Teardrop Procedure Turn as a Course Reversal

[_HAMMER_]

I would like to know how would you execute a Teardrop Procedure Turn. Let´s use the ILS/DME rwy 11 at TNCA as an example.

http://www.vatcar.org/charts/charts/Netherlands_Antilles/TNCA/ILS-11%20(ILS-DME).pdf

I understand that we cannot perform the turn as a standard rate turn. The FAR does not tells you how to do it. It just state that you need to depart the IAF on the publish outbound course followed by a turn to intercept the inbound course at or prior the intermediate fix.

I read that is OK just to initiate a standard rate turn and then stop it in a manner so that you can wait and intercept the inbound course with 45 degrees angle. Other option is to anticipate the requiered bank by using the RMI.

Is there a techique or a formula to figure out how the required bank angle to make one continuos turn from the outbound course to finish the turn while intercepting the inbound course? How does airliners do it?

I know is not something you would use while being vectored in radar environment. But I still would like to know your opinion.

Thanks.

[Roger Greendeck]

A intercept 45degree may be too steep. 30 degrees works better but after a reversal this may put you too close. Cat C/D reversals cater for high speed in the turn which often mean that if you do a rate one turn to set up a 30 degree intercept you will intercept final too far along track.

The easiest option is to set up a 90 degree intercept and with 5 degrees to run on the VOR start a turn onto you final course. This is the same as you would do joining final off a DME arc.

[flyboyike]

If it's in the FMS, just hit NAV.

[Chris Scott]

I'm not familiar with this spec of chart, but am assuming the 'BEA' beacon is a VOR/DME, and not just a DME. Guess it must be, as the hold is based on it.

Mental arithmetic (using the one-in-sixty rule) puts "D10.2 BEA" about 4 nm south of "D10 IBE", implying a radius of turn (as drawn on the chart) of about 2 nm, giving a track distance of about 6 nm for a 180-deg turn. At TAS 180 kt, a rate-one turn (25 deg bank) through 180 deg (60 secs) covers just 3nm. That's in still air, of course. So you can see the curve they've drawn is more like a rate-half if you're doing only 180 kt.

Even if you fly it at a typical minimum-clean jet speed of 210 kt (about 30 deg bank for rate-one), you would still be well inside that curve. And you would probably need to slow down before completing the turn, because you want to be at final-approach speed when intercepting the GS at only 6 nm.

So Roger Greendeck is absolutely right to warn of the probability of intercepting the LLZ (ILS localiser) too close to the runway if you try a 30-degree intercept. I think his suggestion of flying a 90-deg intercept until 5 deg before the inbound track is a good one. That would be the BEA 288 Radial. In still air at 180 kt, that would be early enough to avoid shooting through the LLZ.

In a northerly or NE wind you might have to pause briefly on an intercept heading of about 080. In a southerly, on the other hand, you might need to start the turn a bit earlier if at 180 kt. Also, as always, VORs are only accurate to about 5 degrees, and any errors may not be consistent.

[aterpster]

I'm not familiar with this spec of chart, but am assuming the 'BEA' beacon is a VOR/DME, and not just a DME. Guess it must be, as the hold is based on it.

"D 113.8" is a major clue. :)

[bubbers44]

I have done this approach dozens of times and it is very easy. The hard part is getting a descent clearance at altitude. They don't have a clue how to get you down. I ask for descent fifty miles early and still have to descend in holding do to lousy ATC.

[aterpster]

bubbers44:

I have done this approach dozens of times and it is very easy. The hard part is getting a descent clearance at altitude. They don't have a clue how to get you down. I ask for descent fifty miles early and still have to descend in holding do to lousy ATC.

I know you know, but some of the readers may not. The holding pattern shown must be used in any case to align with the base leg course reversal unless you arrive at the VOR within 30 degrees of the base leg outbound course.

[reynoldsno1]

Teardrop Procedure Turn

It's officially called a 'Base Turn". For Cat C/D it will have been designed using a speed of 250kt IAS, unless a slower speed is specified. If you fly slower than that then you will probably turn inside the inbound course and have to adjust accordingly. The design also incorporates allowances for the effect of an omnidirectional wind -in this case, probably something a little over 50kts.

[bubbers44]

Aterpster, do you have any documentation of mandatory holding pattern entry? My neighbor who is an airline captain also says holding pattern is mandatory. I said no. I never did the holding pattern if number 1 for approach because it made no sense. I did it hundreds of times. I never had anyone question doing a direct outbound arrival from the vor with no hold entry. Why? I know I misspelled your name but this suck iPad is hard to type on.

[Fly3]

It is clearly marked PANS-OPS and therefore the speed during the procedure cannot be as high as 250kts. I think that it should be flown at 185kts IIRC and the intercept adjusted accordingly.

[eflowj]

Since it is a PANS-OPS procedure, look at ICAO DOC 8168. It is also in the Jeppesen Airway Manual, Air Traffic Control tab. Spells out when you can go straight into the Base Turn and when you cannot.

[reynoldsno1]

It is clearly marked PANS-OPS and therefore the speed during the procedure cannot be as high as 250kts. I think that it should be flown at 185kts

It (the base turn) is an initial approach procedure - initial approach speed for Cat D is 250kt(PANS OPS) 185kt is a UK limitation applicable to all approach procedures, istr. Cat A/B is limited to 140kt (PANS OPS).

[Sonny Hammond]

80/260 if theres nothing published and you are above the msa?

[Chris Scott]

reynoldsno1,

I've never flown to Aruba, and that wide-radius turn could probably be folllowed at 250 kt. But maintaining 250 kt until 10 miles from touchdown on an instrument procedure is plainly not to be recommended.

Also, if you start the turn at 250 kt, and then decelerate, you will start to creep inside the bend (unless there's a strong southerly wind). Therefore, you will need to choose an intercept heading, on the lines that Roger Greendeck and I have suggested.

[aterpster]

bubbers44:

Aterpster, do you have any documentation of mandatory holding pattern entry? My neighbor who is an airline captain also says holding pattern is mandatory. I said no. I never did the holding pattern if number 1 for approach because it made no sense. I did it hundreds of times. I never had anyone question doing a direct outbound arrival from the vor with no hold entry. Why? I know I misspelled your name but this suck iPad is hard to type on.

This forum really sucks big-time. It is the only aviation forum I attend that doesn't allow attachments.

Anyway, it is in PANS-OPS 8168. Here is a link to my website with an excerpt from 8168 in PDF format. Also, as someone else stated, it is in the Jepp legend.


Index of /8168 (http://www.terps.com/8168)

[reynoldsno1]

But maintaining 250 kt until 10 miles from touchdown on an instrument procedure is plainly not to be recommended.

I could not agree more, but the purpose of PANS OPS is to design procedures and subsequently assess the resultant drawing or template to determine clearance from obstacles/terrain. 250kt is the 'standard' initial approach speed (maximum) for Cat D, and all calculations are based on that - it does not mean you must fly at that speed. Anything less is fine, and you will be contained within the procedure depicted, but appropriate adjustments will be required as you suggested.

[aterpster]

ReynoldsNo1:

I could not agree more, but the purpose of PANS OPS is to design procedures and subsequently assess the resultant drawing or template to determine clearance from obstacles/terrain. 250kt is the 'standard' initial approach speed (maximum) for Cat D, and all calculations are based on that - it does not mean you must fly at that speed. Anything less is fine, and you will be contained within the procedure depicted, but appropriate adjustments will be required as you suggested

Well stated, but the premise is "the old way."

Eventually, performance based navigation will replace all this old stuff.

RNPA AR already has, but that is both a technical and political club dictated by already existing air carrier equppage.

[galaxy flyer]

Sonny

Maybe that's so in :mad: Idaho, but it ain't so in ICAO Doc 8168 land. :}

[Fantome]

Dear Mr Hammer . . .. .. As you see, there is much detailed and expert advice here which should clarify for you some fairly basic principles and practices.

By the way, you say in another forum -

I am just looking foward to build a solid career as a prossional pilot. Any comment would be appreciated.

Thanks a lot


May I suggest that before you fire off your posts you reread what you have written a little more critically. If you have a struggle with English
for the reason that it is not your native tongue, please do not be offended by anything posted here.

Another thing, looking back to that first post of yours in one of these forums, I must say I am a little puzzled as to why you appear to be fretting about the salary you expect to earn when you qualify. But I digress. Here you ask how to execute "a procedure turn as a course reversal". In the thousands of procedure turns I must have made over many years I cannot think of a single instance where such a turn was made for any other reason than a reversal, a means of doing a one-eighty.

Is a procedure turn the only way? No. A Pitts can easily do a one-eighty.
The manoeuvere is called a 'roll off the top'. Or an 'Immelman'.

Alright, so why so pedantic? Because the career you aspire to is
populated with people who will train and check and assess the knot you make in your tie.

Wishing you every success with your studies and satisfaction in your career, at whatever flight level that may be. As Captain Chesley Sullenberger wants the reader to know in his brilliant book 'Highest Duty', there is no other occupation on earth that comes within a bull's roar. A message he imparts with pride, humility, grace and simple unaffected modesty. Truly a man to look up to.

[Zeffy]

flyboyike
If it's in the FMS, just hit NAV.

The alignment holding pattern won't be in the FMS database.

As others have stated, unless the aircraft is arriving at the facility from the Entry Sector, the alignment hold is required.

http://i202.photobucket.com/albums/aa92/zeffy_bucket/BaseTurnEntryI-4-3-5.png

[Zeffy]

For those seeking references, a wonderful book by Olle Åkerlind and Håkan Örtlund, Instrument Flight Procedures and Aircraft Performance provides explanations and illustrations of PANS-OPS as well as TERPS procedures.

Earlier versions of the book (titled From Takeoff to Landing) were at one time supplied by Honeywell at various aviation meetings.

[tommoutrie]

you could do a bit of maths if you wanted to.
the radius of the base turn is 2.1 miles (10*asin(12))
you can use tan(bank angle)=TAS^2/(11.29*radius of turn in feet)
still wind, no slip, 160 kts gives me a bank angle of 10 degrees.
But you'd never bother to work that out. Use a hold entry or go outbound as appropriate and just use a rate one turn for the base and roll out on a sensible intercept heading (or just use the top of the course bar and then follow it in to intercept).

At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less (plate only gives time and descent rate for up to 160) so a rate one will keep you from going through the localiser (still wind)

Just a guess though, don't really know what I'm on about, not for operational use, caveat emptor and all that.

Its not a procedure turn by the way - a procedure turn is a way to reverse your course and hopefully come out on the reciprocal of the inbound track. The common one's are an 80/260 or a 45/180 with a one minute outbound leg. The immelmann is less common in IFR flying but you might get points for originality.

[cruiseqe2]

Hi

I have been having a look at the chart in the OP message, and following this thread. I am a bit confused, however, at the chart.

In the plan view, it suggests that BEA is close to the beginning of the runway, and that IBE is just beyond the runway.

However, in the profile view, it suggests that IBE is close to the beginning of the runway!

Confused!

[Lonewolf_50]

The immelmann is less common in IFR flying but you might get points for originality
But no points from your passengers if its a revenue flight. :E

[aterpster]

tommoutrie:

At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less (plate only gives time and descent rate for up to 160) so a rate one will keep you from going through the localiser (still wind)

Apples and oranges. The timing table is provided for the LLZ+DME procedureonly and only from the FAF inbound. Having said that, timing tables on DME-required IAPs are superfluous.

The chart posted by the OP is for CAT C and D. There is also a chart for CAT A and B with a narrower base leg. Finally, there is a DME ARC ILS chart, which makes use of the base leg procedures a bit ridiculous under most circumstances since DME is mandatory in any case. (three current charts follow):

http://i201.photobucket.com/albums/aa214/aterpster/1_zps536b444c.jpg


http://i201.photobucket.com/albums/aa214/aterpster/2_zps024adbac.jpg

http://i201.photobucket.com/albums/aa214/aterpster/3_zpsf636e50b.jpg

[Chris Scott]

tommoutrie,

Quote:
“At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less...”

Must say your maths looks more impressive than the mental approximations I made in an earlier post (http://www.pprune.org/tech-log/508340-teardrop-procedure-turn-course-reversal.html#post7704017), but the 194 kt (TAS) figure looked too low to me. So, as your conscientious co-pilot, I decided to do a gross-error check, looking at the first 180 degrees of the base turn.

I’ve made the following assumptions:
Still air;
Rate-one turn = 180 deg/min;
pi = 22/7 (although 3 would have been good enough for gross-error purposes);
r (radius of turn as drawn) = 2.1 nm (your figure, which is close to my earlier 1-in-60-rule approximation of 2nm);
Track miles for the 180-degree arc (semi-circumference) = pi * r

Therefore, as drawn, the first 180 degrees of the turn have a track distance of 22/7 * 2.1nm = 6.6 nm.
Note that this takes 1 minute at rate-one.
Track distance covered in 1 minute @ 194 nm/hr = 3.23 nm.

So the semi-circle of the 180-deg turn would be achieved in 3.2 nm, and that semi-circumference suggests a radius of turn of just over 1 nm. That’s almost exactly half the radius as drawn, so the aircraft would be way inside the drawn curve. Looks like a rate-half turn would be about right for that speed. (I refer you to my previous post.)

Ahem, SIR... Any chance you’ve used 2*pi*r as a formula for semi-circumference? ;)

PS
Meant to point out earlier that rate-one is not achievable (“legally”) at 250 kt in civil ops, Pilots will recall that jet holding patterns are based on 25 deg bank or rate-one, whichever requires the lesser bank. (That means that if TAS is about 190 kt or more, rate-one is not achieved.) So if the pattern is based on 250 kt, it would probably assume 25 deg bank. Can you tell us what turn-rate that would be?


cruisege2,

It’s very simple. The plan (azimuth) view shows the ILS localiser (LLZ) “beam” emitted from an antenna array past the upwind (far end) of the runway. The vertical profile shows the separate glide-slope (GS) “beam” emitted from an antenna to the side of the runway, abeam the touchdown point.

[aterpster]

Since most pilots don't do algebra or trig in the terminal area a better idea might to slow a jet to 200 KIAS, or so, prior to the base leg turn point, and a prop jock to perhaps 140 KIAS, or so.

[tommoutrie]

Hey I did put a caveat and I did point out that I'm totally clueless. And I'd got it a bit wrong. At 250 kts you'd need a bank angle of 34.5 to do a rate one turn. You would need a bank angle of 23.5 to do the base turn depicted on the chart. So I suppose you could fly it at 250 (I couldnt, if I'm not at 160 at about 10 miles I am screwed..) But that doesn't allow for rolling in or rolling out, you need a margin for wind, and that's actually using formula for a weight on a string rather than a plane so it doesn't allow for any slip or skid (yaw) and there are probably other inaccuracies too. One I can't quantify is that if you have 90 degrees of bank your radius of turn is 0 which is obviously rubbish and will have something of an effect at lower bank angles. I suspect the "spinning things round on a string" equation gets less and less accurate the steeper the bank angle.

Its interesting that 185 knots is exactly coincident with the max bank angle that my autopilot can command (27 degrees) and thats the bit of maths I had got wrong. I originally worked that out to 194 but I can't count. I had used 27 degrees as a max bank angle during the base turn. But I don't know if there's actually a max bank angle you can use - in JAA land they get a bit squiffy if you go outbound supersonic but americans have different rules.

the question about the localiser and the DME range - look at the difference in the ranges and you can see how far apart they are (0.2NM or maybe 1200 feet) so the drawing probably isn't awful. They are not usually exactly to scale though - look at the 3.8 distance compared to the 6.

for the OP - you're just trying to establish on the inbound track rather than making a pretty curve that intercepts the final approach track but if it helps, for this geometry, you could try

185 kts, 14 degrees
160 kts, 10 degrees
140 kts, 8 degrees

still wind, and see what happens. If it doesn't work, don't blame me

[reynoldsno1]

The design of the base turn template should include an allowance for an omnidirectional wind of about 52kts. This includes the most adverse effect of that wind on the aircraft during the turn.

The variables are:
TAS, wind speed, rate of turn (max 3deg/sec, can be less), wind effect on turn, fix tolerances, tracking tolerances. If the base turn is timed, then timing tolerances are also included.

It all adds up to a large area ....

[tommoutrie]

I remember finding a reference to 100kmh somewhere when I was in a hotel room and reading about procedure design so that sounds about right. The dodgy channel was broken, the other crew member was ill, there was nothing to do, I didnt meant to read it, it just happened.

[cruiseqe2]

Chris wrote: It’s very simple. The plan (azimuth) view shows the ILS localiser (LLZ) “beam” emitted from an antenna array past the upwind (far end) of the runway. The vertical profile shows the separate glide-slope (GS) “beam” emitted from an antenna to the side of the runway, abeam the touchdown point.


Thank you Chris, that explains a lot, but it does raise one further question. Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!

[Chris Scott]

Quote from tommoutrie:
"...that's actually using formula for a weight on a string rather than a plane so it doesn't allow for any slip or skid (yaw) and there are probably other inaccuracies too. One I can't quantify is that if you have 90 degrees of bank your radius of turn is 0 which is obviously rubbish and will have something of an effect at lower bank angles. I suspect the "spinning things round on a string" equation gets less and less accurate the steeper the bank angle."

No, it remains good. Forgive me for drifting off-topic, but I think tommoutrie's dilemma needs to be put to rest. To maintain level flight (or a steady climb or descent) and achieve a balanced turn (no slip or skid), acceleration ("g") in the normal axis simply has to be increased from the straight-and-level figure of 1.0 to whatever is appropriate for the bank angle.

As he/she knows, the formula is
normal g = 1/cos(bank angle)
Here are some samples of bank angle versus g:
0 deg = 1.0
15 deg = 1.035
30 deg = 1.155
45 deg = 1.414
60 deg = 2.0
66.5 deg = 2.508
75 deg = 3.864
80 deg = 5.759
83 deg = 8.206
85 deg = 11.47
87 deg = 19.11
88 deg = 28.65
89 deg = 57.30
89.5 deg = 114.6
90 deg = infinity

At flying school, we've all done lovely, balanced, steep turns with 60 deg bank, pulling 2g and maintaining height. If you can pull enough g, you can maintain level flight (or a steady climb or descent) in a balanced turn at a given bank angle. But if your aerobatic aeroplane is limited to +6g, it will not be able to sustain a balanced turn at more than 80 deg bank without falling at an increasing rate. And a BALANCED turn with 90 deg bank is impossible.

[Mr Good Cat]

The ident of the DME referred to is under the stated distances I.e. 10.2 with IBE written underneath clearly shows which DME the point is referenced to, if that makes sense?

[aterpster]

Mr. Good Cat:

The ident of the DME referred to is under the stated distances I.e. 10.2 with IBE written underneath clearly shows which DME the point is referenced to, if that makes sense?

It makes sense only to those who are actually trained and actually fly aircraft under instrument flight rules.

[Chris Scott]

Question fom cruiseqe2:
"Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!"

The short answer, of course, is neither! DME ground "reply" transmissions are on a higher UHF frequency than the ILS GS, and the ILS LLZ is on VHF. (Note that the flight crew, if selecting the ILS manually on their radio management panel, have only to dial up the LLZ frequency - 108.7 in this case - to tune all three elements.)

But it is clear from the way the final-approach procedure is drawn that this ILS-DME reads zero, effectively, at the touchdown point. Therefore the ILS-DME receiver-transmitter is probably very close to the GS transmitter, if not on the same spot. The EAG training chart (link (http://www.vatcar.org/charts/charts/Netherlands_Antilles/TNCA/ILS-11%20(ILS-DME).pdf) provided by the original poster) has more detail than the Jeppesens, and the clue seems to be on the profile, which shows a "D" and "IBE" above the touchdown point.

aterpster and others may think I'm being pedantic to labour an obvious point, but it's not always this simple. In the USA, many ILS-DMEs are sited at the LLZ aerial, and read the appropriate DME distance in n.m. at the touchdown point (e.g., 2.0). In the past, I've flown at airfields where the two ILSs on opposite runways used one ILS-DME receiver-transmitter in the middle of the airfield, which biassed its transmissions to read zero at both thresholds. Then there was another airfield, EGKK, with a similar setup except that the DME was not equidistant from the two thresholds. So the bias had to be altered when ATC changed runways. That sometimes caused confusion during the changeover, particuarly when it was being used for departure navigation (SIDs), but I think they later rectified that anomaly.

[aterpster]

Chris Scott:

The Jeppesen chart has no ambiguities for this reader.

[Chris Scott]

Nor this one, aterpster.

Your point being?

[aterpster]

Chris Scott:

Your statement in Post 35:

The EAG training chart (link (http://www.vatcar.org/charts/charts/Netherlands_Antilles/TNCA/ILS-11%20(ILS-DME).pdf) provided by the original poster) has more detail than the Jeppesens

You may or may not have been implying that the Jepp charts were lacking. Thus my comment/point.

[Chris Scott]

Hi aterpster,

I see what you mean. All charts have to be a compromise between need-to-know and nice-to-know, while avoiding clutter, and Jeppesen have got it about right from a pilot's viewpoint. I'm more familiar with what used to be called Aerad, but we always used Jeppesen when in the US. Never seen EAG before.

It happens that, on this occasion, the EAG chart illustrates the point I was making to cruiseqe2 about the siting of the DME. For practical piloting purposes, the Jeppesen charts have everything you need. On the KLAX ILS-DME charts, for example, there's a note at the top giving the DME readings at the thresholds.

BTW, thanks for posting those three.

[aterpster]

Chris Scott:

On the KLAX ILS-DME charts, for example, there's a note at the top giving the DME readings at the thresholds.

Where on the chart is that? The only DME reading for the threshold that I see is in the profile view; for example 24R:

D2.0
IOSS

In any case once I pass the P-FAF (JETSA) I am not concerned about DME readings with a full ILS, including that threshold DME reading. That is for the GS-out fellow. My missed approach point is predicated on DA. The next DME fix I might be concerned about after DA is:

RAFFS
D15.1 LAX

[Chris Scott]

Hi aterpster,

What date is your chart? I'm now kicking myself for choosing KLAX as an example yesterday. The Jeppesen charts I found on the 'net had the note I described, but not the threshold DME marked on the profile (although you can fairly easily calculate it from the distance-to-go marks). I didn't note the dates. 24 hrs on, the only Jeppesens I can find (using the same search engine) are dated April 2002 (yes!) and are as you describe. Seems odd, but I guess the Jeppesen format is constantly evolving.

The plot thickens. In 2002, it appears that all the ILS-DMEs at KLAX were sited with the LLZ antennae of the ILS being used. However, a series of FAA charts (http://airportnavfinder.com/charts/KLAX/) dated 2011 show that the ILS-DMEs were by then all sited at the western LLZ antennae. So, for example, the ILS-DME for Rwy 06L is sited at or near the LLZ antenna for Rwy 24R (and shares the same frequency of Ch 22). That means you fly over it (DME=0) about 0.5 nm before the threshold. Not ideal, IMHO, but that may be how it is right now (probably a money-saving exercise).

Quote:
"In any case once I pass the P-FAF (JETSA) I am not concerned about DME readings with a full ILS, including that threshold DME reading. That is for the GS-out fellow. My missed approach point is predicated on DA. The next DME fix I might be concerned about after DA is:
RAFFS D15.1 LAX"

You are correct to say that, having intercepted the GS and checked your altimeter at JETSA (D8.2), there is no further requirement to monitor the DME, or your distance from touchdown. But I guess you agree it's always useful to monitor your track miles to go, for a variety of reasons, not the least of which are spacial orientation and energy management, particularly in a heavy jet. For example, you may be on a base leg; either self-positioning visually, or under radar. The easiest way to do that is with a DME like the one at Aruba, which is sited close to the touchdown point. But, otherwise, you need to know what the DME will read at touchdown.

[aterpster]

Chris Scott:

What date is your chart? I'm now kicking myself for choosing KLAX as an example yesterday. The Jeppesen charts I found on the 'net had the note I described, but not the threshold DME marked on the profile (although you can fairly easily calculate it from the distance-to-go marks). I didn't note the dates. 24 hrs on, the only Jeppesens I can find (using the same search engine) are dated April 2002 (yes!) and are as you describe. Seems odd, but I guess the Jeppesen format is constantly evolving.

KLAX 24R, dated July 12, 2012. It is current because the folks for whom I do most of my consulting work mantain a subscription for the 50 states. LAX is an airport that I am very familar with. It was my home base for most of my 27 years as an airline pilot.

I don't ever recall DME info being charted other than it is today (once the ILS DMEs were added, that is), but I tend not to recall such minuta. :)


The plot thickens. In 2002, it appears that all the ILS-DMEs at KLAX were sited with the LLZ antennae of the ILS being used. However, a series of FAA charts (http://airportnavfinder.com/charts/KLAX/) dated 2011 show that the ILS-DMEs were by then all sited at the western LLZ antennae. So, for example, the ILS-DME for Rwy 06L is sited at or near the LLZ antenna for Rwy 24R (and shares the same frequency of Ch 22). That means you fly over it (DME=0) about 0.5 nm before the threshold. Not ideal, IMHO, but that may be how it is right now (probably a money-saving exercise).

My memory is not solid on the location of the DMES either. We just used whatever was charted at the time. I do have FAA source for IAPs going back to 1998. I will look up old source for 24R and 6L later on.


"In any case once I pass the P-FAF (JETSA) I am not concerned about DME readings with a full ILS, including that threshold DME reading. That is for the GS-out fellow. My missed approach point is predicated on DA. The next DME fix I might be concerned about after DA is:
RAFFS D15.1 LAX"

You are correct to say that, having intercepted the GS and checked your altimeter at JETSA (D8.2), there is no further requirement to monitor the DME, or your distance from touchdown. But I guess you agree it's always useful to monitor your track miles to go, for a variety of reasons, not the least of which are spacial orientation and energy management, particularly in a heavy jet. For example, you may be on a base leg; either self-positioning visually, or under radar. The easiest way to do that is with a DME like the one at Aruba, which is sited close to the touchdown point. But, otherwise, you need to know what the DME will read at touchdown.

Because of my airline's route structure we usually arrived from the east. Visuals were never done arriving from the east. But, we also flew down from KSFO a fair amount, which brings you over SMO VOR for a visual weather permitting. At that stage of the flight we were constrained by speed assignments and turning onto the correct ILS for reference and regulatory compliance. I certainly didn't use DME for the north visual because it was, and is, predicated on the Los Angeles Coliseum (CVFP, Stadium Visual, Jepp 19-1).

As to IMCs, once passing the P-FAF, our concern was flying the ILS to DA without including the DME in our scan. We were highly standardized for all ILS IAPs on our system, many of which did not have DME in those days.

[Chris Scott]

Aterpster,

Thanks for that. I also grew up in a world where DMEs were not available for ILS procedures, and GS verification was predicated on L-NDBs (locator-NDBs) and/or 75MHz fan-markers. In the case of an initial-approach tear-drop like Aruba, the moment to start the base turn was decided by timing, on the basis of the forecast wind... Since then, you may agree, we all became thoroughly "spoilt" by DMEs and FMS displays. (However, not all our readers will be aware that the compelling nature of an FMS NAV display can get you into a lot of trouble if you fail to recognise map shift when present.)

If I'd known you were a veteran into KLAX, and with access to current charts, I could have saved myself a lot of trouble! Anyway, I've enjoyed trading insults. ;)

[aterpster]

If I'd known you were a veteran into KLAX, and with access to current charts, I could have saved myself a lot of trouble! Anyway, I've enjoyed trading insults. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wink2.gif

Here is a link to a PDF file with:

1. The current 24R/6L Jepp charts.
2. The source documents for April, 2002.
3. The current FAA charts.

Index of /LAX (http://www.terps.com/LAX)

As you can see from Item 2 indeed there were two separate DME transmitters for each runway end then. They are at the far end of each runway. (The FAA never has biased DME transmitters, so these had to be two separate transmitters.)

[Chris Scott]

aterpster,

Many thanks for the links to the current Jeppesen and FAA charts for KLAX ILS Rwy 06L and ILS Rwy 24R, and FAA documentation for the procedures prior to the resiting of the DME station used for the ILS 06L.

For others, and in confirmation of my previous post (http://www.pprune.org/tech-log/508340-teardrop-procedure-turn-course-reversal-3.html#post7711574), the latter show that the old DME for Rwy 06L was withdrawn, and the ILS 06L now uses the same DME as the ILS 24R. This means that, on the ILS 06L, the DME reading at the threshold changed from 2.1 (falling) to 0.5 (rising). That is because, whereas the old siting was beyond the far end of the runway (near the localiser antenna), the new one is 0.5 nm before the threshold (near the 24R localiser antenna). So the DME reads zero at a point 0.5 nm before the threshold, reads 0.5 at the threshold, and about 0.7 at the touchdown point.

The ILS 24R is unaffected, because the DME siting has not changed. The reading remains about 2.0 at the threshold, and about 1.9 at the touchdown point. The change of DME siting seems to have been repeated on the three other reciprocal runways at KLAX, halving the number of DMEs needed.

For those who haven't been following this discussion, the Aruba DME station is sited to the side of the runway, close to the touchdown point and the GS antenna. It has only one approach to serve: ILS Rwy 11. It reads 0.2 at the thresold and zero at the touchdown point.

Quote:
"(The FAA never has biased DME transmitters, so these had to be two separate transmitters.)"

Yes, the biased systems are a device in some other countries to enable one, airfield-sited DME not only to serve two reciprocal runways, but also to read zero at the touchdown points (see my post above (http://www.pprune.org/tech-log/508340-teardrop-procedure-turn-course-reversal-2.html#post7709713)). The DME is normally sited equidistant from the two thresholds, so that the bias does not need to be changed when the duty runway is switched. However, it can lead to a surprise, because the DME may be reading a negative value as you vacate the runway, or (briefly) during a missed approach.

[aterpster]

Chris Scott:

Many thanks for the links to the current Jeppesen and FAA charts for KLAX ILS Rwy 06L and ILS Rwy 24R, and FAA documentation for the procedures prior to the resiting of the DME station used for the ILS 06L.

That FAA chart for the current ILS 24R is quite a mess. The saving grace is that it is unlikely that anyone who flies into LAX uses FAA charts. :)

[Natstrackalpha]

Maybe that's so in http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gif Idaho, but it ain't so in ICAO Doc 8168 land

thats so funny