Dark side of visual approaches.

[Ibra]

4 hours ago, MikeOH said:

 Therefore, it seems like believing that CAT I will be 'certified' below DA is unrealistic.

For LPV, what happens to the GP display after DA/MAP?  Oddly, I'm always looking outside at that point so I've never actually seen if remains active or goes away?

I'm sure I'll be corrected if I'm all wet on any/all of this! Shields up!

Shield up as well, we may need TERPS and ICAO experts 

For the design, LPV and ILS will have a safe geometric glide path in space with obstacle clearance down to DH and the line in space will not penetrate any surface under DH as you have 1:34 surface...

For actual signal and visual guides, you are in the 50 shades of grey,

* CAT2/3 ILS will be on instrument runway, the quality of signal and protection areas is whole topic on it's own 

* ILS is usually on precision runway (*), the signal has to be good between 200ft-100ft, you can actually decend on it: it's not good for auto-pilot coupled and you need to see the ground and runway environment, however, you need to see touchdown to go under 100ft 

* LPV is whole thing on it's own (you don't even need an instrument runway: no approach lights, no papi, no vasi...) to get 200ft DH, GP signal is always good down to GIPP (it becomes one sided and very sensitive above threshold crossing height), still need to see his touchdown from DH 

(*) There are ILS to non-precision runways or even ILS to non-instrument runways in France & Switzerland, I am not sure the US has any? we better let this dog sleep...

ILS: unless it's Cat2/3, visuals have to be obtained at DH and the signal is not guaranteed to be smooth under 200ft-100ft, the lateral guidance goes away passing antennas (actually, in ILS Cat1 glide signal gets bent by surface reflection under 100ft, one pay load of benjies to straighten it up) 

LPV: lateral guidance stays in on runway centerline until other side of the runway, it's smooth like silk, the glide signal disappears at GPIP and LPV remains until other runway end: of course, you still need to know what is ahead under DH (LPV autoland is only reserved for those with SmartGlide button, assuming no one is parked on runway ) 

LNAV lateral guidance depends on equipment the widths on WAAS GPS (angular) and non-WAAS (lateral) are different 

+V advisory guidance on Visual Approch in Garmin (Avydine?) is made on the fly using 50ft threshold crossing, 3deg and FAF (V3NM) at 3nm

On LPV at night, at DH if one sees the runway = continue, then one keep flying GP while looking outside? likely, the only choice one have when ALS or PAPI are not installed...

Edited January 17, 2024 by Ibra

[Ibra]

14 hours ago, GeeBee said:

MDA is one thing, what about the initial and intermediate segments?

Visual Approach is only available after FAF, the discussion is mainly about airport vicinity where MDA is relevant, +V is only showed for conventional overlay 2nm before FAF (or 3nm at V3NM point in visual approach, at least in Garmin under default setting)

The + V guidance won't appear if one is flying airways at nights, let’s say between peaks on 15DME arc inside a valley before turning into some NDB radial on final segment...even in that case, I still think it's healthy to load GPS procedures when doing raw data or getting vectors in mountains at night, I would even add Synthetic-Vision to the screen 

At the end of the day, it's an extra tool (or toy) that one can use for own consumption !

 

 

Edited January 17, 2024 by Ibra

[midlifeflyer]

On 1/14/2024 at 4:12 PM, Mooneymite said:

Hmmmm.  Maybe "difficulty" is not the right word.  I think even the most disciplined cockpit is more relaxed on a visual approach than on a CAT 3 approach to minimums.  Even though the CAT 3 may be completely automated, the vigilance level is generally higher.

There's the problem...experienced pilots might let down their guard on a visual, but a student pilot on a solo cross country is on high alert.

Can’t speak for airlines doing a  CAT 3 but I have seen numerous discussions started by GA instrument pilots expressing lack of knowledge and serious worries about how to do them. Exactly the opposite of relaxed and low vigilance. And exactly the opposite of the article’s comment that they are more complex than pilots think. 
 

Part of it is probably training. We just don’t typically do (or even discuss) visual approaches in instrument training. Even decline them in the IFR cross country because they don’t count. 

Edited January 17, 2024 by midlifeflyer

[GeeBee]

4 hours ago, Ibra said:

Visual Approach is only available after FAF, the discussion is mainly about airport vicinity where MDA is relevant, +V is only showed for conventional overlay 2nm before FAF (or 3nm at V3NM point in visual approach, at least in Garmin under default setting)

The + V guidance won't appear if one is flying airways at nights, let’s say between peaks on 15DME arc inside a valley before turning into some NDB radial on final segment...even in that case, I still think it's healthy to load GPS procedures when doing raw data or getting vectors in mountains at night, I would even add Synthetic-Vision to the screen 

At the end of the day, it's an extra tool (or toy) that one can use for own consumption !

 

 

I believe we are discussing two different things here. The OP was about being cleared for the visual approach in lieu of a full instrument approach. It happens thousands of times a day and generally in the range of 10 to 15 miles from the airport. The IFR flight calls the airport in sight and ATC issues a clearance for a visual approach. The flight continues on an IFR flight plan but the flight is responsible for its own navigation and terrain clearance.  That is a dangerous thing to do at an unfamiliar airport for a variety of reasons. 

What you are discussing when you say "Visual Approach is only available after FAF" is the visual segment of an IAP which was not the subject of the OP. It is worthy of discussion (the most famous being the VOR/GPS 13 L/R at KJFK) but the OP was about visual approaches in lieu of a charted instrument approach procedure. Two entirely different subjects.

[Marc_B]

On 1/13/2024 at 5:27 PM, Ibra said:

What is the difference between IFR visual approach and VFR/SVFR approach

I think the key point regarding IFR Visual Approaches and why we see them used is from the ATC perspective.  The separation requirements are MUCH different for an aircraft on a visual approach vs an aircraft on an instrument approach.  This is a big deal with airports with close parallel runways and especially for very busy airports trying to pack the sequence effectively.  If you have aircraft on visual approaches then that aircraft is responsible for obstacle and aircraft clearance and the required buffered zone around their aircraft that ATC must provide goes down.  (otherwise I think ATC must provide at least 1000 feet vertically / 3nm laterally)  Do we have any controllers here who could clarify?  I think ATC is required to notify you if preceding aircraft is a Heavy and I think that visual separation is not available for a Super.

I routinely use GTN "Visual Approach" during the day as it gives me a 3NM waypoint that is closer than the typical (~5nm) distance for a standard instrument approach.  Otherwise probably makes sense to just load a standard RNAV approach to the runway for backup.  After we had a Key Lime get struck midair by a Cirrus at Centennial a couple years ago, any time I'm landing with parallel runways I pretty much always throw an approach up to make sure I have an extended runway center line that I using to insure I'm on the right runway and don't run wide.  (I hope I am as cool and unfazed as this Keylime pilot if I ever have an emergency...)

I really like this situation (Lufthansa video below) as the first impression to those unaware of the big picture may be seen as "punishing" Lufthansa for declining a visual approach (not the case at all).  But the tower has to take and land all the aircraft coming in for landing aka they have to eat what they're fed.  But it also applies to airports with parallel runways with training traffic in the pattern on the other parallel.  If you accept a visual approach it makes it easier to sequence you without a lot of intervention from ATC.

Here's the ATC handbook/regs in the 7110:  https://www.faa.gov/air_traffic/publications/atpubs/atc_html/chap7_section_4.html

But to the OP's point, when we accept a visual approach it's not without risk (hence why some company's policies prohibit visual approaches, like Lufthansa in the example below).  Also it's important to know that IFR Visual Approaches do not have a missed approach so the tower will have to give instructions and will treat you as a standard go around.

 

[Pinecone]

6 hours ago, Ibra said:

ILS: unless it's Cat2/3, visuals have to be obtained at DH and the signal is not guaranteed to be smooth under 200ft-100ft, the lateral guidance goes away passing antennas (actually, in ILS Cat1 glide signal gets bent by surface reflection under 100ft, one pay load of benjies to straighten it up) 

If you are past the antennas that give you lateral guidance for an ILS you are a BIT long.  Those antennas are off the other end of the runway a good bit.

The glide slope antenna is off to the side of the runway and you can pass that one, but at the point the glide slope is almost ground level.

[GeeBee]

KSFO is a Charlie Foxtrot and there is going to be a really bad accident, (as if Asiana is not bad enough) but they are going to trade paint on approach sooner or later. Why ALPA and the airlines put up with the nonsense is beyond me. ALPA's motto, "Schedule With Safety" should be changed to "Schedule With Safety Except SFO". It is beyond comprehension that it continues to go on and I salute the Lufthansa crew for standing their ground.

[Ibra]

41 minutes ago, Pinecone said:

If you are past the antennas that give you lateral guidance for an ILS you are a BIT long.  Those antennas are off the other end of the runway a good bit.

Yes true, however, for all practical purposes the LOC guidance on Cat1 ILS gets toasted after passing threshold, touchdown or GP antenna (only Cat3 ILS have smooth signal that can be used for guidance all the way)

In LPV, it's different, the lateral signal switch between angular & lateral along the runway and past in smooth fashion, there are no glitches or singularities, the glideslope dies as it hit the ground

I think it's worth trying low pass on the lateral signal of ILS & LPV over the runway? handflying it with flight director ON (or autopilot, maybe at circling height not at 50ft) 

 

Edited January 17, 2024 by Ibra

[Skates97]

5 hours ago, midlifeflyer said:

Part of it is probably training. We just don’t typically do (or even discuss) visual approaches in instrument training. Even decline them in the IFR cross country because they don’t count. 

Agree, there wasn't much discussion in my IFR training about visual approaches and we never flew one in training. The first time I received one it threw me for a couple of seconds. I had been descended and then held at the same altitude for quite a bit, Approach asked if I had the field in sight, I responded that I did, and got "Cleared for the visual, contact tower" response. For a second I thought can I start descending now, do I wait for tower? Then I remembered a discussion about visual approaches on the Opposing Bases podcast and realized, yep, just fly and land like I would do if I was VFR. Began the descent, intercepted final, and landed.

[midlifeflyer]

43 minutes ago, Skates97 said:

Agree, there wasn't much discussion in my IFR training about visual approaches and we never flew one in training. The first time I received one it threw me for a couple of seconds. I had been descended and then held at the same altitude for quite a bit, Approach asked if I had the field in sight, I responded that I did, and got "Cleared for the visual, contact tower" response. For a second I thought can I start descending now, do I wait for tower? Then I remembered a discussion about visual approaches on the Opposing Bases podcast and realized, yep, just fly and land like I would do if I was VFR. Began the descent, intercepted final, and landed.

Except that your cloud clearances are different (clear of clouds rather than VFR minimums for the airspace), that's al it is. If they need something else, they'll tell you.

[Ibra]

8 hours ago, Marc_B said:

But to the OP's point, when we accept a visual approach it's not without risk (hence why some company's policies prohibit visual approaches, like Lufthansa in the example below).  Also it's important to know that IFR Visual Approaches do not have a missed approach so the tower will have to give instructions and will treat you as a standard go around.

I would not be surprised that Lufthansa policy prohibits it, the operator policy tend to be inline with the rules of the state, in Germany, visual approach are not allowed in major airports for large jet aircraft (something to do with noise regulations and requirement for anything above 15T to be on an instrument procedure path or in controlled airspace or pattern), however,

* visual separation is used in good weather conditions and allow ATC to relax separation 

* "Shorty ILS" is also used to expedite in good weather, you get vectored to 6nm (sometimes even near MVA under FAF altitude) in good weather, if you are planning on using GPS for missed everything will gets scrambled, however, they pick you on radar vector quickly (in France, and US, one will not get vector heading to after FAF and rarely under it's altitude)

The point on missed being missing on VA is interesting, I gather requesting to fly pattern as missed is an option? assuming tower ATC approves it (my impression, FAA rules allow one to make visual approach followed by missed along the pattern, all under IFR while clear of clouds of course)

Edited January 17, 2024 by Ibra

[McMooney]

if you decline the visual at kdal you get banished to the runway of shame 8).

you could almost hear the controller thinking why is this bugsmasher messing up my congo line.

I just had to have the KDAL ILS in the logbook, bad bugsmasher, bad

Edited January 17, 2024 by McMooney

[Will.iam]

Ok a few things. My previous airline was doing visual approaches backed up by the ils in the fms. If we had to go around (rare but it does happen) we would just fly the fms published missed approach i. E. The ils. This worked for years until one day a goaround was done and there was traffic over the end of the airport at 4000ft which was the same as the published miss. Tower assumed we would do a standard pattern altitude which for jets is 1500ft AGL after the asap report the company assimilated new procedures that if we were cleared a visual approach you must put in the 1500ft agl altitude into the box so that you would not climb higher as ATC is expecting that for a missed visual approach if they have not given you instructions before then. FYI

CAT IIII and CAT I are usually no different except for redundancy and monitoring. Just like FIKI aircraft have to have certified parts and backup systems where there are other moonies that have the anitice systems but because they don’t have the backups they are not FIKI certified. The CAT III  is certified to 0ft has to have a generator backup must actively have the approach area clear and monitored that all systems are working. When the generator is down for maintenance for example that ILS will be notamed cat II or even CAT I until that redundant aystem is back online. The CAT I does not have to have a backup gen etc so cheaper to operate. We have done autolands on a CAT I approach and the jet autolands beautifully but we have to have CAT I visibility to monitor it and take over if a problem does develop. 
 

second ILS and LPV are similar to us the pilots but are very different in one key area. The GS on an ILS is from a transmitter that is certified by the FAA to be accurate the LPV gets its Glide path from GPS which at best guarantee accuracy is 7,6 meters or 24.9ft   
but here is the kicker that i just learned this past year. Now maybe garmin is different i have not gone out and tested this but in our jets an RNAV approach gets its hight from the baro altimeter NOT the gps! We had a crew that flew into key west and the atis was down so they get the altimeter setting from their Flight Deck pro app. Problem was in the heat of the approach they accidentally put in airport ewr not eyw and put in the wrong altimeter setting which wouldn’t you know Murphy’s law it was different than the local airport by 400ft and put them 400ft lower than what they should have been and the autopilot flew the approach at that lower altitude! The egpws which is supposed to warn of terrain blends out as you get close to the runway as you do not want false alerts when you are trying to land so at 1500ft they were really at 1100ft and then when they started descending after the FAF they were close enough that the egpws warning floor was also lowering as well. They were very lucky they did not hit a tree or something else. 
Bottom line triple check your altimeter is accurate and current for the airport you are landing at as the rnav is based on that setting and it has to be accurate the fms does not crosscheck the gps altitude with the altimeter to give you a warning if you incorrectly set the altimeter. Now had they been on an ILS even though they would have been 400ft low they would not have started  their descent until GS capture and that would have just been a little closer to the airport before they started down to the runway and even though the aitimeter would have shown high when they finally got on the GS they would have been clear of all obstacles. The RNAV unfortunately started down way to early as it was using the wrong baro setting and it was the crew that finally recognized it and took over manually. Had this been  in the weather they would have hit the ocean before getting to their DA. 
i always assumed the RNAV with terrain clearance like the garmin 530W has that it would warn me of terrain and maybe they do but at my airline it didn’t. Someone needs to go out in their mooney and set an altimeter setting like 2000ft low while flying at 2000ft and see if the terrain warning will go off. I would but my plane is in annual so will have to wait. 
 

[larrynimmo]

As a back-up to altitude awareness, by Foreflight data line lists “GPS altitude”. Everytime I fly an approach, I make sure that my Promax, G5, and 6pack alt are reading basically the same

[Ibra]

13 hours ago, Will.iam said:

Tower assumed we would do a standard pattern altitude which for jets is 1500ft AGL after the asap report the company assimilated new procedures that if we were cleared a visual approach you must put in the 1500ft agl altitude into the box so that you would not climb higher as ATC is expecting that for a missed visual approach if they have not given you instructions before then

I think the lack of missed procedure for visual approach makes things open to interpretation, however, I am sure all 4 options: landing, flying visual pattern, flying instrument missed, or flying instrument departure should be available following visual approach (the 4 cases require tower clearance) 

I would hope the tower does not treat visual pattern following visual approach as request for flying VFR pattern or VFR overhead approach? where IFR clearance gets terminated past some fix, altitude or runway threshold

[Ibra]

14 hours ago, Will.iam said:

Now maybe garmin is different i have not gone out and tested this but in our jets an RNAV approach gets its hight from the baro altimeter NOT the gps! We had a crew that flew into key west and the atis was down so they get the altimeter setting from their Flight Deck pro app. Problem was in the heat of the approach they accidentally put in airport ewr not eyw and put in the wrong altimeter setting which wouldn’t you know Murphy’s law it was different than the local airport by 400ft and put them 400ft lower than what they should have been and the autopilot flew the approach at that lower altitude! The egpws which is supposed to warn of terrain blends out as you get close to the runway as you do not want false alerts when you are trying to land so at 1500ft they were really at 1100ft and then when they started descending after the FAF they were close enough that the egpws warning floor was also lowering as well. They were very lucky they did not hit a tree or something else. 

This was similar serious incident using BARO L/VNAV, the crew actually say the ground as wheels were 6ft from it, I am sure one need new trousers after such sight !

https://bea.aero/fileadmin/user_upload/BEA2022-0219_9H-EMU_preliminary_report_for_publication_EN_finalise.pdf

The various glitches from “BARO VNAV” are not a concern on LPV or L/VNAV using “3D GPS” like G530W with WAAS input in most piston GA, if one sets wrong QNH they may misjudge DA or DDA, however, their glide path remains the same: aircraft wheels will be on same touchdown point of the runway, which is the goal at the end of the day?

For terrain awareness, it’s better to have something like “AGL in ForeFlight” or using panel GPS with no flight plan? I had one terrain warning from iPad while altimeter showed sensible reading, it scared the hell out of me, went on the missed climb to get my act together and double check, it turns out to be a spurious one maybe with intermittent gps signal…

Edited January 20, 2024 by Ibra

[GeeBee]

Will.iam is correct. The correct missed approach for a visual approach is straight ahead 1500' jets, 1000' piston follow tower instructions or fly the visual pattern. You do not fly the published missed, because that was not the approach you were cleared for and thus, ATC does not protect the fix or the altitude.

[Will.iam]

3 hours ago, Ibra said:

I think the lack of missed procedure for visual approach makes things open to interpretation, however, I am sure all 4 options: landing, flying visual pattern, flying instrument missed, or flying instrument departure should be available following visual approach (the 4 cases require tower clearance) 

I would hope the tower does not treat visual pattern following visual approach as request for flying VFR pattern or VFR overhead approach? where IFR clearance gets terminated past some fix, altitude or runway threshold

I’m just saying what was explained to us. Our pilot crews were assuming like you are and when there was a near collision our airline found out what I’m explaining to you now. Tower is expecting you to climb to pattern altitude if you did not get any other instructions beforehand. 99 times out of a hundred you are landing and this doesn’t come up or there is not traffic overhead and thus not a conflict, but if you climb the miss instrument approach procedure without getting that approved after you received cleared for the visual you will be the one in the wrong. As geebee also stated this is the way. We have now adjusted accordingly and as they say cleared the visual in goes 1500ft agl in the control panel. Used to be distracting as i was looking on the chart for field elevation and then having to do public math and round up to the nearest hundred until another pilot showed me just look at the automatic cabin controller set altitude as it’s always showing field elevation of landing airport then just add the 1500 to that. 

[Will.iam]

4 hours ago, Ibra said:

This was similar serious incident using BARO L/VNAV, the crew actually say the ground as wheels were 6ft from it, I am sure one need new trousers after such sight !

https://bea.aero/fileadmin/user_upload/BEA2022-0219_9H-EMU_preliminary_report_for_publication_EN_finalise.pdf

The various glitches from “BARO VNAV” are not a concern on LPV or L/VNAV using “3D GPS” like G530W with WAAS input in most piston GA, if one sets wrong QNH they may misjudge DA or DDA, however, their glide path remains the same: aircraft wheels will be on same touchdown point of the runway, which is the goal at the end of the day?

For terrain awareness, it’s better to have something like “AGL in ForeFlight” or using panel GPS with no flight plan? I had one terrain warning from iPad while altimeter showed sensible reading, it scared the hell out of me, went on the missed climb to get my act together and double check, it turns out to be a spurious one maybe with intermittent gps signal…

^^^^THIS RIGHT HERE! Same thing happened to a crew of ours as well. When i read the report i was just stunned. I don’t know why i assumed that other safety checks would save you like the baro altitude is being crosschecked with the gps right? Nope. And in the weather there would be no way to tell except the radio altimeter reading and verifying that with the FAF altitude. This lack of verification reminds me of an oceanic crossing when we were in an older B767 that did not have gps only the 3 IRUs they would start to drift after you got out of range of land based VORs but the drift was slow enough that you could make the ocean crossing with only being a few miles off course. This one trip, i noticed only halfway across the pond that my handheld gps i had stuck by the window was showing us going further and further off the planned route. This prompted us to look at our IRU page to see what each individual iru was doing and sure enough IRU 1 was 40 miles off from what IRU2 and IRU3 were showing. What was scary is that the system did not pop up a warning nor did the system do what it’s supposed to do and that is compare the 3 iru’s and follow the 2 that are close together and not the 1 iru that’s going astray unfortunately the autopilot was following the 1iru and ignoring the other 2. We switched the autopilot to heading mode and followed the 2&3 iru’s but it was distracting seeing our track on the main displays going further and further to the right. On coastin we verifed our position with center and we were where we should be and we wrote up the #1 IRU when we landed but i often wondered what would have happened if i had not had that portable gps with us to alert us that something was wrong because in the cockpit it looked like we were right on track following the magenta line and when you are out over the ocean there are no visible landmarks to verify your position but in reality we were drifting off course. I heard recently that over near IRAN there have been some gps spoofing that slowly feeds in errors so small that the navigation system doesn’t detect the spoof and over time of hours not mins the plane will be 10’s of miles off course enough so that some crews have inadvertently flown into another country’s airspace without out prior approval and it’s gotten them into hot water. 

[PT20J]

I believe that flying a published missed approach requires a clearance. If you are cleared for an approach that has a published missed, that clearance includes the published missed. If you are cleared for a visual approach, you are not cleared to execute the missed approach for a different approach (e.g., ILS) unless you request it.

My understanding is that the TSO-C145 navigators calculate glidepath using GPS. Baro-aiding is used in these units to improve integrity checking. Normally, an APV approach requires solutions from 5 satellites, but baro-aiding can substitute for one satellite.

https://www.faa.gov/sites/faa.gov/files/about/office_org/headquarters_offices/ato/RNAV_QFacts_final_06122012.pdf

Skip

 

[Will.iam]

1 hour ago, PT20J said:

I believe that flying a published missed approach requires a clearance. If you are cleared for an approach that has a published missed, that clearance includes the published missed. If you are cleared for a visual approach, you are not cleared to execute the missed approach for a different approach (e.g., ILS) unless your request it.

My understanding is that the TSO-C145 navigators calculate glidepath using GPS. Baro-aiding is used in these units to improve integrity checking. Normally, an APV approach requires solutions from 5 satellites, but baro-aiding can substitute for one satellite.

https://www.faa.gov/sites/faa.gov/files/about/office_org/headquarters_offices/ato/RNAV_QFacts_final_06122012.pdf

Skip

 

Skip, still curious if you or someone else purposely sets your baro 2kft higher than current setting to see what a garmin will show or do with a gps baro discrepancy and if it does flag it at what altitude deviation is that threshold. It would be interesting to test for that situation now on a clear day so you know what safety if any you have for when you are imc. 

[Ibra]

1 hour ago, Will.iam said:

curious if you or someone else purposely sets your baro 2kft higher than current setting to see what a garmin will show or do with a gps baro discrepancy and if it does flag it at what altitude deviation is that threshold

I think in most Mooney like pistons, the instrument procedures: LPV, L/VNAV (and LNAV+V) systematically get their glide from SBAS signal, the Garmin navigator is not aware of QNH or baro inputs when you fly 3D RNP APCH 

I only come across two exceptions that has BARO navigation like the one in jets: PA46 (2000 model) and SR22 G5 that could do BARO L/VNAV procedure (even when you disable SBAS), nothing gets flagged if you set wrong QNH !

Note that barometric altitude gets used in en-route VNAV glides such as cruise climb or cruise decent, it will use barometric input (in VPATH mode, you bug target  barometric altitude to change level, then Garmin calculate TOD or glide using barometric data), the 3D VNAC magenta builds slope using barometric delta and track miles, if you rotate the QNH on cruise vertical navigation, your glide change...

Edited January 20, 2024 by Ibra

[Ibra]

3 hours ago, PT20J said:

If you are cleared for a visual approach, you are not cleared to execute the missed approach for a different approach (e.g., ILS) unless your request it

Yes, the missed has to be requested by PIC or instructed by ATC, it’s not implied in visual clearance….isn’t this applicable to flying pattern in ATC airport? you are not automatically cleared to join pattern from visual unless you explicitly request it?

In untowred airport, I guess there is one easy answer: visual, pattern, land 

For ATC airport, it’s not clear, no pun intended, what the clearance limit (fix and/or altitude restriction) for a visual approach if one can’t land:

- Runway threshold? is used by tower for visual separation, is further ATC clearance required to go past runway threshold?

- Visual pattern? it make sense as an accepted limit (weather should be ok), does one need further ATC clearance to enter downwind?

- Clearance limit = radar/procedure altitude? ceiling > 500ft than MIA or MVA, hence, one can always self-separate and self-navigate visually under these, can one climb back to FAF altitude?

In busy airports, ATC seems to issue vector and they may even send one to the departure frequency (aka back of the queue rather than N#1 in pattern)

It’s a hypothetical question: one will always get an amended clearance from tower following go-around on visual (in meantime, ATC therapists make tons of money )

Edited January 20, 2024 by Ibra

[EricJ]

I have Scottsdale tower on the scanner in my office all the time.   Traffic from the north gets held high to clear terrain and if 21 is the active runway they'll get cleared for the visual straight in, but many of the jets wind up unprepared and can't get down in time to make the runway.   It's a very frequent thing, and it's not at all unusual to hear a call in sometime after being cleared to land that they'll not be able to make the runway.   The tower either puts them on downwind to circle back or has them fly down the runway and make a pattern back to 21.   It's never a big deal, but I don't think I've ever heard anybody do a missed approach to go try again.

[PT20J]

On 1/20/2024 at 1:32 PM, Will.iam said:

Skip, still curious if you or someone else purposely sets your baro 2kft higher than current setting to see what a garmin will show or do with a gps baro discrepancy and if it does flag it at what altitude deviation is that threshold. It would be interesting to test for that situation now on a clear day so you know what safety if any you have for when you are imc. 

I asked Garmin aviation support the following:

During a RNAV LPV approach, if the altimeter setting is grossly incorrect so that the baro altitude is significantly different than the GPS altitude, how will the GTN be affected? Will any error messages be displayed?

I just received the following answer: 

Thank you for contacting Garmin International. If the barometer is not correct, you could receive warnings for low altitude or busting through minimums on an approach. Once passed a certain point, a missed approach warning could result on the screen. 

I guess I do need to add this to my list of things to test