Narrative:

Dark, rainy, windy, pre-dawn. My first officer and I received our aircraft at the company maintenance hangar, accomplished preflight and originating duties and commenced taxi to departure gates at the passenger terminal for the start of a 7 leg day. 2 required daily system checks remained to be accomplished and elected to do them clear of the maintenance ramp, but before arriving at the gate. Received clearance to hold short of runway 10R on taxiway F. Could not get a satisfactory test of autofeather system, so decided to return to hangar area. Received clearance to return on taxiway F to starting point. Was parked about 10 ft short of runway hold line and left of taxiway centerline. Asked first officer if it was clear right. He peered through his rain-streaked side window, and said 'clear right, plenty of room.' commenced turn. About 70-80 degrees into turn, saw taxi edge lights through windscreen appearing closer than I expected. Locked right brake to caster nosewheel into tighter turn (+/- 120 degrees castering range). Shortly thereafter, heard a 'clunk' from nose area and felt what I thought was an unevenness in the pavement. Not uncommon with the dhc-8 nosegear. As we were about through the turn, I continued, but asked first officer if he thought I had hit something (taxiway edge lights looked close out my side, but I was certain I was clear of them). He didn't think I had hit anything, but said he supposed it was possible, as visibility was somewhat marginal. Arriving at maintenance ramp, I advised maintenance control of the perceived problem with the autofeather system. (Subsequently learned I had skipped the step of energizing the system. This was because we didn't accomplish a before takeoff checklist, since we were just repositioning on the airport surface.) mechanic with flashlights inspected the nose area of the plane, where we had heard the noise from. Noting nothing unusual, after looking out at the taxiway (about 40-50 yards distant) and seeing nothing amiss, I decided we had heard a clunk from the nosegear strut as it transited some uneven pavement. Made a maintenance log entry for the autofeather system I believed to be inoperative, and we took a different airplane to start our day. It was when I was unable to get the same system on the second aircraft to test normally that I learned I had not switched either system on. It was still dark when we taxied via the same taxiway as before. Passing the spot where we had turned around, the first officer looked out and commented that all the taxiway edge lights looked untouched. We completed the day's flts. Upon arriving at pdx that evening, we were informed a smgcs hold line 'wig-wag' light had been flattened where we turned around early that day. I explained I had not made a logbook entry pertaining to the noise we heard, because we both had concluded that it had been a not uncommon sound made by the nosegear strut as we crossed some uneven pavement. I now believe a possible explanation is that my left main gear rode over the wig-wag light and flattened it, and the nose gear 'clunked' as the airplane rocked slightly as the gear rode over the light assembly. This would explain why it felt like the nose gear went through a shallow dip. The dhc-8 has a wide track (26 ft between main gear) and the gear is not visible from the cockpit. I believe I failed to take into account how far out the main gear was, and also misjudged my distance from the lights during the turn. Marginal visibility I believe aggravated this problem. I subsequently learned that 2 blue taxiway edge lights also were damaged. Causal factors I believe include: 1) my decision to attempt a 180 degree turn on a rather narrow taxiway without benefit of a wingwalker. 2) depth perception hampered by rain-streaked windows. 3) feeling of time pressure (self- imposed) to try to make an on-time departure clouded my judgement. I should have taken time to receive clearance to a wide turnaround, such as onto the runway. What I would do differently: 1) accomplish before takeoff checklist before attempting system checks which require switches to be configured for takeoff. If a system doesn't test, consult manual to verify I've completed all steps before returning aircraft to maintenance. 2) find wider spot or get wing walker assistance before turning around, especially with marginal visibility. 3) if I think I even possibly could have hit something with the aircraft, make a maintenance log entry documenting it. 4) never forget that my main gear are 26 ft apart, and I can't see either one of them. 5) don't let 'get goingitis' (or get homeitis) tempt me to take shortcuts.

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Original NASA ASRS Text

Title: DCH-8 TAXIES OVER WIG-WAG LIGHT AND IMPACTS TXWY LIGHTS.

Narrative: DARK, RAINY, WINDY, PRE-DAWN. MY FO AND I RECEIVED OUR ACFT AT THE COMPANY MAINT HANGAR, ACCOMPLISHED PREFLT AND ORIGINATING DUTIES AND COMMENCED TAXI TO DEP GATES AT THE PAX TERMINAL FOR THE START OF A 7 LEG DAY. 2 REQUIRED DAILY SYS CHKS REMAINED TO BE ACCOMPLISHED AND ELECTED TO DO THEM CLR OF THE MAINT RAMP, BUT BEFORE ARRIVING AT THE GATE. RECEIVED CLRNC TO HOLD SHORT OF RWY 10R ON TXWY F. COULD NOT GET A SATISFACTORY TEST OF AUTOFEATHER SYS, SO DECIDED TO RETURN TO HANGAR AREA. RECEIVED CLRNC TO RETURN ON TXWY F TO STARTING POINT. WAS PARKED ABOUT 10 FT SHORT OF RWY HOLD LINE AND L OF TXWY CTRLINE. ASKED FO IF IT WAS CLR R. HE PEERED THROUGH HIS RAIN-STREAKED SIDE WINDOW, AND SAID 'CLR R, PLENTY OF ROOM.' COMMENCED TURN. ABOUT 70-80 DEGS INTO TURN, SAW TAXI EDGE LIGHTS THROUGH WINDSCREEN APPEARING CLOSER THAN I EXPECTED. LOCKED R BRAKE TO CASTER NOSEWHEEL INTO TIGHTER TURN (+/- 120 DEGS CASTERING RANGE). SHORTLY THEREAFTER, HEARD A 'CLUNK' FROM NOSE AREA AND FELT WHAT I THOUGHT WAS AN UNEVENNESS IN THE PAVEMENT. NOT UNCOMMON WITH THE DHC-8 NOSEGEAR. AS WE WERE ABOUT THROUGH THE TURN, I CONTINUED, BUT ASKED FO IF HE THOUGHT I HAD HIT SOMETHING (TXWY EDGE LIGHTS LOOKED CLOSE OUT MY SIDE, BUT I WAS CERTAIN I WAS CLR OF THEM). HE DIDN'T THINK I HAD HIT ANYTHING, BUT SAID HE SUPPOSED IT WAS POSSIBLE, AS VISIBILITY WAS SOMEWHAT MARGINAL. ARRIVING AT MAINT RAMP, I ADVISED MAINT CTL OF THE PERCEIVED PROB WITH THE AUTOFEATHER SYS. (SUBSEQUENTLY LEARNED I HAD SKIPPED THE STEP OF ENERGIZING THE SYS. THIS WAS BECAUSE WE DIDN'T ACCOMPLISH A BEFORE TKOF CHKLIST, SINCE WE WERE JUST REPOSITIONING ON THE ARPT SURFACE.) MECH WITH FLASHLIGHTS INSPECTED THE NOSE AREA OF THE PLANE, WHERE WE HAD HEARD THE NOISE FROM. NOTING NOTHING UNUSUAL, AFTER LOOKING OUT AT THE TXWY (ABOUT 40-50 YARDS DISTANT) AND SEEING NOTHING AMISS, I DECIDED WE HAD HEARD A CLUNK FROM THE NOSEGEAR STRUT AS IT TRANSITED SOME UNEVEN PAVEMENT. MADE A MAINT LOG ENTRY FOR THE AUTOFEATHER SYS I BELIEVED TO BE INOP, AND WE TOOK A DIFFERENT AIRPLANE TO START OUR DAY. IT WAS WHEN I WAS UNABLE TO GET THE SAME SYS ON THE SECOND ACFT TO TEST NORMALLY THAT I LEARNED I HAD NOT SWITCHED EITHER SYS ON. IT WAS STILL DARK WHEN WE TAXIED VIA THE SAME TXWY AS BEFORE. PASSING THE SPOT WHERE WE HAD TURNED AROUND, THE FO LOOKED OUT AND COMMENTED THAT ALL THE TXWY EDGE LIGHTS LOOKED UNTOUCHED. WE COMPLETED THE DAY'S FLTS. UPON ARRIVING AT PDX THAT EVENING, WE WERE INFORMED A SMGCS HOLD LINE 'WIG-WAG' LIGHT HAD BEEN FLATTENED WHERE WE TURNED AROUND EARLY THAT DAY. I EXPLAINED I HAD NOT MADE A LOGBOOK ENTRY PERTAINING TO THE NOISE WE HEARD, BECAUSE WE BOTH HAD CONCLUDED THAT IT HAD BEEN A NOT UNCOMMON SOUND MADE BY THE NOSEGEAR STRUT AS WE CROSSED SOME UNEVEN PAVEMENT. I NOW BELIEVE A POSSIBLE EXPLANATION IS THAT MY L MAIN GEAR RODE OVER THE WIG-WAG LIGHT AND FLATTENED IT, AND THE NOSE GEAR 'CLUNKED' AS THE AIRPLANE ROCKED SLIGHTLY AS THE GEAR RODE OVER THE LIGHT ASSEMBLY. THIS WOULD EXPLAIN WHY IT FELT LIKE THE NOSE GEAR WENT THROUGH A SHALLOW DIP. THE DHC-8 HAS A WIDE TRACK (26 FT BTWN MAIN GEAR) AND THE GEAR IS NOT VISIBLE FROM THE COCKPIT. I BELIEVE I FAILED TO TAKE INTO ACCOUNT HOW FAR OUT THE MAIN GEAR WAS, AND ALSO MISJUDGED MY DISTANCE FROM THE LIGHTS DURING THE TURN. MARGINAL VISIBILITY I BELIEVE AGGRAVATED THIS PROB. I SUBSEQUENTLY LEARNED THAT 2 BLUE TXWY EDGE LIGHTS ALSO WERE DAMAGED. CAUSAL FACTORS I BELIEVE INCLUDE: 1) MY DECISION TO ATTEMPT A 180 DEG TURN ON A RATHER NARROW TXWY WITHOUT BENEFIT OF A WINGWALKER. 2) DEPTH PERCEPTION HAMPERED BY RAIN-STREAKED WINDOWS. 3) FEELING OF TIME PRESSURE (SELF- IMPOSED) TO TRY TO MAKE AN ON-TIME DEP CLOUDED MY JUDGEMENT. I SHOULD HAVE TAKEN TIME TO RECEIVE CLRNC TO A WIDE TURNAROUND, SUCH AS ONTO THE RWY. WHAT I WOULD DO DIFFERENTLY: 1) ACCOMPLISH BEFORE TKOF CHKLIST BEFORE ATTEMPTING SYS CHKS WHICH REQUIRE SWITCHES TO BE CONFIGURED FOR TKOF. IF A SYS DOESN'T TEST, CONSULT MANUAL TO VERIFY I'VE COMPLETED ALL STEPS BEFORE RETURNING ACFT TO MAINT. 2) FIND WIDER SPOT OR GET WING WALKER ASSISTANCE BEFORE TURNING AROUND, ESPECIALLY WITH MARGINAL VISIBILITY. 3) IF I THINK I EVEN POSSIBLY COULD HAVE HIT SOMETHING WITH THE ACFT, MAKE A MAINT LOG ENTRY DOCUMENTING IT. 4) NEVER FORGET THAT MY MAIN GEAR ARE 26 FT APART, AND I CAN'T SEE EITHER ONE OF THEM. 5) DON'T LET 'GET GOINGITIS' (OR GET HOMEITIS) TEMPT ME TO TAKE SHORTCUTS.

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.