I’ve got 3 questions for all you experts at flight plan interpretation.
On several flight plans, I have noticed an entry that consists of a VOR plus a number. For example, a very common KMKE-KIND routing is KMKE OBK J84 WORDY VHP311 JAKKS KIND. I understand everything except the VHP311. I know VHP is the Brickyard VOR, and I suspect the 311 is a radial. So my guess is that this portion of the routing means, “after WORDY, follow the VHP 311 radial to JAKKS.” But this seems redundant. Since WORDY and JAKKS are both on the 311 radial, you can’t help but fly this radial. So why not simply KMKE OBK J84 WORDY JAKKS KIND?
Here is another example: KJFK NEION J223 CORDS ULW ULW306 BENEE KBUF. Again, what’s the purpose for the ULW306 entry, since BENEE lies on the ULW 306 radial?
This question involves redundancy of a different sort. Here is a routing that illustrates it: KDEN PLAIN4 HCT J128 OBH J128 DBQ JVL VEENA2 KMKE. My flight instructor constantly emphasized that everything in aviation communication should be as concise as possible. So why is this route not shortened to simply KDEN PLAIN4 HCT J128 DBQ JVL VEENA2 KMKE? Is there a reason that I am missing for including the intermediate waypoint OBH?
I have noticed some waypoints whose format differs from the usual 5 letters. Here is a route that contains two of them: KSFO DUMB6 LIN PEONS INSLO DTA KD57S KK51C EMP JHAWK6 KMCI. Although the 5-letter system produces nearly 11.9 million possible waypoint names, I know that the guidelines required that they be pronounceable (so a name like BBFTG would be impossible). Even with this limitation, has the list of acceptable waypoint names been exhausted already? Or is there some other system at work here?
Let’s answer this question with another question. What if the aircraft in question isn’t capable of using GPS or anything advanced RNAV? If an aircraft is /A equipped (DME, and Transponder capable of Mode C) or /U (no DME, with a Transponder capable of Mode C), they won’t be able to go directly to a fix after leaving the airway. So they’ll have to join the radial to get to the next waypoint on their route. AAL still has some MD80s that are /U, that this route would be an example to fly.
Here is another example: KJFK NEION J223 CORDS ULW ULW306 BENEE KBUF. Again, what’s the purpose for the ULW306 entry, since BENEE lies on the ULW 306 radial?
Same as the above. They couldn’t do directly to the fix without knowing what the fix is defined as. So they’d have to join the radial to get to the fix. BENEE is defined as the ULW R-306, 63DME. But, with an aircraft being /U, they wouldn’t know that. Hence, the radial to get to the fix.
This question involves redundancy of a different sort. Here is a routing that illustrates it: KDEN PLAIN4 HCT J128 OBH J128 DBQ JVL VEENA2 KMKE. My flight instructor constantly emphasized that everything in aviation communication should be as concise as possible. So why is this route not shortened to simply KDEN PLAIN4 HCT J128 DBQ JVL VEENA2 KMKE? Is there a reason that I am missing for including the intermediate waypoint OBH?
Good question here. J128 goes completely through OBH. However, I could see them being redundant here because 3 different airways intersect at OBH: J84, J100, and J128. They may just be re-iterating that they want to stay on J128.
I have noticed some waypoints whose format differs from the usual 5 letters. Here is a route that contains two of them: KSFO DUMB6 LIN PEONS INSLO DTA KD57S KK51C EMP JHAWK6 KMCI. Although the 5-letter system produces nearly 11.9 million possible waypoint names, I know that the guidelines required that they be pronounceable (so a name like BBFTG would be impossible). Even with this limitation, has the list of acceptable waypoint names been exhausted already? Or is there some other system at work here?
Thanks in advance for any help you can provide.
Dammit… stumped me on this one! I’m not sure on why they did this one!
But for your first 2 questions, if you found the route here, check the equipment suffix for the aircraft in question. If they were RNAV equipped, my guess is that their RNAV equipment was INOP, or they were non-RNAV the entire time.
Looks like waypoints like KD57S happen every 30’ latitude and 2 degrees of longitude. I think they provide a grid of named waypoints across the country.
Now that mduell and porterjet have explained mystery #3, I see those faint green characters on the Hi-Altitude Enroute charts. Since they don’t use the traditional waypoint symbols, I never made the connection. With the information you both provided, I was able to find more information on the Internet. Apparently they are part of the Navigation Reference System. Here is a government paper describing them.
And BL’s answer to #1 is also much appreciated. I had considered that equipment might be a possible factor. But the same flight plan is used with varied equipment, including E135/L, CRJ2/L, and B722/W, among three different carriers. (Which is one of the reasons I was originally confused by it.) My understanding of the equipment suffix is limited – would /L and /W equipment have the limitations that are described?
Anyway, thanks everyone for clearing these mini-mysteries up!
/L means the aircraft is RVSM approved as well as having GNSS including GPS or WAAS with enroute and terminal capability.
/W depends on whether the flight plan is domestic US or ICAO. Domestic it means RVSM plus RNAV, but not advanced RNAV. In the ICAO format it means RVSM, the flight plan would then include other codes to indicate navigation capability. This is the equipment I’m currently flying, we can do PTP (point to point), no database navigation. with old fashioned 9 waypoint INS’s. You should see us departing some airports in Europe where the SID contains 7 waypoints in the first 45 miles. Talk about keeping busy.
The ICAO format contains space for multiple codes, the FAA format only allows one.
I also see a lot of what you mentioned in your first question, namely routes filed ABC J1 DEF J1 GHI J1 JFK J1 XYZ etc. Unlike your instructor mine said keep it simple, file ABC J1 XYZ.
