Flight Visibility on non-precision approaches
 

I am familiar with determining flight visibility on precision approaches with being able to see the decision bar from and a couple of additional lights to confirm I have 1/2 mile flight visibility. But how do you determine flight visibility on non-precision approaches, especially when your decision point is the VDP? Every article I find online references precision approaches only.

you are over thinking it. VDP IS a visual descent point, if you are in a position to land and have the runway in sight at the VDP continue the descent and land. If one of those 3 are not met, go missed. If you are beyond your VDP, you will probably not be able to complete a stabilized approach and landing anyway. Provided you have the environment in sight at the VDP, you will have the flight visibility in all real world situations.

in what real world, actually-happened, situation has anyone asked you, to you yourself come up with "flight visibility"

(unless after landing and "what do you estimate the visibility" from ATC)

ever?

If one were to exercise one's part 91 option to go down and take a look, and the official vis was reporting too low, it's conceivable that you might need to explain your flight vis. Or if RVR dropped after the marker for 121.

But if the official reported vis is good, then it should never be an issue.

when regional interview gouges stop mentioning stuff like this, or once I'm past that phase of my career, I'll let it go

If you're at minimums, your only concern is 'do I see the runway environment and can I descend from MDA?' If you have the approach lights, you can descend 100' below, and if you have the runway, come on down. That's not the time to be guessing what the visibility is. You needed the appropriate legal visibility to start the approach. To finish it, you need to be able to see the runway environment.

I believe JohnBurke's response above summed things up correctly.

Practically I agree. Technically you might need published vis.

But after-the-fact there might be situations where it would be beneficial to articulate how you estimated flight vis, if you choose to put yourself in such situations.

What am I missing here?
Isnt this where you just use the 3:1 rule?
If the minimums are 400 (AGL) the VDP is at 1.2 NM so if you see the runway at VDP the visibility is……..mathematically slightly more then 1.2 and for all practical purposes a mile.

As defined by the FARs, Flight Visibility means the average forward horizontal distance from the cockpit of an aircraft in flight at which prominent unlighted objects may be seen and identified by day, and prominent lighted objects may be seen and identified by night. As such, the required flight visibility is met if at approach minimums (MDA, DA, DH) and the approach lights are in sight.

The following reference is from FAR 121.651, takeoff and landing minimums:

On the Final Approach Segment (FAS), if the weather report indicates below-minimum conditions, the approach may continue to DA/DH or MDA. Upon reaching DA/DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DA/DH or MDA if the following requirements are met:

(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 where 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 procedure being used;

(3) Except for Category II or Category III approaches where any necessary visual reference requirements are specified by authorization of 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;

I know that is typical FAA legal language, but to summarize, to descend out of the MDA/DA/DH, you must have white lights (approach light system) in sight. To descend below 100' TDZE, you must see colored lights or concrete.

Eh…..let’s not overthink this because someone had a lazy CFII.

All, good, but it's not 100' below mins, it's down to 100' AGL.

JB is correct that having the approach lights in sight allow you to continue below MDA.
You need a ground reference to continue below 100' AGL, you need to see more than just the approach lights.

Yes you can go down to 100' AGL (above TDZE).

The 100' below mins is a common misconception since your typical CAT I has a DA which equates to 200' AGL... so 100' below that is the same as 100' AGL.

One can continue to one hundred feet, but that wasn't really the point.

The point was that one does not need to have, or verify, approach weather minimums (ceiling or visibility) when approaching minimums. What's being reported isn't nearly as important as what's outside the window. One is looking outside, or half-in-half-out, depending on one's role for the approach, and at such time as one looks up and sees the required visual references (and acknowledges them, as one's SOP may dictate ("continue," "landing, etc), one isn't asking at that moment in time if the current, up-to-the-second weather is still reporting above minimums, because one is inside the FAF/GSIA and looking for visual references. Those references may be the runway, or simply pre-runway references that allow one to descend a little lower, until one acquires the runway (or must go around).

That was the point. The question regarded whether one must have legal reported weather minimums, when arriving at minimums, and the answer is that one has what one sees out the window, at that point. It was noted by some that one should have the charted (or approved; eg, OpSpec, etc) minimums, but this is not correct. Those were needed to begin the approach; arrival at MDA on a constant descent approach, or DH/DA, one isn't going to (and shouldn't) check weather to see if there are changes; one is looking for the necessary visual references (Except cat III procedures when one may not see the runway before touchdown). So long as the necessary minimums were reported in order to begin the final approach segment, that element of the approach has been satisfied. Upon arrival at minimums, what's seen out the window is the order of the day. What's required and the altitude to which we can go depends entirely upon the procedure, the nature of the approach, in some cases the aircraft, in all cases of certificate holders, the certificate holder's approvals and authorizations, and of course, also the pilot and his or her qualification (and currency).

Cat II & Cat III require the weather to remain at or above minimums throughout the approach. However, that’s not the flight crew’s job to determine. If ATC happens to provide an update to RVR while they’re inside the PFAF and that update is below the charted minima a missed approach is required.

That's not accurate. Cat II/III approaches may continue if established on the FAS. From a previous post:

This is also explicit in AC 120-118 and OpSpec C060: C060 g. Operating Limitations. "(f) Once established on the FAS, all operations conducted using automatic rollout systems, or FP HUD rollout guidance, may continue if any RVR report decreases below the authorized minimums."

Some countries have specific caveats to this. For example, in the UK, the approach may be flown regardless of the WX/RVR but may not descend below a 1000' AFE if the weather is below minimums. Conversely, the approach may continue if below 1000' and the weather degrades below the applicable minimum.

I reread the airway manual and you are correct

we are limited though on the 73 (and I guess the 717 as well) must do a missed on a cat iii if rvr reports below minimums even when established on the FAS.

ICAO (a United Nations Agency) Annex 6 to the Convention on International Civil Aviation, Part 1 states in paragraph 4.4.1.2:

"An instrument approach shall not be continued below 300 m (1 000 ft) above the aerodrome elevation or into the final approach segment unless the reported visibility or controlling RVR* is at or above the aerodrome operating minima."

Refer to the country's specifics of operations Aeronautical Information Publication for differences in Approach Bans.

The following paragraph to that quoted above, 4.4.1.3, stipulates that (barring alteration by the State criteria), the procedure may be continued once inside the final approach segment (below 300m/1000') if the RVR falls below minimums. In this case, the procedure may be continued to MDA/DH, but is not authorized below (without appropriate visual references required at MDA/DH/DA).

http://www.smolenskiefakty.com/icao_annex_6_part_1_section_4_4.pdf

The crucial element at arrival at minimums continues to be not if meteorological reported minimums are at or above charted minimums, but whether one has the necessary references to continue the procedure below minimums; it comes down to whether one can see the approach or runway lights to either continue, or land.

Some airlines have 737"s with HUDs that have rollout guidance. In those, you can continue.

I don’t believe we can continue with our HUDs. We are simply limited to going missed if weather reports below mins on Cat III inside the PFAF. We should have rollout guidance since we can do 300 RVR takeoffs if you dial an ILS.

It's not technically it's in the FAR you must maintain the charted visibility requirement in the visual segment to 100' If it has a ILS lights well they are designed to tell to you at a glance what the inflight visibility is ie do you see the decision bar etc. I have a great article written by IFR Flying explaining it much better than I can, I will see if I can find it.

https://www.ifr-magazine.com/techniq...r-can-you-see/

Upon arrival at minimums, the "inflight visibility" is irrelevant. You must see the approach lights to descend, and then the runway environment to descend further.

For a full Cat III, you may not see the approach lights, and probably won't, or much, if anything, of the runway until touchdown. For a Cat I approach, there is no requirement to verify flight visibility at MDA/DDA/DA/DH. Do you have the visual references to land? Then land. Do you not see the visual references? Missed approach. You see it, you call it, you land. You don't see it, you call it, you go. It really is that simple.

Actually and respectfully on a ILS Cat 1 approach at mins to go to 100' if the runway is not in sight you still have to have the required published VIS requirements visually to continue to 100'. You determine that by the ILS approach lighting system it's actually designed so a glance tells you what you need ie the decision bar etc. Then at 100' is when the landing environment red terminating bars etc. come into play. Cat I non percision approachs are governed by the same requirement to maintain the charted VIS requirements past DA/MDA.

FAR 91.175(c) outlines three requirements:

• You must always be able to make a descent to landing on the intended runway using normal maneuvers and a normal descent rate,
• The flight visibility (that you observe) must meet or exceed the minimums published for the approach, and
• You must be able to distinctly identify one of the approved visual references for the runway (often called the "runway environment")

Cat II AND Cat IIIs are different and not really what we were talking about.

The flight visibility is what you determine it to be, not what is reported by the tower or runway transmisiometer.

What kind of idiot would later say he arrived at minimums, saw the runway lights and continued down, then saw the runway environment and landed, but didn't have the necessary flight visibility?

If you arrive at minimums and see the runway lights, you continue and if you see the runway you land. Period. You do not count the bars on the approach lights to determine if you have adequate visibility. You do not attempt to ascertain if you have a legal flight visibility. You see the requisite visual references? You land.

What is flight visibility? The ability to see a prominent unlighted object in the day, or a lighted object at night. You see the runway lights, approach lights, red terminatin bars, runway markings, yada, yada, yada? You're seeing that prominent object. You have your visibility. You land. Go figure.

https://www.ecfr.gov/current/title-1...apter-A/part-1

​​​​​​​It really is that simple.

I used to teach this all the time and sadly the inflight visibility requirement exists for a reason.

Oh there are quit a few. I remember a rather gusty day in EWR. Most planes landing reported +/-15 knots on final, but then one plane lands and says, "+30/-20 at 500 feet."

It does. To see the approach lights and subsequent runway environment, and yet we fly cat III approaches to a touchdown without a hint of either one.

Surely when you used to teach "this all the time," you didn't teach arriving at minimums, seeing approach lights, and counting the lights, calculating an in-flight visibility, and then determining whether to continue based on that calculation?

Didn't think so.

Nobody does.

Your only concern upon arrival at minimums and for those still not doing constant descent approaches, the VDP (et al), is whether you see the necessary visual references to continue. That's inflight visibility.

The published numbers are not your required in-flight visibility at minimums, unless you're prepared to lie to me and tell me you have the ability to accurately determine it, passing minimums, to the eighth of a mile and nth degree. No, you're looking for the approach lights and runway environment, like everyone else, and if you see them, there's your inflight visibility. If you don't see them, you're going missed. Again, it really is that simple.

I've yet to hear a briefing that includes "upon arrival at minimums, we'll count the approach lights, calculate our inflight visibility, make a determination if we can continue, and then elect to either press on, or go missed. That would, of course, be idiotic.

Cat III S are different animals and yes some Cat IIIs require you to see something to continue at alert height.

The FAR is clear and no not counting lights but like the publication's I posed reference a quick glance at the approach lights on a std CAT I at 200' minimums you should see the decision bar etc. However you are free to continue doing what you want.

I think what JB and several others are trying to say is that inside the FAF, it no longer matters what tower or approach say the visibility is. What matters is the inflight visibility YOU observe through looking at the approach lights and runway environment. How precisely you do that probably falls into technique as there are a lot of ways to assess distance (visibility).

Yous guys are way over thinking it. If you see the runway environment at 100 above tdze on Cat 1 appr you are good to go. Just that simple.

Can you point to any training program, anywhere in the world, which teaches arriving at minimums and determining inflight visibility equivalent to the approach visibility, before continuing? If there is, I've never heard of it, and such a program would be truly idiotic. Upon arrival at minimums, there is but one consideration (approach lights/runway environment in sight), and under no circumstances does one attempt to determine if a specific visiblity value exists.

It's nothing to do with what I want. If you arrive at minimums and have the requisite visual references in sight (eg, approach lights or runway environment), then YOU HAVE THE REQUISITE FLIGHT VISIBILITY.

Technically it's 100 ft below minimums, not 100' above TDZE.

That usually works out to be the same, but not all CAT I have a 200' min, at least some are 250' or maybe 300'.

Strike that, reverse it.

100' above TDZE is specifically referenced in the FAR that lets you continue an ILS below the DA/DH.

Not on a non-precision.

We are saying probably the same thing buy some people think you can go below CAT I miminums to 100' by just seeing a few rabbit lights not most of the ILS approach lights for example. Also actually the FAA being the FAA designed the ALS system for rapid identification of the required visibility to continue.

You can use this light bulb yardstick when you reach minimum altitude on an instrument approach and need to find the runway. If you know what you're looking for, you know the shape, color, whether it flashes or not, and the length. That length is your measurement for visibility.

Most Cat-I ILS or LPV approaches require 2,400 feet (half a mile) of visibility. Not surprisingly, any approach requiring less than 3/4-mile must have an ALSF-2, ALSF-1, SSALR or MALSR, all of which are 2,400 feet long.

When you reach 200 feet AGL on a standard three-degree glideslope, you're 2,800 feet from the threshold. If you can see to the far end of the approach light system, you have more than the required 2,400 feet of visibility to continue.

If you can only see to the 500-foot barrette, visibility is closer to 2,300 feet. I wouldn't quibble over 100 feet on the edge of legal. However, I'll reiterate: Even though the ALSF-2 provides some roll and yaw information, it says nothing about glideslope. The PAPI or VASI is about 1,000 feet beyond the threshold, so fly attitude and resist any pitch changes. With only 2,400 feet of visibility, you probably won't see a visual glidepath until the roll bar has passed under the nose.

If you reach a 200-foot DA and can't see the roll bar that's 1,000 feet short of the threshold, you have less than 1,800 feet of visibility. Few ILS approaches, and no LPV approaches, allow visibility that low without special equipment or authorization. Also, if you can't see past the roll bar, you can't see "the red terminating bars or the red side row bars" anyway.

Therefore, seeing only to the roll bar by DA means missed approach---even though you can see 1,400 feet of approach light system ahead of you. Legally speaking.

However, a missed does make it more likely you'll make it to another trivia night.

Never said that we are talking in flight visibility and charted visibility.

You're absolutely correct. However, both you and JB were following up on comments others had made about going missed if tower or approach announced visibility less than mins inside the FAF. I was simply trying to highlight that the visibility out the window is what matters inside the FAF and there are multiple ways to determine that. I think you and JB both have reasonable ways of determining that in the short amount of time available...

I said nothing about reported visibility; neither RVR nor tower-reported visibility in statue miles (or meters, as the case may be). This more recent part of this discussion is very specifically about flight visibility, which is what the pilot sees. The present discussion regards only flight visibility, and is restricted to what the pilot can see from the cockpit, while flying the approach.

What I'm describing isn't a "reasonable way" of determining flight visibility. It's the only way. It's also regulatory. We'll explore that (again).

Note that we're talking about flight visibility, which is not a specific value. It's defined as an average value, an important distinction. Unlike runway visual range flight visibility does not require that we pin down an exact distance value, nor is that possible, most of the time. By definition, we either see a prominent object, or we don't, and it's an "average" distance, especially given that our seeing at that range is subject to individual determination. What's a half-mile to one person may appear so to another. We're moving. Perception of distance varies with visibility: close objects look farther away in lower visibility. Our distance to the object is changeing continuously. It's an average value, and one we must judge based on what we see, looking out the window. We reference average distance to a prominent object, and that prominent object, for our purposes when flying an approach, is the approach lighting system, and then the runway environment, as spelled out in 14 CFR 91.175(c) and (d).

With few exceptions, visibility is controlling for an approach, not ceiling. Minimum altitudes are not connected with ceiling, but with terrain clearance. The requirement for the procedure is a minimum altitude to which we can descend, and a minimum visibility with which we can see the runway, or at which we must find the approach lights or runway, in order to continue below minimums and subsequently land. This visibility is what we see out the window. If the tower tells us visibility is ten miles, but we arrive at minimums and can find neither approach lights, nor the runway environment (as spelled out in 14 CFR 91.175(c) and (d)), then we must execute a missed approach, regardless of what is reported by the airport RVR transmissiometer, or by the tower. The guy in the tower cab might be able to see just fine, but he isn't looking for the runway from minimums on the approach. It is for this reason, and this reason ONLY, that the regulation specifies "flight visibility."

Many of us have flown approaches when we could see the airport and runway overhead, but not on the approach, or when reported visibility was fine, but on the procedure, at minimums, was insufficient. Many of us have arrived at minimums at some point or another, to find actual conditions not the same as reported, and of course there are those days when it's quite clear below a low overcast, but we see nothing at minimums, or a fog bank is clear on one side, and pea soup on the other, sometimes half-way across the airport, or runway. What we concern ourselves with in discussing flight visibility, is what we see out the window.

At NO TIME is a pilot expected to determine flight visibility to the nth degree, be it an exact half-mile or some specific eighth-mile fraction, based on a cockpit guestimate. Instead, the pilot is given a simple requirement: see the approach lights, or see the runway environment. The pilot is not required to guess what part of the approach lights can be seen: the regulation simply states "approach light system," and then notes that the red terminating row bars, or the red side row bars must be "distinctly" visible AND identifiable.

Nowhere in the regulation, aeronautical information manual, or any recognized reference, will there be found any requirement to calculate flight visibility while in the cockpit on an approach, based on the number of lights seen, or runway markings, in order to make the decision to continue beyond minimums. The pilot must have the flight visibility prescribed for the procedure. Prior to starting the approach, the pilot requires reported visibility, because the pilot isn't there to see it for himself. At minimums, the only thing he needs to see is the runway environment, or to continue below minimums, the approach lights, and then subsequently the runway environment.

If the pilot can see the approach lights, that constitutes having the necessary flight visibility to continue the approach. If the pilot arrives at 100' above the touchdown zone elevation, having descended below minimums based on the necessary flight visibility to see the approach lighting system and the requisite terminating red row bars or side row bars, then the pilot has a specific list of items that he must see in order to continue below that 100' threshold. These visual references are clearly specified to ensure the pilot is identifying the runway, and not something else, which is why the regulation doesn't stipulate "a big dark spot" or "something that looks a lot like a runway." The regulation cites items that make it clear that the pilot has found the end of the runway and what lies beyond it. These, then, become the metric for determining flight visibility. To be clear, at minimums, either the approach lighting system, or the runway sighting, constitute adequate flight visibility to continue. Flight visibility is the distance at which a prominent unlighted object is seen in daylight, or a lighted object at night; the approach lighting system, and the runway environment are the prominent objects used to determine flight visibility; either we see them, or we don't.

Threshold, threshold markings, threshold lights, or runway end identifier lights identify the first thing we see of the runway: the end of the runway. Additionally, the regulation specifies references beyond the end of the runway: a visual glideslope indicator (which, while not on the runway or a part of it, is a dedicated guidance device to the runway and not something that is part of something that might look like a runway, but not actually be a runway); touchdown zone or touchdown zone markings, touchdown zone lights, runway or runway markings, or runway lights. That's it.

There are two parts to the flight visibility question: what we see to continue below minimums and subseuquently below 100' above the touchdown zone elevation, and a second requirement that we have adequate flight visility to land, each spelled out in separate sub paragraphs of 91.175. The former is specified by 91.175(c), and the latter by 91.175(d). Specifically, for a 121 operation, 91.175(d)(2) states that to land, one ust have the flight visility prescribed by the instrument aproach procedure being used. Just as one does not arrive at minimums and count lights to calculate flight visibility before making a decision to continue, one does not land based on counting runway lights or stripes to calculate flight visibility and then land. If anyone is doing this, they're an idiot. The necessary flight visibility prescribed for that procedure, is what's required: what the pilot sees out the window.

There are additional requirements that apply to the descend from minimums to the runway, and to land on the runway, of course; normal descend, normal rate, normal maneuvers, landing in the touchdown zone, and so forth (or as one arrogant airline retiree once told me "what we like to call, the airline touchdown zone"). This discussion is about flight visibility. We know the distance between runway lights, centerline markings, and other standard features of the runway environment. We don't count them or calculate them to determine if we have the requisite flight visibility to continue below minimums, below 100', or to land. We are required to have the flight visibility prescribed for the instrument approach in use. We determine that by looking out the window at a prominent object that's unlighted in the daylight, or lighted at night, and that prominent object is, for the purpose of landing, the runway. If one is taking the time to count runway stripes or lights while landing the airplane, then one is what we like to call "a god damn idiot," and an unsafe one, at that.

We don't count these elements and calculate them at minimums. We don't count or calculate them at 100' above the touchdown zone, and we don't count or calculate them when we're landing.

We are not required to see all of the approach lighting system and calculate the distance as a half-mile. The regulation is very clear about what we must see with that approach lighting system, or runway environment, to constitute the requisite flight visibility, or in other words, that golden prominent object. Not every procedure is a half-mile visibility. The PANC ILS 7R uses 1/2 mile. Does one count anything to arrive at that number? No. One sees the approach lights and then the runway, and for operations when approach lights or other features are out of service, adjusts accordingly. If the approach lighting system is out, visibility jumps to 3/4 miles. Counting anything or calculating? No. However, at minimums if one can't see a prominent object (the runway, as specified by 91.175), then one is going missed. If the glideslope is out and one is flying the localizer-only procedure to 7R, visibility is 5/8 mile. is one using any metric to calculate 5/8 mile? No. How does one determine that he has that additional 1/8 mile above the standard half-mile visibility? He looks out the window and sees the runway, threshold, runway end identifier lights, touchdown zone, yada, yada, yada. If (s)he's doing the ILS 7R loc-only procedure with no appraoch lights, then it's 1 1/4 miles flight visibility needed, and the same thing is used to determine the flight visibility is there. Are we looking out the window and counting objects? NO. We are looking out the window for the only lighted/unlighted prominent object we need to see, or care about, and that's the runway and the specific features of the runway or runway environment that the regulation spells out.

The question of this thread (original post) casts aside landing from a precision approach, and asks specificall about determining visibility on a non-precision approach, and refers to the "decision bar" in approach lights. First, there is no "decision bar," nor does the regulation refer to one. Secondly, the requirement for visual reference remains the same regardless of whether the approach procedure is precision, nor non-precision. In neither case is one attempting to divine visibility down to the fractional eighth of a mile. One is looking out the window for the necessary visual references: first, the approach lighting system, then for the runway environment, as specified in the regulation (91.175).

https://www.ecfr.gov/current/title-1...section-91.175

Flight visibility, again, is the distance that a prominent object can be seen, from the cockpit, and the definition of flight visibility is regulatory.

https://www.ecfr.gov/current/title-1...t%20visibility)