Part 91 Instrument Approach Question

[kaj837]

I know, or at least I am pretty sure, that under Part 91 it is legal to start an approach even though the reported visibility is below landing minimum, and that when you arrive at the DA or MAP the pilot becomes the official observer, and can land if he has the required minimum visibility, regardless of what is being officially reported. My question is where is this written? Is it somewhere in Part 97? This is to settle an argument and I cannot find the reference.

 

[A Squared]

I know, or at least I am pretty sure, that under Part 91 it is legal to start an approach even though the reported visibility is below landing minimum, and that when you arrive at the DA or MAP the pilot becomes the official observer, and can land if he has the required minimum visibility, regardless of what is being officially reported.

That is correct

My question is where is this written? Is it somewhere in Part 97? This is to settle an argument and I cannot find the reference.

It isn't written. That's why it's legal. Part 135 and part 121 have specific regulations which tell you that you may not beging an approach without certain minimum weather conditions. THere is nothing in Part 91 forbidding begining an approach.

Regulations in general tell you what you cannot do, not what you can do. In the very rare cases where a regulation tells you that you can do something, It is because that thing would be otherwise forbidden by another regulation.

If you want to settle the argument, ask your friend; OK, if it's forbidden, and I did it with a fed on board, which regulation would they charge me with violating?

He won't be able to point to a regulation which you have broken, so, you must conclude that it's actually legal. If you were flying 135 or 121 it would be very easy to point to which regulation you've violated, no such regulation existes in Part 91. Part 97 is not regulations for flying aircraft, it is regulations for designing approaches.

 

[kaj837]

Thanks A-Squared. That is exactly the line of my argument. I generally take the stance that that which is not prohibited is allowed. The other participant in this debate, who happens to be my son-in-law has been flying 121 so long that I think he forgot that anyone flies under Part 91.

Do you, or anyone, know if it is written anywhere that the pilot becomes the official observer at the DA or MAP, or is that simply the logic of the situation? Am I correct about that?

 

[A Squared]

Thanks A-Squared. That is exactly the line of my argument. I generally take the stance that that which is not prohibited is allowed. The other participant in this debate, who happens to be my son-in-law has been flying 121 so long that I think he forgot that anyone flies under Part 91.

Ahhh, I see. If he needs more convincing, tell him to look up 121.651(b), remind him that's the reg whhich prohibits him from begining an approach without the required visibility. Now, challenge him to find anything even remotely like it in Part 91. If he's still not convinced, have your daughter divorce him before they have kids and perpetuate those genes

Do you, or anyone, know if it is written anywhere that the pilot becomes the official observer at the DA or MAP, or is that simply the logic of the situation? Am I correct about that?

Yeah you're correct. Take a look at the regulation. 91.175(b). it specifies that you may not descend below DH or MDA unless the flight visibility is greater than the minimum. Now go read the definition of "Flight Visibility" in Part 1. There is only one person that can determine the flight visibility, and that is the pilot. (Or I guess 2 persons in the case of a 2 pilot crew) It's impossible for an observer on the ground to determine how far you can see from the cockpit, and that is what flight visibility is.

Now, at this point in the discussion, your son-in-law may claim that RVR, if available, takes precedence over flight visibility (can you tell I've been through this argument before?) It does not. If he insists, ask him to show you where that is rated. He will not be able to.

 

[kaj837]

Thanks again A-Squared. Now I remember where it is written, it's been a while since I had to know that.

Unfortunately it is too late for a divorce, but he is actually a pretty good guy, and is now convinced.

 

[WindBraker]

i thought 121.651(b) does not prohibit from begining the approach, but prohibits from continuing beyond the final approach fix if the vis is below landing min's? (unless you are already established on the final approach segment

 

[paulsalem]

Ahhh, I love part 91.

 

[A Squared]

i thought 121.651(b) does not prohibit from begining the approach, but prohibits from continuing beyond the final approach fix if the vis is below landing min's? (unless you are already established on the final approach segment

Yes, you're right. I wasn't thinking when I wrote that. Thanks for catching that.

 

[minitour]

So RVR can be reporting 800 and I can still claim "oh yes sir...I could see 1/2 mile from the airplane" and land my chickenhawk legally?

I'm wondering if RVR is reporting that low, how believable would it be to have 1/2 mile flight visibility.

Anyone know of a legal ruling on such a "case"?

-mini

 

[A Squared]

So RVR can be reporting 800 and I can still claim "oh yes sir...I could see 1/2 mile from the airplane" and land my chickenhawk legally?

I'm wondering if RVR is reporting that low, how believable would it be to have 1/2 mile flight visibility.

Anyone know of a legal ruling on such a "case"?

-mini

It's going to come down to whether it's plausible or not. If the reported weather is calm, vis < 1/4 mile, ceiling obscures and RVR is reporting 800 ft, I don't think anyone is goign to believe you. If an inspector was around, and he wanted to, he could certainly initiate an enforcement. I don't hink it would be a surprise to anyone if you were violated. The next step is an appeal before an ALJ. THe ALJ when faced with on one hand a MEtar showing a very very foggy day, and an inspector who was there testifying to the bad vis and on the other hand there's you who claims to have had 1/2 mile vis, he will make a "finding of credibility" in other words, decide who to beleive. You think he's going to beleive you? DOn't bet on it.


If on the other hand, you need 1/2 mile vis and the RVR is 2200 and the weather conditions are clear with blowing snow on the surface, you probably *do* have more than 1/2 mile flight visibility, (especially at night) in fact, you can probably see every single runway light from the outer marker. I've been in those conditions, and it's quite possible. If I were Part 91, I wouldn't hesitate to fly the approach and land. Of course, the times I've encountered this situation, I've been Part 121, so you hold, and fly circles in the clear sky, looking at the runway lights, until the RVR comes up.

 

[pilothouston123]

asos indefinant ceiling, vis 1/8 wind calm


remote airport with full ILS. the only thing you will see is appraoch lights and runway lights at night. Pretty cool
I did it 20 times when I was flying my buddies to gamble.

 

[b350capt]

per the FAA:

...Enforcement action would only be taken in those cases in which the pilot could not resonably conclude flight visibility was at or above approach minimunms, but the pilot nevertheless proceeded to land.......

 

[A Squared]

per the FAA:

...Enforcement action would only be taken in those cases in which the pilot could not resonably conclude flight visibility was at or above approach minimunms, but the pilot nevertheless proceeded to land.......

Thanks, I thought I remembered reading those words in an interpretation, but didn't have a chance to sort through them to find the quote.

 

[gsrcrsx68]

Yeah you're correct. Take a look at the regulation. 91.175(b). it specifies that you may not descend below DH or MDA unless the flight visibility is greater than the minimum. Now go read the definition of "Flight Visibility" in Part 1. There is only one person that can determine the flight visibility, and that is the pilot. (Or I guess 2 persons in the case of a 2 pilot crew) It's impossible for an observer on the ground to determine how far you can see from the cockpit, and that is what flight visibility is.

Now, at this point in the discussion, your son-in-law may claim that RVR, if available, takes precedence over flight visibility (can you tell I've been through this argument before?) It does not. If he insists, ask him to show you where that is rated. He will not be able to.

I had this question as part of my practical. I was told better not land if RVR was below mins. Where would I look to support that? Well first I'd start with an approach would specify RVR, then I'd look 91.175(h)(1)...That specifies Ground visibility, not flight visibility be substituted for lack of rvr reported.

Then I'd go to ground visibility in part one and realise that I am not an accreddited observer or the U.S. National weather service or for that matter near the earths surface(although I guess that could be open for interpretation) and could not declare the visibility myself. I don't see anywhere I am allowed to convert RVR to flight visibility.

 

[minitour]

I don't see anywhere I am allowed to convert RVR to flight visibility.

You don't have to.

You don't need ground visibility to descend below MDA/DH and/or land. You just need flight visibility. All that 91.175(h) tells you is that, if RVR is specified in the approach, but it isn't reported (except for cat 2 and 3) as RVR for that runway, you should know that (for example) 3200 RVR = 5/8 Mile...ground visibility.

...assuming it's believable enough that the 3200RVR lets you in on an approach that you need 1 mile to land...

Good thread here...big thanks to the poster!

-mini

 

[A Squared]

I had this question as part of my practical. I was told better not land if RVR was below mins. Where would I look to support that? Well first I'd start with an approach would specify RVR, then I'd look 91.175(h)(1)...That specifies Ground visibility, not flight visibility be substituted for lack of rvr reported.

Then I'd go to ground visibility in part one and realise that I am not an accreddited observer or the U.S. National weather service or for that matter near the earths surface(although I guess that could be open for interpretation) and could not declare the visibility myself. I don't see anywhere I am allowed to convert RVR to flight visibility.

As Minitour pointed out, all 91.175(h) does is allow you to substitute Ground Vis for RVR if needed. It has nothing to do with whether you can descend below MDA/DA. that is governed by 91.175 (c) ...and that specifies flight visibility.

 

[gsrcrsx68]

You don't have to.

You don't need ground visibility to descend below MDA/DH and/or land.
-mini

Unless RVR is unavailable...then you need it To Land. True, 91.175 (c)(2) does allow you to operate under the DH, but operating under the DH does not mean you have met landing minimums...You can operate below the DH until 91.175(c)(1) is no longer possible.

The question morphed a bit from the original. The word "Land" got tossed in along the way. I still wont be landing if RVR is below landing minimums...Actually I wont even be flying then...

 

[paulsalem]

Unless RVR is unavailable...then you need it To Land. True, 91.175 (c)(2) does allow you to operate under the DH, but operating under the DH does not mean you have met landing minimums...You can operate below the DH until 91.175(c)(1) is no longer possible.

The question morphed a bit from the original. The word "Land" got tossed in along the way. I still wont be landing if RVR is below landing minimums...Actually I wont even be flying then...

(2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used; and

RVR is NOT FLIGHT VISIBILITY

 

[gsrcrsx68]

(2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used; and

RVR is NOT FLIGHT VISIBILITY

Nobody said RVR is Flight Visibilty. However you do find RVR under Visibility in the pilots glossary.

So are you saying you would be ok to land if a SIAP specified RVR and RVR was reported to be less than the minimum but you had the required flight visibility? I wouldn't do it.

Plus the allowed substitution for the landing minimums (where RVR is specified) is ground visibilty, not flight visibility.

The only thing I stated was I didn't believe you'd be ok to land...

 

[paulsalem]

Nobody said RVR is Flight Visibilty. However you do find RVR under Visibility in the pilots glossary.

So are you saying you would be ok to land if a SIAP specified RVR and RVR was reported to be less than the minimum but you had the required flight visibility? I wouldn't do it.

Plus the allowed substitution for the landing minimums is ground visibilty, not flight visibility.

The only thing I stated was I didn't believe you'd be ok to land...

By the letter of the law it would be legal.

 

[gsrcrsx68]

By the letter of the law it would be legal.

Really? At what point would you have met landing minimums specified in RVR?

 

[paulsalem]

If the fed came up to be and said you landed w/o the requried vis. I'd say "Sir, when I saw the runway environment, I had the flight visibility required for the published IAP. I am operating under FAR 91."

Don't misunderstand me, I'm not talking about lying about flight vis here. I'm simply saying that you COULD land if the RVR was below mins under part 91 IF you had the required flight visibility.

This is how I understand it.

 

[gsrcrsx68]

good enough...we gots a different view.

I spent too much time thinking this about this!

Thanks All.

 

[paulsalem]

I'm a little confused. Can you quote me a reg that states you must have RVR or Ground Visibility to land?

 

[gsrcrsx68]

Well RVR would be specified on the instrument appoach chart, making it the visibility portion of the landing minimum.

91.175(h)(2) specifies that if RVR is not reported then the RVR minimum shall be converted to ground visibility and that shall be the minimum the visibility minimum.

 

[paulsalem]

Well RVR would be specified on the instrument appoach chart, making it the visibility portion of the landing minimum.

91.175(h)(2) specifies that if RVR is not reported then the RVR minimum shall be converted to ground visibility and that shall be the minimum the visibility minimum.

Well i see where you are comming from. But 91.175(h)(2) only give you the ability to convert RVR into Ground Vis. This would only be useful IF ground vis/RVR was required for the approach (part 121, 135).

Below you'll read that for part 91 fight viibility is all thats required.

91.175

(d) Landing. No pilot operating an aircraft, except a military aircraft of the United States, may land that aircraft when—

(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.

No where does it say that the ground vis is required. If you belive otherwise can you quote it to me?

IF you still don't belive me, maybe ASquared will chime in, or someone else with more experience than us.

 

[gsrcrsx68]

Well i see where you are comming from. But 91.175(h)(2) only give you the ability to convert RVR into Ground Vis. This would only be useful IF ground vis/RVR was required for the approach (part 121, 135).

(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.

No where does it say that the ground vis is required. If you belive otherwise can you quote it to me?

I like your line of thought. That is good lawyering. If I ever get in a bind over this it will certainly be my defense. The word visibility(above) includes RVR and/or Ground Visibility prescribed by the procedure(pilots glossary). So in a way it almost adds an addtional burden of being sure that flight visibility is above the RVR prescribed on the chart. I have still not seen a reg that would allow me to operate in a way that is different from what is prescribed on a SIAP. Do you have a reg that states you may fly the procedure differently than what is printed on an approach chart?

(h)(2) tells you that if rvr is not reported then ground vis shall be(not may) used for an approach requiring RVR.

I would like to know if anyone has ever been violated on landing below the mins.

I still wouldn't do it...though I like your thinking.

 

[Doc Holiday]

paulsalem is correct. But I think where the confusion is coming from is the whole Part 91/135/121 thing. If you are at the DA/MDA on an approach, it does not matter what rules you are operating under (civilian), all you need is the required FLIGHT visibility to continue lower.

The difference between 91 and 135/121 happens way before you get to this point. Under Part 135/121 you may NOT start an approach if the airport is below minimums, and you may NOT pass the FAF if the weather is below minimuns for that particular approach. (minimums = RVR if reported or visibility)

gsrcrsx68, this is where the whole converting RVR to ground visibility and all that stuff you've be referencing comes into play - it is required for 135/121 to pass the FAF. After you're inside the FAF, the rules are the same. You just need the required FLIGHT visibilty.

 

[A Squared]

I would like to know if anyone has ever been violated on landing below the mins.

Probably. I couldn't find an NTSB decision that exactly addresses this but I did find one that is interesting in the larger context of the discussion.

http://www.ntsb.gov/o_n_o/docs/AVIATION/4338.PDF

Briefly the guy landed when reported vis was 1/16 SM and ran off the runway. He claimed that he had the runway lights in sight at 1500 ft. The FAA attelpted to violate him for a whole bunch of stuff, including a violation of 91.175(d). In his intital appeal, the ALJ accepted his statement that he had hte runway lights from 1500 ft, so the 91.175(d) chahrge was dismissed. This document linked is his appeal to the full board on the other charges, which was denied, but it does discuss how the 91.175(d) charge was dismissed in the previous appeal.

Two lessons:

1) Yes it is possible to beat a 91.175(d) violation if the judge beleives that you did have the flight visibilty, even though the reported vis is below minimums.

2) If you run of the runway and bend an airplane while landing when the reported vis is lower than the minimum , you're going to get violated for something, probably 91.13

 

[Donsa320]

Probably. I couldn't find an NTSB decision that exactly addresses this but I did find one that is interesting in the larger context of the discussion.

http://www.ntsb.gov/o_n_o/docs/AVIATION/4338.PDF

Briefly the guy landed when reported vis was 1/16 SM and ran off the runway. He claimed that he had the runway lights in sight at 1500 ft. The FAA attelpted to violate him for a whole bunch of stuff, including a violation of 91.175(d). In his intital appeal, the ALJ accepted his statement that he had hte runway lights from 1500 ft, so the 91.175(d) chahrge was dismissed. This document linked is his appeal to the full board on the other charges, which was denied, but it does discuss how the 91.175(d) charge was dismissed in the previous appeal.

Two lessons:

1) Yes it is possible to beat a 91.175(d) violation if the judge beleives that you did have the flight visibilty, even though the reported vis is below minimums.

2) If you run of the runway and bend an airplane while landing when the reported vis is lower than the minimum , you're going to get violated for something, probably 91.13

On the other hand if you land with the RVR or reported visibility at or better than required and you then run off the runway or have some other incident, you cannot claim that you could not see enough to make a safe landing. It is always the pilot's responsibility to see that the visibility is really at or above the required visibility minimum. IMHO

DC