What does "RW 18 PAPI unusable beyond 7 deg right of centerline" mean to you?

What does "RW 18 PAPI unusable beyond 7 deg right of centerline" mean to you?

  • The PAPI will not be visible at greater than 7 deg offset from centerline

    Votes: 13 17.1%

  • The PAPI will be visible on that side, but may not work right (like the angle may not be accurate)

    Votes: 32 42.1%

  • The PAPI will be visible on that side, but can't be followed because of an obstacle (tree, etc.)

    Votes: 19 25.0%

  • I really have no idea, I've never noticed this kind of note before

    Votes: 5 6.6%

  • Other (please explain in comments)

    Votes: 7 9.2%
  • Total voters
    76
RussR

RussR

Final Approach
Joined
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Location
Oklahoma City, OK
Display Name
Russ
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In the Chart Supplement, or occasionally in NOTAMS, you will see a restriction on the VGSI (PAPI, VASI), something like "RW 18 PAPI unusable beyond 7 deg right of centerline." In my day job, we are the ones who determine that restriction and cause it to be published.

So I know what it is intended to mean.

But I'm doing some informal research *, and would like to know what the general flying community THINKS such a note means. I've listed a few poll options, please vote as appropriate. Unless you really can't help yourself, PLEASE don't look it up before answering **.

And in the comments, please let me know if and how this would affect your flying (traffic pattern, instrument approach, day/night operations, etc).

* I have some "opinions" about these restrictions, but need to know what pilots think they're for before I share what those are.

** Note - I couldn't find a reference in the usual pilot manuals about such a restriction. I looked in the PHAK, IPH, IFH, AIM, Chart User's Guide, Chart Supplement legend, and maybe a few other places and couldn't find any discussion or even mention that such restrictions even exist. So I imagine most people don't know about them or what they mean, but I could be wrong. But if you do know of a reference that is a normal pilot manual, please let me know.
 
I guess "normal" is in the eye of the beholder, but I think the only place it's discussed is in the FAA Order that discusses NOTAM contents, 7930.2.
 
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RussR said:
In the Chart Supplement, or occasionally in NOTAMS, you will see a restriction on the VGSI (PAPI, VASI), something like "RW 18 PAPI unusable beyond 7 deg right of centerline." In my day job, we are the ones who determine that restriction and cause it to be published.

So I know what it is intended to mean.

But I'm doing some informal research *, and would like to know what the general flying community THINKS such a note means. I've listed a few poll options, please vote as appropriate. Unless you really can't help yourself, PLEASE don't look it up before answering **.

And in the comments, please let me know if and how this would affect your flying (traffic pattern, instrument approach, day/night operations, etc).

* I have some "opinions" about these restrictions, but need to know what pilots think they're for before I share what those are.

** Note - I couldn't find a reference in the usual pilot manuals about such a restriction. I looked in the PHAK, IPH, IFH, AIM, Chart User's Guide, Chart Supplement legend, and maybe a few other places and couldn't find any discussion or even mention that such restrictions even exist. So I imagine most people don't know about them or what they mean, but I could be wrong. But if you do know of a reference that is a normal pilot manual, please let me know.
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Didn’t do the poll. If some of those ‘wills’ had been ‘may’ I might have. To me it means beyond 7 degrees it may not be safe to rely on it.
 
Huh. I reckon it would mean you should not use the PAPI if you're more than 7 degrees to the right of the centerline.
 
It may not work AND be obstructed. That wasn't an option.

For me, all I know is that if I'm >7º right of center, don't rely on the PAPI for guidance. Why is really irrelevant. Could be equipment issues, could be obstruction issues, could be both, could be neither and something else entirely. Sort of like the note on the charts in NE Minnesota/Isle Royale, MI. Does it really matter why?

As far as how it affects me, I don't bother with PAPI's during day VFR, so flying the pattern or what not because of a wonky PAPI is a yawner. I don't even turn them on at our field. And I better not be more than 7º off when on an instrument approach.
 
I would say answer 1, 2, or 3. The PAPI is unusable either because it is not visible or inaccurate. As a pilot, I can't think of anytime or reason I would be referencing the PAPI unless I was aligned on final. Also, how do I determine 7 degrees from centerline?

I would classify this like an obstruction NOTAM, just noise, part of which makes the NOTAM system "garbage" as the chair of the NTSB once called it. Yes you are required to report something that is out of tolerance just as we do at the airport, but as a pilot what am I supposed to do when I read this NOTAM. Is this NOTAM going to alter my plans? Am I not going to use this runway or even the PAPI?
 
Flying in, I would be more than normal striving to be on runway centerline. I would be inclined to fly the approach as if the PAPI did not exist.

Expectations of the nature of the problem?

Most likely, the mower clipped the lens, and that end is cracked.

Next, a small tree top just outside the airport property is obstructing visibility.
 
I'd say one of the first two. The PAPI is unusable. It may be visible or not, but you can't use it. I wouldn't make any assumption about the airspace or obstacles or safe approach angles because the note doesn't say anything about those things.
 
If I saw that I would assume that the data from the PAPI isn't reliable beyond 7 degrees even if I could see something. The reason the data isn't reliable doesn't really matter. So I would not use it as a reference right of centerline.
 
EdFred said:
As far as how it affects me, I don't bother with PAPI's during day VFR, so flying the pattern or what not because of a wonky PAPI is a yawner. I don't even turn them on at our field. And I better not be more than 7º off when on an instrument approach.
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Look at 91.129 Operations in Class D Airspace (e) (3). You may argue this only applies to large or turbine-powered aircraft, but that is not what it says.
 
It means when they were flight checking it the guy doing it got a text from his tinder date and looked down to answer it just as they were passing through 7 degrees. Told the pilot we gotta go around and do it again. Pilot said nah, we’re running’ late. Just unusable it
 
How does a pilot know what 7° looks like from the cockpit?

The only thing a pilot can be sure of is whether they are on centerline, and which side of it they are off to if not. So, fly the approach on or left of CL; no problem. Anyone really curious can set up for a stabilized approach on CL, then drift right to see how the sight picture and VASI change, and when.

7°≥ 6°= 1/60th of a circle = 1/15th of a right angle -- not much help there.

Runway dimensions are known. You don't specify the airport, but I learned to fly at KHWV, where the runways were unusually wide for the traffic (my CFI was sure to take me skinnier places). Both runways were 4200 ft long; one 150' wide, the other 100'. For small deviations from centerline (and I suggest single-digit degrees qualifies), sin(x)≈x [rad]; 6° = 1% of runway length = 420' which is about 3 widths of the wide runway at the approach end, 4 widths of the narrow[er] one, in parallax with the departure end. Not precise, but its something.
 
Like many others, I read as don't use it if much off centerline. Could be any of the reasons in the poll.
 
I chose option 2, but I mostly think of it as "don't use the papi unless lined up on the centerline". I guess I am not inquisitive enough, as I don't really care the reason why the papi is unusuable. :)
 
Day vfr (flying under Sport Pilot rules) papi is always out of service or something... I just would ignore the NOTAM.
 
FYI...at a mile from the runway, 7 degrees off the center line would only be a little over 600 feet...at 1000 feet, it would be 121 feet....
 
I voted for "other" because I think it could be (a) or (c), though I assumed (c) was the most common reason.

I am not sure if (b) is physically possible, based on how a PAPI works.
 
Gilbert Buettner said:
Look at 91.129 Operations in Class D Airspace (e) (3). You may argue this only applies to large or turbine-powered aircraft, but that is not what it says.
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I am not aware of any class D airports with pilot controlled PAPI's during the day.
 
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MauleSkinner said:
It’s not about “pilot controlled,” it’s about “bothering with.”
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I don't bother with them because when I do glance at them when VFR I don't see any red until power has been pulled to idle.
 
Well I'm glad I did that poll, because the results are pretty interesting, in that very few people actually know what the restriction means, and for all I know the ones that did may have been guessing. This is not surprising since the only place I've found it mentioned is in the NOTAM regulation, 7930.2 (thanks @midlifeflyer!)

The correct answer is the first one. If the PAPI is published as unusable outside of a certain angle from centerline, it will not be visible outside that angle. That is typically because we found obstacles outside of that angle that did not allow a safe approach. When this happens, the ground tech will install/adjust internal baffles in each light so that the lights aren't visible beyond that angle, and therefore they can't be followed (obviously).

The standard service volume for a PAPI system is 10 deg right to 10 deg left.

My "issues" with such a restriction are 1) while publishing the restriction is technically correct, I can't see how it helps anybody, especially since 2) apparently few people even know what it means. Since the lights aren't visible in the unusable area, you are unable to follow them anyway. And of course you have to get over to centerline eventually on any landing, so at some point you will see the lights and can follow them. There are a few TERPS considerations with an offset approach being outside the usable service volume, but that would be transparent to pilots as well. And as several have said, there's no (realistic) way for a pilot to know how far off centerline they are in degrees anyway.

A related story. I was inspecting a new installation of PAPI lights. The lights were "visible" the full 10 deg either side of centerline, but that's only because it was winter and the trees didn't have any leaves on them. On the left side of centerline we were seeing the lights through the branches of a tree! Obviously that wasn't going to work, so we had the tech baffle them to 4 degrees left of centerline, and that's how the restriction reads now. The airport manager was concerned that such a restriction was going to somehow limit their operations, but really I can't think of any impact such a restriction would have on an airport (he was ready to run out there with a chainsaw right then, until we pointed out that the offending tree appeared to be on private property).

Thanks all, that was enlightening (pun somewhat intended).
 
RussR said:
My "issues" with such a restriction are 1) while publishing the restriction is technically correct, I can't see how it helps anybody, especially since 2) apparently few people even know what it means. Since the lights aren't visible in the unusable area, you are unable to follow them anyway. And of course you have to get over to centerline eventually on any landing, so at some point you will see the lights and can follow them.
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All that would appear to apply to all the navaid “unusable” beyond a certain range NOTAM, including those indicating degrees off making a LOC or DME signal unusable or in some way restricted. Even not knowing why or how it’s been restricted, I’m not sure that the information is worthless. When I see any one of those, I’m like, “ok, that’s nice to know.” I may know the reason or I may not, but at least I know that if I happen to notice something seems off, it ain’t me. So I’m a bit on the fence about need.

If it didn’t bloat the NOTAM system even more, it would be nice to have a short explanation, although sometimes there’s another NOTAM where we can put 2 and 2 together. We’ve seen a number of variations due to some runway work here. (My fav was when our ILS LOC was unusable but the glideslope was :D).

Maybe the answer is a blurb about it in the AIM or other ”normal” pilot publications rather than tossing it?
 
I don't know why a navaid (visual or radio) may be unusable under some conditions, I don't care. I read it as "don't use it under those conditions, don't trust the data under those conditions". In this specific case, I'd read it as "approach from left if possible, once established, stay on centerline (as we should anyway), if I drift right and I need the PAPI, go around". There was one airport we used for training in NJ where the PAPI was useful during day VFR due to powerlines. You really didn't want to be low! There were many lessons in that lesson about pre-flight planning for airports, obstacle clearance, PAPI and glideslope.
 
midlifeflyer said:
All that would appear to apply to all the navaid “unusable” beyond a certain range NOTAM, including those indicating degrees off making a LOC or DME signal unusable or in some way restricted. Even not knowing why or how it’s been restricted, I’m not sure that the information is worthless. When I see any one of those, I’m like, “ok, that’s nice to know.” I may know the reason or I may not, but at least I know that if I happen to notice something seems off, it ain’t me. So I’m a bit on the fence about need.
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I think there's a fundamental difference, though. With a VOR/LOC/DME restriction, you may very well receive the VOR/LOC/DME when in the restricted areas (in fact, you almost certainly WILL receive something). It's just not accurate for various reasons.

But with a PAPI or VASI, within the restricted area, you can't "receive" (see) the signal at all. There's nothing to follow, therefore there's no misleading information. It's actually the best type of restriction since there is no possibility of using inaccurate information.

midlifeflyer said:
If it didn’t bloat the NOTAM system even more, it would be nice to have a short explanation, although sometimes there’s another NOTAM where we can put 2 and 2 together. We’ve seen a number of variations due to some runway work here. (My fav was when our ILS LOC was unusable but the glideslope was :D).

Maybe the answer is a blurb about it in the AIM or other ”normal” pilot publications rather than tossing it?
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Restrictions like this should be in the Chart Supplement, since typically they're not going away any time soon. While a NOTAM may be temporarily appropriate (as in, right after we discover it), it should be then put into the CS.

I wonder if providing a reason actually makes the situation less clear. If the note said "PAPI unusable beyond 7 deg left of centerline due to trees", that may imply it's still visible, just you can't use it.
 
RussR said:
The airport manager was concerned that such a restriction was going to somehow limit their operations, but really I can't think of any impact such a restriction would have on an airport (he was ready to run out there with a chainsaw right then, until we pointed out that the offending tree appeared to be on private property).
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That's my kind of manager! Sounds like something I would do too! Tree in the way, let me get my saw!
 
Russ: In my thinking, a short reason why it's unusable is actually a big help. You wouldn't need to go into any real details, but a descriptor such as: "due to obstructions, or construction, maintenance, damage or threshold displacement" would be quite helpful. It would give one a clue on where some extra vigilance is needed.
 
Craig said:
Russ: In my thinking, a short reason why it's unusable is actually a big help. You wouldn't need to go into any real details, but a descriptor such as: "due to obstructions, or construction, maintenance, damage or threshold displacement" would be quite helpful. It would give one a clue on where some extra vigilance is needed.
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I would also add, knowing that @RussR has the power to change these things:lol:, verbiage to he effect that the PAPI is baffled to block usability beyond 7 degrees right of centerline would be more useful.
 
The correct answer is not there.

The PAPI should not or cannot be used if you are more than 7 degrees to the right. It gives no information about the visibility or about the cause. Unusable has multiple possible causes, all of which come back to "don't use it."
 
bflynn said:
The correct answer is not there.

The PAPI should not or cannot be used if you are more than 7 degrees to the right. It gives no information about the visibility or about the cause. Unusable has multiple possible causes, all of which come back to "don't use it."
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Who, if anyone, are you responding to?
That's basically what I said, but you wrote the TL;DR version.
Cap'n Jack said:
I don't know why a navaid (visual or radio) may be unusable under some conditions, I don't care. I read it as "don't use it under those conditions, don't trust the data under those conditions". In this specific case, I'd read it as "approach from left if possible, once established, stay on centerline (as we should anyway), if I drift right and I need the PAPI, go around". There was one airport we used for training in NJ where the PAPI was useful during day VFR due to powerlines. You really didn't want to be low! There were many lessons in that lesson about pre-flight planning for airports, obstacle clearance, PAPI and glideslope.
Click to expand...
 
bflynn said:
The correct answer is not there.

The PAPI should not or cannot be used if you are more than 7 degrees to the right. It gives no information about the visibility or about the cause. Unusable has multiple possible causes, all of which come back to "don't use it."
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Since the question was, what does this mean to “you”? I would agree.

But the answer to what it means to the FAA is there.
 
Craig said:
Russ: In my thinking, a short reason why it's unusable is actually a big help. You wouldn't need to go into any real details, but a descriptor such as: "due to obstructions, or construction, maintenance, damage or threshold displacement" would be quite helpful. It would give one a clue on where some extra vigilance is needed.
Click to expand...

As an airport manager, I've said the same thing. For example, I've thought it would be helpful to add a descriptor to a Runway Closure, closed due to construction, emergency, disabled aircraft, etc. Unfortunately neither @RussR nor I have enough pull with ICAO and the FAA to change NOTAM formatting.
 
While it's nice to know the "why", it's not really essential.
 
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