Twin beech 18 shot an approach and landed when the prevailing visibility was one half mi and the RVV...

Attributes
ACN	357079
Time
Date	199612
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mwh
State Reference	WA
Altitude	agl bound lower : 0 agl bound upper : 200
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mwh
Operator	common carrier : air taxi
Make Model Name	Twin Beech 18
Operating Under FAR Part	Part 135
Flight Phase	descent : approach landing other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 190 flight time total : 3100 flight time type : 370
ASRS Report	357079
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
Publication	Unspecified

Narrative:

I departed bfi at XA20 with a little less than an hour en route to moses lake, wa. I was on a downwind leg for the ILS runway 32R. The ATIS was calling the visibility a half mi in fog. I don't recall the rest of the WX. Contacting approach control, I was again advised 'visibility half mi.' when the controller gave me the base leg vector, he advised me 'RVV three sixteenths - five sixteenths, prevailing visibility one half mi.' I do know RVV stands for runway visual value, and from what I can gather, it is basically the same thing as RVR but given in fractions of mi. At a very busy point on the approach I was advised of something I wasn't sure what it meant. Can I legally shoot the approach under part 135? What is controling RVV or prevailing visibility? I did have time to glance down at the approach plate to see if RVV was mentioned on the minimums section, it was not. I was also talking to other freight pilots on a company frequency who also weren't sure what was controling, one of whom shot the approach behind me. I continued the approach and landed with the required half mi visibility.

Original NASA ASRS Text

Title: TWIN BEECH 18 SHOT AN APCH AND LANDED WHEN THE PREVAILING VISIBILITY WAS ONE HALF MI AND THE RVV WAS GIVEN AS 5 SIXTEENTHS TO 7 SIXTEENTHS. THE MINIMUMS ARE ONE HALF MI. AFTER A DILIGENT SEARCH, RPTR WAS UNABLE TO DETERMINE, FOR SURE, WHETHER OR NOT RVV IS CTLING.

Narrative: I DEPARTED BFI AT XA20 WITH A LITTLE LESS THAN AN HR ENRTE TO MOSES LAKE, WA. I WAS ON A DOWNWIND LEG FOR THE ILS RWY 32R. THE ATIS WAS CALLING THE VISIBILITY A HALF MI IN FOG. I DON'T RECALL THE REST OF THE WX. CONTACTING APCH CTL, I WAS AGAIN ADVISED 'VISIBILITY HALF MI.' WHEN THE CTLR GAVE ME THE BASE LEG VECTOR, HE ADVISED ME 'RVV THREE SIXTEENTHS - FIVE SIXTEENTHS, PREVAILING VISIBILITY ONE HALF MI.' I DO KNOW RVV STANDS FOR RWY VISUAL VALUE, AND FROM WHAT I CAN GATHER, IT IS BASICALLY THE SAME THING AS RVR BUT GIVEN IN FRACTIONS OF MI. AT A VERY BUSY POINT ON THE APCH I WAS ADVISED OF SOMETHING I WASN'T SURE WHAT IT MEANT. CAN I LEGALLY SHOOT THE APCH UNDER PART 135? WHAT IS CTLING RVV OR PREVAILING VISIBILITY? I DID HAVE TIME TO GLANCE DOWN AT THE APCH PLATE TO SEE IF RVV WAS MENTIONED ON THE MINIMUMS SECTION, IT WAS NOT. I WAS ALSO TALKING TO OTHER FREIGHT PLTS ON A COMPANY FREQ WHO ALSO WEREN'T SURE WHAT WAS CTLING, ONE OF WHOM SHOT THE APCH BEHIND ME. I CONTINUED THE APCH AND LANDED WITH THE REQUIRED HALF MI VISIBILITY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Twin beech 18 shot an approach and landed when the prevailing visibility was one half mi and the RVV was given as 5 sixteenths to 7 sixteenths. The minimums are one half mi. After a diligent search, reporter was unable to determine, for sure, whether or not RVV is controling.