121 v 91 was not really part of the discussion. I had a brain fart while formulating my response. I apologize for the confusion. Since I seem to be obfuscating instead of clarifying I'll drop this for now.
Understanding the whole of IFR
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Snglcoil-thanks for contributing!
Ravioli
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Dear God, NO.
And you meant to write "Here is a brief synopsis..." Or "Here are some brief synopseis..."
Well alrighty then how about the question of you are shooting an ILS when the glide slope disappears (transmitter or receiver you don't know which). What do you do? Why are you choosing to do it?
Remember, the goal is to spark thought and discussion...
Remember, the goal is to spark thought and discussion...
dtuuri
Final Approach
Questions like these come up so frequently IMO it's best to wait until the next iteration by a genuine student (or student of the "game") seeking advice. Then you can cast your opinions with the rest of us and the student can weigh the evidence.
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IF I'm still in the soup I'm going missed. I don't have any faith in losing half of the ILS system that the other half is fully operational. If you're below the LOC only MDA, you don't have any choice. You now no longer are on a known part of the approach.
Bill
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Depends on a lot of things, like where/when on the approach GS goes TU.
luvflyin
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If the Localizer is fine and I'm above MDA and the WX is such that I'm likely to be able to land, I continue with LOC minimums if there are any. Knowing the MDA and the Missed Approach Point is part of my briefing on Approaches with both, so I can make the transition instantly. Comes in handy if you get hung way up on a slam dunk by Approach. Happened to me on my IR checkride. Controller hung me way up. When I got the Clearance I told the Examiner I was continuing with the LOC and announced the MDA. When I was able to get stabilized on the Glideslope from above I announced the DH and continued with ILS. He was happy and I passed.
Bill
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If the GS dies before the FAF, then yeah, fly it as a LOC. If it dies after the FAF, then you can only fly the LOC if you happened to hack the clock at the FAF to time the missed. Although this all may be moot, as it may be a trick question. There may be a reg that if any part of the guidance system goes TU during the approach, you go missed. But I aint' looking it up...
That's if you do it at the NON PRECISION FAF. The lightning bolt and the maltese cross aren't necessarily the same point. Usually they are coincident but there are a handfull where it's not the case.
luvflyin
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Yeah. Like I said in that post "...Knowing the MDA and the Missed Approach Point is part of my briefing on Approaches with both, so I can make the transition instantly..." If it's a time to MAP, I do that. Even without the thing about losing the Glideslope it's important to know where the Missed Approach Point is if the Missed Approach Procedure has turns that start there. If you have to miss early you can climb immediately to the Missed Approach Altitude but you can't start the turns until there so you should know where it is. DA/DH is of no help in that situation. I dunno either about a reg about discontinuing if any component goes nips up. Far as I'm concerned the Glideslope is not a component if your doing the LOC, even if you started LOC'ing after Glideslope'ing. I'm probably wrong 'reg wise' about this. I'm sure this whole thing is going to lead to a discussion about how ILS Approaches with Localizer only minimums are named nowadays. If anyone knows of an Approach out there that doesn't have the new naming convention yet, speak up.
luvflyin
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If your taking the time to time it, which I think you should do, then yeah, you time it from the cross, not the bolt. But I don't think it's ever a significant difference. What's the farthest displacement you've ever seen between 'bolt and cross?'
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If you're on the glideslope and hit the DA, you're at a point you can start turning. That *IS* the MAP.
Not much. AOO's ILS in profile makes it look like it's a 2 mile difference, but at only 25 feet vertically, it can't be more than a tenth of a mile.
luvflyin
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OK. You're on the Approach, inside the FAF/PFAF descending. You're gear light goes from green to amber or some other thing happens that you can't continue the Approach. Maybe it's because you lose the Glideslope. Maybe it's because you've gotten so far behind the plane you can't stay on it and must abandon the Approach. Anything that requires you to abandon the Approach and miss. You ain't gonna continue descending to the "DH/DA 'is the' MAP." If the Missed Approach Procedure has turns, you need to know 'where' the point is.
luvflyin
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Well some that involve turns have you go straight ahead for a bit before starting the turn. Like climb to so many feet and then turn. But that is predicated on the whole thing starting at geographic point where the Glideslope at DH/DA is over the earth. If the procedure says climb to some altitude then turn, you decide to abandon the Approach and miss way out yonder you can't just say gee, I'm already above that altitude so I'm just going to start the turn now. You are required to proceed to the geographic location of the Missed Approach Point before beginning turns.
I don't think you're saying anything in contradiction to what I said. I was countering that your statement that the "DA is of no help" which isn't true if you are on the glideslope.
RussR
En-Route
No, you need to time it from the maltese cross. That's where the timing table is developed from, the distance from the non-precision FAF (the cross) to the MAP.
You will generally only see a difference between the lightning bolt and the cross if the non-precision FAF is based on an OM, LOM, or NDB (in other words, a fixed, physical facility).
A few I know of:
PWA ILS OR LOC RWY 17L, 74 feet difference, about 1/4 nm. https://skyvector.com/files/tpp/1910/pdf/00739IL17L.PDF
TUL ILS OR LOC RWY 36R, 76 feet, 1/4 nm. https://skyvector.com/files/tpp/1910/pdf/00432IL36R.PDF
ICT ILS OR LCO RWY 1R, 85 feet, https://skyvector.com/files/tpp/1910/pdf/00987IL1R.PDF
A particularly odd one, CVO ILS OR LOC RWY 17, 300 feet, about 1 nm! That will definitely throw off your timing if you start it at the wrong point. https://skyvector.com/files/tpp/1910/pdf/00782IL17.PDF
Another one with a significant difference is SBD ILS OR LOC Z RWY 6, 182 feet, a little over a half nm. https://skyvector.com/files/tpp/1910/pdf/00547ILZ6.PDF
luvflyin
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Oops. Post edited. I really meant to say cross, not bolt.
luvflyin
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Gotcha
luvflyin
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Here’s a fun one.
https://skyvector.com/files/tpp/1910/pdf/00363I31.PDF
It’s one of them ILS without LOC only minimums ones. DME available but you don’t need it if you have ADF. You’d have to make up you’re own timing table based on the 11.7 NM distance from UAD to threshold. I wouldn’t actually do that though. The SNS VOR being right on the field would be close enough to the Missed Approach Point to use it. You’d already have it dialed in for the Missed. Unless you only had one NAV in the plane. Yeah, there probably isn’t an airplane left out there with ADF, one NAV and nuthin else. Just an academic discussion