RNAV vectors

Roy Smith wrote:

Sam Spade wrote:

Offsets are a feature in TSO 145/146 (WAAS capable) sets. The smart
money will use a slight offset to fly a Victor Airway to greatly reduce
the opposite direction mid-air potential. Minor offsets are already
approved on the North Atlantic.


The CNX-80 has offsets. I didn't realize they were required by the TSO.
The story I had heard was the CAP wanted offsets so they could fly box
search patterns, and Apollo put the feature in to close a big sale to them.

More than you ever wanted to know:

2.2.1.3.16 Parallel Offsets

The parallel offset is defined as a route parallel to, but offset from,
the original active route. The basis of the offset path is the original
flight plan leg(s) and one or more offset reference points as computed
by the navigation system. The computed offset reference point is located
so that it lies on the intersection of lines drawn parallel to the host
route at the desired offset distance and the line that bisects the track
change angle. An exception to this occurs if there is a route
iscontinuity (or end of route). In this case, the offset reference
point is located abeam of the original flight plan waypoint at the
offset distance.

The offset path and associated waypoint must be created to the same
standards as the host route. The earth model must be WGS-84 and the
offset reference point must have the same or better resolution than the
host route waypoint. The parallel offset function shall be available for
enroute TF and the geodesic portion of DF leg types at a minimum.
Note: The parallel offset function enables an aircraft to be flown on a
flight path offset from the center line of a route while maintaining all
characteristics of that flightpath, as if it were being flown centrally
on the route. Examples for the use of offsets are weather avoidance, air
traffic conflict avoidance, etc.The system shall have the capability to
fly parallel tracks at a selected offset distance.

When executing a parallel offset, the navigation mode and all erformance
requirements of the original route in the active flight plan shall be
applicable to the offset route. The system shall provide for entry of
offset distance in increments of 1 nm, left or right of course. The
system shall be capable of offsets of at least 20 nm. The fact that the
system is operating in offset mode shall be clearly indicated to the
flight crew. When in offset mode, the system shall provide reference
parameters (e.g., cross-track deviation, distance-to-go, time-to-go)
relative to the offset path and offset reference points.

An offset shall not be propagated through route discontinuities,
unreasonable path geometries, or beyond the initial approach fix.
Annunciation shall be given to the flight crew prior to the end of the
offset path, with sufficient time to return to the original path. Once a
parallel offset is activated, the offset shall remain active for all
flight plan route segments until removed automatically, until the flight
crew enters a Direct-To routing, or until flight crew (manual) cancellation.

Note: RTCA/DO-236A provides additional information on parallel offsets.

On Thu, 21 Dec 2006 08:41:10 -0600, "Stan Prevost"
wrote:


"Sam Spade" wrote in message
...
Roger wrote:


And here I always though they were VOR offsets. Although I have to
admit it's been well over 10 years since I actually heard any one give
an RNAV off set. :-))
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Offsets are a feature in TSO 145/146 (WAAS capable) sets. The smart money
will use a slight offset to fly a Victor Airway to greatly reduce the
opposite direction mid-air potential. Minor offsets are already approved
on the North Atlantic.

Offsets should not be used for instrument approach or departure
procedures.

I thought Roger was talking about radial/DME offsets like used in KNS80 and
other RNAV boxes to define RNAV waypoints.

He we-)) As in LAN 27015 (I think that was the way they were
worded) Actually I filed an RNAV offset coming out of OSH a few years
ago when MTW VOR was out of service. I used an offset from GRB that
was very close to MTW. The clearance sounded something like OSH
direct GRB17025 Direct LDM, Direct 3BS(I don't remember the numbers
now but that conveys the general idea)



But course offsets were a feature of my old Northstar M3 IFR GPS. Not
mandated by TSO back then, though. I noticed the course offsets in the
GNS430W while reading the manual and wondered why they appeared.

Hard to imagine the FAA mandating course offsets to avoid center-of-airway
conflicts, given the following:

§ 91.181 Course to be flown.
Unless otherwise authorized by ATC, no person may operate an aircraft within
controlled airspace under IFR except as follows:

(a) On a Federal airway, along the centerline of that airway.

(b) On any other route, along the direct course between the navigational
aids or fixes defining that route. However, this section does not prohibit
maneuvering the aircraft to pass well clear of other air traffic or the
maneuvering of the aircraft in VFR conditions to clear the intended flight
path both before and during climb or descent.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

"Stan Prevost" wrote in message
...

Did you ever actually read the post I responded to? I responded to a
statement, not a question.


I believe I wrote the post you responded to. Actually reading the question
may have allowed you to understand the statement.



Do you understand my response?


Your response indicated you did not understand the previous message.



Do you understand that all these nice
design features of specific GPS boxes that we have been discussing are not
necessary to nagivate to a fix along a specified course?


Of course.



What experience do you have flying vectors for approaches?


I've held an instrument rating since 1983.



None, but I have experience flying them. And I can read.


Your messages in these forums suggest you cannot read very well.



What does experience have to do with what the rules say about vectors to
approaches?


What rule are you having trouble with?

"Stan Prevost" wrote in message
...

It would seem to suggest no such thing.


It does, actually.



You seem to think that FAAO
7110.65 is only advisory and that the design approach taken by some
equipment manufacturer actually defines the rules you should use for
vectoring aircraft to approaches.


What led you to that incorrect conclusion?



Perhaps you should become familiar with FAAO 7110.65 and the P/CG if you
want to know about vectoring to final on GPS approaches.


I am thoroughly familiar with both and I know everything about vectoring for
all types of approaches.

"Sam Spade" wrote in message
...

Yes, it is sufficiently special that a lot of controllers can't do it in
accordance with 5-9-1.


How so?