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#21
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On Sat, 21 Feb 2004 22:40:09 GMT, "Bob Gardner" wrote:
MSA is not an operational altitude...it is for emergency use only. Read 5-4-5 AIM. Agreed. However, the context of this discussion seems to be pilot-nav random routing and the reason for a procedure turn at this particular approach. It is not a vectors-to-final routing where ATC may assign an altitude. 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. Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA) |
#22
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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? 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 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. Michael |
#23
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#24
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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 |
#25
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"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 |
#26
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#27
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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 |
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