ILS question

Yep, seen this one before. Look at KADS - Addison, TX. Same setup. The localizer and glide slope are installed on both ends of the runway, but use the same frequency. Depends on which runway they are landing. If they are landing on runway 3, they turn that system on. If they are landing rwy 21, they turn the system for rwy 3 off and turn the transmitters for rwy 21 on. Notice that the IAF is different and the morse identifiers are different too.

Actually got into a 30 minute discussion with the FAA Inspector about this on my CFII initial. He threw out a "what if" on the morse code difference. I explained to him that KADS was the only system that I was aware of that had ILS glideslope and localizers on both ends of the same runway and the differences. Because, most of the time, almost all runways have one single ILS system and will make a backcourse approach specifically for using the less frequent side of the runway for landing. He asked....what if you are landing rwy 15 and the morse transmitting on the ILS freq is for rwy 33....do you still shoot the approach? Well, I said....only if you want to die. Then he told me about an incident where the ILS was transmitting for rwy 33 and they had switched to rwy 15 about 30 minutes earlier. He said that a few people got fired over that incident. Always Tune, ID, monitor...especially that ILS system.
 
There was a good post about this in the AOPA forums recently. Read this if you have access: http://forums.aopa.org/showthread.php?t=39537

If you can't access the above forum, I'll try and summarize...

Two pilots were flying into an airport (KMHT) while on VFR in VMC and practicing approaches (One pilot flying under the hood, the other acting as safety pilot). After the completion of a couple ILS approaches on RWY 35, ATC switched runways and told them to shoot the opposite ILS approach on RWY 17, which used the same frequency. The pilot had the correct frequency set and changed to the correct approach plates, but failed to identify the localizer. He was having difficulty getting on glide slope, and on the localizer course. He figured out that he was getting reverse sensing on the needle, but he couldn't figure out why this was happening. He went missed and everything was fine because they were VFR after all, but if he had been in the soup, things could have been much, much worse. The problem was that he failed to ID the localizer when ATC switched runways. He checked the frequency, which he had entered correctly, had the correct approach plate, but he failed to ID the localizer. When ATC changed runways, the guys in the tower forgot to flip the switch for the ILS from RWY 35 over to RWY 17.
 
Here is a quiz for you Cam.

Why is there a charted holding pattern over COE when nothing on the chart talks about that navaid being used?

How have you been doing? I heard you called Irene yesterday.
 
Wing_96 said:
There was a good post about this in the AOPA forums recently. Read this if you have access: http://forums.aopa.org/showthread.php?t=39537

If you can't access the above forum, I'll try and summarize...
Click to expand...


If you don't, the AOPA thread was a rehash of this one:

http://www.purpleboard.net/~purplebo/forums/showthread.php?t=2700

Although they diverge a bit with some info being posted on one and not the other.

The bottom line is that these are two completely separate ILS systems. If you check throughout the US, you'll see that there are just so many ILS frequencies - the same ILS frequency is used in many places - the only thing unusual with this situation is that they are at the same airport.

In normal (ILS in use for approaches) it should not be an issue. If ATIS is reporting "ILS 21 in use" for example, ATC has flipped the switch to bring the right one online. There's not a lot of material on this from the FAA; AFAIK it's not even discussed in the AIM, IFH or IPH. All I've ever come across are the two blurbs from the ATC handbook that are quoted in the two threads:

==============================
4-7-10.d. Advise pilots when the ILS/MLS on the runway in use is not operational if that ILS/MLS is on the same frequency as an operational ILS/MLS serving another runway.
==============================

and

==============================
4-7-13. SWITCHING ILS/MLS RUNWAYS
TERMINAL
When a change is made from one ILS to another or from one MLS to another at airports equipped with multiple systems which are not used simultaneously, coordinate with the facilities which use the fixes formed by reference to these NAVAIDs.
==============================

But you will notice from the charts that the identifiers of the two localizers are different - so the rule that we both tune =and= identify has special meaning.

BTW, another of these is at KFTG, just east of KDEN, where the ILS 17 and 35 share the same frequency.
 
Cessnaflyer said:
Here is a quiz for you Cam.

Why is there a charted holding pattern over COE when nothing on the chart talks about that navaid being used?

How have you been doing? I heard you called Irene yesterday.
Click to expand...

My answer would be that, that is the alternate missed approach holding point.

I have been doing well, just started working at XN Air now and stuff. Still looking to get my CFI....seems like its never going to happen lol. How about you? Whats new in Moses?
 
CameronF said:
My answer would be that, that is the alternate missed approach holding point.

I have been doing well, just started working at XN Air now and stuff. Still looking to get my CFI....seems like its never going to happen lol. How about you? Whats new in Moses?
Click to expand...

Ah good answer!

Doing well here in Moses. Hopefully I can do the flight portion of my CFII done here soon if the weather is good enough (How ironic is that). Then I should finally get my twin here in the next few weeks.
 
Cessnaflyer said:
Ah good answer!

Doing well here in Moses. Hopefully I can do the flight portion of my CFII done here soon if the weather is good enough (How ironic is that). Then I should finally get my twin here in the next few weeks.
Click to expand...

Sounds good dude. I am really pissed that Big Bend screwed me last year about the CFI ground school. I would have been so much better off had i been able to do the CFI while i was there. But i guess thats life, right?
 
Yep, I've seen this at KDET. I remember it very well, because they were vectoring me for the approach when the ILS was set for the other runway. I'm very glad I did the ident. It ended up being a big CF before they got me back around and the ILS switched over.
 
CameronF said:
Sounds good dude. I am really pissed that Big Bend screwed me last year about the CFI ground school. I would have been so much better off had i been able to do the CFI while i was there. But i guess thats life, right?
Click to expand...

Yeah that really sucks. Are you at least keeping current while you are over there?
 
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