Being asked to "verify direct XXX"

"Paul Folbrecht" wrote in message
...

I realized nobody's had an answer to my original question - how far
off-course can you be before being officially violated?


There is no fixed standard for that. You will likely only be violated if
your course deviation results in a loss of separation.

"Roy Smith" wrote in message
...

There is one official way you communicate to ATC what navigational
capabilities your aircraft has, that that's the equipment suffix on your
type code. File /U, and they'll give you clearances you can execute with
VOR receivers. File /A, and they'll expect you to be able to identify DME
fixes. File /G, and they'll expect you to be able to go direct to any
en-route fix and fly GPS approaches.


Whether you file /U, /A, or /G, ATC will expect you to be able to fly
whatever you file. If ATC must issue a reroute it should not require any
capability beyond what you indicated in your equipment suffix.



On the other hand, if you file /U and put "VFR GPS on board", you're
leaving it to them to guess what you want, since "VFR GPS on board" has no
official meaning. The most common guess seems to be "treat me as if I had
filed /G", so they do. It turns out that this is indeed what most people
want, so it works out and everybody's happy. You seem to be wanting
something different, but I'm not sure what it is.


What about those folks that file /A and airways and put "VFR GPS" in
remarks? What do they want?

In article ,
Roy Smith wrote:

Paul Folbrecht wrote:
I really still wonder about the whole thing and marvel at the fact that
they'll expect me to navigate under IFR with this thing without a
current database (I don't keep the DB current and there's certainly no
reason at all they should expect that I do).

Controllers are not pilots (some are, but it's not a requirement and most
are not), and don't understand the nuances of things like GPS database
currency. Putting "VFR GPS" in the remarks, while having no official legal
significance, says to the controller, "I want to be given direct
clearances". You ask for them, he'll give then to you. Then it's up to
you to decide if you can safely execute them. If you can't, say, "unable",
and he'll come up with a different clearance.

FWIW it has been my understanding that ATC cannot legally assign you
"direct" to some fix you cannot navigate to using the equipment suffix
you've filed with; if you file /U or /A you can't be expected to
navigate directly to a fix not defined by VORs.

Of course it is YOUR responsibility to figure out what you can navigate
to, and to tell ATC you're "unable" if ATC tries to clear you somewhere
that would require use of a GPS; a VFR hand-held GPS is irrelevant as
far as "official" navigation is concerned.

That said, I've also understood that adding "VFR GPS" in the remarks
might encourage ATC to give assign you a HEADING somewhere, maybe with
"direct when able" or something, on the assumption that with the aid of
your VFR GPS you'll be able to head somewhere with surprising accuracy,
which helps everyone.

You could also ask for "Radar vectors" to somewhere, perhaps as in
"request heading 242 degrees, radar vectors FUBAR"; with "VFR GPS" in
the remarks ATC might go along, assuming you'll end up making a nice
beeline for FUBAR. Officially you're on Radar Vectors and ATC retains
responsibility for you; in practice you're no added trouble because you
can head somewhere better than without your "VFR GPS" on board.

That's the reason I've always understood for "VFR GPS ON BOARD" and why
I occasionally specify it filing IFR.

Cheers,
-Patrick.

"Patrick Dirks" wrote in message
news:no-spam-to-pwd-90E9E7.16470019042005@localhost...

FWIW it has been my understanding that ATC cannot legally assign you
"direct" to some fix you cannot navigate to using the equipment suffix
you've filed with; if you file /U or /A you can't be expected to
navigate directly to a fix not defined by VORs.


There is no such restriction.



Of course it is YOUR responsibility to figure out what you can navigate
to, and to tell ATC you're "unable" if ATC tries to clear you somewhere
that would require use of a GPS; a VFR hand-held GPS is irrelevant as
far as "official" navigation is concerned.


For IFR enroute navigation off-airways or beyond normal usable navaid limits
a VFR hand-held GPS is just as relevant as an IFR certified unit.



That said, I've also understood that adding "VFR GPS" in the remarks
might encourage ATC to give assign you a HEADING somewhere, maybe with
"direct when able" or something, on the assumption that with the aid of
your VFR GPS you'll be able to head somewhere with surprising accuracy,
which helps everyone.


You fly a heading with your DG, not your GPS. If you want to proceed direct
somewhere with your handheld GPS then just ask for direct.



You could also ask for "Radar vectors" to somewhere, perhaps as in
"request heading 242 degrees, radar vectors FUBAR"; with "VFR GPS" in
the remarks ATC might go along, assuming you'll end up making a nice
beeline for FUBAR.


Or you could drop all the silliness and just ask for direct FUBAR.



Officially you're on Radar Vectors and ATC retains
responsibility for you; in practice you're no added trouble because you
can head somewhere better than without your "VFR GPS" on board.


ATC is just as responsible for you if you're proceeding direct to FUBAR.



That's the reason I've always understood for "VFR GPS ON BOARD" and why
I occasionally specify it filing IFR.


"VFR GPS ON BOARD" tells ATC you have a VFR GPS on board and nothing else.
Stop playing these silly games. If you want to proceed direct them just
file direct. Doesn't matter if you file /U, /A, /G, or put "VFR GPS" in
remarks.

Steven P. McNicoll wrote:
For IFR enroute navigation off-airways or beyond normal usable navaid limits
a VFR hand-held GPS is just as relevant as an IFR certified unit.

negative.

AIM 1-1-21. Global Positioning System (GPS)
Part e. Section 1. GPS Navigation......Visual Flight Rules (VFR)
and hand-held GPS systems are not authorized for IFR navigation....
during IFR operations they may be considered only an aid to situational
awareness.


You fly a heading with your DG, not your GPS. If you want to proceed direct
somewhere with your handheld GPS then just ask for direct.

and in the case of lost comms, do you just dead reckon? Do you base
your life off of something completely untested? Note, all of this
I assume your talking about flying to a point 300 nm away where
all nav systems (other than IRU's, VOR-DME FMS, etc. that large
aircraft have) do not work at such long distance.


Gerald Sylvester

"G. Sylvester" wrote:
For IFR enroute navigation off-airways or beyond normal usable navaid
limits a VFR hand-held GPS is just as relevant as an IFR certified
unit.

negative.

AIM 1-1-21. ...

You're looking in the wrong book.

"G. Sylvester" wrote in message
m...

negative.

AIM 1-1-21. Global Positioning System (GPS)
Part e. Section 1. GPS Navigation......Visual Flight Rules (VFR)
and hand-held GPS systems are not authorized for IFR navigation....
during IFR operations they may be considered only an aid to situational
awareness.


The AIM is not regulatory and there is no requirement that limits usage to
authorized units.



and in the case of lost comms, do you just dead reckon?


Why would I switch from GPS to dead reckoning if I lost comms?



Do you base your life off of something completely untested?


Are tested units failure-proof?



Note, all of this
I assume your talking about flying to a point 300 nm away where
all nav systems (other than IRU's, VOR-DME FMS, etc. that large
aircraft have) do not work at such long distance.


Where is this place where all nav systems (other than IRU's, VOR-DME FMS,
etc. that large aircraft have) do not work?

"Paul Folbrecht" wrote:
Anyway, on to my question. A couple times now, when I've been
navigating direct, either to a fix or airport identifiable by VORs or
one that isn't (such as an uncontrolled field with no navaid), I've
been asked to "verify direct XXX" when I'm off course by a quite small
amount - no more than 10 degrees.

They may not be asking because they think you're off course, they may
simply want to verify what clearance you're flying. I get this question
almost every time I fly IFR direct from Mobile to Dothan, AL. It's a
short trip, but it uses the airspaces of four TRACONS, so maybe that has
something to do with it. Thanks to the GPS's being coupled to the
autopilot, I'm never off course by more than 100 feet, but I still get
asked.

1) Should I be concerned at all by being asked such a question by ATC?

Nah.

And 2) Just _what_ is the IFR "heading tolerance", anyway?? Meaning,
what sort of heading deviance is large enough that you can be violated
for it?

Well, controllers can only infer your heading from the motion of your
radar target; their displays don't have a heading readout. They aren't
going to react until you've been off heading long enough to look like
you're going somewhere other than expected. You usually won't get
written up for a violation unless you create a hazard, such as a breach
of separation minimums.
--
Dan
C172RG at BFM

On Sat, 16 Apr 2005 04:29:32 GMT, Paul Folbrecht
wrote:

My two-part question is 1) Should I be concerned at all by being asked
such a question by ATC?

Perhaps. It may just be controller confusion (can't remember if you
were cleared direct or not). However, there is a very good chance
your groundtrack is not matching up with 'direct ABC VOR', so the
controller is either prompting you to get back on course or wants to
make sure that you are indeed going to ABC VOR.

Does your GPS have an HSI display? It makes holding the course much
easier.

And 2) Just _what_ is the IFR "heading tolerance", anyway??

I don't think there is one (other than as defined by the PTS during
your IR checkride). The only way a controller knows if you are off
heading is if your ground track changes. Given the sample/update rate
of radar displays, I would think most short term heading deviations go
unnoticed.

***Question for the controllers on the newsgroup: How often does your
radar display update? Every 15 seconds? 30?

Realistically, an occasional heading excursion of 10degrees should not
matter (grabbing a chart), but I do think 25 is excessive (even if
only temporary). If you are in IMC and drifting that far off heading,
you need to work on your scan and control, or limit the activities
that cause the distraction (grabbing maps, lunch, etc).

-Nathan

Oh, I agree entirely. I should have mentioned that was only once, and I
also might have mentioned that we had a total vacuum failure within 5
minutes of that and the DG may already have been spinning down (we were
in VMC with me wearing foggles).

I got quite good at holding heading very accurately during my training.
I just have to learn to not let distractions interfere with that,
even momentarily.

Man, even a single-axis AP would be nice!

Realistically, an occasional heading excursion of 10degrees should not
matter (grabbing a chart), but I do think 25 is excessive (even if
only temporary). If you are in IMC and drifting that far off heading,
you need to work on your scan and control, or limit the activities
that cause the distraction (grabbing maps, lunch, etc).

-Nathan