LOC approach on an ILS

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I've always been taught (and taught my students) that when doing a circling approach off of an ILS to follow the GS down to cirlcing mins and then commence the cirlce.

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That's a good question, and I teach to ride the GS down to the circling mins and then plug from there, and go missed @ the LOC DME/time as well. However, I've always wondered what would be allowed.

If you think about it, if you execute the LOC only portion, there is an MDA. If you execute the circling approach, there is an MDA which is typically higher than the straight-in MDA's. So, if you're using the same component but flying higher, I can't see how you'd be wrong in just diving to the circling MDA from the FAF! The obstacle clearence you'd get would be the same or more than the straight in LOC only. Using the GS would just allow a more controlled desent down to such MDA.

Also, I believe it's the controllers responsibility to inform the pilot when they are cleared for an approach if a component is OTS. Anyone have the ATC handbook handy? So, if cleared for an ILS but with the GS OTS, the controller SHOULD state that the GS is inop. But you're still cleared for the "ILS".

Except for ATC looking out for you, why would there care if you shot the LOC only portion of the ILS? For all they know, your GS indicator could be inop (not required to tell them if it happened before the flight). It's not like they're seperating traffic on the final approach course or anything. Once you're on the approach, that airspace is yours. Do whatever floats your boat
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, atleast IMO. Granted telling them is always a good idea, especially if its not too busy. It can't hurt...

~wheelsup
 
well now,

the REAL question then is THIS:

On on ILS, the altitude listed is the DECISION HEIGHT
On an LOC-only, the altitude listed is the MINIMUM DESCENT altitude.

On a cicle approach, the altitude listed is ?????? my vote is it is a decision height.
 
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You'll be flying in cruise and atc will tell you to descend and maintain 3000'. And the pilot will do so. How can you do this without being on a vector?

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Good point.[thinking aloud] Being on an MEA implies you're on an airway, in which case you need navigational coverage to remain there, which the MEA gives you. If you go below that, there's no guarentee (sp?) that you'd be able to keep guidence on the airway, even if your aircraft was in a MVA sector.

That's a good one. I'll be sure to watch out for it - and ask for a heading if they take me below the MEA. Maybe the aircraft are all /G equipped? Hmm.

~wheelsup
 
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On a cicle approach, the altitude listed is ?????? my vote is it is a decision height.

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It is 100000% an MDA. If you have access to Jeppesen charts, check out mins section for the Circle-To-Land. It clearly states MDA (H) above the minimums. Hence, you'd go missed (or atleast start the turn) reaching the LOC MAP, which would either be distance or time.

~wheelsup
 
You might as well not even bother. They will probably tell you to say heading. Then they'll give you a 'vector' by telling you to fly present heading.
 
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It is 100000% an MDA. If you have access to Jeppesen charts, check out mins section for the Circle-To-Land. It clearly states MDA (H) above the minimums. Hence, you'd go missed (or atleast start the turn) reaching the LOC MAP, which would either be distance or time.

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Alright, I've got to bow out of this discussion for now. I have three hours before I have to get up to be wheels-off by 0430.
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On on ILS, the altitude listed is the DECISION HEIGHT

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Cat-I you're really looking at the altitude but I think I know what you're getting at!
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In fact, we don't even set the radio altimeter on Cat-I approaches because it's theoretically useless information in regard to Cat-I.

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On an LOC-only, the altitude listed is the MINIMUM DESCENT altitude.

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Yes

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On a cicle approach, the altitude listed is ?????? my vote is it is a decision height.

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MDA.

Think of it like this, DH/DA is a function of being on a glideslope at a predetermined geographic position. You can descend quickly to MDA after crossing the FAF and putter along until reaching the MAP (missed approach point).
 
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i still would ride that GS down to that MDA though, unlike Mister KC-135 guy.

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Yep, and it's easier because you don't have to worry about stepdowns. Maybe he needed to get down early, in order to setup because he was used to going so fast? I dunno.

~wheelsup
 
It could be a military thing as well. Somebody may be able to chime in on that. They do a whole lot of stuff that is different, some of it really useful to the civilian world and some of it not so useful. That said, if I'm bored I've started to call tower with "Seminole whatever, left base, gear down". Ah yes, the ways to fight complacency.

Ethan
 
Okay, I'm looking at the ILS or LOC RWY 7 (exactly what it says on the chart) for KORL. Now, if you want to shoot the LOC approach, Orlando is gonna say "Well, we can give you the ILS, and you can fly the LOC approach if you want." Trust me on that one. I've heard it several times. Now, on the chart GS intercept is 2000, same as the FAF for the LOC. So you should be at the same height there. Now, you can then step down to 1200. In this airspace, you'll almost ALWAYS get handed to tower outside the FAF. If Approach sees you doing anything different, they're gonna assume you're GS indicator went out, if you had one in the first place. That's why I suggest telling tower when you call 'em up "N7260A on the LOC for 7" on the call up. Then they know. MDA is higher than DH, so obstacle clearance isn't a factor. It's one of those "know the way ATC handles the airspace." In Orlando, they'll treat you like an idiot if you try to file a LOC approach. Maybe in Ohio, they want you to request the LOC instead of the ILS. Depends on how they control it and even who's at the scope that day.

Now, as far as going missed on losing the GS, here's the way I remember it. Everyone starts that timer at GS intercept, right? Right? If the GS goes out, congrats, you're flying a LOC approach. To me, there's no need to go missed unless you feel bad about the approach or you're below a step down fix or MDA.
 
I would advise of the LOC vs the ILS. Case in point is for reporting procedures. ILS GS intercept and LOC FAF aren't always coincident. So, if you're flying a LOC approach on an ILS, and tower requests you report FAF, where would you report? At the GSI point?

And that would be incorrect. The correct point would be where the maltese cross point is located.

Realistically, at most places, you can request a LOC approach, and you'll be cleared for the ILS, or be cleared for the LOC; it really depends.

On the question of flying the GS down to circling mins, why bother? Ladies and gentlemen, what's the point of a circling approach? It's to get to MDA forthwith at the appropriate time so you can get the airport in sight and have time to maneuver to the landing runway. 135 pilot is correct. Past the FAF, it's imperitive to get down to MDA so you can hopefully be under the WX early and maybe maneuver as necessary early in order to get the runway in sight and land. Is it illegal to fly the GS down to the MDA? No, it's perfectly legal. I just don't think it's the best planning to do so, since again you're leaving the potential of seeing the airport behind you by dicking around with maintaining the GS, instead of getting down to MDA where you're freaking supposed to be, and finding the field.
 
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Everyone starts that timer at GS intercept, right?

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What's the point of starting the time? You mentioned it in your post - to determine the MAP if for some reason the GS goes out and you don't have DME (or its not a published distance). So, you'd start the time at the same place that you'd start it on doing the regular LOC approach - at the outer maker.

Also, RE: (MideD) approach telling you to contact them at the FAF, has anyone ever heard this wording on an ILS? I haven't. I'll get either contact tower at the outer marker, or the fix name. I'd still stick to the cross depicted on the plate, because that's probably what the mean anyway.

~wheelsup
 
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135 pilot is correct. Past the FAF, it's imperitive to get down to MDA so you can hopefully be under the WX early and maybe maneuver as necessary early in order to get the runway in sight and land...I just don't think it's the best planning to do so, since again you're leaving the potential of seeing the airport behind you by dicking around with maintaining the GS, instead of getting down to MDA where you're freaking supposed to be, and finding the field.

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That's what I thought, and for a larger aircraft its even more important to get 'er down so you have plenty of time. However, it got me thinking - and I ran a litte trig.

Using 2.3 miles as the minimum distance to manuever (CAT D) if your MDA is higher than 733' above TDZE you could ride the GS down, because the point at which you'd be able to make manuevers would conincide or be closer to the airport with your GS intercept altitude.

If you can imagine a triangle, I took the tangent of 3 degrees (normal GS) and multitplied it by (2.3 x 6086) to get a distance in feet. That gives 733' for your altitude on the GS 2.3 miles out (from where you'd get DA, so its actually a little more from the runway).

If your MDA is less than that, it would be better to drop to the lower altitude at the last stepdown fix.

For the Cessna/Piper drivers (myself included) and those in CAT B or less, your manuevering distance is 1.5 miles or less from the runway end. With the same trig, I found if your MDA was 478' or more it would be possible to ride the GS down without any consequence. Interesting stuff...hopefully I didn't bore anyone too much!

~wheelsup
 
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135 pilot is correct. Past the FAF, it's imperitive to get down to MDA so you can hopefully be under the WX early and maybe maneuver as necessary early in order to get the runway in sight and land...I just don't think it's the best planning to do so, since again you're leaving the potential of seeing the airport behind you by dicking around with maintaining the GS, instead of getting down to MDA where you're freaking supposed to be, and finding the field.

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That's what I thought, and for a larger aircraft its even more important to get 'er down so you have plenty of time. However, it got me thinking - and I ran a litte trig.

Using 2.3 miles as the minimum distance to manuever (CAT D) if your MDA is higher than 733' above TDZE you could ride the GS down, because the point at which you'd be able to make manuevers would conincide or be closer to the airport with your GS intercept altitude.

If you can imagine a triangle, I took the tangent of 3 degrees (normal GS) and multitplied it by (2.3 x 6086) to get a distance in feet. That gives 733' for your altitude on the GS 2.3 miles out (from where you'd get DA, so its actually a little more from the runway).

If your MDA is less than that, it would be better to drop to the lower altitude at the last stepdown fix.

For the Cessna/Piper drivers (myself included) and those in CAT B or less, your manuevering distance is 1.5 miles or less from the runway end. With the same trig, I found if your MDA was 478' or more it would be possible to ride the GS down without any consequence. Interesting stuff...hopefully I didn't bore anyone too much!

~wheelsup

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The problem is, you're screwing around with flying a glideslope, when you should be stabilized at MDA as early as safely possible. So you get down to MDA after riding the GS down, now you attention is focused on arresting the descent, trimming up, etc, when it should be focused outside finding the runway and where to maneuver to get there. You're making the focus now flying/stabilizing the airplane if you rode the GS to MDA, while you're burning precious time and area behind you. IMO, the priorities are off doing it this way, and hence why I strongly don't recommend it.

Also, nice computations, but they assume you maintain these descent gradients down to MDA. Barring what I wrote above, if you don't maintain those gradients (on the shallow side), then you overshoot where you want to be, again wasting precious time on flying the airplane to stabilize it at MDA and leaving distance and time to look for the runway behind you. The last place you want to be doing math in public is inside the FAF figuring out descent rates, etc. You primary job in IMC is to make life easy on yourself, not harder.
 
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Everyone starts that timer at GS intercept, right?

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What's the point of starting the time? You mentioned it in your post - to determine the MAP if for some reason the GS goes out and you don't have DME (or its not a published distance). So, you'd start the time at the same place that you'd start it on doing the regular LOC approach - at the outer maker.

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You mean at the FAF. OM and FAF may not always be coincident. At the maltese cross is where you'd hack the clock, ILS or LOC.

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Also, RE: (MideD) approach telling you to contact them at the FAF, has anyone ever heard this wording on an ILS? I haven't. I'll get either contact tower at the outer marker, or the fix name. I'd still stick to the cross depicted on the plate, because that's probably what the mean anyway.

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Not approach, but tower asking to me to contact them at the FAF, to me, the maltese cross in any event. You can also get the OM, fix name, or a specific DME.
 
I think the more important question would be is the "maltese cross" actually from Malta?
 
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What's the point of starting the time? You mentioned it in your post - to determine the MAP if for some reason the GS goes out and you don't have DME (or its not a published distance). So, you'd start the time at the same place that you'd start it on doing the regular LOC approach - at the outer maker.

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FAF is what I meant. That's what I get for looking at a plate where they are the GS intercept and FAF are more or less the same, I guess.
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