Someone who knows explain RVR.

[siucavflight]

As it pertains to 121 operations. I know that if you are inside the FAF and RVR falls below the required for landing, but does it have to come back up in order to land?
And what about RVV?

 

[ksu_aviator]

You can continue (once inside the FAF) and you can land provided, in your observation, that you believe you have the landing minimums. It is not uncommon for RVR to be wrong, it is a machine and it is only observing one very small area. However, you might consider that if anything ever happens you'll have to find a way to prove that the RVR was wrong and you where right.

 

[charter dog]

Beat me to it!

 

[propsarebest]

You can continue (once inside the FAF) and you can land provided, in your observation, that you believe you have the landing minimums. It is not uncommon for RVR to be wrong, it is a machine and it is only observing one very small area. However, you might consider that if anything ever happens you'll have to find a way to prove that the RVR was wrong and you where right.

That's all fine and dandy, but RVR is controlling, meaning if it is reporting 1100 1100 and 1100, and u think its more than 1/4 mile,u still cant land.

 

[Guitar rocker]

That's all fine and dandy, but RVR is controlling, meaning if it is reporting 1100 1100 and 1100, and u think its more than 1/4 mile,u still cant land.

Not so if inside the FAF....refer to KSU aviator above. He's got it right. Like he said, if anything happens to yah though, you'll need a good lawyer.

 

[CRJDispatchKid]

...and you only need the touchdown RVR above 1200 feet (CAT I) to begin the approach. The midpoint and rollout can be below, and you are still legal to shoot an approach. RVR is always controlling.

Here's what you're looking for from the FAR (121.651):
(c) If a pilot has begun the final approach segment of an instrument approach procedure in accordance with paragraph (b) of this section, and after that receives a later weather report indicating below-minimum conditions, the pilot may continue the approach to DH or MDA. Upon reaching DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DH or MDA if either the requirements of §91.175(l) of this chapter, or the following requirements are met:

blah blah blah

 

[Princedietrich]

The key word here is flight visibility. Once you're inside the FAF, it doesn't matter what the RVR or the reported visibility drop to. You can continue the approach all the way to DH or the MAP and then act upon whatever flight visibility conditions you find there. Flight visibility can only be determined by the pilot.

In other words, if you get to DH and you see the rabbits or the approach lights, go down to 100 above TDZ. When you get there, if you see REILS or a row of green lights in front of you, land. If anyone questions you, all you have to say is that you had adequate flight visibility as required by 91.175

 

[A Squared]

That's all fine and dandy, but RVR is controlling, meaning if it is reporting 1100 1100 and 1100, and u think its more than 1/4 mile,u still cant land.

I beleive that this is a myth. I have looked through the regs on several occasions, and I have never been able to find anything which supports this. Could you supply a reference?

 

[Sampson]

I beleive that this is a myth. I have looked through the regs on several occasions, and I have never been able to find anything which supports this. Could you supply a reference?

Its in the Ops Specs for the individual Airline. It also depends what Category your A/C is on how low you can go.

 

[ksu_aviator]

91.175
(c) Operation below DH or MDA. Except as provided in paragraph (l) of this section, where a DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or continue an approach below the authorized 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

Most 121 and 135 carriers operate using this rule. I don't know of a rule that superscedes this particular regulation.

§ 121.567 Instrument approach procedures and IFR landing minimums.

No person may make an instrument approach at an airport except in accordance with IFR weather minimums and instrument approach procedures set forth in the certificate holder's operations specifications.

So you'll have to consult your ops specs to see if your company restricted landings to ground observation visibility or (if omitted) you still operate on 91.175

 

[A Squared]

Its in the Ops Specs for the individual Airline.

Which Ops spec is it written into? Is this common? Can someone give me an example of the specific wording from their ops specs? I've never seen it, but then the only Ops Specs I've studied are the ones at my airline. Obviously, if it's written into a company's ops specs than it is controlling for that particular companies operations. However, I think that "RVR is controlling" as a general statement is still incorrect, It's not controlling if it's not written into the Ops Specs, (and it's not in mine) and it's not controlling for Part 91 operations.

 

[A Squared]

I think I've found the source of the myth.

I was thumbing thorough my Ops Specs. looking for something else, and I saw that in the Ops spec for takeoff minimums (CO56) it says that If RVR is measured for a runway, it is controlling for takeoff operations on that runway.

That's a long way from being controlling for landing. I think probably that folks have read this, and have not quite remembered that it was for takeoff visibility.

I also came across this legal interpretation which states specifically that RVR is controlling over flight visibility.

FAA Legal Interpretation:
March 10, 1986

Mr. Larry K. Johnson

Dear Mr. Johnson:
This is in response to your letter of February 6 requesting an interpretation of Federal Aviation Regulation (FAR) Part 91, Section 91.116.

Specifically, you request clarification of the term "flight visibility" in connection with the requirement in FAR 91.116(c) that an aircraft not be operated below a published decision height or minimum descent altitude if the flight visibility is less than the visibility prescribed in the standard instrument approach procedure being used. The question arises as to whether descent below the DH or MDA can be made when the runway visual range (RVR) is reported at less than the published minimum RVR for the approach but the flight visibility is greater than that minimum.

The flight visibility is controlling. If the flight visibility exceeds the published minimum for the approach, than the pilot may proceed as long as the other requirements of paragraph 91.116(c) are met regardless of the reported RVR. The National Transportation Safety Board (NTSB) has upheld this interpretation in several enforcement cases. However, the pilot's judgment of flight visibility is not necessarily conclusive if there is a question as to the actual flight visibility conditions at the time of the approach. Reported visibility and other evidence of record may be considered by the Federal Aviation Administration and the NTSB in determining the actual flight visibility.


Enforcement action would be taken only in those cases in which the pilot could not reasonably conclude that flight visibility was at or above approach minimums, but the pilot nevertheless proceeded to land or descent below DH or MDA.

Sincerely, David L. Bennett
Manager, Airspace and Air Traffic Law Branch
Regulations and Enforcement Division

Of course I suppose it could be written in some Ops specs, somewhere, but I'm skeptical. If that's the case, I'd be interested to see the wording from the Ops specs. Sampson?????

I

 

[NEDude]

There is a reason as to why approach lighting is configured the way it is. I am on the road right now, but somewhere I have a graphic which shows visual references on the ALS. For instance at 200' above TDZE, if you can see xxxx on the ALS, you have 2400' of flight visibility. It shows it for 100' above TDZE elevation as well. The chart comes from the FAA, and the criteria has been used successfully to defend pilots who have landed below RVR. When I get home I will try and find it and give more details. But the key is flight visibility is the controlling element for landing, not RVR. And if you can prove you have it, there shouldn't be an issue.