VASI or PAPI

[skygirls]

I wanted to gain insight into the world of 91.175. I am wondering if anyone knows the answer? The FAR's state under 91.175 a visual approach slope indicator. Does this also include a Papi? I can't seem to find a concrete answer. What does everyone think?

Thanks ahead of time!!!

 

[SmoovFlight]

91.175

If you read it in 91.175, it just says "The Visual Approach Slope Indicator" so I would take that to mean just the VASI. What about the runway lights? Does that include the runway centerline lights and the runway edge lights? The FAR's don't really specify. One of those "so called" gray areas I guess.

 

[firstthird]

interesting question, maybe there is a ruling somewhere but straight from the definitions I would say that legally, no, a papi is not a vasi. Info below is quoted from a 2001 AIM/FAR so beware (ain't got no job, can't afford the 2003)

talking about what visual references are required to descend below DH or MDA, at least one of the following, of which part vi is one.
FAR.91.175.c.
ii. the threshold
iii. the threshold markings
v. the REILs
vi. the VISUAL APPROACH SLOPE INDICATOR
vii. the touchdown zone or TDZ markings

AIM under the pilot/controller glossary.
Airport Lighting - g. Visual Approach Slope System (VASI). An airport lighting facility providing vertical visual approach slope guidance to aircraft during approach to landing ... red and white focused beams...some airports serving large aircraft have three-bar VASIs... .

AIM under Chapter 2 - Aeronautical lighting and other airport visual aids.
2-1-2. Visual Glideslope Indicators
a. Visual Approach Slope Indicator (VASI)
b. Preciscion Approach Path Indicator (PAPI)
c. Tri-color system.
etc

So, it appears that reg 91.175 should say Visual Glideslope Indicator if it meant to include PAPIs and all the other ones. That being said, I would think a reasonable man theory would say that a PAPI is a VASI is a PAPI for runway evironment purposes. But, what is reasonable and what is legal might be different.

I would think that for a pilot, you are likely to see something else that could be used to continue the descent besides just the PAPI like thresehold lights, etc. So the whole question is really more academic unless maybe you shoot an approach to a runway with all lighting systems out but the PAPI and you land using only that, not very likely. I think I'd be looking for better weather or an airport with all the bells and whistles working. Bad weather approaches are tough enough without stacking the deck against you.

 

[tarp]

91.175

How about this? You are flying an approach down almost to minimums breaking out of the "clag". You are bouncing around, it has been almost total gray/black and then you break out into the misty, hazy environs of the airport and you are low to the ground.

What does 91.175 define for you?

It defines things that you can positively say "YES" that's the airport there!

You see the runway numbers, let's go down. You see those distinctive threshold marks, let's go down. You see the approach light field and then the very bright red terminating bars followed by the green threshold lights - we're good to go.

OK, now let's get less obvious. You see the VASI hopefully red over white. Which side of the runway was that VASI on? Basically you only see two light sources peering at you through the clag - how do you know you are in a position to make a safe landing?

Now let's go down even further. You see one flashing white strobe light? Are you going to descend on that? It could be one-half of the REIL - but which one? It could be a PLASI? But then that would be a thousand feet from the REIL. It could be one of the ODALS flashers short of the runway. Heck, it could be an anti-collision light on top of a building.

So why VASI and not PAPI? Because a VASI is a "field of lights" not a single source. And in fact, every other listing under 91.175 is a field of vision. REIL's are two distinct and separate lights and you need BOTH of them to identify. The runway lights define a field. The markings define a field. The approach lights are a field. Everything in 91.175 is dimensional.

A single PLASI is not. A single Tri-color is not. A single PAPI light bar is not (Think about it, two cars on a highway side-by-side could give you the same picture as four white PAPI).

I really don't care what all the dime-store lawyers think - I'm not descending until I "know" there's a runway out there. In my mind I have to be able to recognise the markings or the light pattern and say "Yes, there it is - land!"

Fly safe.

 

[btflyer2]

This section relates to reg interviews

You might want to post this thread under the FAR section on the Message Board, I am sure there is lots of discussion there relating to FAR's.