ILS/DME Question
Thread Starter
ILS/DME Question
A bit of background first, using the Perth TCA. The Rottnest Twin NDB appch indicates that if DME at Perth is US then radar will provide radar distances for you....Question
You are ILS equiped but NOT DME or IFR GPS equiped. Inbound to Perth and Runway 03 ILS/DME is being used. If conditions are below circling minima appch ie use R24 ILS or for traffic flow reasons can you request or except radar distance readouts at the key points in you R03 appch.
Forgive me if there is an obvious answer to this but I have not found a reasonable answer yet.
You are ILS equiped but NOT DME or IFR GPS equiped. Inbound to Perth and Runway 03 ILS/DME is being used. If conditions are below circling minima appch ie use R24 ILS or for traffic flow reasons can you request or except radar distance readouts at the key points in you R03 appch.
Forgive me if there is an obvious answer to this but I have not found a reasonable answer yet.
HEALY
The RWY 03 ILS at Perth in an ILS/DME approach. There are no marker beacons for this runway otherwise it would be called the ILS, ILS/DME RWY03. AIP 7.2c states that if markers aren’t available then another means must be available to do the altimeter check on the glide path. AIP DAP 1.1 states you can’t use any navigation facility not on the plate to do the approach. So in answer to your question, no you can’t use Perth Approach radar to obtain the necessary DME distance to do an Altimeter check for wry 03. When I was still flying in Australia, I remember some rule that stated to do an ILS you had to have DME and/or Marker Beacon receivers. The AIP and DAPS don’t look the same as they did a few years back and I can no longer find that reference.
The RWY 03 ILS at Perth in an ILS/DME approach. There are no marker beacons for this runway otherwise it would be called the ILS, ILS/DME RWY03. AIP 7.2c states that if markers aren’t available then another means must be available to do the altimeter check on the glide path. AIP DAP 1.1 states you can’t use any navigation facility not on the plate to do the approach. So in answer to your question, no you can’t use Perth Approach radar to obtain the necessary DME distance to do an Altimeter check for wry 03. When I was still flying in Australia, I remember some rule that stated to do an ILS you had to have DME and/or Marker Beacon receivers. The AIP and DAPS don’t look the same as they did a few years back and I can no longer find that reference.
404.............can't speak for the DAP's, but the section you refer to is addressed in Jeppesen Terminal AU-17 paragraph 3.1
It is too lengthy to reproduce here, but basically covers what you said.
It is too lengthy to reproduce here, but basically covers what you said.
Join Date: Sep 2003
Location: S37.54 E145.11
Posts: 639
Likes: 0
Received 0 Likes
on
0 Posts
ILS and DME
AIP ENR 1.5-32 para 7.2 “ILS Failures” refers.
Interesting subject this, as I also have a question with respect to the non-availability of DME on an ILS approach, which is a slight variation on the original question.
The above reference provides guidance on the procedures to be followed in the event of a failure of any of the ILS sub-system components ie the Locator, GP and Markers. Failure of the Locator or GP equipment is understood, however, I note that some locations have ILS approaches that don’t consist of Marker Beacons eg Albany R14 (WA), Perth R03 and Sydney R34R. These approaches rely on DME or GPS for distance to threshold and a failure of a DME in these instances does not appear to be covered by AIP. Therefore, my question is this:
What happens if you’re in IMC, cleared for (of commence if OCTA) the approach and the DME fails when you are halfway down the LLZ? Obviously, common sense would dictact immediate application of all the “ups” and the commencedment of a climb to (at least) the 10nm MSA whilst maintaining track guidance via the LLZ, although I can’t find an actual AIP reference to support this action in the event of a DME failure.
Under AIP, a pilot cannot commence the missed approach (tracking) procedure until the MAPt has been reached, however, how does one determine where the MAPt is without the DME (assume no GPS available), as the MAPt is normally indicated as a DME distance from the threshold? In a radar environment (eg the Sydney R34R or Perth R03 ILS), I guess the controller would most likely take responsibility for your missed approach and obstacle clearance by radar vectoring you onto the missed approach track above the minimum radar vectoring altitude. But what happens if the airport is uncontrolled, outside of radar coverage and the missed approach track is not a continuation of the LLZ track (luckily at Albany the missed approach track is also the LLZ track)? Or wouldn’t an OCTA ILS procedure be designed with a missed approach track that was offset to the LLZ track?
Whilst Jeps may be specific on this issue, I agree with HEALY - I can't find a specific reference in AIP re the procedures to be followed in the event of DME failure whilst conducting a no-marker ILS approach.
Enlighten me, someone, please!
Interesting subject this, as I also have a question with respect to the non-availability of DME on an ILS approach, which is a slight variation on the original question.
The above reference provides guidance on the procedures to be followed in the event of a failure of any of the ILS sub-system components ie the Locator, GP and Markers. Failure of the Locator or GP equipment is understood, however, I note that some locations have ILS approaches that don’t consist of Marker Beacons eg Albany R14 (WA), Perth R03 and Sydney R34R. These approaches rely on DME or GPS for distance to threshold and a failure of a DME in these instances does not appear to be covered by AIP. Therefore, my question is this:
What happens if you’re in IMC, cleared for (of commence if OCTA) the approach and the DME fails when you are halfway down the LLZ? Obviously, common sense would dictact immediate application of all the “ups” and the commencedment of a climb to (at least) the 10nm MSA whilst maintaining track guidance via the LLZ, although I can’t find an actual AIP reference to support this action in the event of a DME failure.
Under AIP, a pilot cannot commence the missed approach (tracking) procedure until the MAPt has been reached, however, how does one determine where the MAPt is without the DME (assume no GPS available), as the MAPt is normally indicated as a DME distance from the threshold? In a radar environment (eg the Sydney R34R or Perth R03 ILS), I guess the controller would most likely take responsibility for your missed approach and obstacle clearance by radar vectoring you onto the missed approach track above the minimum radar vectoring altitude. But what happens if the airport is uncontrolled, outside of radar coverage and the missed approach track is not a continuation of the LLZ track (luckily at Albany the missed approach track is also the LLZ track)? Or wouldn’t an OCTA ILS procedure be designed with a missed approach track that was offset to the LLZ track?
Whilst Jeps may be specific on this issue, I agree with HEALY - I can't find a specific reference in AIP re the procedures to be followed in the event of DME failure whilst conducting a no-marker ILS approach.
Enlighten me, someone, please!
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
QSK?... taking first things first, the guidance issued here is to identify the MAPt by DR... the well known SWAG (scientific wild-ass guess). Yes, there are problems with this but, as you will have initiated the climb prior to reaching the MAPt, there should be a fairly good margin for error. I had to do it once and, as soon as I'd recovered from a feeling of being completely alone and totally vulnerable, I managed to come up with a rough timing to the MAPt and it all seemed to work out okay.
It's not something that I can recommend tho. I didn't involve the controller in helping me to locate the MAPt because I was far too busy with the climb and time calculation. In any event, I was below the minimum vectoring altitude when it all went pear-shaped, so there was nothing that an ATCO could have done for me straight away.
It is not unusual for a turn to be specified in a missed approach, even with an ILS or LLZ procedure. The fact that you have to make a guess as to when to make that turn is a problem but, again, as you've started climbing prior to the MAPt., you will probably have some sort of error margin to work with. In my case, I didn't have to worry about that as I already knew how far away the hill was and had plenty of error margin to work with.
I take it that your company has no written procedures to cover the situation that you've described? Might be time that they gave it some thought. I reckon that CASA would probably expect that.
It's not something that I can recommend tho. I didn't involve the controller in helping me to locate the MAPt because I was far too busy with the climb and time calculation. In any event, I was below the minimum vectoring altitude when it all went pear-shaped, so there was nothing that an ATCO could have done for me straight away.
It is not unusual for a turn to be specified in a missed approach, even with an ILS or LLZ procedure. The fact that you have to make a guess as to when to make that turn is a problem but, again, as you've started climbing prior to the MAPt., you will probably have some sort of error margin to work with. In my case, I didn't have to worry about that as I already knew how far away the hill was and had plenty of error margin to work with.
I take it that your company has no written procedures to cover the situation that you've described? Might be time that they gave it some thought. I reckon that CASA would probably expect that.
Join Date: Oct 2002
Location: Australia
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Unfortunately with the Perth 03ILS, GPS is not permitted in liu of DME as the DME is co located with the GP, not the Perth DME. From my discussion with the TCU, the missed approach proceedure with a failed DME would be to maintain the LLZ track and thence runway heading, from which Radar Vectoring will be issued.
PT
PT
Join Date: Sep 2003
Location: S37.54 E145.11
Posts: 639
Likes: 0
Received 0 Likes
on
0 Posts
OzExpat:
Thanks for the response.
I notice that on US and UK plates that I have seen, there is a box that gives times from the FAP to MAPt for the various GS. Why don't the Oz plates contain same? Also looking at US guidance notes on how to conduct an ILS, they all seem to recommend the pilot time the approach from the OM.
To answer your question, I'm not with any airline or charter company - just a PPL coming to the end of my MECIR training.
Thanks for the response.
I notice that on US and UK plates that I have seen, there is a box that gives times from the FAP to MAPt for the various GS. Why don't the Oz plates contain same? Also looking at US guidance notes on how to conduct an ILS, they all seem to recommend the pilot time the approach from the OM.
To answer your question, I'm not with any airline or charter company - just a PPL coming to the end of my MECIR training.
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
QSK?...
I don't know for sure, but guess it's for much the same reason that I don't put timing on PNG's charts. The fact is that, it makes a huge difference to the area that needs to be protected in the missed approach. That extra protection area invariably means that more and higher obstacles have to be considered in the design. This can lead to the need for a higher MDA.
Maybe you should ask the flying school if they have any SOPs for the situation that you've described. If not, you could ask the CFI what action he/she would expect you to take.
Why don't the Oz plates contain same?
Maybe you should ask the flying school if they have any SOPs for the situation that you've described. If not, you could ask the CFI what action he/she would expect you to take.
Join Date: Jun 2001
Location: Living next door to Alan
Posts: 1,521
Likes: 0
Received 0 Likes
on
0 Posts
Under AIP, a pilot cannot commence the missed approach (tracking) procedure until the MAPt has been reached, however, how does one determine where the MAPt is without the DME (assume no GPS available), as the MAPt is normally indicated as a DME distance from the threshold?
Join Date: Sep 2003
Location: S37.54 E145.11
Posts: 639
Likes: 0
Received 0 Likes
on
0 Posts
OzExpat/Hugh Jarse:
Thanks for both responses, much appreciated.
OzExpat, yeah I did consult my CFI on this question but he wasn't too sure either, hence my initiative to go to PPrune to access the wider wisdom of the world. Appreciate your inputs, particularly as I notice that you're a procedure designer.
Thanks, HJ you're right about the positiion of the MAPt but how do I determine the MAPT if, as I indicated in my earlier posting, the DME fails after I have commenced the ILS approach, and I immediately commence (before reaching the DA) a climb to the MSA which takes me off the GP? All I have now is the LLZ tracking guidance and my altimeter. I'd be interested in how you would fly such a missed approach, either against any published guidelines (if there are any) or simply based on your flying experience.
Thanks for both responses, much appreciated.
OzExpat, yeah I did consult my CFI on this question but he wasn't too sure either, hence my initiative to go to PPrune to access the wider wisdom of the world. Appreciate your inputs, particularly as I notice that you're a procedure designer.
Thanks, HJ you're right about the positiion of the MAPt but how do I determine the MAPT if, as I indicated in my earlier posting, the DME fails after I have commenced the ILS approach, and I immediately commence (before reaching the DA) a climb to the MSA which takes me off the GP? All I have now is the LLZ tracking guidance and my altimeter. I'd be interested in how you would fly such a missed approach, either against any published guidelines (if there are any) or simply based on your flying experience.
Last edited by QSK?; 18th Jun 2004 at 01:29.
QSK?
You also have a watch. I routinely do mental calculations in my head for minutes and seconds to MDA or DA once on the approach. It only has to be a rough estimate as you will already be climbing and clear of obstacles at the MAPT if the DME fails.
You also have a watch. I routinely do mental calculations in my head for minutes and seconds to MDA or DA once on the approach. It only has to be a rough estimate as you will already be climbing and clear of obstacles at the MAPT if the DME fails.
Join Date: Sep 2003
Location: S37.54 E145.11
Posts: 639
Likes: 0
Received 0 Likes
on
0 Posts
Thanks 404.
Yeah, as you and OzExpat have confirmed, the timer seems to be the logical answer. Guess I'll have to start developing the good habit of estimating the time to MDA/DA on each approach.
Cheers QSK?
Yeah, as you and OzExpat have confirmed, the timer seems to be the logical answer. Guess I'll have to start developing the good habit of estimating the time to MDA/DA on each approach.
Cheers QSK?
Join Date: Jun 2001
Location: Living next door to Alan
Posts: 1,521
Likes: 0
Received 0 Likes
on
0 Posts
Thanks, HJ you're right about the positiion of the MAPt but how do I determine the MAPT if, as I indicated in my earlier posting, the DME fails after I have commenced the ILS approach, and I immediately commence (before reaching the DA) a climb to the MSA which takes me off the GP? All I have now is the LLZ tracking guidance and my altimeter. I'd be interested in how you would fly such a missed approach, either against any published guidelines (if there are any) or simply based on your flying experience.
Another aspect we could look at is if the DME fails before or after the glideslope check using an ILS/DME (in comparison to an ILS which only needs marker beacons, ie 16R YSSY or 16 YMML). From a practical perspective, if I had done my glideslope check using DME, and decided to continue (ie, no discrepancy), then the DME were to fail, I'd probably elect to continue to the DA, assuming a valid Glideslope was available. If not visual at the DA I'd carry out the published missed approach. Bear in mind that the DME is primarily there (ILS/DME) for fixing the IAF and glidepath check in the absence of marker beacons on the ground or in the plane. Once past the glidepath check the DME really has served its purpose.
On the other hand, if the DME were to fail prior to carrying out the glideslope check, then I'd go around.
This is where Titan's procedure would work well, particularly with respect to obstacle clearance.I'm open to suggestions
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
From a procedure design perspective, there's only a finite number of ways to identify the MAPt and still maintain procedure integrity. That makes it impossible for regulators to specify an escape methodology, so the best you'll find in official documents is something along the lines of "ya'll be careful now"! 
However, from a logical perspective, most of the latest generation of aircraft can easily exceed the 2.5% missed approach climb gradient, even in a OEI situation. This gives them a huge advantage in obstacle clearance and a consequently greater margin for error in guesstimating the location of the MAPt. Perversely, of course, the latest generation aircraft are also equipped with RNAV and or GNSS capability, making it much simpler to positively identify the MAPt location very accurately.
So it all comes down to the older, lower performance aircraft, especially those in GA, which may not be so well equipped. I can't think of a better justification for installing an IFR-certified GNSS receiver in those aircraft. The fact of the matter is that, while timing can be useful and will probably get you out of trouble, the calculation is invariably pretty rough and the risk of error is consequently huge. But, of course, it's better than nothing... but not much.
However, from a logical perspective, most of the latest generation of aircraft can easily exceed the 2.5% missed approach climb gradient, even in a OEI situation. This gives them a huge advantage in obstacle clearance and a consequently greater margin for error in guesstimating the location of the MAPt. Perversely, of course, the latest generation aircraft are also equipped with RNAV and or GNSS capability, making it much simpler to positively identify the MAPt location very accurately.
So it all comes down to the older, lower performance aircraft, especially those in GA, which may not be so well equipped. I can't think of a better justification for installing an IFR-certified GNSS receiver in those aircraft. The fact of the matter is that, while timing can be useful and will probably get you out of trouble, the calculation is invariably pretty rough and the risk of error is consequently huge. But, of course, it's better than nothing... but not much.
Join Date: Jun 1999
Location: Australasia
Posts: 362
Likes: 0
Received 0 Likes
on
0 Posts
Folks,
My understanding of the use of radar as a substitute for DME is a little different - unless the approach is designed to the appropriate containment area and therefore is titled "RADAR VOR RWY 12" as was the case for Jeppesen plate 13-2 at Adelaide, then radar distances are not able to be used.
HJ, as for the missed approach point for the ILS, I don't think that it always the intersection of the GS and the DA in practice since many plates very specifically ident the MApt as the MM. If you do not have a serviceable DME or IFR GPS in those cases, I do not think that you can conduct the approach.
Stay Alive,
My understanding of the use of radar as a substitute for DME is a little different - unless the approach is designed to the appropriate containment area and therefore is titled "RADAR VOR RWY 12" as was the case for Jeppesen plate 13-2 at Adelaide, then radar distances are not able to be used.
HJ, as for the missed approach point for the ILS, I don't think that it always the intersection of the GS and the DA in practice since many plates very specifically ident the MApt as the MM. If you do not have a serviceable DME or IFR GPS in those cases, I do not think that you can conduct the approach.
Stay Alive,
Join Date: Jun 2001
Location: Living next door to Alan
Posts: 1,521
Likes: 0
Received 0 Likes
on
0 Posts
Gidday 4Dogs,
Bet you use Jepps (like me).
The MAPt for an ILS is indeed the intersection of the Glideslope with the DA (or DH/RH). I don't have my Jepps with me but if you take a look at the AIP stuff, the MAPt on their charts have (LLZ) at the MM/equivalent DME distance. Jepps omit that information on their charts, which can lead to uncertainty.
Sure, when you fly an ILS in anger, you will get to the DA around the MM (actually past it), but in the strict sense it still is an altitude/glideslope thing as far as I'm aware.
To clarify, take a look at 16R or 34R ILS at YSSY. If you were to go around at the MAPt depicted on the chart (LLZ), assuming you are on slope, then for 16R you would be at approx 350', and for 34R, 480'. The DA for 16R is 220', and for 34R 290' respectively.
Hope this helps.
Bet you use Jepps (like me).
The MAPt for an ILS is indeed the intersection of the Glideslope with the DA (or DH/RH). I don't have my Jepps with me but if you take a look at the AIP stuff, the MAPt on their charts have (LLZ) at the MM/equivalent DME distance. Jepps omit that information on their charts, which can lead to uncertainty.
Sure, when you fly an ILS in anger, you will get to the DA around the MM (actually past it), but in the strict sense it still is an altitude/glideslope thing as far as I'm aware.
To clarify, take a look at 16R or 34R ILS at YSSY. If you were to go around at the MAPt depicted on the chart (LLZ), assuming you are on slope, then for 16R you would be at approx 350', and for 34R, 480'. The DA for 16R is 220', and for 34R 290' respectively.
Hope this helps.
Join Date: Jun 1999
Location: Australasia
Posts: 362
Likes: 0
Received 0 Likes
on
0 Posts
Huge,
You are quite correct!
I think that little cabernet-induced brainfart add-on of mine proves that I was much better at drinking than at thinking. I guess I can add another subject to the rapidly increasing list of things I clearly know ****-all about!
Stay Alive,
You are quite correct!
I think that little cabernet-induced brainfart add-on of mine proves that I was much better at drinking than at thinking. I guess I can add another subject to the rapidly increasing list of things I clearly know ****-all about!
Stay Alive,
Join Date: Jun 2001
Location: Living next door to Alan
Posts: 1,521
Likes: 0
Received 0 Likes
on
0 Posts
I don't mind the odd glass of merlot myself
I would be happy to take any spare bottles you might have lying around off your hands. Purely as a means of preventing further "brain farts" of course.
I would be happy to take any spare bottles you might have lying around off your hands. Purely as a means of preventing further "brain farts" of course.
Join Date: Nov 2003
Location: The land of Oz
Posts: 91
Likes: 0
Received 0 Likes
on
0 Posts
Well I'm Confused at the replies.
As far as I am aware a MAPt only applies to non precision approaches, and DA/RH apply to precision approaches. For an ILS app the DA is an altitude, not a point on space, so if you reach your DA and are not visual, you must carry out a missed approach. So in the case of a DME failure for an ILS, the distance is not needed, if you are within tolerances on GS and at your DA.
AIP ENR 1.5 1.10.1
$0.02
As far as I am aware a MAPt only applies to non precision approaches, and DA/RH apply to precision approaches. For an ILS app the DA is an altitude, not a point on space, so if you reach your DA and are not visual, you must carry out a missed approach. So in the case of a DME failure for an ILS, the distance is not needed, if you are within tolerances on GS and at your DA.
AIP ENR 1.5 1.10.1
$0.02