Confused with 91.175

bdhill1979

Gone West
FAR 91.175 (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:
(i) The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
(ii) The threshold.
(iii) The threshold markings.
(iv) The threshold lights.
(v) The runway end identifier lights.
(vi) The visual approach slope indicator.
(vii) The touchdown zone or touchdown zone markings.
(viii) The touchdown zone lights.
(ix) The runway or runway markings.
(x) The runway lights.
So does that mean a PAPI does not count?


I have had this question in the back of my head for awhile and today just as I was teaching it to a student the DPE walked in and I asked him about it. This turned into a 3 CFIs and the DPE opening their respective FAR/AIMs looking for the answer. He said to check the definitions in FAR 1 to see if a visual approach slope indicator might be defined as a catch all term. No mention there.

In AIM 2-1-2 titled "Visual Glideslope indicators", the VASI is the first one listed, along with the PAPI, Tri-Color VASI, Pulsating VASI, and Alignment of Elements systems. The published visual ranges in the AIM are the same.

We concluded that there was no definite answer but that it is most likely just another poorly written FAR.

Thoughts?
 

bLizZuE

Vaxxed and ready to P-A-R-T-Y!
I would conclude that reference is referring to THE visual approach slope indicator not A visual approach slope indicator.
 

Sidious

Well-Known Member
I would conclude that reference is referring to THE visual approach slope indicator not A visual approach slope indicator.

:yeahthat:

Had the same question a while back and I couldn't find a definite answer either. Its these questions that drive me up a wall because I like everything black and white when anything seldom is.

tgrayson in 3.... 2.... 1....
 

bdhill1979

Gone West
I would conclude that reference is referring to THE visual approach slope indicator not A visual approach slope indicator.

Why would all the other "Visual glideslope indicators" (as referenced in the AIM) not count?

What makes a VASI any better than a PAPI?
They are equally visible and provide the same information to the pilot.

If you come down on an approach and the runway happens to be equipped with a PAPI instead of a VASI and you reach DA/MDA and have the PAPI in sight but nothing else must you go missed?

Just looking for clarity, the examiner was stumped on this.
 

minitour

New Member
Why would all the other "Visual glideslope indicators" (as referenced in the AIM) not count?

What makes a VASI any better than a PAPI?
They are equally visible and provide the same information to the pilot.
Because the reg says "THE" Visual approach Slope Indicator. Not the Visual Glideslope Indicator. Nor does it say "or Precision Approach Path Indicator".

-mini
 

CaptainChris87

New Member
So does that mean a PAPI does not count?


I have had this question in the back of my head for awhile and today just as I was teaching it to a student the DPE walked in and I asked him about it. This turned into a 3 CFIs and the DPE opening their respective FAR/AIMs looking for the answer. He said to check the definitions in FAR 1 to see if a visual approach slope indicator might be defined as a catch all term. No mention there.

In AIM 2-1-2 titled "Visual Glideslope indicators", the VASI is the first one listed, along with the PAPI, Tri-Color VASI, Pulsating VASI, and Alignment of Elements systems. The published visual ranges in the AIM are the same.

We concluded that there was no definite answer but that it is most likely just another poorly written FAR.

Thoughts?


THE visual approach slope indicator...I would assume whatever type of visual slope indicator the specifc runway for the approach has (VASI, or PAPI) you can proceed....

However If you read wikipedia it says the PAPI is the standard FAA and ICAO's "Standard visual approach slope"

according to wikipedia: "These have a similar purpose to basic visual approach slope indicators, but the additional lights serve to show the pilot how far off the glide slope the aircraft is.
When the lights show White-White-Red-Red the aircraft is on the correct glide slope for landing, usually 3.0°. Three red lights (White-Red-Red-Red) indicate that the aircraft is slightly below glide slope (2.8°), while four red lights (Red-Red-Red-Red) indicate that the aircraft is significantly below glide slope (<2.5°).
Conversely, three white lights (White-White-White-Red) indicate that the aircraft is slightly above glide slope (3.2°), and four white lights (White-White-White-White) indicated that the aircraft is significantly above glideslope (>3.5°).
Most large airports utilize this system. Although most airports use a PAPI based on a 3.0° glide slope, some airports may use a glide slope as great as 4.5° in order to have proper obstruction clearance."


http://en.wikipedia.org/wiki/Visual_Approach_Slope_Indicator

So I would guess that the PAPI is more specfic when it comes to figuring out your exact degree of hegiht over the runway as opposed to a VASI which is less specific. its why that is defined as "THE" visual approach indicator. Which would make mroe sense if your shooting an approach to mins.
 

bLizZuE

Vaxxed and ready to P-A-R-T-Y!
Why would all the other "Visual glideslope indicators" (as referenced in the AIM) not count?

What makes a VASI any better than a PAPI?
They are equally visible and provide the same information to the pilot.

If you come down on an approach and the runway happens to be equipped with a PAPI instead of a VASI and you reach DA/MDA and have the PAPI in sight but nothing else must you go missed?

Just looking for clarity, the examiner was stumped on this.
I think the reference in 91.175 is talking about any visual approach slope indicator. It just so happens that one is called a VASI. I think if you can see anything indicating the visual glide, you're cool.
 

CaptainChris87

New Member
Because there's an authoritative source on aviation, or anything for that matter...:rolleyes::sarcasm:

-mini
lol :) Yes..Wikipedia and goole superceedes any FAA certified document or textbook :)......
I implied that becasue the first 3 posts already stated they could not find it in the FAR/AIM and other FAA certified books. And also check the references for that wikipedia page.
 

ghogue

Well-Known Member
Perhaps this will shed some light on the subject.
_______________________________________________

U.S. Department
Of Transportation

Federal Aviation Administration
Northwest Mountain Region
Colorado, Idaho, Montana
Oregon, Utah, Washington
Wyoming


1601 Lind Avenue, SW
Renton, WA 98055-4099
Tel: (425) 227-2007
Fax: (425) 227-1007

Office of the Regional Counsel

May 30, 2006

Re: Request for Interpretation of 14 CFR Section 91.175(c)(3)(vi)

Dear Mr. Ison:

We are in receipt of your letter, dated May 8, 2006, addressed to the Regional Counsel. In it, you asked whether 14 CFR 91.175(c)(3)(vi) is restricted specifically to the visual approach slope indicator, as mentioned, or whether it includes all visual guide slope indicators.

The Regional Counsel assigned the matter to me. I, in turn, referred your request to Flight Standards because I perceived your question to be more technical than legal in nature. David Miller, an operations regional specialist in the Flight Standards Regional Office, located here in Renton, was kind enough to review your letter and he responded as follows (paraphrased):

"A pilot may not substitute any other visual glide slope indicator, such as the precision approach path indicator (PAPI), for the visual approach slope indicator (VASI). This is because the rule is very specific about what visual reverences may be used by the pilot to descend below decision height (DH) or minimum descent altitude (MDA). The rule provides for ten specific visual reference options but does not incorporate language permitting substitutions."

I will only add that I reviewed the regulation, and Mr. Miller's analysis is consistent with general principles of legal interpretation, specifically, that, absent some reason to do otherwise, language statutes and regulations are given their ordinary meaning. I concur with Mr. Miller's reading of the rule.

I hope this answers your inquiry satisfactorily. If you have any further questions on this issue, please feel free to contact me further at the number below, or you may contact Mr. Miller at (425 7-2263.

SRI
David F. Shayne FAA Attorney (425) 227-2165
 

tgrayson

New Member
Had the same question a while back and I couldn't find a definite answer either.
I have no other information other than it refers to the VASI, not the PAPI, and that's the way I teach it. Note that ghogue posted as "Regional" Counsel endorsing that point of view.

For Part 121 guys, ops specs take precedence and Pinnacle at least has in their FOM that the PAPI counts as a VASI. Seems to indicate that not including it in the regulation is an oversight, rather than there being a fundamental flaw in PAPI.
 

Firebird2XC

Well-Known Member
I think the reference in 91.175 is talking about any visual approach slope indicator. It just so happens that one is called a VASI. I think if you can see anything indicating the visual glide, you're cool.

Is it possible that the language regarding 91.175 predates the PAPI and other forms of visual glidepath reference beside the VASI system specifically?

i.e., was the language written in respect to "whatever visual glideslope data present" but as the VASI was the only system in use at the time, it was written that way with the assumption in mind?
 

bdhill1979

Gone West
Perhaps this will shed some light on the subject.
_______________________________________________

U.S. Department
Of Transportation

Federal Aviation Administration
Northwest Mountain Region
Colorado, Idaho, Montana
Oregon, Utah, Washington
Wyoming


1601 Lind Avenue, SW
Renton, WA 98055-4099
Tel: (425) 227-2007
Fax: (425) 227-1007

Office of the Regional Counsel

May 30, 2006

Re: Request for Interpretation of 14 CFR Section 91.175(c)(3)(vi)

Dear Mr. Ison:

We are in receipt of your letter, dated May 8, 2006, addressed to the Regional Counsel. In it, you asked whether 14 CFR 91.175(c)(3)(vi) is restricted specifically to the visual approach slope indicator, as mentioned, or whether it includes all visual guide slope indicators.

The Regional Counsel assigned the matter to me. I, in turn, referred your request to Flight Standards because I perceived your question to be more technical than legal in nature. David Miller, an operations regional specialist in the Flight Standards Regional Office, located here in Renton, was kind enough to review your letter and he responded as follows (paraphrased):

"A pilot may not substitute any other visual glide slope indicator, such as the precision approach path indicator (PAPI), for the visual approach slope indicator (VASI). This is because the rule is very specific about what visual reverences may be used by the pilot to descend below decision height (DH) or minimum descent altitude (MDA). The rule provides for ten specific visual reference options but does not incorporate language permitting substitutions."

I will only add that I reviewed the regulation, and Mr. Miller's analysis is consistent with general principles of legal interpretation, specifically, that, absent some reason to do otherwise, language statutes and regulations are given their ordinary meaning. I concur with Mr. Miller's reading of the rule.

I hope this answers your inquiry satisfactorily. If you have any further questions on this issue, please feel free to contact me further at the number below, or you may contact Mr. Miller at (425 7-2263.

SRI
David F. Shayne FAA Attorney (425) 227-2165
Thank you sir!

Now that just leaves me the less important question of why?

Edit: Odd that this letter is not listed in my Summit database. No wonder I couldn't find it.
 

germb747

Well-Known Member
The bottom line is that you get to minimums, and at that point you have the runway environment picked out and are in a safe position to land, or you aren't and you're going missed. It's a great academic discussion for FAA lawyers, but this all happens so fast it's really a judgment call.
 
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