Can GPS be *too* accurate? Do I need some XTE??

Bill Denton ) wrote:

You might want to rethink your reply

Easy there, Bill. There is no need for that.

A pilot in clouds or other IMC cannot provide separation to any traffic he
cannot see.

I am discussing IFR/VFR separation, not IFR/IFR separation. Hopefully,
no VFR aircraft will be in IMC, but that point is irrelevant since most
times ATC does not know if it is IMC or VMC; they only have blips on
their screen.

Consider this: It is quite possible that a) a VFR aircraft is climbing
or descending through an IFR aircraft's cruise altitude, or b) an IFR
cruise altitude is below 3,000 AGL, which means that a VFR aircraft
could be at any altitude 3,000 feet AGL or below s/he desires, including
that IFR aircraft's altitude.

Will ATC provide traffic callouts and or vectors around VFR traffic in
either scenario above? Most likely. Are US controllers required to?
Outside of class B airspace, the answer is no.

--
Peter

I had a minute so I looked this up; you misread the AIM.

4-4-10. IFR SEPARATION STANDARDS

b. Separation will be provided (by ATC - my note) between all aircraft
operating on IFR flight plans except during that part of the flight (outside
of Class B airspace or a TRSA) being conducted on a VFR-on-top/VFR
conditions clearance. Under these conditions, ATC may issue traffic
advisories, but it is the sole responsibility of the pilot to be vigilant so
as to see and avoid other aircraft.

To paraphrase and clarify: If you are "outside of Class B airspace or a
TRSA" and flying on a "VFR-on-top/VFR conditions clearance", "ATC may issue
traffic advisories, but it is the sole responsibility of the pilot to be
vigilant so as to see and avoid other aircraft". Otherwise, "Separation will
be provided (by ATC - my note) between all aircraft operating on IFR flight
plans".




"Peter R." wrote in message
...
Bill Denton ) wrote:

And I don't know if this is a trick question, but if you are at 6000 (no
+500) wouldn't you be on an IFR flight plan, talking to ATC, and
receiving
traffic advisories?

In the US and outside of class B airspace, it is the pilot, not ATC, who
is ultimately responsible for IFR/VFR traffic separation. A VFR traffic
advisory to an IFR aircraft is a courtesy offered by ATC; it is not a
guarantee.

--
Peter

"Icebound" wrote in message ...
In the "good old" VOR days, it must have been pretty difficult to fly down
the centerline of an airway (or of any direct track).

So an eastbound VFR/IFR aircraft descending from 7500/7000 to his
destination, was more than likely to avoid traffic... on the reciprocal
track passing him by at 6500 or 6000... by some significant horizontal
error-distance, even if they didn't see each other (big sky theory :-) ).

GPS horizontal accuracy with WAAS is already in the order of magnitude of a
Cessna's wingspan, and some are talking about getting it down to mere
inches.

So the question is: If my Westbound Cessna at 6000 feet (with the autopilot
keeping it happily on the GPS-track centerline) meets the descending Bonanza
on the reciprocal track between the same two airports (using a similar
GPS/a-p combo), there is a distinct possibility that the horizontal
clearance may be zero...

...so is there anything in the current crop of GPS and/or Autopilot systems
that allow me to maintain a small cross-track error of my choosing, without
actually entering off-navaid-off-airport waypoints? ...or do we care; am I
overly concerned???

********************************************
Way overly concerned. I've been flying nearly 50 years, logged over
21,700 hours in general aviation, done a lot of IFR, without a lot of
GPS. I've not had any problems. As for the offset idea, what is to
prevent the other pilot from doing an offset that puts them directly
in your path? Whatever happened to eyeballs and watching out for
traffic?
As for being difficult to fly the VOR, it was/is no more difficult
than flying a compass heading and holding it.....which many pilots
seem unable to do anymore. They would prefer that electronic gadgets
do their flying for them and no thoughts as to what happens when the
electrodes take a vacation.
Ol Shy & Bashful - and unrepentant demanding grumpy old CFII

Bill Denton ) wrote:

I had a minute so I looked this up; you misread the AIM.

You and I have been through this before. The AIM is not regulatory and
perhaps you might want to re-read that passage. It appears to me that
you have misinterpreted it.

Let's break this down:

b. Separation will be provided (by ATC - my note) between all aircraft
operating on IFR flight plans except during that part of the flight (outside
of Class B airspace or a TRSA) being conducted on a VFR-on-top/VFR
conditions clearance.

Please show me where in that passage above does it say anything about
IFR aircraft being separated from VFR aircraft. Note the operative
word "between" being used there. I interpret the passage to be
discussing IFR aircraft being separated from IFR aircraft.

To paraphrase and clarify: If you are "outside of Class B airspace or a
TRSA" and flying on a "VFR-on-top/VFR conditions clearance", "ATC may issue
traffic advisories, but it is the sole responsibility of the pilot to be
vigilant so as to see and avoid other aircraft". Otherwise, "Separation will
be provided (by ATC - my note) between all aircraft operating on IFR flight
plans".

There, you stated it, too. "BETWEEN all aircraft operating on IFR
flight plans." Where does it say anything about ATC's responsibility
about separation between those aircraft on IFR flight plans and those on
VFR flight plans? Not in that passage it doesn't.



--
Peter

My comments in text:



"Peter R." wrote in message
...
Bill Denton ) wrote:

I had a minute so I looked this up; you misread the AIM.

You and I have been through this before. The AIM is not regulatory and
perhaps you might want to re-read that passage. It appears to me that
you have misinterpreted it.

Regulatory/no-regulatory is immaterial. This portion of the AIM simply
states what services will be offered to pilots by ATC.




Let's break this down:

b. Separation will be provided (by ATC - my note) between all aircraft
operating on IFR flight plans except during that part of the flight
(outside
of Class B airspace or a TRSA) being conducted on a VFR-on-top/VFR
conditions clearance.

Please show me where in that passage above does it say anything about
IFR aircraft being separated from VFR aircraft. Note the operative
word "between" being used there. I interpret the passage to be
discussing IFR aircraft being separated from IFR aircraft.

The separation of VFR/IFR aircraft is not covered in this section; the
separation of ALL aircraft is discussed in the previous section.

The purpose of this section is to remind VFR-on-top-pilots that while they
are on an IFR flight plan, ATC has allowed them to deviate and fly under VFR
rules (including see and avoid) and that ATC is not obligated to provide
traffic guidance.



To paraphrase and clarify: If you are "outside of Class B airspace or a
TRSA" and flying on a "VFR-on-top/VFR conditions clearance", "ATC may
issue
traffic advisories, but it is the sole responsibility of the pilot to be
vigilant so as to see and avoid other aircraft". Otherwise, "Separation
will
be provided (by ATC - my note) between all aircraft operating on IFR
flight
plans".

There, you stated it, too. "BETWEEN all aircraft operating on IFR
flight plans." Where does it say anything about ATC's responsibility
about separation between those aircraft on IFR flight plans and those on
VFR flight plans? Not in that passage it doesn't.

As I stated above, VFR-on-top operations are conducted on IFR flight plans
and the purpose of this section is to explain the services to be provided or
not provided by ATC to VFR-on-top pilots.






--
Peter

Bill Denton ) wrote:

The separation of VFR/IFR aircraft is not covered in this section; the
separation of ALL aircraft is discussed in the previous section.

Then why are you and I having this disagreement?

You asked about separation of an aircraft flying at 6,000 feet,
presumably on an IFR flight plan, I maintained all along about the fact
that IFR flights are not separated from VFR flights and presented two
scenarios where an IFR aircraft at 6,000 feet might encounter a VFR
aircraft, yet you quote a passage that admittedly has nothing to do with
my posts.


The purpose of this section is to remind VFR-on-top-pilots that while they
are on an IFR flight plan, ATC has allowed them to deviate and fly under VFR
rules (including see and avoid) and that ATC is not obligated to provide
traffic guidance.

I am not sure what your point about VFR-on-top is, but as a reminder to
you, in the US VFR-on-TOP is a specific IFR clearance that must be
requested.

Simply being on an IFR flight plan in visual conditions is not the same
as VFR-on-top. In the case of the IFR flight in VMC, the pilot is still
guaranteed ATC separation between other IFR aircraft, but not VFR
aircraft (excluding class B).

Thus, to your question in your first post, an IFR aircraft at 6,000 feet
is still at risk of a mid-air collision.

--
Peter

"Bill Denton" wrote in message
...
[...]
As I stated above, VFR-on-top operations are conducted on IFR flight plans
and the purpose of this section is to explain the services to be provided
or
not provided by ATC to VFR-on-top pilots.

"VFR-on-top" is still an IFR operation. That's not what Peter is talking
about.

Basically, your belief that a pilot flying on an instrument flight plan is
immune from the scenario posted in the original message is simply wrong.
All it takes is a pilot on an instrument flight plan (satisfying the 6000'
cruise altitude), and another pilot flying VFR (not "VFR-on-top"...just
plain old VFR) climbing on the airway as described by the original poster.

Pete

VFR-on-top:

1. Is requested by pilot flying on an IFR flight plan.

2. Is flown under Visual Flight Rules.

3. May or may not be flown following the IFR flightplan's route.

4. Ends when the pilot cancels IFR or returns to the original flight plan at
a waypoint on that plan.

Very simple; it's in the book.

-----------------------------------------------------

A pilot flying VFR is required to observe "see and avoid". One pilot
observing "see and avoid" and taking appropriate evasive action can avoid a
collision.

If a VFR pilot is climbing/descending, it is his responsibility to avoid
pilots above him or below him.

A pilot flying IFR under VMC who is not observing "see and avoid" is not a
very smart pilot.


"Peter Duniho" wrote in message
...
"Bill Denton" wrote in message
...
[...]
As I stated above, VFR-on-top operations are conducted on IFR flight
plans
and the purpose of this section is to explain the services to be
provided
or
not provided by ATC to VFR-on-top pilots.

"VFR-on-top" is still an IFR operation. That's not what Peter is talking
about.

Basically, your belief that a pilot flying on an instrument flight plan is
immune from the scenario posted in the original message is simply wrong.
All it takes is a pilot on an instrument flight plan (satisfying the 6000'
cruise altitude), and another pilot flying VFR (not "VFR-on-top"...just
plain old VFR) climbing on the airway as described by the original poster.

Pete

"Peter R." wrote in message
...
Bill Denton ) wrote:

The separation of VFR/IFR aircraft is not covered in this section; the
separation of ALL aircraft is discussed in the previous section.

Then why are you and I having this disagreement?

You asked about separation of an aircraft flying at 6,000 feet,
presumably on an IFR flight plan, I maintained all along about the fact
that IFR flights are not separated from VFR flights and presented two
scenarios where an IFR aircraft at 6,000 feet might encounter a VFR
aircraft, yet you quote a passage that admittedly has nothing to do with
my posts.

No, the orignal poster presented the scenario. I simply pointed out that a
6000 feet he would be on an IFR flight plan, talking to ATC, and receiving
traffic from ATC.

You introduced the passage and misinterpreted it. I provided a correct
interpretation.


The purpose of this section is to remind VFR-on-top-pilots that while
they
are on an IFR flight plan, ATC has allowed them to deviate and fly under
VFR
rules (including see and avoid) and that ATC is not obligated to provide
traffic guidance.

I am not sure what your point about VFR-on-top is, but as a reminder to
you, in the US VFR-on-TOP is a specific IFR clearance that must be
requested.

And if you are granted that clearance, you will be flying under what are
essentially Visual Flight Rules, you will be allowed to deviate from your
as-filed flight plan, and ATC is not obligated to provide traffic guidance
outside of Class B's and TRSA's.They still have an open IFR flight plan;
they must either cancel IFR, or they must rejoin that flight plan at a
waypoint on the plan and continue fllying that flight plan.



Simply being on an IFR flight plan in visual conditions is not the same
as VFR-on-top. In the case of the IFR flight in VMC, the pilot is still
guaranteed ATC separation between other IFR aircraft, but not VFR
aircraft (excluding class B).

Thus, to your question in your first post, an IFR aircraft at 6,000 feet
is still at risk of a mid-air collision.

But a pilot flying on a VFR flight plan is required to observe "see and
avoid", and if he is observing it and taking appropriate evasive action, a
collision cannot occur.

Keep in mind that separation is not provided only by ATC traffic guidance
and "see and avoid", it's also provided by "east is odd, west is even, VFR
+500" altitudes and other things.



--
Peter

== Peter R writes:

Bill Denton ) wrote:
And I don't know if this is a trick question, but if you are at 6000 (no
+500) wouldn't you be on an IFR flight plan, talking to ATC, and receiving
traffic advisories?

In the US and outside of class B airspace, it is the pilot, not ATC, who
is ultimately responsible for IFR/VFR traffic separation. A VFR traffic
advisory to an IFR aircraft is a courtesy offered by ATC; it is not a
guarantee.

I thought Class C services included IFR/VFR separation. Is that old/wrong
information?

dan.

--
PGP key at http://www.longhands.org/drg-pgp.txt Key Id:0x507D93DF