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#11
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OK, then why have the requirements that prohibit GPS substitution when
picking an alternate for filing? When you ask why, you are making the assumption that the FAA makes rules for valid and comprehensible reasons. That's not an assumption that is supported by the facts Seriously, the logic, if you can call it that, is that GPS is an unproven technology, and thus one should have a backup plan that does not rely on it. The FAA would rather you rely on a 30-year-old ADF receiver pointing at a WWII-era NDB transmitter. Getting out of the alternate rathole, any thoughts about the general rules of GPS substitution, specifically applying them to the questions I had on the Minuteman approach? The rules are clear enough - any approved GPS may be substituted for DME or ADF on any approach except that you may not use a GPS to fly an NDB approach unless it is an approach-certified GPS being used to fly a published overlay. Now those are rules. Your question regards procedures. As a Part-91 operator, you can pretty much use whatever procedures make sense to you - if it's not prohibited, it's allowed. In your particular case, the DME is used in conjunction with the VOR to identify the IAF/FAF (EGORE, 210 rad 20.0 DME MHT) and the MAP (210 rad 25.1 DME MHT). If you like, you can configure the GPS to point to the MHT VOR and read distance just as you would off the DME. That would be fine. Or you can configure it to point to EGORE, and call the MAP at 5.1 from there. That would be fine. Or you can configure it to point to the MAP, and call 5.1 from that the IAF/FAF. That would be fine. Or you could write yourself a flight plan that would take you to the IAF and then the MAP, so you could get a readout of distance counting down to the IAF/FAF, and then the MAP. That would be fine. And if someone has already done that for you (in this case the manufacturer who provided the software for approach monitoring) and you're comfortable that he did the job properly, that's fine too. Use whatever procedure works for you. The question become more interesting when GPS is substituted for ADF, especially when the NDB is the missed approach holding point. One option (if available) is to use the missed approach sequencing provided by the GPS for the approach monitoring function (some will even depict the hold and tell you which entry to use) but anything you care to do, up to and including setting up the display to read out the bearng and distance to the NDB and flying the hold off the numbers is acceptable. If you would tell us more about what kind of equipment you have in the cockpit, we might be able to make more intelligent suggestions about what procedures would be optimal. Michael |
#12
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On 11 Feb 2005 11:49:43 -0800, "Michael"
wrote: In your particular case, the DME is used in conjunction with the VOR to identify the IAF/FAF (EGORE, 210 rad 20.0 DME MHT) and the MAP (210 rad 25.1 DME MHT). If you like, you can configure the GPS to point to the MHT VOR and read distance just as you would off the DME. That would be fine. Or you can configure it to point to EGORE, and call the MAP at 5.1 from there. That would be fine. Or you can configure it to point to the MAP, and call 5.1 from that the IAF/FAF. That would be fine. Or you could write yourself a flight plan that would take you to the IAF and then the MAP, so you could get a readout of distance counting down to the IAF/FAF, and then the MAP. That would be fine. And if someone has already done that for you (in this case the manufacturer who provided the software for approach monitoring) and you're comfortable that he did the job properly, that's fine too. Use whatever procedure works for you. Using the GPS to point at MHT and read DME like that I can understand. The rest seems awfully like a GPS overlay to the VOR approach, but this isn't a "VOR or GPS", it's a VOR/DME. Using named waypoints (and then using the GPS to locate them) makes sense too, but in this case the MAP isn't a named fix, it's a radial/DME. I guess I'm just making this more complicated than it needs to be..... The question become more interesting when GPS is substituted for ADF, especially when the NDB is the missed approach holding point. One option (if available) is to use the missed approach sequencing provided by the GPS for the approach monitoring function (some will even depict the hold and tell you which entry to use) but anything you care to do, up to and including setting up the display to read out the bearng and distance to the NDB and flying the hold off the numbers is acceptable. If you would tell us more about what kind of equipment you have in the cockpit, we might be able to make more intelligent suggestions about what procedures would be optimal. it's a pretty vanilla stack with an HSI, KLN94, MFD, and dual VOR. |
#13
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Using the GPS to point at MHT and read DME like that I can
understand. If that's what it takes to make you feel comfortable, then go with it. The rest seems awfully like a GPS overlay to the VOR approach Except it's not. You still have the VOR, not the GPS, driving your HSI needle, right? That makes it a VOR (or, in this case, VOR/DME) approach. Using named waypoints (and then using the GPS to locate them) makes sense too, but in this case the MAP isn't a named fix, it's a radial/DME. So? You could, if you wished, enter it into the GPS and use it. Once you accept that, is it really a stretch to say that you could also have someone else enter it? I guess I'm just making this more complicated than it needs to be..... Well, what's happening is that you are confusing the sensor and the presentation. There is no difference whatsoever in having the GPS give a distance to MHT vs EGORE vs the MAP of the approach. All of those waypoints were entered into the database by the manufacturer. You have no compelling reason to trust one more than another, and the position is calculated the same way always. It's just a question of how you want the presentation done, and that's up to you. Since the KLN94 provides sequencing for approach monitoring, there's precious little reason not to use it - it gives you a line to follow on the MFD and a convenient countdown to the next fix. I don't know if putting the unit in OBS mode will draw a line corresponding to the selected course on your map - if it will, there is little difference. If not, that's a compelling reason to use the approach sequencing instead. Michael |
#14
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wrote in message ... On 11 Feb 2005 11:23:14 -0800, "Michael" wrote: I think I'd interpret "as appropriate" as meaning that the GPS essentially meets the definition of "DME or ADF avionics", since the rules say it can be substituted for such, I do not concur, and believe such an interpretation is contrary to the intent if the statement. (8) For TSO-C129/129A users, any required alternate airport must still have an approved instrument approach procedure other than GPS that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly. If the non-GPS approaches on which the pilot must rely require DME or ADF, the aircraft must be equipped with DME or ADF avionics as appropriate. I believe the last statement means what it says - that for purposes of selecting a valid alternate, one must select an approach that can be completed without reliance on GPS. Michael "What it says" depends on how one interprets "as appropriate". (a) Since it is "appropriate" to substitute GPS for DME and ADF on non-GPS approaches, then it's acceptable as far as I am concerned. Furthermore, (b) The aircraft is "equipped to fly" the non-GPS approach.and (c) they'll never catch me anyway even if I'm wrong. Well, my 2 cents says that "as appropriate" specifically applies to the phrase "DME or ADF", meaning the equivalent to the following rewrite: "If the non-GPS approaches on which the pilot must rely require DME, the aircraft must be equipped with DME; if the non-GPS approaches on which the pilot must rely require ADF , the aircraft must be equipped with ADF". I agree that other readings are possible, but that's the way I would normally use and/or hear that idiom. Cheers, John Clonts Temple, Texas N7NZ |
#15
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The whole point of all this is to be sure you are not stuck with no
approach because GPS goes dead. Nothing at alternate can require GPS. That's what it means (I think). John Clonts wrote: wrote in message ... On 11 Feb 2005 11:23:14 -0800, "Michael" wrote: I think I'd interpret "as appropriate" as meaning that the GPS essentially meets the definition of "DME or ADF avionics", since the rules say it can be substituted for such, I do not concur, and believe such an interpretation is contrary to the intent if the statement. (8) For TSO-C129/129A users, any required alternate airport must still have an approved instrument approach procedure other than GPS that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly. If the non-GPS approaches on which the pilot must rely require DME or ADF, the aircraft must be equipped with DME or ADF avionics as appropriate. I believe the last statement means what it says - that for purposes of selecting a valid alternate, one must select an approach that can be completed without reliance on GPS. Michael "What it says" depends on how one interprets "as appropriate". (a) Since it is "appropriate" to substitute GPS for DME and ADF on non-GPS approaches, then it's acceptable as far as I am concerned. Furthermore, (b) The aircraft is "equipped to fly" the non-GPS approach.and (c) they'll never catch me anyway even if I'm wrong. Well, my 2 cents says that "as appropriate" specifically applies to the phrase "DME or ADF", meaning the equivalent to the following rewrite: "If the non-GPS approaches on which the pilot must rely require DME, the aircraft must be equipped with DME; if the non-GPS approaches on which the pilot must rely require ADF , the aircraft must be equipped with ADF". I agree that other readings are possible, but that's the way I would normally use and/or hear that idiom. Cheers, John Clonts Temple, Texas N7NZ |
#16
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"Bill J" wrote in message ... The whole point of all this is to be sure you are not stuck with no approach because GPS goes dead. Nothing at alternate can require GPS. That's what it means (I think). I think that is correct, but only for purposes of fuel planning and filing flight plan. |
#17
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"Michael" wrote in message
oups.com... I believe the last statement means what it says - that for purposes of selecting a valid alternate, one must select an approach that can be completed without reliance on GPS. Is a radar approach (presumably requiring no avionics but a Com radio) authorised for use as an alternate? Julian Scarfe |
#18
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On Sat, 12 Feb 2005 09:21:53 GMT, "Julian Scarfe"
wrote: "Michael" wrote in message roups.com... I believe the last statement means what it says - that for purposes of selecting a valid alternate, one must select an approach that can be completed without reliance on GPS. Is a radar approach (presumably requiring no avionics but a Com radio) authorised for use as an alternate? Julian Scarfe Sure. Orlando, Pensacola, Jacksonville all publish alternate minima for their radar approaches. Presumably, if no alternate minimums are specified and the airport has a radar approach, then standard minimums apply. |
#19
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OK, if my IFR GPS goes out (and my handheld goes out), I am down to
just my VOR/GS. No DME, no ADF, no GPS, no Marker Beacons. Am I legal to fly an ILS? The only way I have of identifying the outer marker is ATC radar, so certainly I would need radar coverage. So, lets say I have radar coverage and its just a plain ILS, no DME or ADF requirement? Legal? Safe? |
#20
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On 12 Feb 2005 20:56:18 -0800, "Doug"
wrote: OK, if my IFR GPS goes out (and my handheld goes out), I am down to just my VOR/GS. No DME, no ADF, no GPS, no Marker Beacons. Am I legal to fly an ILS? The only way I have of identifying the outer marker is ATC radar, so certainly I would need radar coverage. So, lets say I have radar coverage and its just a plain ILS, no DME or ADF requirement? Legal? Safe? I think it would depend on how you identify the missed approach holding point. If the MHP is an NDB, you have no way of navigating to it or holding at it. Course, in a radar environment it's unlikely they'll tell you to go hold as published, but what happens if you have to go missed and lose comms too? |
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