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#51
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Tauno Voipio wrote:
Steven P. McNicoll wrote: "Bob Moore" wrote in message . 122... Well Steven, why don't you just come right out and tell them about the Middle Marker? Because they're disappearing. There should be a co-located (and associated) DME if there are no markers, and in can be used instead of the markers. In the USA, the MM used to be a required part of the ILS system. Now, nothing is required to replace the MM (not even DME), so most have been removed. John |
#52
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JPH wrote:
Tauno Voipio wrote: Steven P. McNicoll wrote: "Bob Moore" wrote in message . 122... Well Steven, why don't you just come right out and tell them about the Middle Marker? Because they're disappearing. There should be a co-located (and associated) DME if there are no markers, and in can be used instead of the markers. In the USA, the MM used to be a required part of the ILS system. Now, nothing is required to replace the MM (not even DME), so most have been removed. It's a weird interpretation of the ICAO rules, but that would not be the first time FAA does not respect the internationally accepted rules. I'll check from the relevant ICAO docs as soon as I get to the office. AFAIK, there should be at least either operative outer and middle marker or a co-located DME. The markers are positioned so that outer marker is roughly at the crossing of the intermediate approach altitude and glideslope (the point where glide starts) and middle marker at the crossing of glideslope and MDA. -- Tauno Voipio tauno voipio (at) iki fi |
#53
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Steven P. McNicoll wrote:
Hilton wrote: I'm a CFI-I. I find that rather hard to believe. Steven, I really enjoy reading your posts. I think you bring a lot of knowledge to these NGs. It's a real pity that you have to resort to insults to try make a point. [zap] Let's assume that the GS fails at 2700' (MSL), the DH is at 357' (MSL), a 3 degree glideslope, an 'ILS' airspeed of 100 knots, a climb airspeed of 80 knots. For simplicity, let's assume no wind conditions. Simple. I'm 2300' above DH when the GS fails (I'm rounding off to the nearest hundred), 2300 divided by 300 is 8 miles (Inside the FAF and still 8 miles from the MAP? Where is this approach?) Try ACV ILS 32 - it starts you at 5200 - I made it easy for you. 8 miles at 80 knots will take 6 minutes. Now let's use the actual numbers to see how accurate that is. 2700' less 357' is 2343' above DH, 2343' at 318' per mile makes it 7.4 miles from the MAP, 7.4 miles at 80 knots takes 5.6 minutes. In your no wind condition I'd have overshot the MAP by 3600', I'm probably over the runway. OK, so you suggest teaching IFR pilots that *while they are doing important stuff* that I mentioned before (power, gear, cowl flaps etc), they have to do this math in their heads: (2700-357) / 300 * 60 / 80 = 6 minutes. And getting back to my original comment, no, I don't think that every IFR pilot is able to make these calculations correct 100% of the time - hence the comment about luck. I certainly wouldn't guarantee myself that I could get these calculations correct 100% of the time during the 'missed' high-workload portion of the flight. I know and understand my limitations (there Steven, huge opportunity for another snide remark ), and I'm willing to do anything that will reduce my workload and that of my students in IMC during a high-risk part of the flight. Hilton |
#54
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Tauno Voipio wrote:
There should be a co-located (and associated) DME if there are no markers, and in can be used instead of the markers. In the USA, the MM used to be a required part of the ILS system. Now, nothing is required to replace the MM (not even DME), so most have been removed. It's a weird interpretation of the ICAO rules, but that would not be the first time FAA does not respect the internationally accepted rules. I'll check from the relevant ICAO docs as soon as I get to the office. AFAIK, there should be at least either operative outer and middle marker or a co-located DME. The markers are positioned so that outer marker is roughly at the crossing of the intermediate approach altitude and glideslope (the point where glide starts) and middle marker at the crossing of glideslope and MDA. When DME is used as a substitute for the Outer Marker (OM) in the USA, it doesn't even have to be co-located. As long as the DME source is within 6 degrees of the final course, it can be used as a replacement for the OM (Even more if the FAA provides a waiver). For the military, they only require that the DME be within 23 degrees of the final course. Many airports use VORTACs or VOR/DME facilities to provide the DME for an ILS localizer FAF. The FAA's policy is that if DME is available, it will be used to provide a localizer FAF at the same point as the glideslope intercept point (called a PFAF), and the OM or LOM will no longer be used if the DME is available (most do not allow a common PFAF, because they are not perfectly placed at the point where an even 100' altitude increment and the glideslope are overhead. In other words, the glideslope altitude at the OM might be 2367, but the PFAF will be placed at either the 2400 or 2300 point, and DME will be used instead of the OM. The downside is that there are a lot more approaches getting the title "ILS or LOC/DME" instead of "ILS or LOC" because of this, requiring DME in order to fly the localizer procedure. The FAA policy is if the DME is out of service, the ILS (precision) can still be flown, because the glideslope intercept defines where the final approach begins, and DH defines where missed approach begins. This is part of the reason for this current discussion; many procedures have no way of marking the LOC missed approach point in the USA other than the time-distance table, because no MM or DME is available. John |
#55
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On Sun, 11 Sep 2005 20:38:20 GMT, Tauno Voipio
wrote: AFAIK, there should be at least either operative outer and middle marker or a co-located DME. The markers are positioned so that outer marker is roughly at the crossing of the intermediate approach altitude and glideslope (the point where glide starts) and middle marker at the crossing of glideslope and MDA. Even if there is, I thought that we are talking about the case where you don't have a MM, the GPS is broken, you aren't carrying DME (since US regs allow GPS substitution for DME, with a few exceptions) and you just lost your glideslope somewhere on the approach, and how you could then identify the MAP. |
#56
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"Tauno Voipio" wrote in message ... It's a weird interpretation of the ICAO rules, but that would not be the first time FAA does not respect the internationally accepted rules. Just like many other nations. |
#57
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"Peter Clark" wrote in message ... Even if there is, I thought that we are talking about the case where you don't have a MM, the GPS is broken, you aren't carrying DME (since US regs allow GPS substitution for DME, with a few exceptions) and you just lost your glideslope somewhere on the approach, and how you could then identify the MAP. Me too. |
#58
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On Sun, 11 Sep 2005 20:50:46 -0400, Peter Clark
wrote: On Sun, 11 Sep 2005 20:38:20 GMT, Tauno Voipio wrote: AFAIK, there should be at least either operative outer and middle marker or a co-located DME. The markers are positioned so that outer marker is roughly at the crossing of the intermediate approach altitude and glideslope (the point where glide starts) and middle marker at the crossing of glideslope and MDA. Even if there is, I thought that we are talking about the case where you don't have a MM, the GPS is broken, you aren't carrying DME (since US regs allow GPS substitution for DME, with a few exceptions) and you just lost your glideslope somewhere on the approach, and how you could then identify the MAP. In the examples you gave at BED, there would be no need to ID the MAP prior to executing the missed approach. For those where it is necessary, other methods have been mentioned in this thread. Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA) |
#59
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Hilton wrote:
Firstly, please note that after the word "butt", I had "(it may be less dramatic when surrounded by flatter terrain)." So, we're assuming mountainous terrain or other nearby obstacles. When would you start flying the missed? How would you start flying the missed? Are you guaranteed to be flying the missed approach as published? You start climbing when the G/S fails. That is flying the missed even though you have not reached the MAP (DA point with ILS) If the missed approach track is straight ahead you are home free. If the missed approach is a track reversal back to the LOM or a VOR behind you, you are also home free because all the airspace is protected from the P-FAF to the DA point (plus 1.5 miles after that) on the turn side. If the turn is less than a 180 (or thereabouts) then the simple math Stephen suggests will get you well within protected missed approach airspace. And, who knows, you might be at a location where ATC can help you with radar. ;-) This is the 21st Century, so anybody who doesn't have GPS to preempt these types of "1950s" problems probably needs to find another, safer hobby. ;-) |
#60
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"Hilton" wrote in message ink.net... Steven, I really enjoy reading your posts. I think you bring a lot of knowledge to these NGs. It's a real pity that you have to resort to insults to try make a point. I don't resort to insults, I use facts and logic to make my points. I truly do find it hard to believe that someone with your knowledge of ILS could be a CFI-I. Try ACV ILS 32 - it starts you at 5200 - I made it easy for you. That's very interesting. Let me make sure I understand your position. You're saying that if the GS fails when I'm in IMC at 2700 MSL on the ACV ILS RWY 32 approach I'm screwed and only luck will save my butt if I haven't started the timer. Is that correct? Do you really teach your students to begin timing an ILS at the precision approach FAF? Most pilots start the clock at the nonprecision approach FAF, that's the one used in the timing table. But at 2700 MSL on the glideslope the nonprecision approach FAF, ACATA, is still three miles ahead. I don't have to do any arithmetic at all to determine my distance from the MAP, I can just start the clock when I reach ACATA. But I don't even have to do that, I can identify the MAP with DME or ADF or marker beacon. By the way, DH on that approach is 418 MSL, not 357. OK, so you suggest teaching IFR pilots that *while they are doing important stuff* that I mentioned before (power, gear, cowl flaps etc), they have to do this math in their heads: (2700-357) / 300 * 60 / 80 = 6 minutes. You still don't get it. This isn't an argument about timing vs. not-timing an ILS. You claimed you're screwed if you don't time an ILS and the GS fails, we're just trying to show you that that's not the case. Do you now understand why your position was incorrect? And getting back to my original comment, no, I don't think that every IFR pilot is able to make these calculations correct 100% of the time - hence the comment about luck. I certainly wouldn't guarantee myself that I could get these calculations correct 100% of the time during the 'missed' high-workload portion of the flight. I know and understand my limitations (there Steven, huge opportunity for another snide remark ), and I'm willing to do anything that will reduce my workload and that of my students in IMC during a high-risk part of the flight. But you think any IFR pilot can determine the distance from the MAP to the precision approach FAF and correctly compute the time required to cover it 00% of the time. Apparently arithmetic is only a problem when it's used to prove you wrong. |
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