Far 91.175
11-09-2012, 01:45 PM
#1
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Far 91.175
Hi Folks,
I am currently in a debate with a friend of mine who is a captain at an airline and that according to their (the airlines) interpretation of 91.175 they can go down to 100 feet above TDZE if they see the approach lights even though the flight visibility is determined to below minimums. The argument here is that you just cannot land unless you have at least the required min flight visibility.
Please help me understand this. The way I read 91.175 is that you need 3 things to descend below MDA/DH and one of them is the required flight visibility. The approach lights to 100 TDZ clause says pretty clearly that you need the red side rows or terminating bars to descend below this altitude; 100 above TDZE. It does not say anywhere in 91.175 that if the pilot sees the approach lights he can ignore the visibility and descend from MDA/DH to 100 feet above TDZE.
I understand this reg to say that if at DH/MDA and you do not have the flight visibility applicable to your category you must go missed approach no matter what you see.
Any thoughts?
Don't laugh, I am tired, I meant FAR not Far. It won't let me change it.
I am currently in a debate with a friend of mine who is a captain at an airline and that according to their (the airlines) interpretation of 91.175 they can go down to 100 feet above TDZE if they see the approach lights even though the flight visibility is determined to below minimums. The argument here is that you just cannot land unless you have at least the required min flight visibility.
Please help me understand this. The way I read 91.175 is that you need 3 things to descend below MDA/DH and one of them is the required flight visibility. The approach lights to 100 TDZ clause says pretty clearly that you need the red side rows or terminating bars to descend below this altitude; 100 above TDZE. It does not say anywhere in 91.175 that if the pilot sees the approach lights he can ignore the visibility and descend from MDA/DH to 100 feet above TDZE.
I understand this reg to say that if at DH/MDA and you do not have the flight visibility applicable to your category you must go missed approach no matter what you see.
Any thoughts?
Don't laugh, I am tired, I meant FAR not Far. It won't let me change it.
11-09-2012, 02:28 PM
#2
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In our op specs it says the same as 91.175 that visibility is above the mins being used. For Cat I approaches.
As for Cat II, it does not apply because you are 100 ft. And you can sometimes go to 500RVR.
However, his airline might have approved op specs approved by the FAA to do that in Cat I. It all depends. So my suggestion would be to ask him to prove it in his op specs.
As for Cat II, it does not apply because you are 100 ft. And you can sometimes go to 500RVR.
However, his airline might have approved op specs approved by the FAA to do that in Cat I. It all depends. So my suggestion would be to ask him to prove it in his op specs.
11-09-2012, 02:35 PM
#3
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I do not think it is an Opspec for Cat 1.
Allot of people interpret this way and I just have to agree to disagree. But I seem to be one of the very few outliers on this so maybe I am missing something here.
Allot of people interpret this way and I just have to agree to disagree. But I seem to be one of the very few outliers on this so maybe I am missing something here.
11-09-2012, 02:40 PM
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Flight visibility isn't what the tower is stating the visibility is from his transometer, so when the crew gets to that point they can use the lights to go another 100 feet about TDZE because they the crew had the flight visibility, I agree many ops specs for many airlines are all written differently , so by asking for answers from a forum may lead to several answers as airway airlines ops specs are written for them only, In my opinion it is sort of a grey area.
Same concept when they discuss passing the FAF after the tower via has gone below mins. Cause the inflight visibility is what the crew claims they have ....
Greyish my friend , grayish
Same concept when they discuss passing the FAF after the tower via has gone below mins. Cause the inflight visibility is what the crew claims they have ....
Greyish my friend , grayish
11-09-2012, 03:12 PM
#5
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This is the heart of the debate here in that I do not believe this is a grey area. I also do not believe an Opspec exists for this specific example of being able to ignore the visibility clause in 91.175 down to 100 TDZE.
I'll give you an example. The classic question of the Reno ILS where it has a 7sm min visibility. The question is can you, at DH continue the approach with ONLY the approach lights in sight? Well, I was corrected after saying you cannot. If you break out at DH on this approach and can only see the approach lights than you only have 6 miles. If you had 7 than you could see up to the mid point of the airport. So since your flight visibility is below mins you must execute a missed approach. The argument here that I disagree with is that you can descend to 100 above TDZE because you see the approach lights and can do it below minimums until reaching 100 feet and then you must have visibility minimums to proceed below that point. I do not believe this is a grey area here because it clearly states you need 3 things (again unless I am missing something which has been known to happen before):
1. Stabilized approach - Aircraft in a position to make descent using normal maneuvers.
2. Flight visibility - At least the minimum published applicable to your category.
3. Approach lights or runway - Except you cannot use just the approach lights beyond 100 TDZE unless you have the red side rows or terminating bars, then you can.
When it talks about the 100 foot above TDZE it is simply placing a limitation on using the approach lights. Not using them in leu of the visibility minimums. Otherwise, as government regulations are written, their would be wording such as "not withstanding" yadda yadda if the pilot sees the approach lights he can continue descent in leu of visibility minimums, etc.
I am interested if any FAA guys are here and can chime in.
I'll give you an example. The classic question of the Reno ILS where it has a 7sm min visibility. The question is can you, at DH continue the approach with ONLY the approach lights in sight? Well, I was corrected after saying you cannot. If you break out at DH on this approach and can only see the approach lights than you only have 6 miles. If you had 7 than you could see up to the mid point of the airport. So since your flight visibility is below mins you must execute a missed approach. The argument here that I disagree with is that you can descend to 100 above TDZE because you see the approach lights and can do it below minimums until reaching 100 feet and then you must have visibility minimums to proceed below that point. I do not believe this is a grey area here because it clearly states you need 3 things (again unless I am missing something which has been known to happen before):
1. Stabilized approach - Aircraft in a position to make descent using normal maneuvers.
2. Flight visibility - At least the minimum published applicable to your category.
3. Approach lights or runway - Except you cannot use just the approach lights beyond 100 TDZE unless you have the red side rows or terminating bars, then you can.
When it talks about the 100 foot above TDZE it is simply placing a limitation on using the approach lights. Not using them in leu of the visibility minimums. Otherwise, as government regulations are written, their would be wording such as "not withstanding" yadda yadda if the pilot sees the approach lights he can continue descent in leu of visibility minimums, etc.
I am interested if any FAA guys are here and can chime in.
11-09-2012, 03:25 PM
#6
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Flight visibility can ONLY be determined by the pilot(s) flying the approach once you break out.
Once you're inside the FAF and visibility drops below mins it is being reported by the WX reporting machines on the ground. If the airport has a tower they could report surface visibility, or if the airport is equipped, RVR which is controlling of course.
Only the pilot(s) flying the approach can determine if they have the required flight visibility to land the aircraft within the FARs. If they do and the WX is reported below mins they better be able to back it up somehow. How they'd do that is beyond me.
Once you're inside the FAF and visibility drops below mins it is being reported by the WX reporting machines on the ground. If the airport has a tower they could report surface visibility, or if the airport is equipped, RVR which is controlling of course.
Only the pilot(s) flying the approach can determine if they have the required flight visibility to land the aircraft within the FARs. If they do and the WX is reported below mins they better be able to back it up somehow. How they'd do that is beyond me.
11-09-2012, 04:13 PM
#7
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Originally Posted by captain152
Flight visibility can ONLY be determined by the pilot(s) flying the approach once you break out.
Once you're inside the FAF and visibility drops below mins it is being reported by the WX reporting machines on the ground. If the airport has a tower they could report surface visibility, or if the airport is equipped, RVR which is controlling of course.
Only the pilot(s) flying the approach can determine if they have the required flight visibility to land the aircraft within the FARs. If they do and the WX is reported below mins they better be able to back it up somehow. How they'd do that is beyond me.
Once you're inside the FAF and visibility drops below mins it is being reported by the WX reporting machines on the ground. If the airport has a tower they could report surface visibility, or if the airport is equipped, RVR which is controlling of course.
Only the pilot(s) flying the approach can determine if they have the required flight visibility to land the aircraft within the FARs. If they do and the WX is reported below mins they better be able to back it up somehow. How they'd do that is beyond me.
11-09-2012, 04:57 PM
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Paragraph 495 of FAA Order 8400.10, Air Transportation Operations Inspector's Handbook:
“The following is a list of statements which describe what RVR is not:
(a) RVR is not a measure of meteorological visibility.
(b) RVR is not a measure of surface visibility or tower visibility.
(c) RVR is not a measure of seeing conditions on taxiways, ramps, or aprons.
(d) RVR is not a measure of seeing conditions at or near MDA or DH.
(e) In the U.S., RVR is not measured or reported by a human observer.
(f) RVR IS NOT ‘VISIBILITY.’ "
The Pilot/Controller Glossary defines flight visibility:
“Flight Visibility - 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.”
AC 120-29A
4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II.
a. Section 91.175 and Standard OpSpecs specify that for operation below the DA(H) or MDA(H) on an
instrument approach, the required visual reference to continue the approach must be established. Unless otherwise authorized by the CMO (e.g., POI or APM for a particular type) the required visual reference may be considered to
be those provisions as listed in section 91.175 items (c) and (d).
b. Circumstances in which the operator may request and the CMO may authorize use of alternative visual
reference provisions might be situations such as certain Category I and II minima are based on use of autoland or
HUD (see paragraph 10.5.3). In this instance provisions such as those shown in section 91.175 (c) (3) (i) for “red
terminating bars” or “red side row bars” may not be necessary or appropriate. This is because these particular
approach lighting visual references or configurations may not always be needed when operations are predicated on
HUD or autoland use. They may not even be installed or applicable as a part of the approach lighting system for the
runway or runways to be specially authorized. Conversely, for operations such as the ones noted above for autoland
or HUD, it may be determined by the operator and CMO that continued descent below the DA(H) based solely on
visual contact with a VGSI (which may in instances be otherwise permitted by 14 CFR), but without having sight of
either the runway, runway lights, touchdown zone lights, centerline lights, or runway markings would not be
appropriate. In this instance, the CMO may authorize the operator to define and use alternate visual references or
visual reference combinations for Category I and II operations, rather than relying solely on the sighting of a VGSI
as a basis for continued descent below a DA(H).
§ 91.175 Takeoff and landing under IFR.
(c) Operation below DA/ DH or MDA. Except as provided in paragraph (l) of this section, where a DA/DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, below the authorized MDA or continue an approach below the authorized DA/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; and
(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.
(d) Landing. No pilot operating an aircraft, except a military aircraft of the United States, may land that aircraft when—
(1) For operations conducted under paragraph (l) of this section, the requirements of (l)(4) of this section are not met; or
(2) For all other part 91 operations and parts 121, 125, 129, and 135 operations, the flight visibility is less than the visibility prescribed in the standard instrument approach procedure being used.
_____________________________________________
From the references above, flight visibility is not approach visibility. On approaches with a DA/DH, where a decision is being made, once established on the final segment, the approach may be continued even when the reported WX vis is below the published approach mins. Once at DA/DH(or MDA), as long as any approach lights are in sight the approach may continue. At 100' the lighting listed in 91.175 (c) must be in sight.
As a rule we would teach, at MDA/DA any lights, at 100' must see colored lights to continue.
“The following is a list of statements which describe what RVR is not:
(a) RVR is not a measure of meteorological visibility.
(b) RVR is not a measure of surface visibility or tower visibility.
(c) RVR is not a measure of seeing conditions on taxiways, ramps, or aprons.
(d) RVR is not a measure of seeing conditions at or near MDA or DH.
(e) In the U.S., RVR is not measured or reported by a human observer.
(f) RVR IS NOT ‘VISIBILITY.’ "
The Pilot/Controller Glossary defines flight visibility:
“Flight Visibility - 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.”
AC 120-29A
4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II.
a. Section 91.175 and Standard OpSpecs specify that for operation below the DA(H) or MDA(H) on an
instrument approach, the required visual reference to continue the approach must be established. Unless otherwise authorized by the CMO (e.g., POI or APM for a particular type) the required visual reference may be considered to
be those provisions as listed in section 91.175 items (c) and (d).
b. Circumstances in which the operator may request and the CMO may authorize use of alternative visual
reference provisions might be situations such as certain Category I and II minima are based on use of autoland or
HUD (see paragraph 10.5.3). In this instance provisions such as those shown in section 91.175 (c) (3) (i) for “red
terminating bars” or “red side row bars” may not be necessary or appropriate. This is because these particular
approach lighting visual references or configurations may not always be needed when operations are predicated on
HUD or autoland use. They may not even be installed or applicable as a part of the approach lighting system for the
runway or runways to be specially authorized. Conversely, for operations such as the ones noted above for autoland
or HUD, it may be determined by the operator and CMO that continued descent below the DA(H) based solely on
visual contact with a VGSI (which may in instances be otherwise permitted by 14 CFR), but without having sight of
either the runway, runway lights, touchdown zone lights, centerline lights, or runway markings would not be
appropriate. In this instance, the CMO may authorize the operator to define and use alternate visual references or
visual reference combinations for Category I and II operations, rather than relying solely on the sighting of a VGSI
as a basis for continued descent below a DA(H).
§ 91.175 Takeoff and landing under IFR.
(c) Operation below DA/ DH or MDA. Except as provided in paragraph (l) of this section, where a DA/DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, below the authorized MDA or continue an approach below the authorized DA/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; and
(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.
(d) Landing. No pilot operating an aircraft, except a military aircraft of the United States, may land that aircraft when—
(1) For operations conducted under paragraph (l) of this section, the requirements of (l)(4) of this section are not met; or
(2) For all other part 91 operations and parts 121, 125, 129, and 135 operations, the flight visibility is less than the visibility prescribed in the standard instrument approach procedure being used.
_____________________________________________
From the references above, flight visibility is not approach visibility. On approaches with a DA/DH, where a decision is being made, once established on the final segment, the approach may be continued even when the reported WX vis is below the published approach mins. Once at DA/DH(or MDA), as long as any approach lights are in sight the approach may continue. At 100' the lighting listed in 91.175 (c) must be in sight.
As a rule we would teach, at MDA/DA any lights, at 100' must see colored lights to continue.
11-10-2012, 10:06 AM
#9
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Thanks for that cougar,
I have been saying FLIGHT visibility all along, not approach or reported. So than, if the pilot determines that at DH the FLIGHT visibility is below the minimum for the approach, i.e. he can only see 500 feet in front on an 1800 rvr approach the pilot is allowed to continue below DH?
AC 120-29A
4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II.
a. Section 91.175 and Standard OpSpecs specify that for operation below the DA(H) or MDA(H) on an
instrument approach, the required visual reference to continue the approach must be established. Unless otherwise authorized by the CMO (e.g., POI or APM for a particular type) the required visual reference may be considered to
be those provisions as listed in section 91.175 items (c) and (d).
So their I am breaking out at DH on an ILS, I see only the first bar of the ALSF 2 giving me about 500 feet of visibility. I am then allowed to descent to 100 feet above TDZ where I then see some red side row bars and the flight visibility has now improved to 1800 (minimums) which means I can now descend further and land. So that trip from DH to 100 feet above TDZ with 500 feet of FLIGHT visibility seen by me the pilot was a legal maneuver?
Thanks for the patience on this one.
I have been saying FLIGHT visibility all along, not approach or reported. So than, if the pilot determines that at DH the FLIGHT visibility is below the minimum for the approach, i.e. he can only see 500 feet in front on an 1800 rvr approach the pilot is allowed to continue below DH?
AC 120-29A
4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II.
a. Section 91.175 and Standard OpSpecs specify that for operation below the DA(H) or MDA(H) on an
instrument approach, the required visual reference to continue the approach must be established. Unless otherwise authorized by the CMO (e.g., POI or APM for a particular type) the required visual reference may be considered to
be those provisions as listed in section 91.175 items (c) and (d).
So their I am breaking out at DH on an ILS, I see only the first bar of the ALSF 2 giving me about 500 feet of visibility. I am then allowed to descent to 100 feet above TDZ where I then see some red side row bars and the flight visibility has now improved to 1800 (minimums) which means I can now descend further and land. So that trip from DH to 100 feet above TDZ with 500 feet of FLIGHT visibility seen by me the pilot was a legal maneuver?
Thanks for the patience on this one.
Last edited by Denver; 11-10-2012 at 10:17 AM.
11-10-2012, 11:14 AM
#10
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Posts: 219
Originally Posted by cougar
From the references above, flight visibility is not approach visibility. On approaches with a DA/DH, where a decision is being made, once established on the final segment, the approach may be continued even when the reported WX vis is below the published approach mins. Once at DA/DH(or MDA), as long as any approach lights are in sight the approach may continue. At 100' the lighting listed in 91.175 (c) must be in sight.
As a rule we would teach, at MDA/DA any lights, at 100' must see colored lights to continue.
As a rule we would teach, at MDA/DA any lights, at 100' must see colored lights to continue.
GA/Part 91 world, flight visibility = visibility out the window and nobody knows that except the pilots. As someone stated before, if SFC Vis and/or RVR are both WAY below the min flight vis required, you may have a hard time defending your decision to continue during an enforcement action but according to the letter or the law, it is legal IF you actually had the min flight vis. Unfortunately, when it comes to this type of "gray area", it's not 100% what was legal to the T, but more about what you can prove / defend / justify when brought in to a hearing during a possible enforcement action. A good general rule for pilots... C.Y.A. and don't be stupid.
Common Example: If the runway is 10,000 ft long and the departure end (where the visibility sensor is) is <1/4 SM and you have the approach end in sight 10 miles out where a fog bank, quite literally, splits the runway (Oregon coast during the spring and fall!!!)... I'd say you're fine.
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