CNF fixes on Victor airways.

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John777

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Hi everyone,

I am preparing for the instrument oral, and currently have nobody to ask questions because he left for his job quiet long ago...

My question is that there are sometimes CNF fixes on Victor airways which are not for ATC routing but in GPS database. When navigating on victor airways with CNFs, does it require us to have GPS(suitable RNAV)?

John
 
John777 said:
Hi everyone,

I am preparing for the instrument oral, and currently have nobody to ask questions because he left for his job quiet long ago...

My question is that there are sometimes CNF fixes on Victor airways which are not for ATC routing but in GPS database. When navigating on victor airways with CNFs, does it require us to have GPS(suitable RNAV)?
Click to expand...

No, you can use VOR.
 
John777 said:
Hi everyone,

I am preparing for the instrument oral, and currently have nobody to ask questions because he left for his job quiet long ago...

My question is that there are sometimes CNF fixes on Victor airways which are not for ATC routing but in GPS database. When navigating on victor airways with CNFs, does it require us to have GPS(suitable RNAV)?

John
Click to expand...
How would you propose to "legally" navigate using a compute navigation fix without an approved form of computer navigation?

Go back to that FAR every talks about with stupid mnemonics about burning fruit some other idiotic mnemonic for the IFR part. What does it say about required navigational equipment?
 
John777 said:
Hi everyone,

I am preparing for the instrument oral, and currently have nobody to ask questions because he left for his job quiet long ago...

My question is that there are sometimes CNF fixes on Victor airways which are not for ATC routing but in GPS database. When navigating on victor airways with CNFs, does it require us to have GPS(suitable RNAV)?

John
Click to expand...
The requirement in 91.205(d)(2) is for equipment suitable for the route to be flown. The CNF fixes that I've seen on victor airways are intersections formed by VOR radials. Their purpose, as I understand it, is to facilitate using RNAV systems, including GPS, to fly victor airways, not to require those systems. If you have been cleared or instructed to fly a victor airway, the requirement is to remain within the boundaries of the airway, and properly operating VOR receivers give you that capability.
 
John777 said:
Hi everyone,

I am preparing for the instrument oral, and currently have nobody to ask questions because he left for his job quiet long ago...

My question is that there are sometimes CNF fixes on Victor airways which are not for ATC routing but in GPS database. When navigating on victor airways with CNFs, does it require us to have GPS(suitable RNAV)?

John
Click to expand...
No, you don't need any GPS to navigate along a victor airway if you meet all other requirements (altitude, distance to VOR. Etc.) The CNF simplifies transitioning from one victor airway to another using a GPS when there isn't a fix at the intersection of the two.
 
Sorry everyone, I should have added an example for you. Yes I am aware of regulatory requirements but should have put question in other way.

So if you look up a CNF called 'AWIZO' on V208 the route has course change at AWIZO.
How would you navigate?
 
John777 said:
Sorry everyone, I should have added an example for you. Yes I am aware of regulatory requirements but should have put question in other way.

So if you look up a CNF called 'AWIZO' on V208 the route has course change at AWIZO.
How would you navigate?
Click to expand...

With a VOR receiver? Track the 080 radial outbound from GCN until you intercept the TBC 231 radial inbound. Easiest if you have two nav radios.
 
John777 said:
Sorry everyone, I should have added an example for you. Yes I am aware of regulatory requirements but should have put question in other way.

So if you look up a CNF called 'AWIZO' on V208 the route has course change at AWIZO.
How would you navigate?
Click to expand...

I would track the GCN R-080 until I intercept the TBC R-231 and then track the latter, or, I would track the TBC R-231 until I intercept the GCN R-080 and then track the latter.
 
Thanks.
But I wonder why the CNF AWIZO is there on Victor airways.. cannot find out the reason why..
 
John777 said:
Thanks.
But I wonder why the CNF AWIZO is there on Victor airways.. cannot find out the reason why..
Click to expand...
Although victor airways are designed to be flown using terrestrial navaids, pilots also have the option of using a GPS or other RNAV system to follow them.

A CNF gives the GPS a designator for a fix that doesn't otherwise have a name. A bend in a victor airway is an example of such a fix.

AIM 1-1-17b5(i)(2) gives the official answer as follows:

A Computer Navigation Fix (CNF) is
also a point defined by a latitude/longitude coordinate
and is required to support Performance−Based
Navigation (PBN) operations. The GPS receiver uses
CNFs in conjunction with waypoints to navigate from
point to point. However, CNFs are not recognized by
ATC. ATC does not maintain CNFs in their database
and they do not use CNFs for any air traffic control
purpose. CNFs may or may not be charted on FAA
aeronautical navigation products, are listed in the
chart legends, and are for advisory purposes only.
Pilots are not to use CNFs for point to point
navigation (proceed direct), filing a flight plan, or in
aircraft/ATC communications. CNFs that do appear
on aeronautical charts allow pilots increased
situational awareness by identifying points in the
aircraft database route of flight with points on the
aeronautical chart. CNFs are random five-letter
identifiers, not pronounceable like waypoints and
placed in parenthesis. Eventually, all CNFs will begin
with the letters “CF” followed by three consonants
(for example, CFWBG). This five-letter identifier
will be found next to an “x” on enroute charts and
possibly on an approach chart. On instrument
approach procedures (charts) in the terminal
procedures publication, CNFs may represent unnamed
DME fixes, beginning and ending points of
DME arcs, and sensor (ground-based signal i.e.,
VOR, NDB, ILS) final approach fixes on GPS
overlay approaches. These CNFs provide the GPS
with points on the procedure that allow the overlay
approach to mirror the ground-based sensor
approach. These points should only be used by the
GPS system for navigation and should not be used by
pilots for any other purpose on the approach. The
CNF concept has not been adopted or recognized by
the International Civil Aviation Organization
(ICAO).​
 
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