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.