Narrative:

This event involved problems of perception, fixation, crew coordination, distraction and conflicting information. While inbound to pasco, wa, airport in IMC conditions at night as PIC of a 2 pilot crew, several pieces of conflicting information led to an inadvertent descent below assigned altitude, and could have led to more serious deviations for a safe approach and landing. While being vectored inbound for the approach we established ground contact at approximately 4000' MSL (3500' AGL). Visibility was initially poor, but improved to approximately 3 mi as we neared 3000' MSL. We were cleared to turn left to 020 degrees for the VOR 30 approach. The approach already had been thoroughly briefed before this point. While turning to 020 degrees the center controller asked us to verify our heading. I immediately verified our compass systems with each other and with the magnetic compass. While I was doing this my copilot called out airport in sight and emphatically pointed to an area a few miles to our left. At the same time center cleared us for an intercept and for the approach with descent to 2100' upon becoming established on the approach. I noticed that our altitude had reduced to approximately 400' below the 3000' still assigned until intercept. I immediately climbed while continuing to try to see the airport the copilot was so emphatic about. As I intercepted and then descended back to 2100' the copilot said we would have to circle to land as the airport was passing under us. I again said I didn't have it and pointed to the DME and navigation indications. I took the approach plate from him and verified our position and fixes for further descent on the approach. I continued descent as published. I concluded that the copilot had mistaken parallel rows of red lights for the airport. Within a minute the copilot again called out the airport saying, 'I've really got it.' I checked and verified it was the correct airport this time and continued the approach, primarily by visibility reference. The airport was spotted approximately 3 mi out and a safe landing was accomplished. I later discussed this event in detail with my copilot and pointed out the areas we both could improve our performance and crew coordination. I had done my best to follow the published procedure in a difficult situation and I pointed out that we must believe our navaids and center's radar, check and double check these against other sources of information and not descend for an airport or perceived airport unless all sources of information agree. Cockpit coordination and discipline must be maintained, altitudes and accomplishing checklists. He did call out runway in sight, as was also his duty, but it was not the correct airport and didn't believe me when I indicated it could not be.

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Original NASA ASRS Text

Title: CHARTER SMT ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: THIS EVENT INVOLVED PROBS OF PERCEPTION, FIXATION, CREW COORD, DISTR AND CONFLICTING INFO. WHILE INBND TO PASCO, WA, ARPT IN IMC CONDITIONS AT NIGHT AS PIC OF A 2 PLT CREW, SEVERAL PIECES OF CONFLICTING INFO LED TO AN INADVERTENT DSCNT BELOW ASSIGNED ALT, AND COULD HAVE LED TO MORE SERIOUS DEVIATIONS FOR A SAFE APCH AND LNDG. WHILE BEING VECTORED INBND FOR THE APCH WE ESTABLISHED GND CONTACT AT APPROX 4000' MSL (3500' AGL). VISIBILITY WAS INITIALLY POOR, BUT IMPROVED TO APPROX 3 MI AS WE NEARED 3000' MSL. WE WERE CLRED TO TURN LEFT TO 020 DEGS FOR THE VOR 30 APCH. THE APCH ALREADY HAD BEEN THOROUGHLY BRIEFED BEFORE THIS POINT. WHILE TURNING TO 020 DEGS THE CENTER CTLR ASKED US TO VERIFY OUR HDG. I IMMEDIATELY VERIFIED OUR COMPASS SYSTEMS WITH EACH OTHER AND WITH THE MAGNETIC COMPASS. WHILE I WAS DOING THIS MY COPLT CALLED OUT ARPT IN SIGHT AND EMPHATICALLY POINTED TO AN AREA A FEW MILES TO OUR LEFT. AT THE SAME TIME CENTER CLRED US FOR AN INTERCEPT AND FOR THE APCH WITH DSCNT TO 2100' UPON BECOMING ESTABLISHED ON THE APCH. I NOTICED THAT OUR ALT HAD REDUCED TO APPROX 400' BELOW THE 3000' STILL ASSIGNED UNTIL INTERCEPT. I IMMEDIATELY CLBED WHILE CONTINUING TO TRY TO SEE THE ARPT THE COPLT WAS SO EMPHATIC ABOUT. AS I INTERCEPTED AND THEN DSNDED BACK TO 2100' THE COPLT SAID WE WOULD HAVE TO CIRCLE TO LAND AS THE ARPT WAS PASSING UNDER US. I AGAIN SAID I DIDN'T HAVE IT AND POINTED TO THE DME AND NAV INDICATIONS. I TOOK THE APCH PLATE FROM HIM AND VERIFIED OUR POS AND FIXES FOR FURTHER DSCNT ON THE APCH. I CONTINUED DSCNT AS PUBLISHED. I CONCLUDED THAT THE COPLT HAD MISTAKEN PARALLEL ROWS OF RED LIGHTS FOR THE ARPT. WITHIN A MINUTE THE COPLT AGAIN CALLED OUT THE ARPT SAYING, 'I'VE REALLY GOT IT.' I CHKED AND VERIFIED IT WAS THE CORRECT ARPT THIS TIME AND CONTINUED THE APCH, PRIMARILY BY VIS REF. THE ARPT WAS SPOTTED APPROX 3 MI OUT AND A SAFE LNDG WAS ACCOMPLISHED. I LATER DISCUSSED THIS EVENT IN DETAIL WITH MY COPLT AND POINTED OUT THE AREAS WE BOTH COULD IMPROVE OUR PERFORMANCE AND CREW COORD. I HAD DONE MY BEST TO FOLLOW THE PUBLISHED PROC IN A DIFFICULT SITUATION AND I POINTED OUT THAT WE MUST BELIEVE OUR NAVAIDS AND CENTER'S RADAR, CHK AND DOUBLE CHK THESE AGAINST OTHER SOURCES OF INFO AND NOT DSND FOR AN ARPT OR PERCEIVED ARPT UNLESS ALL SOURCES OF INFO AGREE. COCKPIT COORD AND DISCIPLINE MUST BE MAINTAINED, ALTS AND ACCOMPLISHING CHKLISTS. HE DID CALL OUT RWY IN SIGHT, AS WAS ALSO HIS DUTY, BUT IT WAS NOT THE CORRECT ARPT AND DIDN'T BELIEVE ME WHEN I INDICATED IT COULD NOT BE.

Data retrieved from NASA's ASRS site as of August 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.