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)