RVR question

Inverted

Inverted

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Inverted
If the approach plate gives a statute mile visibility figure, but the weather at the airport is only giving RVR, can you shoot the approach?
 
Inverted said:
If the approach plate gives a statute mile visibility figure, but the weather at the airport is only giving RVR, can you shoot the approach?
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Yes, but why doesn't the weather observation include visibility? Is this a hypothetical or did you encounter this situation? What airport?
 
This is assuming the visibility figure is missing I think. This is an interview question I am helping a friend with. I think the context is, your approach plate has a SM visibility figure, but the airport for whatever reason is ONLY reporting RVR.
 
Inverted said:
If the approach plate gives a statute mile visibility figure, but the weather at the airport is only giving RVR, can you shoot the approach?
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Yes, you can convert RVR to visibility in SM and vice versa. As pointed out in the previous post, visibility should also be reported in a weather observation (usually).

Chapters%208%20to%2012_img_57.jpg
 
5-4-20. Approach and Landing Minimums ​
a. Landing Minimums. The rules applicable to landing minimums are contained in 14 CFR Section 91.175. TBL 5-4-1 may be used to convert RVR to ground or flight visibility. For converting RVR values that fall between listed values, use the next higher RVR value; do not interpolate. For example, when converting 1800 RVR, use 2400 RVR with the resultant visibility of 1/2 mile.
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BTW, that table above is found in the FAA AeroNav Terminal Procedures books and the AIM Table 5-4-1. It's probably in the Terminal section of the Jepp books, too.
 
Thank you much. Usually when somebody asks me a question that I find the answer obvious, I sometimes question whether I am right or not lol.
 
Inverted said:
This is assuming the visibility figure is missing I think. This is an interview question I am helping a friend with. I think the context is, your approach plate has a SM visibility figure, but the airport for whatever reason is ONLY reporting RVR.
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Well, the visibility figure could only be missing from a non-augmented automated observation. I'd be surprised to find RVR at such locations.
 
FWIW, depending upon where he's interviewing, most places have it in their OpSpecs that RVR is controlling. So even if the vis is missing (or is below mins), but the RVR is above mins, you're good to go.

EX: Normal ILS calls for 1/2 mile or 1800RVR. Well, according to Jason's chart above, 1/2sm is 2400RVR. So, the AWOS/ATIS can be missing or reporting 1/4sm (or less), but as long as the RVR is >=1800, you're good to go. On the flip side, in the unlikely event that the box says vis is 1/2 but RVR is 1600, you're gonna be holding.
 
Teller1900 said:
FWIW, depending upon where he's interviewing, most places have it in their OpSpecs that RVR is controlling. So even if the vis is missing (or is below mins), but the RVR is above mins, you're good to go.
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I wouldn't worry about their OpSpecs until I got hired. If the ask they question in the interview, I think they'll be happy if he knows the book answer, not the company's own rules. Those rules will get taught during training.
 
Ron Levy said:
I wouldn't worry about their OpSpecs until I got hired. If the ask they question in the interview, I think they'll be happy if he knows the book answer, not the company's own rules. Those rules will get taught during training.
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From the Instrument Procedures Handbook,

FAA said:
It should be noted that the controlling factor for determining whether or not the aircraft can proceed is reported visibility. Runway visual range (RVR), if available, is the controlling visibility report for determining that the requirements of this section
are met. The runway visibility value (RVV), reported in statute miles (SM), takes precedent over prevailing visibility.
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I don't think it would be an unfair question to expect them to know that RVR is controlling. I wouldn't expect them to know numbers, such as what is the lowest allowable t/o RVR (as that is specific to a company's OpSpecs), but RVR vs. Vis doesn't seem unfair if it's a 121 or 135 interview.

HPNPilot1200 said:
With operational touchdown zone and centerline lights, yes. Without, mins normally go up to 2400 RVR. :D
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Fair enough. So I was mostly right...that's better than usual!
 
Teller1900 said:
From the Instrument Procedures Handbook,


I don't think it would be an unfair question to expect them to know that RVR is controlling. I wouldn't expect them to know numbers, such as what is the lowest allowable t/o RVR (as that is specific to a company's OpSpecs), but RVR vs. Vis doesn't seem unfair if it's a 121 or 135 interview.
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Except that wasn't the question. The question was:
Inverted said:
If the approach plate gives a statute mile visibility figure, but the weather at the airport is only giving RVR, can you shoot the approach?
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In that case, you convert RVR to miles using the chart in the AIM and the TP book, and compare the resulting distance in miles on the chart to see if you're legal. The RVR is still "controlling," but you have to convert it to miles to be able to compare it to the limiting value on the chart, and you are permitted to do so. The company may have other, stricter rules, but that's the basic FAA answer.
 
Ron Levy said:
Except that wasn't the question. The question was:
In that case, you convert RVR to miles using the chart in the AIM and the TP book, and compare the resulting distance in miles on the chart to see if you're legal. The RVR is still "controlling," but you have to convert it to miles to be able to compare it to the limiting value on the chart, and you are permitted to do so. The company may have other, stricter rules, but that's the basic FAA answer.
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My interpretation was: if you don't have vis, but you do have RVR, can you shoot the approach? And the simple answer is yes. I think we're arguing the same point.
 
Teller1900 said:
My interpretation was: if you don't have vis, but you do have RVR, can you shoot the approach? And the simple answer is yes. I think we're arguing the same point.
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If by that you mean the PV is not being reported but the RVR is, we're on the same page, and I think that's the same page as the OP. OTOH, I don't think the OP was asking "what do you do if the prevailing visability (PV) is below mins but the RVR is." The answer that question may also be "use the RVR, convert to miles, and compare to the approach chart vis in miles," but not for the same reason. In the first case, it's the RVR conversion issue driving the answer. In the second, it's the fact that RVR trumps PV for an approach for which an RVR min is published.

For example, the reported RVR is 2800, the vis min on the chart is 1/2 mile, and there's no PV reported. Since 2800 converts to better than 1/2 mile, you're OK to fly the approach. That said, I've never seen a case where RVR was reported, but not PV, so I don't think the question ever arises.

OTOH, what about the reverse? RVR mins are prescribed, but only PV is being reported, not RVR. Then 91.175(h)(1) covers the situation. Say the RVR min is 1800, no RVR is reported, but the PV is reported as 1/2 mile. Since 1800 converts to 1/2 mile using the round-up procedure in the AIM, and you have 1/2 mile reported, you're OK to fly the approach.

Now, what do you do if both are reported, RVR is above the RVR min on the chart, but PV is below the converted RVR min (e.g., RVR min is 1800 RVR is reported 2000, and PV is reported 1/4 mile which converts to 1600 RVR)?. I'd say the IPH makes it clear that the reported RVR is controlling, and you're legal to fly the approach on that basis despite the low PV.

Finally, what happens if the chart says 1/2 mile, they're reporting both RVR and PV, and the PV is 1/4, while the RVR is 2800. Can you land legally? Frankly, I don't think this happens. I think if there's RVR for the runway, the ILS should show an RVR min for straight-ins rather than a PV, so the question shouldn't arise.

Note this is all about 135/121 -- for Part 91, you get to decide from the cockpit if the vis meets mins or not. And for 135/121, the OpSpecs can always be more restrictive, although one would not expect to be held responsible for knowing a company's OpSpecs during a pre-hire interview.
 
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