Question regarding failures of ILS equipment

MN_Flyer

MN_Flyer

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MN_Flyer
I posted this on another forum, but thought I would re-post here to see if anyone has any other ideas:

I am an IFR student and experienced something unexpected today on an ILS approach and would like to learn more about what happened.

Long story short, when identifying the localizer, the morse code seemed faster than normal and I did not think I heard the dashes, just the dots. My attention was divided and my instructor thought he had a positive ID, but agreed that it was difficult to hear.

I was vectored onto final and watched the localizer needle come alive. I was not able to center the needle though and it indicated a left correction was needed, despite my being right of coarse according to the GPS. 2miles to faf, I saw a flag briefly come up on the localizer needle and was ready to go missed. My instructor reported the aronious indications to the tower and they reset the localizer. After this, all was normal and I was able to get back on coarse just inside of the faf.

So.... How common is this type of failure of ILS equipment on the ground? I called the tower later and the controller said that this just happens sometimes. I think I would have chased the needle a little more had I not been /g. The field did not have radar service, so I was on my own.

Also, how is the morse code generated on a localizer? My theory is that one side of the localizer may have been inop or intermittent, so my indicator was showing only that frequency and was missing the other frequency to compare to. I wonder if the morse code is generated by a combination of the two sides of the localizer. This would explain why it sounded strange.

Thank you for any help that you can provide. I am glad that I experienced this and want to learn how to better protect myself from any similar failures in IMC in the future.
 
Only failures I've seen on ILS approaches were issues with the aircraft's equipment. I'm sure others will chime in, but my one comment would be that if you're not certain you've positively identified the localizer don't shoot the approach. The morse code should be loud and clear by the time you're within the ILS's service volume.
 
I watched my wife trying to navigate one day and the two of them were having difficulty. I findally couldn't stand it any more and pointed out the ID (which they had going continuously) was sending TEST. My wife should know better. She's an Advanced Class amateur radio operator and passed the test back when you had to know morse code.
 
A month or two ago I reported erratic readings similar to yours on the LOC BC 27L at PTK. But I wasn't, and am still not, sure whether the failure was with the ground equipment vs. a failure of the BC feature on my 480. I think I posted about it here, but I'm too lazy to find the thread now.
 
I've seen similar at airports where two different ILS transmitters shared a frequency and the tower forgot to manually select the one for the approach they cleared me for.

What airport?
 
matthammer said:
Only failures I've seen on ILS approaches were issues with the aircraft's equipment. I'm sure others will chime in, but my one comment would be that if you're not certain you've positively identified the localizer don't shoot the approach. The morse code should be loud and clear by the time you're within the ILS's service volume.
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Agreed tuned AND identified!!!
 
denverpilot said:
I've seen similar at airports where two different ILS transmitters shared a frequency and the tower forgot to manually select the one for the approach they cleared me for.

What airport?
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I think you hit it on the head. The airport was KSTC http://www.airnav.com/airport/KSTC

Upon further review, they DO have the same frequency for the localizers for runways 13 and 31. If I could listen to the morse code again, I'm sure I would hear the STC identifier for runway 31 instead of the BPM that I was trying to hear for runway 13. This would also explain why the indicator was showing left although I was off course to the right. My indicator was reverse sensing on the backcourse.

I did not realize that some localizer installations required the tower to switch between runways using the same frequency. Thank you for this information.
 
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matthammer said:
Only failures I've seen on ILS approaches were issues with the aircraft's equipment. I'm sure others will chime in, but my one comment would be that if you're not certain you've positively identified the localizer don't shoot the approach. The morse code should be loud and clear by the time you're within the ILS's service volume.
Click to expand...

I agree with your comment. I am glad that I was able to learn this lesson and still be here to seek advice about what happened. I expressed my concern to my instructor about 5 miles before the faf and we did not descend from there. I should have gone with my gut though when we weren't 100% positive that we had the localizer frequency positively identified. This would have given us much more time to troubleshoot and come up with a better plan of action. Still a situation that could have gone much worse. I will not be repeat this type of a test flight again.

Thanks again for your input everyone.
 
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MN_Flyer said:
I think you hit it on the head. The airport was KSTC http://www.airnav.com/airport/KSTC

Upon further review, they DO have the same frequency for the localizers for runways 13 and 31. If I could listen to the morse code again, I'm sure I would hear the STC identifier for runway 31 instead of the BPM that I was trying to hear for runway 13.

I did not realize that some localizer installations required the tower to switch between runways using the same frequency. Thank you for this information.
Click to expand...

WOW, Never heard of that before, learn something new everyday.
 
MN_Flyer said:
I expressed my concern to my instructor about 5 miles before the faf and we did not descend from there. I should ....
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I think you did fine. Five miles before the FAF and you haven't descended -- sounds safe to me.
 
MN_Flyer said:
I think you hit it on the head. The airport was KSTC http://www.airnav.com/airport/KSTC

Upon further review, they DO have the same frequency for the localizers for runways 13 and 31. If I could listen to the morse code again, I'm sure I would hear the STC identifier for runway 31 instead of the BPM that I was trying to hear for runway 13. This would also explain why the indicator was showing left although I was off course to the right. My indicator was reverse sensing on the backcourse.

I did not realize that some localizer installations required the tower to switch between runways using the same frequency. Thank you for this information.
Click to expand...
AFaIK, the controls are supposed to be interlocked so that there's no way to switch both on at the same time. If that's true, they obviously have a malfunction of some sort.
 
snoboy said:
WOW, Never heard of that before, learn something new everyday.
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Happens at just about every airport I've been to that has ILS's on both ends of the runway. Even Washington Dulles has this. Sometimes the controller will warn you if you're flying (even a visual approach) and they've got the ILS going the other way, but it's still incumbent on you to check for sure.
 
MN_Flyer said:
So.... How common is this type of failure of ILS equipment on the ground? I called the tower later and the controller said that this just happens sometimes.
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Heh, heh. Yeah, it happens every time the controller is napping. :rolleyes: Equipment failure? Since when is an alarm clock part of the ILS? :)

dtuuri
 
MN_Flyer said:
I was vectored onto final and watched the localizer needle come alive. I was not able to center the needle though and it indicated a left correction was needed, despite my being right of coarse according to the GPS. 2miles to faf, I saw a flag briefly come up on the localizer needle and was ready to go missed. My instructor reported the aronious indications to the tower and they reset the localizer. After this, all was normal and I was able to get back on coarse just inside of the faf.
Click to expand...

Reset capability in the tower? That seems unlikely. It's unlikely the tower would take any action at all when only a single report of a problem has been received, especially if the tower monitors the ILS and everything is in the green. If this runway had an ILS on both ends the wrong direction may have been selected, the "reset" may have been switching to the correct one. What airport?
 
roncachamp said:
"reset" may have been switching to the correct one
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I'm pretty sure that's what happened...

They just said "oh, we'll reset it"

Sounds better than "whoops! silly me, I had the wrong ILS selected! glad you noticed and did not blindly follow it to your death"
 
dell30rb said:
I'm pretty sure that's what happened...

They just said "oh, we'll reset it"

Sounds better than "whoops! silly me, I had the wrong ILS selected! glad you noticed and did not blindly follow it to your death"
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Sort of like when you oops an altitude by 300' and need to "cycle the transponder."

ATC: 345, I'm showing you 300' above your altitude, verify altimeter setting of 992.

Pilot: Altimeter set correctly, let me cycle the transponder and see if that fixes it.

(turn off transponder descend back to assigned altitude turn back on)

Pilot: How do I show now?

ATC: 345, currently showing assigned altitude

Pilot: *whistles innocently to himself*
 
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MN_Flyer said:
I think you hit it on the head. The airport was KSTC http://www.airnav.com/airport/KSTC

Upon further review, they DO have the same frequency for the localizers for runways 13 and 31. If I could listen to the morse code again, I'm sure I would hear the STC identifier for runway 31 instead of the BPM that I was trying to hear for runway 13. This would also explain why the indicator was showing left although I was off course to the right. My indicator was reverse sensing on the backcourse.

I did not realize that some localizer installations required the tower to switch between runways using the same frequency. Thank you for this information.
Click to expand...

Like others have noted, it's opposite directions. The interlocks switch antennas and the CW ID and there's monitoring gear in the Tower that continually indicates which transmitter is on air and if its transmitting... yadda yadda. It's a "system", but it requires a human look and confirm as they say "cleared ILS..." and it can get missed.

In some older towers, the switches are inconveniently placed and not right in the Local controller's view. (I saw that personally in the old/former BJC tower. They were significantly off to the side. During a runway change they had to roll the chair over or get up and flip the transmitter switch. The ATIS recording handset was WAY out of the way for the Ground controller. But I liked the laminated flip cards mounted above it for which letter they were on... :) )

There's probably some engineering rule about where the indicators have to be located, nowadays. Kinda like how far out of the pilot's view a GPS screen can be without remote annunciators.

If you could've copied the CW, it's fun to ask the controller if they want you to fly the backcourse. :) ;) :)

If I recall correctly, KLNK was handling downwind approaches to 18 simultaneously with us doing stuff to 36 on one of my days/evenings with Jesse alternating us with the ANG jets.

We had to ask them to flip it every approach. :)
 
I guess the FAA learns some things from human factors over the years.
When they built the new tower at DCA I commented it was the first one I'd ever been in that didn't have the FAA standard walnut grained formica countertops in it. It's sort of a cool deep blue color. Best view of DC out the controller's bathroom one flight below the cab. Also had the new cordless signal lamps.
 
Heard the controllers at APA asked to do some light gun stuff recently, and a transmission that the cordless one "didn't seem to be charged up", and they were going to hit the student and CFI with the corded one instead on their next lap around. Heh. Or they had a spare or something. Transmission didn't have enough detail but it was enough to make me chuckle at the bad design.
 
Not the first time Tower folks have done this, and probably won't be the last. A few years ago, I was flying with a client into Bedford MA (KBED). They'd been on 11 all day due to crummy weather, but the front came through, the air cleared, and the wind shifted to the northwest while we were on our way back. When we got here, they were running visuals to 29, but we asked Boston for the ILS instead (for training). They turned us to the base leg, and the needles came active, but didn't look right. Checked the Morse, and it was I-BED -- the ILS for 11 on the same freq as the ILS to 29 (I-ULJ). Tower had forgotten to throw the big switch to change the ILS. Quick call Boston Approach, a few seconds later the needles go dead, then come alive looking right and the Morse is now I-ULJ. Had we been in the goo and not checked the Morse, it could have been ugly.

Lesson Learned: Tune and identify.
 
I have a bad habit of leaving the Nav audio on all the time. (Drove Jesse nuts actually.) ;)

It stems from various things...

- ADF approaches long long ago.

- A distrust of 30 year old transmitters since I regularly am squeezed into little buildings fixing such things on tips of mountains... For um, "fun".

- A solid ability to tune out multiple audio sources in my head from ham radio contesting ops (Jesse would say, "you going to turn that off?" and I honestly wasn't even aware it was on, the DSP filter between the ears is well-adjusted).

- And a warm fuzzy feeling from continually copying Morse in my head as a background task (again, ham radio), instead of hearing static.

I made a conscious effort to turn then off after ID during the Instrument ride as to not annoy the DPE. He later commented that I was really vigilant about tune and identify which is a common problem area during Instrument rides these days with GPS-trained students.

I joked back that I was glad we'd yanked out ADF when it failed, with the winds aloft the day of my ride.

An NDB approach would have been a PITA. But I do kinda miss them. I doubt I'd miss them much in Actual but they're a butt kicker with the right winds in VMC as a skill builder.

He laughed. He probably has thousands of them in Actual in his logbook. I didn't ask. You could just tell from that faraway look that fleeted across his eyes for a moment.

Summary: I actualky like to listen to navaids. Maybe someday it'll save my ass. Maybe not. But I don't mind having that particular eccentricity.

If it's bugging the pilot in the other seat, I'll happily turn it off, just say it's annoying. I understand. I probably mentally tuned it out, but if it went noisy or silent it would be to me as noticeable as someone flipping off a light switch off in a dark room.
 
Ron Levy said:
If you are right of course, you really do need a correction to the left, so I don't see a discrepancy there.
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I said that wrong. I was left of course and it was indicating for me to correct left (until the flag flashed up). Thanks for all your posts on this forum. Good info for us others.
 
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