Narrative:

I was cleared for the sea VOR runway 16 approach. The ILS to runway 16R was OTS and WX was at minimums. When handed to tower, I was cleared to land on runway 16R and told to expect break- out at minimums. The approach was normal with needles centered on both sides. I reached MDA at approximately 3.8 DME. The threshold to runway 16R is approximately 1.7 DME. The missed approach is at the VOR adjacent to runway 16L. I was flying in ragged bases and did not break-out with forward visibility until over the approach lights of runway 16L. I was lined up perfectly with runway 16L, with just a slight offset to the west. The approach lights and runway lights were medium to high intensity. I don't recall seeing any lights to runway 16R in peripheral vision, probably because I was not lined up with that runway, and had broken out almost beyond the runway 16R approach lights. The ambient lighting at the field was low with drizzle and fog. Time approximately XA30L. Our company policy with concurrence of sea tower is to land mid-field and exit at taxiway M or north to minimize interference with aircraft taxiing to runway 16. I determined a normal approach and landing could be made from my position and altitude, and began final confign and landing checks. At this point human error entered the picture. The physical picture I saw, and the mental picture from previous ILS approachs to minimums led me to believe I was cleared to land on the runway in front of me. I saw no traffic on the runway and proceeded to execute a normal landing. After touchdown I heard an air carrier crew query the tower about a small twin landing in front of them after receiving a clearance for takeoff. I can only speculate that the aircraft jetstream was moving onto the runway as I passed overhead at approximately 300 ft AGL. The alertness of the jetstream crew averted a more serious incident caused by human error on my part, and tower's failure to determine my position or status regarding missed approach before issuing a clearance for takeoff in airspace I was still occupying. Contributing factors: use of nonstandard approach to sea, WX at minimums, alignment of VOR runway 16 approach to left runway -- used for departures, failure on my part to remember type of approach and correct landing clearance after breaking out at minimums, tower's issuance of takeoff clearance before determining if I was landing on the right or executing a missed approach, and not detecting lights to runway 16R which would have cued me to decide which runway I was cleared to land on.

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Original NASA ASRS Text

Title: AN ATC PA31-50 WAS CLRED TO LAND ON RWY 16L. HE LANDED ON RWY 16R WHICH WAS OCCUPIED.

Narrative: I WAS CLRED FOR THE SEA VOR RWY 16 APCH. THE ILS TO RWY 16R WAS OTS AND WX WAS AT MINIMUMS. WHEN HANDED TO TWR, I WAS CLRED TO LAND ON RWY 16R AND TOLD TO EXPECT BREAK- OUT AT MINIMUMS. THE APCH WAS NORMAL WITH NEEDLES CTRED ON BOTH SIDES. I REACHED MDA AT APPROX 3.8 DME. THE THRESHOLD TO RWY 16R IS APPROX 1.7 DME. THE MISSED APCH IS AT THE VOR ADJACENT TO RWY 16L. I WAS FLYING IN RAGGED BASES AND DID NOT BREAK-OUT WITH FORWARD VISIBILITY UNTIL OVER THE APCH LIGHTS OF RWY 16L. I WAS LINED UP PERFECTLY WITH RWY 16L, WITH JUST A SLIGHT OFFSET TO THE W. THE APCH LIGHTS AND RWY LIGHTS WERE MEDIUM TO HIGH INTENSITY. I DON'T RECALL SEEING ANY LIGHTS TO RWY 16R IN PERIPHERAL VISION, PROBABLY BECAUSE I WAS NOT LINED UP WITH THAT RWY, AND HAD BROKEN OUT ALMOST BEYOND THE RWY 16R APCH LIGHTS. THE AMBIENT LIGHTING AT THE FIELD WAS LOW WITH DRIZZLE AND FOG. TIME APPROX XA30L. OUR COMPANY POLICY WITH CONCURRENCE OF SEA TWR IS TO LAND MID-FIELD AND EXIT AT TXWY M OR N TO MINIMIZE INTERFERENCE WITH ACFT TAXIING TO RWY 16. I DETERMINED A NORMAL APCH AND LNDG COULD BE MADE FROM MY POS AND ALT, AND BEGAN FINAL CONFIGN AND LNDG CHKS. AT THIS POINT HUMAN ERROR ENTERED THE PICTURE. THE PHYSICAL PICTURE I SAW, AND THE MENTAL PICTURE FROM PREVIOUS ILS APCHS TO MINIMUMS LED ME TO BELIEVE I WAS CLRED TO LAND ON THE RWY IN FRONT OF ME. I SAW NO TFC ON THE RWY AND PROCEEDED TO EXECUTE A NORMAL LNDG. AFTER TOUCHDOWN I HEARD AN ACR CREW QUERY THE TWR ABOUT A SMALL TWIN LNDG IN FRONT OF THEM AFTER RECEIVING A CLRNC FOR TKOF. I CAN ONLY SPECULATE THAT THE ACFT JETSTREAM WAS MOVING ONTO THE RWY AS I PASSED OVERHEAD AT APPROX 300 FT AGL. THE ALERTNESS OF THE JETSTREAM CREW AVERTED A MORE SERIOUS INCIDENT CAUSED BY HUMAN ERROR ON MY PART, AND TWR'S FAILURE TO DETERMINE MY POS OR STATUS REGARDING MISSED APCH BEFORE ISSUING A CLRNC FOR TKOF IN AIRSPACE I WAS STILL OCCUPYING. CONTRIBUTING FACTORS: USE OF NONSTANDARD APCH TO SEA, WX AT MINIMUMS, ALIGNMENT OF VOR RWY 16 APCH TO L RWY -- USED FOR DEPS, FAILURE ON MY PART TO REMEMBER TYPE OF APCH AND CORRECT LNDG CLRNC AFTER BREAKING OUT AT MINIMUMS, TWR'S ISSUANCE OF TKOF CLRNC BEFORE DETERMINING IF I WAS LNDG ON THE R OR EXECUTING A MISSED APCH, AND NOT DETECTING LIGHTS TO RWY 16R WHICH WOULD HAVE CUED ME TO DECIDE WHICH RWY I WAS CLRED TO LAND ON.

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.