Non-standard ILS?
 

What does "non stadard ILS" imply on the jeppesen charts? :hmm:

It could have a DH higher than 200ft or steep GP etc. Which plate you are referring to?

Or it could be an offset localiser (in which case, technically, it isn't actually an ILS).

MUC 26L/R is labelled as non standard. It has 3° GP, 200' DH and runways are separated enough for independent paralell approaches. Only thing unusal is that DME is not colocated with GP but then it's the same as on 08R/L and those 2 ILSes are considered to be standard. Also procedure didn't change much over the years and all of a sudden I found out I might have been flying non standard ILS all the time.:uhoh: Can anyone shed some light on this?

If there is ILS on both ends of the runway, DME should be sited exactly midway between the two GP aerials. If it's not, then it would be non-standard and there should be a note on the plate saying DME does not give range to touchdown point(or similar)

While I've noted use of the word "should" in the above quote, this sounds like a country-specific policy. I've never heard of it in this part of the planet and, as far as I'm aware, none of our ILS approaches have ever been considered as "non-standard". For many years, we had a DME that wasn't sited very conveniently, but have always provided a DME/Altitude table - and continued this practice after solving the problem by installing DME at each GP.

I'm no technical expert, but as far as I know in the UK, an airfield with ILS on both ends of its runway which both operate on the same frequency (transmitters being interlocked so only one transmits at any time) has a single DME which is adjusted so that instead of reading zero at the transmitter, it reads zero at each touchdown point, hence it's centrally placed between GP aerials. Course if your ILS has different frequencies at each end, then you'll need two DME's as well as they'll be 'frequency paired'.
Sorry if it sounds complicated, but although you obviously need LLZ and GP on both ends, if they're the same frequency you really only need one DME. Maybe it's airport operators economising.

I'm a procedure designer, among other things which do not include being a navaid tech. Thus I have no idea as to how a centrally-located DME can be adjusted so that it produces a "zero" reading at each THR. Are there any navaid specialists out there who could explain this to me?

OzEx, old chap, how you doing?
I'm no techie either, but while we wait for someone who is - I find it sufficient to understand that the DME equipment merely measures the time for the DME interrogation and response, and then does speed x time calculations to work out distance. Relatively straightforward, then, to "frig" ("introduce a correction factor to"!) the calculation the equipment does, in order to get the DME to read zero at THR.

A little more techie than keithl -

The aircraft end of the DME sends out a signal, which a short time later arrives at the ground transponder. The ground transponder waits 50 microseconds (I think), then replies. The aircraft gets the reply a short time later.

The range calculation is as follows: measure the time duration from initial transmission to final reception back at the aicraft, subtract 50 microseconds, then divide the answer by two. This is converted to distance like keithl says.

If you get the ground station to wait only 10 microseconds before sending a reply, the aircraft gets the signal 40 microseconds sooner, and thinks that it is closer to the ground station. 6000 meters closer actually!

So you can put the DME ground station abeam the middle of the runway, and reduce the inbuilt time delay so the aircraft thinks the ground station is actually at the near end of the runway.

HTH,
O8

What a wonderful forum of technical knowledge we have here! I ask a question from Port Morbid and get responses from Scotland and NZ! :ok:

G'day keithl! Been a long time since we've compared notes on a subject in here. Apart from phone line hassles that severely limit my online time these days, my complaints are few. Still sweating by day and night! :E

Thanks for that Oktas8. I'd actually started thinking about it at work today and had come to the same conclusion but couldn't quite believe it. Now I see the practicality of it, I shall make enquiries of our own techie "stars" to see if they know anything about it. Provided that they can keep the DMEs serviceable (not a forgone conclusion :{ ), it would massively simplify things for us here.

My thanks to both of you! :)

Great; I knew what it did but didn't know how to explain it!
This system as I said is in common use in the UK.

:hmm:

Caution.

Is it not a cunning device on the part of Jeppesen to draw your attention to the fact that the decision height and RVR for the ICAO ILS category are not standard?
It is axiomatic that in this case the 'minima', for want of a better word, will always be higher than either the ICAO or the US standard categories?

:cool:

Following on from the previous discussion I have the following question.

Consider an airfield that has 2 ILSs (same freq) and a common DME transmitter sited half way between the runways. The DME system, I understand, has an electronic "adjustment" so that the DME for each ILS reads zero at the threshold. So far so good.

However, if the SID for a runway in use, uses the ILS DME to initiate a turn where is the DME measured from? I assume the electronic "adjustment" is effectively a negative correction (say 0.7 mile) so that at touchdown the DME reads 0.

But after lift off, the aircraft flies towards the DME transmitter and then flies passed it before initiating the turn so if the turn is at say 2.0 DME - is the effective turn taken at 2.0 + 0.7 dme passed the DME station? (which is actually 3.4 DME from the start of the landing threshold)

HP

If the DME is located at the mid point of the runways, I'm struggling to think how you would be flying towards it after take off on a sid!:confused:

That aside,I would imagine the SID designers were made aware of the DME location and characteristics and drew the sid and calculated distances accordingly.(i.e. any distance corrections are accounted for in the turning point distance).:ok:

The question is basically this (and I apologise for if I did not make it clear).

Once airborne the turn is initiated at say 2.0 dme based on the ILS DME (of the landing runway). Assuming the DME is exactly between the landing thresholds (to read 0 when landing) where EXACTLY does the turn begin at?

I know it is intiated when the pilot's DME reads 2.0 but what does that mean in practise? Is is 2.0 DME from the landing threshold of the runway in use or is it 2.0 DME from the landing threshold of the runway not-in-use? If a constant electronic "adjustment" of the DME is used (say 0.7 in this example) and all readings are reduced by this same 0.7 DME then the turn ACTUALLY begins at 2.0 from the landing threshold of the runway not-in-use.

And, if we have a long runway and a small aircraft - you will actually fly towards the dme transmitter!

HP

In our case we have designed the procedure so that we intend the aircraft to commence its turn at 2.5 DME from the upwind threshold, ie the aircraft equipment will start to count upwards from this point, having counted down to zero from start of TOR.

Heh heh, never thought of it that way. Good point well made!:}

president - "What does "non stadard ILS" imply on the jeppesen charts?"

I have also noticed this on some charts eg ILS 23R at DUS.

It tells me that I should plan ILS 23L as this is the preffered rwy for landing. ATC could however give us 23R.

the ATIS just says RWY 23 in use.


Another point is if we consider a complete comms failure. As the wind is the same for both 23L and 23R and both have ILS it takes the confusion out of which rwy to use when 'non standard' is written on one of them.

Well, regarding the MUC non-standard ILS for rwy 26R, I was enlightened the other night.

During LOFT session in A320 sim, we developed G+Y dual hydraulic failure while flyng from DUS to NUE. As FRA was lousy weatherwise, we decided the diversion to MUC was the best solution. There were no ILS MUC charts in our Jeppessens, so we took out ones from sim´s chart library. They turned out to be LIDO´s and printed on them was the solution to ILS mistery:And that´s all there is to it.

It seems that 11 feet more on threshold crossing was enough for LBA to qualify the ILS as non-standard and Jepp dully passed the info without further explanation. And with 4000m of runway available and flying ATR, I was never worried about TCH. At least now I know where too look next time i´m faced with non-std ILS caption.