Reasoning behind course reversal

On 25 Feb 2004 07:40:02 -0800, (Michael) wrote:

Ron Rosenfeld wrote
Are you of the opinion that the IFR charts suggest that when on a random
route and NE of ALIKE (but south of the BJC 090 radial) that 7300 is a
perfectly OK altitude to use?

My teaching has been that when not on a "solid black line" or receiving
radar vectors from ATC, to not go below the MSA, OROCA, etc., for that
area.

The relevant regulation is 91.177 - other than when on approach, 1000
ft above any obstacles within 4 nm of course, or 2000 in designated
mountainous areas. If you meet that, you're complying with 91.177.
The question is how to best comply with this?

On a solid black line, the altitude is published. On vectors, it's
ATC's responsibility. On a random route, it's your responsibility -
sort of. It is relatively common (at least in my neck of the woods)
to have approaches where the FAC is not depicted on the controller's
scope. In this situation, RADAR services are available, but vectors
to final are not. It's fairly common (in my experience) to get a
clearance direct to the IAF (NOT a vector) at an altitude lower than
anything published - OROCA, MSA, or even the published minimum
altitude for crossing the FAF. Clearly the controller is using his
MVA for this. Are you suggesting that accepting such a clearance is
improper?

No, and I thought I was clear about that. If the controller is providing
vectors, they are responsible for ensuring you are at an acceptable
altitude. The procedure is (should be) to instruct you to maintain an
altitude that will ensure obstacle clearance until you are established on a
segment of a published route or instrument approach.

As a matter of fact, radar is not even necessary to receive that sort of
service. I will usually be cleared for approach to my local airport, with
a restriction to maintain a specific altitude until crossing the IAF. And
radar services are terminated well before my arrival (usually about 25+
miles out). AAMOF, we don't even have radio services below about 4000 ft.


Even without RADAR services, it's not all that clearcut. Certainly if
you maintain OROCA or MSA, you're complying, and in many cases this is
the way to go. However, this is often not practical. For example, in
my next of the woods there are tethered balloons going to 15000 ft,
and that makes OROCA just over 16000 for the sector. This would make
direct routings impossible for anyone without turbos. In reality, the
minimum altitudes for direct routings in most of that sector are in
the 2000-4000 range.

I've seen a similar situation apply to the MSA, where an entire sector
had an MSA about 1500 ft higher than it would have been had it not
been for ONE tower, about 23 nm away from the fix. I have to believe
that in mountainous terrain, this is even more common, since airports
tend to be in valleys.

Under Part 91, there is really no defined requirement for where the
data you use to comply with 91.177 should come from. However, I have
to believe that any FAA-recognized chart is fair game.

I agree with what you have said. However, the 91.177 1000/2000/4 altitudes
apply only if there is no applicable minimum altitude prescribed in Part 95
or 97. It is not clear to me whether the MSA, even though it is prescribed
in Part 97, is an "applicable minimum altitude". If so, it may be even
lower than the 91.177 minimums as it only provides 1000' of clearance.

However, given that the area is controlled airspace, the likelihood is that
an a/c arriving from the NE segment will be cleared for the approach by
ATC. I'm not familiar with exactly what goes on in the BJC area, but I'd
guess that the pilot will either receive vector to final, in which case the
issue of course reversal is moot; or he will receive an altitude to
maintain until crossing ALIKE and will be obliged to execute the course
reversal procedure. Looking at some of the airways in the vicinity, it
seems the MEA/MOCA is higher than 7200'. And one would have to be down to
7200 outside of ALIKE in order to intercept the Glide Slope from below.


I have no idea
if 7300 is OK in the area you describe, because I have not seen the
relevant VFR chart. It might be. If the obstructions that make the
MSA in the sector 10,500 are 20 miles away, and the local terrain is
much lower, then maybe it is. However, with only the infomation on
the approach plate, I sure wouldn't try it.

My point, exactly.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Ron Rosenfeld wrote
The procedure is (should be) to instruct you to maintain an
altitude that will ensure obstacle clearance until you are established on a
segment of a published route or instrument approach.

Right. My point is that you're not on vectors, you're not on a solid
black line, you're below OROCA/MSA, and you're still OK.

I agree with what you have said. However, the 91.177 1000/2000/4 altitudes
apply only if there is no applicable minimum altitude prescribed in Part 95
or 97. It is not clear to me whether the MSA, even though it is prescribed
in Part 97, is an "applicable minimum altitude".

Well, I think that was the point - it's an emergency altitude only,
and thus not an applicable minimum altitude. Ref 97.3(l) MSA means
minimum safe altitude, an emergency altitude expressed in feet above
mean sea level, which provides 1,000 feet clearance over all
obstructions in that sector within 25 miles of the facility on which
the procedure is based (LOM in ILS procedures).

However, given that the area is controlled airspace, the likelihood is that
an a/c arriving from the NE segment will be cleared for the approach by
ATC. I'm not familiar with exactly what goes on in the BJC area, but I'd
guess that the pilot will either receive vector to final, in which case the
issue of course reversal is moot; or he will receive an altitude to
maintain until crossing ALIKE and will be obliged to execute the course
reversal procedure. Looking at some of the airways in the vicinity, it
seems the MEA/MOCA is higher than 7200'. And one would have to be down to
7200 outside of ALIKE in order to intercept the Glide Slope from below.

The point is that without access to the MVA charts, we don't know what
altitude he will be cleared to. And the whole point of the thread is
that if he is cleared to 7200 or less and approaches ALIKE from a
reasonable direction, the procedure turn is basically a waste of time
but legally he is still required to execute it.

Given that on RADAR vectors we are routinely set up for a 30 degree
intercept right at the FAF, I would think that it's reasonable to have
aircraft approaching at the correct altitude and within 30 degrees of
the FAC skip the procedure turn as a general rule. I have actually
seen approaches which exempt a certain arc from PT requirements - HUM
VOR RWY 12 is one example I've actually
shot.(http://www.myairplane.com/databases/...l/HUM_vr12.pdf)
In my opinion, something like this ought to be a general rule, rather
than a specific. Those who do not feel like they can get established
can always request the course reversal.

Michael

"Michael" wrote in message
om...
Given that on RADAR vectors we are routinely set up for a 30 degree
intercept right at the FAF, I would think that it's reasonable to have
aircraft approaching at the correct altitude and within 30 degrees of
the FAC skip the procedure turn as a general rule. I have actually
seen approaches which exempt a certain arc from PT requirements - HUM
VOR RWY 12 is one example I've actually

shot.(http://www.myairplane.com/databases/...l/HUM_vr12.pdf
)
In my opinion, something like this ought to be a general rule, rather
than a specific. Those who do not feel like they can get established
can always request the course reversal.

Michael

Thanks for the approach reference. This is exactly what I was talking about
when I started the thread.

Michael

On 26 Feb 2004 06:59:12 -0800, (Michael) wrote:

Given that on RADAR vectors we are routinely set up for a 30 degree
intercept right at the FAF, I would think that it's reasonable to have
aircraft approaching at the correct altitude and within 30 degrees of
the FAC skip the procedure turn as a general rule.

I would disagree with you that that should be a general rule.

There is a very specific rule that says if you are getting vectors to
final, than you don't do a course reversal (without notifying ATC). In
order for ATC to safely give you VTF, certain requirements must be met at
their end.

And you should NOT be getting a turn on AT the FAF unless you have
specifically requested it. Furthermore, (and one of the controller's may
correct me here), the interception angle should not be more than 20° unless
you are a few miles (?2?) outside of the approach gate, which itself will
be outside of the FAF.

If ATC is giving you a 30° intercept at the FAF without you requesting it,
I believe they are acting contrary to their manual, and engaging in a
potentially dangerous practice.


I have actually
seen approaches which exempt a certain arc from PT requirements

The one you cite is a LOT different from the circumstance we are
discussing. The approach you cite is NoPT for arrivals at the IAF if you
are ON AIRWAYS (V198 or V552) leading to an IAF (TBD VORTAC) which is
separated from the FAF by a five mile intermediate segment.

The procedure you are proposing at BJC has you arriving at ALIKE (which is
a collocated IAF/FAF) and essentially using it as an FAF. Skipping the PT
in that circumstance is not something I feel is safe "as a general rule".


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Ron Rosenfeld wrote
If ATC is giving you a 30° intercept at the FAF without you requesting it,
I believe they are acting contrary to their manual

This may well be, but I find it's more the norm than the exception.

and engaging in a potentially dangerous practice.

Maybe I'm just used to it, but it really doesn't seem to be. Now when
they give me a 60 degree intercept inside the FAF...

Michael