In the FAR/AIM?

[tboy]

Have a question. Regarding operation below DH or MDA, during IFR flight. My CFI once told me that he read in the FAR/AIM that if you had a visual on PAPI (Precision Approach Path Indicator) it was the same as if you had visual on the VASI (visual approach slope indicator), and could decsend to 100' above touchdown zone elevation. It says nothing about PAPI's in FAR part 91.175, only mentions VASI's and REILs.

Alright now to the question. Does anyone know where it is he was talking about. Or was he seeing things?

Thanks

Troy

[FlyNHighNFast]

Have a question. Regarding operation below DH or MDA, during IFR flight. My CFI once told me that he read in the FAR/AIM that if you had a visual on PAPI (Precision Approach Path Indicator) it was the same as if you had visual on the VASI (visual approach slope indicator), and could decsend to 100' above touchdown zone elevation. It says nothing about PAPI's in FAR part 91.175, only mentions VASI's and REILs.

Alright now to the question. Does anyone know where it is he was talking about. Or was he seeing things?

Thanks

Troy

 

Going below MDA for any flight segment will get you killed eventually. That said, I could not find anything in 91.175 on PAPIs either, but like the VASI, if you on or above the glide slope, you don't have to worry about hitting anything.

[PhotoFlyer]

If you can see the VASI or the PAPI then you should be able to see the approach lights. If you can see the approach lights (essentially the runway environment) then you can descend an additional 100 feet.

Edited July 13, 2007 by PhotoFlyer

[Collective Down!]

If you can see the VASI or the PAPI then you should be able to see the approach lights. If you can see the approach lights (essentially the runway environment) then you can descend an additional 100 feet.

 

Not all runways have approach light systems, so don't expect to see a VASI and approach lights to welcome you home at the same time. Not all of them have VASIs either for that matter.

 

If you can see the approach lights, and ONLY the approach lights you can descend to 100 feet above the touchdown zone elevation (not to be confused with: descend another 100 feet below MDA) unless you have the red terminating bar (ALSF-1 system) or red siderow bars (ALSF-2 system) in sight... In which case you can go even lower. It's not fair to say that seeing the approach lights is "essentially having the runway in sight" because some of those approach light systems extend out a half mile from the runway.

 

According to 91.175, if all you can see is the VASI, then that meets one of the runway environment requirements, so you can keep truckin' as long as the required visibility is there, you can make normal maneuvers to land, and you can land in the touch down zone if you're 135 or 121.

 

To answer the original question: "Is a PAPI a VASI?"... Well I think it's safe to assume that YES a PAPI is a visual approach slope indicator. Look up Visual approach slope indicators in the AIM (2-1-2) and it will list 5 types of visual approach slope indicators....

a) VASI

PAPI

c) tri-color

d) puslating

e) alignment of elements

[joker]

Well I think it's safe to assume that YES a PAPI is a visual approach slope indicator.

 

Sorry, have to disagree.

 

Think VASI specifically means VASI.

 

Look at AIM (2-1-2) carefully. Your list states 5 kinds of VGI (Visual Glideslope Indicators). Of which PAPI and VASI are two. Not 5 kinds of VASI.

 

I'm not at home, so don't have my usual references, but consider this:

 

With a PAPI it is possible to have only one light showing. The FAA don't want you to continue (PAPI in sight) with only one light showing. Add to that, if you have only one light on a PAPI you are below glideslope anyway and should be consider correcting or going around.

 

VASIs won't ever have only one light showing.

 

More about this later.

 

Joker

Edited July 13, 2007 by joker

[EnglishBob]

With a PAPI it is possible to have only one light showing. The FAA don't want you to continue (PAPI in sight) with only one light showing.

...

VASIs won't ever have only one light showing.

 

That's not quite right.

 

A PAPI has 4 lights, and always shows 4 lights whether they are all white (above GS) to all red (below GS) [AIM 2-1-2 paragraph b. , fig 2-1-5]

 

The tri color and puslating systems are also termed in the AIM as visual approach slope indicators (VASIs), and both of those types have only a single light.

 

It seems odd that 91.175 would exclude a PAPI which is easily as good in restricted visibility as a single light tri-color VASI and PVASI.

 

Perhaps the term "visual approach slope indicator" in 91.175 could or should actually be "visual glideslope indicators"? Apart from them being separated in the AIM could you not say that an 'approach slope' and a 'glideslope' are essentially the same thing? They aren't defined in Part 1 of 14 CFR though.

 

(I have just started studying this in my home ground schooling as it happens)

[Collective Down!]

Look at AIM (2-1-2) carefully. Your list states 5 kinds of VGI (Visual Glideslope Indicators).

 

Joker

 

 

Good catch... I was trying to use the internet version of the AIM last night and it was hard as hell to figure out which are sub-paragraphs. After looking at my printed AIM, that's alot easier to see.

 

Being that a PAPI is a VISUAL GLIDESLOPE INDICATOR, I'll have to succeed to Joker and agree that a PAPI is not a VASI. Who knows if the FAA meant to include or exclude the PAPI though.

 

Now, the tri-color and pulsating systems say they are "visual approach slope indicators"... Are those included?

[joker]

Well, back at home now. Done some more research, and it seems that I stand to be corrected.

 

PAPIs of course do have all lights showing at all times. The Note in the AIM is more specifically at the tri-colour light, I suppose. Its been too long since I discussed this to shoot from the hip!

 

That then deflates my main arguement about the reason why PAPIs might not be included!

 

However, it still remains that the aim does list each of the items as VGIs and sub-lists VASIs and PAPIs as distinct items. Indeed often that distinction is made elsewhere.

 

BUT, in an AC regarding Cat I and Cat II minimums, it lists VASIs and PAPIs as both being classified as Visual Approach Slope Indicating systesm. It also says that this classification is defined in FAA Order 8260.3 (TERPS).

 

Thus, it would seem like the use of 'visual approach slope indicator' refers not to the specific electro-optical equipment we call a VASI, but to an entire set of equipment in this classification.

 

AC 120-29A Criteria for Approval of Category I and Category II Weather Minima for Approach

 

Visual Glide Slope Indicator

An electro-optical device that provides a visual indication of vertical position in

relation to a defined glidepath. Specific systems in this classification include the

Visual Approach Slope Indicator (VASI), the Precision Approach Path Indicator

(PAPI), and Precision Landing Aid Slope Indicator (PLASI). This term is

defined in FAA Order 8260.3, U.S. Standard for Terminal Instrument Procedures

(TERPS).

This is the only FAA source that I have found so far that defines the two systems in the same classification.

 

I would like to find that TERPS reference just for piece of mind as there is strong evidence that the two systems are not classed together. For the meantime though, I will go with that definition above. i.e , PAPI and VASI are both acceptable to meet 91.175!

 

Maybe someone can trawl through TERPS and get that reference.

 

Appologies for any confusion.

 

Joker

 

Edit after CollectiveDown's post!: It just shows how limited the FAR is. To be honest, I really don't know. The answer must be out there, as the question has been asked before. Just finding that 'official' source is the secret. The AC is probably about the most official so far.

Edited July 13, 2007 by joker

[RockyMountainPilot]

No, a Papi in sight does not allow you to descend. All lights that allow you to descend are comprised of two or more seperate stations. If you see a single strobe, are you going to assume its a REIL and the other one is inoperative? If you see a single green light, are you going to assume it is a tri-color system? You might end up landing at a party store, or on an intersection.

 

And to descend below 100 feet above TDZE, one must also insure the red terminating bars or the red side row bars are also distinctly visible and identifiable. So, you can have the rabbit in sight and go down to 100 feet above TDZE, but you can't descend below that until you have the red terminating bars or the red side row bars in sight as well.

[joker]

My god,

 

How funny. I seem to be going back and forth (up and down) like a yo-yo on this. Sorry.

 

Just got back from the pub and I just read the extract from that AC which I quoted.

 

I noted the heading was: Visual Glide Slope Indicator , not VASI. This would agree with the AIM; that VASIs and PAPIs are actually both classified together as VGIs, but are separate entitities.

 

So that would agree with Rocky Mountain Pilot (and my original hunch), that they are different and that PAPIs do not satisfy the requirement of 91.175!!!! The issue of the 'single light source' is what I was stabbing at earlier. I think this is quite an important issue.

 

Rocky Mountain Pilot, while my heart tells me that you are right above, I still need a reference or source. That would relieve me somewhat.

 

Despite this, in almost every text that I read, the VASIs and PAPIs are included together. There is evidence (by the weatlth of texts) that either can be sufficient.

 

So to save myself from further embarrassment, I will go so far as to say that either could be right depending on interpreation! Furthermore, I must refrain from commenting further until someone comes up with some definitive source. Until then, I must say I am not convinced either way anymore.

 

Joker

 

What fun! Good question too.

[RockyMountainPilot]

My god,

 

How funny. I seem to be going back and forth (up and down) like a yo-yo on this. Sorry.

 

Just got back from the pub and I just read the extract from that AC which I quoted.

 

I noted the heading was: Visual Glide Slope Indicator , not VASI. This would agree with the AIM; that VASIs and PAPIs are actually both classified together as VGIs, but are separate entitities.

 

So that would agree with Rocky Mountain Pilot (and my original hunch), that they are different and that PAPIs do not satisfy the requirement of 91.175!!!! The issue of the 'single light source' is what I was stabbing at earlier. I think this is quite an important issue.

 

Rocky Mountain Pilot, while my heart tells me that you are right above, I still need a reference or source. That would relieve me somewhat.

 

Despite this, in almost every text that I read, the VASIs and PAPIs are included together. There is evidence (by the weatlth of texts) that either can be sufficient.

 

So to save myself from further embarrassment, I will go so far as to say that either could be right depending on interpreation! Furthermore, I must refrain from commenting further until someone comes up with some definitive source. Until then, I must say I am not convinced either way anymore.

 

Joker

 

What fun! Good question too.

 

 

91.175 is the reference you need. It gives what is allowed to be used as specific as it can be.

 

AIM 2-1-2 descripes the VGI's and lists them all as different devices. VASI is simply a VASI and does not include PAPI, Pulsating systems, tri-color systems, etc.

 

The real confusion is that they call the tri-color systems VASI as well, but they are not allowed to be used for descent.

 

http://www.faa.gov/airports_airtraffic/air...p2/aim0201.html

[tboy]

This is definately making me think. Thank you for all the input.

I misquoted the FAR and Collective Down caught me. You have to have the approach lighting system in sight to include the red terminating bars or the red side row bars, to descend below 100 ft above TDZE. Then if you have the runway environment in sight you can continue your decsent. Correct me if I'm wrong again.

 

I am still looking around but feel if the VASI and PAPI are both members of the Visual Glideslope Indicators, you could use the PAPI as part of the runway environment. In AIM 2-1-2 both systems have a range of 5 mile during the day and 20 miles at night. It also says the PAPI uses light units similar to the VASI.

 

Of course even if we find something in the AIM that says they are the same, the FARs are the regulations and the AIM is aeronautical information. A DPE once asked me on a checkride which one would I follow, when the AIM had different info than the FAR. I guess VASI is the one to go by.

 

Still if anyone finds the answer, I'd be interested in reading the info.

 

Troy

[Barks111]

Have a question. Regarding operation below DH or MDA, during IFR flight. My CFI once told me that he read in the FAR/AIM that if you had a visual on PAPI (Precision Approach Path Indicator) it was the same as if you had visual on the VASI (visual approach slope indicator), and could decsend to 100' above touchdown zone elevation. It says nothing about PAPI's in FAR part 91.175, only mentions VASI's and REILs.

Alright now to the question. Does anyone know where it is he was talking about. Or was he seeing things?

Thanks

Troy

 

Great question and one that I have spent some time researching this afternoon. I read the other posts on this thread and here is my opinion for what it is worth.

 

The FAA FARs carry the final word in these things, so we should look to the regulations for the answer and not the AIM.

 

Assuming that the pilot complies with the rest of the regulation on his instrument approach, namely, (extract from FAR Part 91.175):

 

© Operation below DH or MDA. Except as provided in paragraph (l) of this section, where a DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or continue an approach below the authorized DH unless-- ]

(1) The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;

(2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used;

 

We arrive at the stumbling block in the next requirement (extract Part 91.175 (3)(vi)):

 

(3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:

 

(vi) The visual approach slope indicator.

 

Note: Other posts dealt with the requirement for visual lighting references and descent below 100 feet above the touchdown zone elevation, which is covered in 91.175(3)(i).

 

I believe that the Visual Approach Slope Indicator wording refers to the VASI, but in actuality it could be worded differently to include the Precision Approach Path Indicator (PAPI) as I see both facilities as Visual Glide Slope Indicators (VGSI). They both perform the same function, to the same level of accuracy and effective ranges. Using either as a visual reference seems to me to be acceptable and having come from the UK military environment my personal experience is that they are treated equally in this regard.

 

Now, this does not answer your need to see it in black and white and I scoured the FAR for a definition or clarification but could not find anything to clarify the point. I did, however, log the question with the FAA via their Web site and they say they will have an answer in 24 hrs, so I will post their response when I get it. Whilst thinking about the equality (?) of VASI/PAPI I thought about PLASI too and wondered if this approach aid was also considered a suitable visual reference in the same circumstances? I have never seen one or flown to one but I asked the FAA if the PLASI is also in the same classification as the VASI and PAPI and if the regulation could be rewritten to replace Visual Approach Slope Indicator with Visual Glide Slope Indicator, which would sweep up all the VGSIs (VASI, PAPI and PLASI) into one and clarify the regulation. Let's wait and see what they have to say on this.

 

If you read all of this, you are a brave man/lady, or definitely a CFII!!

 

Stay Safe.

[Gomer Pylot]

If any of the referenced systems - runway lights, VASI, PAPI, REIL, the runway, etc are visible, you can LAND. The 100 foot reference is only for the approach lights. If the approach lights are in sight, you can descend to 100 feet above the touchdown zone, but not below that unless the red side bars, or any of the other elements, are visible. The only time the red side bars come into it at all is that you can't descend below 100' above the touchdown zone, using ONLY the approach lights, unless they are visible. If anything else in the runway environment is visible, you can land, and there is no 100' restriction at all. I've been doing this as an IFR PIC for a long time, and I've answered this on almost every ATP oral, every 6 months, that I've ever undergone.

 

Again, if anything in the runway environment is visible, you can descend below MDA and land. There is no 100' restriction. If you can see the approach lights, and nothing else, you can descend below MDA, but not below 100' above the touchdown zone elevation, until you can see something else, including the red side bars, REIL, VASI, PAPI, the runway, runway lights, or anything else listed in 91.175 (a)(3) (ii) through (x). As soon as you see any of those, you can land.

[RockyMountainPilot]

If any of the referenced systems - runway lights, VASI, PAPI, REIL, the runway, etc are visible, you can LAND. The 100 foot reference is only for the approach lights. If the approach lights are in sight, you can descend to 100 feet above the touchdown zone, but not below that unless the red side bars, or any of the other elements, are visible. The only time the red side bars come into it at all is that you can't descend below 100' above the touchdown zone, using ONLY the approach lights, unless they are visible. If anything else in the runway environment is visible, you can land, and there is no 100' restriction at all. I've been doing this as an IFR PIC for a long time, and I've answered this on almost every ATP oral, every 6 months, that I've ever undergone.

 

Again, if anything in the runway environment is visible, you can descend below MDA and land. There is no 100' restriction. If you can see the approach lights, and nothing else, you can descend below MDA, but not below 100' above the touchdown zone elevation, until you can see something else, including the red side bars, REIL, VASI, PAPI, the runway, runway lights, or anything else listed in 91.175 (a)(3) (ii) through (x). As soon as you see any of those, you can land.

 

PAPI is not listed under 91.175, so you can not proceed for landing if all you see is the PAPI.

[joker]

Guys,

 

A question of legal interpretation!

 

We're going round in circles here.

 

If any of the referenced systems - runway lights, VASI, PAPI, REIL

Gomer, the PAPI is not actually referenced. That's the debate.

 

RMP, I (we) know what is written in the FAR! That's the whole point of this whole debate.

 

You talk like you've been flying for long enough to know that the FAR is open to interpretation. You have seen this so often in other aspects. This is the problem here.

 

You are trying to apply a literal interpretation to this rule. That we all would agree with you. It says 'Visual approach slope indicator' not PAPI!

 

What is in question is whether the use of the term 'Visual approach slope indicator' in 91.175 is a generic term for an electro-optical system to provide glideslope information. If so, then you would agree that a PAPI is such a thing. Note there, no acronym is used and the lower case letters.

 

Indeed, in the ECCAIRS 4.2.6 Data Definition standard (for incident reporting) an entry on PAPIs would be as follows:

 

PAPI The visual approach slope indicator system used was precision approach path indicator.

 

So, as I said before, please someone come up with either an explanation or legal interpretation as to why the literal interpretation of this rule is correct. Why should the literal interpretaion prevail over the overwhelming evidence that the two systems provide equally valid information.

 

For example, I have read that the VASI maintenance is always done by FAA and PAPIs may not be. Also, the level of accuracy in the setup is greater for VASIs. That might support the literal interpretation.

 

So I reiterate here, RMP we are talking about the interpretation of this rule, not the black and white itsself. Please come up with more than that FAR reference, because I can read the FAR myself. I agree with you!

 

However, I am not 100% convinced that that interpretation is what is intended. As you well know, in statutory interpretation, it is acceptable for a judge to apply the Golden Rule or Original Intent if the literal interpretation leads to absurdity. Don't get caught thinking the FAR is so perfect. It's not.

 

That's why I said before, either interpretation could be right, until a court of law finalises the situation, or until someone gives me practical and sensible reasons why PAPIs are so differernt to VASIs.

 

Joker

 

P.S. And one little pet hate...please, you don't have to quote entire posts when replying! Use the 'add reply' at the bottom rather than the 'reply' at the end of each post!

 

 

Edited after RMPs post below: I agree with RMP here. In the absence of a 'legal' opinion, then we must accpet the literal interpretation of the FARs. That would mean that PAPIs are NOT included in 91.175. That's why we need to find the legal interpretation.

Edited July 15, 2007 by joker

[RockyMountainPilot]

The opinions of an FAA Inspector, FSDO, or Director of the FAA don't mean squat. Unless you have a Chief Counsel Opinion take everything in the FAR's literally. In all my years of flying and writing for the FAA, that is the best advice I can offer.

[Gomer Pylot]

I've never seen an approach/runway environment in which all you could see was a PAPI, or a VASI. A PAPI is, in my opinion, a visual approach slope indicator, and I would land if I could see it, but I can't imagine a situation in which that is all I could see. There should be runway lights, approach lights, REILS, etc, which you should be able to see as well as a PAPI. If you can see any of these lights, you can land. None of them limit you to 100', as I said above. That limit is only for the approach lights alone.

[Superman]

I’ve made a few approaches in the fixed wing at night into fog and snow covered surroundings in which the only thing I could see at Minimums were the approach lights, the VASI the runway end lights and maybe 2 or 3 lights down the runway, everything else was white, until under the fog. I also have gone missed, been able to look straight down and see the runway as I flew over but unable to land because the forward visibility was nil, fly 15 miles away and land VFR….. Fog can be a mysterious thing.

 

As far as the FAR/AIM question, I think Gomers Answer in post 14 is good as you can get.

 

My Answer......

As long as you don’t ball the thing up on short final, it won’t be an issue

 

Geeese.....just kiddin'

 

Fly Safe

Clark

[Gomer Pylot]

I've made many night approaches with 1/4 mile visibility, on which I could see only the approach lights under me at DH, and at 100' got the REILs and first runway lights in sight. The PAPI didn't even come into it, couldn't see it until later, or at least I wasn't looking for it. This whole discussion is moot, and really has no practical application.