing. The LTOWN 1 (RNAV) specifies an OUTBOUND leg length of 7 NM for both patterns. I've never seen that before.


Anyway, that gets us to the last part of the arrival. The WLDER 4 drops us off at CLARK with a magnetic heading. As you know, ATC often adjusts this heading for winds, so that we generally parallel the north/south runways. The LTOWN 1 (RNAV) uses the "last" for the arrival "pair" to the south as the next point. OLIVV is the last point on the HOLLY arrival, so it's the point after CLARK on the LTOWN 1. (Similarly, CLARK is the point after OLIVV on the LARUE 1 (RNAV), the RNAV "complement" to the HLI Arrival.) So, back on the LTOWN 1 (RNAV), we hit CLARK, then go to OLIVV (roughly parallelling the north/south runways), and then to a new point, NDREA. (Using the terminology you used above, we go from one pivot point to another, and then to a new point.)


Unless there's a strong crosswind, I don't see how flying either procedure will place the airplane in a much different place. Back up to the feeder routes, even. Whether it's a 727 wandering left and right of a VOR signal, or a DC-10 going point to point with an INS, or and MD-11 with RNP of 2.0, I don't think you'll see much variation from what you see today. We're all trying to get from one point to the next with whatever tools we have on board.


Now, that's just my take on it from the perspective of having looked at the procedure on paper. Give us a chance to fly it and I might see something different.

(I don't know about the other operators in MEM, but the FedEx 727s and DC-10s won't be doing the RNAV arrivals. Count on the MD-11/10s and that Airbuses.)




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AUS_ATC

TonyC,

Thanks for the reply. My comments are listed below.

The Charts that I'm looking at were downloaded off of AirNav.com. The dates, serial numbers and etc. all correspond to the FLIPs at work that are printed in paper/bound format.

Compare the BEERT 1 Arrival with the GILMORE 3 Arrival. Now take a look at the FSM Transition from FSM to HERTZ Intersection. The GILMORE Arrival indicates the FSM R-076, while the BEERT Arrival indicates the the FSM R-082. That's six degrees difference over the course of 103 miles between FSM and HERTZ.

We have a tool at the sector that allows us to plot these angular differences. According to my plots last night at work, there is a 9.53 mile difference in the location of HERTZ between the two arrivals. I'm not up to speed on the formulas required to calculate this by hand. 9.53 miles is fairly significant in my world of ATC.

Yes, it's all very unusual to me as well. I've seen a number of chart changes, additions and updates over the years, but never the number of slight differences that exist with these 8 overlying procedures.

These types of procedures are supposed to reduce workload and help pilots and ATC by reducing the frequency congestion, as well as provide standardized routings in/out of the Terminal area. If I have to guess or ask each aircraft which STAR Procedure he's flying, or if I fall back into the habit of issing a heading at the "pivot point" and then relaying this information to the next sector -- then I've negated some of the positive benefits of implementing these new RNAV STAR Procedures.

As usual, thanks for your input. I'll post anything unsual from the ATC side.

Take care,

MEM_ATC

Overnitefr8

Are there LAT/LONG's associated with the HERTZ intersection on your charts? Hopefully they are the same, even though the RNAV and VOR courses are different.

HoursHore

If the Lat Longs match, Thats the line the plane will fly. The Radials and Courses there for reference only.

The Plane just plots a Great circle between Points. The only things that matters is the LAT Longs of each point.

TonyC

OK, HERTZ is a good example. The printed chart for the GILMORE 3 Arrival shows HERTZ at N35 34.8 W092 10.8. The textual descrition I have for the BEERT 1 Arrival (RNAV) also shows HERTZ at the same exact coordinates. Now, how we get from FSM to HERTZ is another story. Jeppesen may calculate one radial off of FSM using data published 8 years ago, and LIDO might take a different chart and different data and come up with a different number. I honestly don't know who is the more accurate, but we've gone from using the former to the latter. The only people that use that information anyway are the VOR-only airplanes, and they won't be doing the RNAV approaches. The airplanes already equipped with INS aren't using those numbers (R-076 or R-082) to get to HERTZ, they're just going direct to a LAT/LONG. I see those radials not as definitions of the waypoint, but as an aid to get there.

But for the sake of conversation, I'm going to go out on a limb and postulate a possible explanation for the apparent discrepancy. If I'm using the VOR to navigate, I should use the FSM R-076 radial. Since VORs don't get regular maintenance, it's likely that the alignment of that NAVAID has drifted off of magnetic north since it was last certified. It's likely cocked a bit to the east, say, maybe even as much as 6 degrees. What's important, though, is that to get to HERTZ, I should set the 076 degree course on my cockpit instrument and keep that course centered.

If, on the other hand, I'm not using that cockpit instrument, I might find that the actual magnetic course between FSM and HERTZ is 082 degrees. I might find this by plotting the course on a chart, or I might flight test it. Either way, the magnetic course between the points is different from the magnetic course that I would set off of the FSM NAVAID. They both would get me to the same geographical fix, HERTZ.

I do NOT know that the above IS the case, but I believe that it MIGHT be the case, and it would explain the apparent discrepancy.



I believe we'll see more and more of these RNAV procedures as time gose on. I think it's important to understand what's going on now so we can keep up as the pace of change quickens.



Well, you don't HAVE to assign a heading at the pivot point, at least from my perspective. The procedure on the STARS is to turn to the published heading at those points, period. There's no "EXPECT" caveat attached to them. The only thing different is the heading. In the case of the old arrivals, we'll turn and drift; in the case of the RNAV arrivals, they'll go directly to the opposite pivot point. Depending on the crosswinds, you should be able to pick out who's doing what by the direction they're going.


Thanks. This should be a good learning experience for us all.





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