B737 crew reports runway centerline lights buried in snow during CAT III approachs at den.

Attributes
ACN	721680
Time
Date	200612
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	agl single value : 200
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : den.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 177 flight time type : 177
ASRS Report	721680
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : became reoriented none taken : anomaly accepted
Supplementary
Problem Areas	Airport
Primary Problem	Airport

Narrative:

CAT III approachs assumes not only onboard equipment is working; but also the landing runway has all the required electronic and approach/runway lighting. When we landed at den everything was in working order with 1 major caveat. Snow was covering the runway centerline lights and made them unusable. We had the approach lights well out on final (I would estimate forward visibility at CAT I ranges) but we are looking at a completely white picture so the runway is not very distinct. On short final I picked up the runway edge lights and got somewhat disoriented because I thought they were the runway centerline as I'm trained to look for. The disorientation was compounded because we had an 8 KT crosswind from the left and as we got closer in; the lights in front were those right edge lights which lead me to believe that somehow I went from on course to left of course. It probably would have been easier if this was a night approach because the runway centerline might have been visible through the snow. A quick discussion with the first officer confirmed we were correct and I landed the aircraft. Simply put: are we legal to land from a HUD CAT III approach if a portion of required runway lighting is available but not usable? This is a safety concern. Are CAT III approachs authority/authorized if runway ctrlines are covered with snow and are unusable?

Original NASA ASRS Text

Title: B737 CREW RPTS RWY CTRLINE LIGHTS BURIED IN SNOW DURING CAT III APCHS AT DEN.

Narrative: CAT III APCHS ASSUMES NOT ONLY ONBOARD EQUIP IS WORKING; BUT ALSO THE LNDG RWY HAS ALL THE REQUIRED ELECTRONIC AND APCH/RWY LIGHTING. WHEN WE LANDED AT DEN EVERYTHING WAS IN WORKING ORDER WITH 1 MAJOR CAVEAT. SNOW WAS COVERING THE RWY CTRLINE LIGHTS AND MADE THEM UNUSABLE. WE HAD THE APCH LIGHTS WELL OUT ON FINAL (I WOULD ESTIMATE FORWARD VISIBILITY AT CAT I RANGES) BUT WE ARE LOOKING AT A COMPLETELY WHITE PICTURE SO THE RWY IS NOT VERY DISTINCT. ON SHORT FINAL I PICKED UP THE RWY EDGE LIGHTS AND GOT SOMEWHAT DISORIENTED BECAUSE I THOUGHT THEY WERE THE RWY CTRLINE AS I'M TRAINED TO LOOK FOR. THE DISORIENTATION WAS COMPOUNDED BECAUSE WE HAD AN 8 KT XWIND FROM THE L AND AS WE GOT CLOSER IN; THE LIGHTS IN FRONT WERE THOSE R EDGE LIGHTS WHICH LEAD ME TO BELIEVE THAT SOMEHOW I WENT FROM ON COURSE TO L OF COURSE. IT PROBABLY WOULD HAVE BEEN EASIER IF THIS WAS A NIGHT APCH BECAUSE THE RWY CTRLINE MIGHT HAVE BEEN VISIBLE THROUGH THE SNOW. A QUICK DISCUSSION WITH THE FO CONFIRMED WE WERE CORRECT AND I LANDED THE ACFT. SIMPLY PUT: ARE WE LEGAL TO LAND FROM A HUD CAT III APCH IF A PORTION OF REQUIRED RWY LIGHTING IS AVAILABLE BUT NOT USABLE? THIS IS A SAFETY CONCERN. ARE CAT III APCHS AUTH IF RWY CTRLINES ARE COVERED WITH SNOW AND ARE UNUSABLE?

Data retrieved from NASA's ASRS site as of January 2009 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.