ILS auto pilot coupled approach NA

NoHeat

NoHeat

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Why would they do this?

A nearby class C airport, KCID, uses rwy 27 more frequently than other runways. Starting in October, there has been a notam that autopilot-coupled approaches are NA below 1910 for ILS 27. That means no autopilot for the last 1040' of descent. I can't guess why they do that, especially since There is no similar restriction on the GPS 27 approach.

Any ideas?
 
Probably some sort of RF reflection or signal strength problem with the Localizer or Glideslope noted by a Flight Check aircraft, if it only affects the ILS and not the GPS approach.
 
denverpilot said:
Probably some sort of RF reflection or signal strength problem with the Localizer or Glideslope noted by a Flight Check aircraft, if it only affects the ILS and not the GPS approach.
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Ok, but why would it be okay to fly the approach by hand? It is the same signal either way. Maybe a momentary deflection of the CDI that the human eye would ignore, but would trick an autopilot?
 
NoHeat said:
Ok, but why would it be okay to fly the approach by hand? It is the same signal either way. Maybe a momentary deflection of the CDI that the human eye would ignore, but would trick an autopilot?
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High autopilot gain sensitivity in approach mode. It's probably a glideslope issue (interference).

If flying the approach with a flight director and you are stabilized, you should be able to "see through the flight director" and continue descending at the same approximate rate of descent if the glideslope suddenly deviates on its own and then recenters.
 
NoHeat said:
Ok, but why would it be okay to fly the approach by hand? It is the same signal either way. Maybe a momentary deflection of the CDI that the human eye would ignore, but would trick an autopilot?
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Pretty sure you answered your own question. Fluctuations of the GS signal could cause the autopilot to respond while humans are too slow to see or react.
 
Can't answer that question, but an ILS we flew regularly in the KC area had a very pronounced "wiggle" over the railroad tracks just south of the field. Pilots learned to ignore the temporary needle deflections that occurred, as they would almost immediately revert to normal indications, but the first time it happened could result in a pretty good rodeo ride for an unsuspecting pilot.

NoHeat said:
Ok, but why would it be okay to fly the approach by hand? It is the same signal either way. Maybe a momentary deflection of the CDI that the human eye would ignore, but would trick an autopilot?
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A new truckstop with the typical big sign was built this year about 10 degrees off course and 1.2 NM from the beginning of the runway. Maybe that did it?
 
At 1860 feet or so there's a slight anomaly in the glide slope that could affect an auto coupled approach. It's not an out of tolerance condition but it does force the issue of a NOTAM. 50 feet has to get added to the altitude the anomaly starts at for an aircraft on the approach. This NOTAM is not new. It's been on the books for a long time.
 
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wabower said:
Can't answer that question, but an ILS we flew regularly in the KC area had a very pronounced "wiggle" over the railroad tracks just south of the field. Pilots learned to ignore the temporary needle deflections that occurred, as they would almost immediately revert to normal indications, but the first time it happened could result in a pretty good rodeo ride for an unsuspecting pilot.
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IXD???
 
NoHeat said:
A new truckstop with the typical big sign was built this year about 10 degrees off course and 1.2 NM from the beginning of the runway. Maybe that did it?
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Could be reflecting RF, could be an unintentional RF radiator. (Is it electronic with a changing display?)

Or they may not know, the Flight Check aircraft just measure, they usually don't have time to guess what's causing it.
 
NoHeat said:
A new truckstop with the typical big sign was built this year about 10 degrees off course and 1.2 NM from the beginning of the runway. Maybe that did it?
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I can't imagine that would not allow the use of the autopilot. If that sign is too close it would alter the whole approach and not just the use of an autopilot.

Go up and try the approach in VMC with the autopilot coupled and see what happens:dunno: That is a strange one. I have never seen that note before.
 
Fast n' Furious said:
At 1860 feet or so there's a slight anomaly in the glide slope that could affect an auto coupled approach. It's not an out of tolerance condition but it does force the issue of a NOTAM. 50 feet has to get added to the altitude the anomaly starts at for an aircraft on the approach. This NOTAM is not new. It's been on the books for a long time.
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Hey! Guys! The answer right here! Speculation can stop now.
 
Greg Bockelman said:
True statement. But I bet a lot of guys around here don't know WHY the speculation can stop.
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You mean "because Ted said so" isn't reason enough? :dunno:;)

Glad to see you back around these parts, John.
 
Hi everyone! Yeah I don't contribute too much anymore but I do visit often. Lots of new folks with new perspectives. Auto couple NOTAMs aren't all that rare and the objective is to get them on the chart where the pilot can use them best as opposed to just in the AFD. They aren't a restriction for CAT 1 approaches but they are for higher levels of service. You might not see the issue that the equipment in the flight check aircraft reports when you fly it but it's there or it wouldn't get the NOTAM. Hi from Wisconsin!
 
It's worth noting that an issue Flight Check may find might be something that would only impact 1% of folks. But that 1% wouldn't want to hit a mountain. I, for one, am glad that they're out there checking these approaches for me. I have no desire to roll my own, especially into an unfamiliar airport in the middle of nowhere with mountains.

Y'all be careful out there. And next time you see that big ugly King Air (John, why on earth do they paint them such a bad scheme?), make sure to thank the folks for keeping you safe.

BTW, John, I owe you a beer.
 
The ILS Rwy 25 at Palmdale CA used to have a pronounced dip and recover about 300-400ft AGL. It would cause concern to students that would chase it, and then suddenly find themselves below glide path approaching DH?

I do not remember reading any restrictions on the approach about the dip, or autopilots.
 
Ted DuPuis said:
It's worth noting that an issue Flight Check may find might be something that would only impact 1% of folks. But that 1% wouldn't want to hit a mountain. I, for one, am glad that they're out there checking these approaches for me. I have no desire to roll my own, especially into an unfamiliar airport in the middle of nowhere with mountains.

Y'all be careful out there. And next time you see that big ugly King Air (John, why on earth do they paint them such a bad scheme?), make sure to thank the folks for keeping you safe.

BTW, John, I owe you a beer.
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I think the ugly paint scheme was designed to make people think the work wasn't all that much fun. The new scheme is better especially the orange accents.
Beer? Oh.....I like beer.
Can't say too much about Palmdale but I can say a lot about KCID. My operating initials are still on the NOTAM.
 
I haven't seen the orange scheme. Last time I saw one of the Flight Check planes was when I ran into you at MSN summer of last year with that ugly blue.

Y'all can't fool me, though. Looks like fun.
 
The Atlanta guys are flying the ProLine airplanes now complete with the new paint scheme. Neat airplane! I'm flying that big ol' desk right now and getting home every night which is just fine with me but I do fly the Mooney regularly.
 
I went from flying the Navajo, Commander, and Cheyenne regularly to flying a desk and the Aztec/310.

While the desk has crappy takeoff performance and an abysmal service ceiling, being home every night sure is nice.
 
Fast n' Furious said:
I think the ugly paint scheme was designed to make people think the work wasn't all that much fun. The new scheme is better especially the orange accents.
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As long as the orange is just "accents". Either that or we would accuse you of copycatting! :rofl:
 
Fast n' Furious said:
This NOTAM is not new. It's been on the books for a long time.
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Oops, Fast n' Furious is right. Before I started the thread I read the NOTAM that the autopilot-coupled approach is NA, and my attention was drawn to the date, which was in October.

I failed to notice that it was October of 2010. So it can't be the new truck stop reflecting RF signals. Must be something at least two years older that's causing the anomaly.

Thanks, Fast n' Furious. I take it from your post that you flew the flight check yourself, for that approach, and what you found was the reason for the NOTAM?

Anyway, if a NOTAM for an approach is so long-lasting, I'm wondering why the restriction on the approach isn't noted on approach plates?
 
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NoHeat said:
Oops, Fast n' Furious is right. Before I started the thread I read the NOTAM that the autopilot-coupled approach is NA, and my attention was drawn to the date, which was in October.

I failed to notice that it was October of 2010. So it can't be the new truck stop reflecting RF signals. Must be something at least two years older that's causing the anomaly.

Thanks, Fast n' Furious. I take it from your post that you flew the flight check yourself, for that approach, and what you found was the reason for the NOTAM?

Anyway, if a NOTAM for an approach is so long-lasting, I'm wondering why the restriction on the approach isn't noted on approach plates?
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Take at look at the NACO plate for the approach. Upper left hand portion of the briefing strip. Autocouple NA below 1910 or something like that....voila! NOTAM. And it's not a restriction....it's a NOTAM.
 
Fast n' Furious said:
And it's not a restriction....it's a NOTAM.
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Okay, thanks.

I guess the distinction between the colloquial term 'restriction' and a notam notation that something is 'NA' is a subtlety that's lost on me. I thought 'NA' was an abbreviation for 'Not Authorized', which to me sounds like I'm restricted from doing something.

So what is the regulatory impact of NA? Is it a strong regulatory statement that is a 'bust' if violated, or is it merely a remark that draws attention to a hazard? I'm just asking because I want to learn.
 
NoHeat said:
Okay, thanks.

I guess the distinction between the colloquial term 'restriction' and a notam notation that something is 'NA' is a subtlety that's lost on me. I thought 'NA' was an abbreviation for 'Not Authorized', which to me sounds like I'm restricted from doing something.

You are....you are restricted from using the autocouple function (if installed in your airmachine) below 1910 feet. The glideslope is available to you throughout it's service volume but the issue I mentioned earlier may cause your autopilot some unhappiness. You can certainly handfly all the way to DA however. Handflying BTW....is good.

Now if you had a note on the chart that said GS is unusable below 1910...that's a restriction to the service volume.

So what is the regulatory impact of NA? Is it a strong regulatory statement that is a 'bust' if violated, or is it merely a remark that draws attention to a hazard? I'm just asking because I want to learn.

[/QUOT
Not a hazard. Just something you Mr. Pilotguy should be aware of when coupled to the glideslope.

Regulatorily speaking...not my department. Thankfully.

I know, this flying stuff can be mighty confusing at times. Sometimes it's best not to read all that far into stuff. Sometimes.
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Thank you.

Another question: It seems to me that if the concern is how the autopilot will react to an anomaly in the glideslope, besides handflying the approach it should be okay to use the autopilot in a mode that doesn't make use of the glideslope, e.g., using the HDG and VS modes which rely only on flight instruments, unlike the NAV mode which relies on the navaid signal. Is that right?

I'm asking because the term "auto-pilot coupled approach" is mentioned in the FAA instrument procedures book, but I didn't see the term actually defined, so I don't know for sure how narrowly defined it is, in terms of what the autopilot does.
 
I'll humbly defer to the folks that can answer that question far better than I can. In the meantime all I can tell ya for sure is to spend some quality time learning what that chart is trying to tell you and fly that airplane like your life depended on it because it pretty much does. Have fun...be safe.

Sent from my Desire HD using Tapatalk 2
 
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