Interpretation of a fix

the400kid

the400kid

Pre-takeoff checklist
Joined
Sep 2, 2013
Messages
131
Display Name
Display name:
FLAAV8R
I've seen this shorthand a few times but am not quite sure how to interpret it.

Examples:

SBJ113035

CCC315015
 
the400kid said:
That's what I pretty much thought but needed verification. The other question is, I assume that this is what the ATC computer generates but would I actually be given this in a clearance?
Click to expand...

The computer often generates fixes like these as fix postings but relatively rarely in a route. It's unlikely they would be given in a clearance when the pilot has not filed a route in a similar manner.
 
Never was given a fix like that in a clearance, but I was given a clearance to fly heading intercept a radial (both as an initial portion of a clearance which isn't too unexpected) and in the middle of a route.
 
The preferred route from the SE over PMM and Lake Michigan to the 2013 Oshkosh fly in NOTAM had this route: PMM PMM333064 GAYLE V510 FAH ...
 
I guess my question wasn't as off-the-wall as I thought.
 
the400kid said:
I guess my question wasn't as off-the-wall as I thought.
Click to expand...

No, and you can use these types of fixes in your FAA flightplan. It helps to have a DME, but you can use an IFR GPS to locate the point as a user waypoint. ForeFlight also supports the format.
 
John Collins said:
No, and you can use these types of fixes in your FAA flightplan. It helps to have a DME, but you can use an IFR GPS to locate the point as a user waypoint. ForeFlight also supports the format.
Click to expand...

I'm not quite clear why I would specifically file a fix like this. Can you provide an example?
 
the400kid said:
I'm not quite clear why I would specifically file a fix like this. Can you provide an example?
Click to expand...

In the late 1970's and 1980's before LORAN and GPS was available, area navigation computers were available that allowed navigation to a waypoint established by a radial and distance from a VOR. These were called Area Navigation units at the time and later took on the description of Rho-Theta area navigation or DME-VOR RNAV units. An example of such a navigator that was popular was the KNS80. It had a built in VOR, DME, GS receiver and a RNAV computer and supported up to 4 waypoints defined by a frequency. radial, distance. I still have one in my panel. In the past I have used it for direct-to navigation to airports that did not have a VOR located at them. There also used to be charts that allowed you to quickly chart a direct course and eyeball the distance off of the cardinal headings of VORTAC stations.

Now a days, it is often used to define a waypoint location along an airway for a switch over point or to be able to file a flightplan to intercept an airway. It can also be used as a means of skirting a Class B or other special airspace.

The NOTAM to Oshkosh was to provide a point along V510 that could be filed by using the 333 radial of PMM. The alternative for filing the route would be to determine the latitude and longitude of the airway intercept point. Most pilots and controllers can understand 64 NM from PMM along the 333 radial and have a rough idea of where it is located.
 
My Kns 80 was a great unit. A clearance like above was common.
 
John Collins said:
In the late 1970's and 1980's before LORAN and GPS was available....
Click to expand...

Thanks for the explanation. Just as I thought, there isn't much use for a fix of this type with our miracle in the sky systems.

I never did get the hang of the KNS80 and never used it to its full potential when I had access to one.
 
John Collins said:
The NOTAM to Oshkosh was to provide a point along V510 that could be filed by using the 333 radial of PMM. The alternative for filing the route would be to determine the latitude and longitude of the airway intercept point. Most pilots and controllers can understand 64 NM from PMM along the 333 radial and have a rough idea of where it is located.
Click to expand...

I think all of the controllers concerned have an excellent idea of where it is located. It's where the PMM R-333 hits V510, about 11 miles southeast of GAYLE. But you won't be able to navigate that route using VOR, the Falls radials that define V510 are unusable.

And they were unusable last summer too.
 
roncachamp said:
I think all of the controllers concerned have an excellent idea of where it is located. It's where the PMM R-333 hits V510, about 11 miles southeast of GAYLE. But you won't be able to navigate that route using VOR, the Falls radials that define V510 are unusable.

And they were unusable last summer too.
Click to expand...

Interesting, FAH is only used to define V510 west of GAYLE as it is the cross-over point on the airway segment. The PMM333064 intercepts V510 on the east side of GAYLE as you indicated, where the MKG VORTAC 296 degree radial defines V510 up to GAYLE, so navigation using V510 west of GAYLE still requires the "unusable" radials of FAH.
 
the400kid said:
I'm not quite clear why I would specifically file a fix like this. Can you provide an example?
Click to expand...
When R-4006 is active, you can't go direct from Baltimore MD to Salisbury MD above 3000 feet. OTOH, the airway routing you'd get would take you about 30 miles out of the way. Potomac and Patuxent Approaches picked a point off the BAL VOR to use as a detour that is just north of the top of the R-area and adds only like 5 miles over the straight-line distance -- BAL133037, IIRC (it's saved in my 530 in my plane). Your clearance is "fly runway heading for vectors to the Baltimore 133 radial, then Baltimore 133 radial to the 37 DME fix, then direct Salisbury." You get the usual vectors out of BWI, then something like "fly heading 160, join the Baltimore 133 radial". When the needle centers, you fly the BAL133 radial out to 37 miles, then go direct SBY VOR. There's a radial/DME off SBY to go the other direction.
 
You must log in or register to reply here.
Back
Top