SMA DEPARTS WITH NAV LIGHTS OFF.

Narrative

I WAS TO DEPART LINCOLN; NE; ON OCT/XX/91; FOR A BRIEF FLT TO OMAHA TO PICK UP PAX FOR A LONGER FLT TO SCOTTS BLUFF; NE; IN AN SMA TWIN. THE EARLY MORNING WX BRIEFING PORTENDED NOTHING MORE THAN HIGH CIRRUS AND THE TEMPS WERE WARM FOR THAT TIME OF YR. AN EARLY DEP OUT OF LINCOLN XA00 AM; LEFT ME IN THE DARK. THE PREFLT WITH THE ACCOMPANYING FLASHLIGHT TOOK A BIT LONGER THAN USUAL. AFTER NORMAL IN COCKPIT CHKS I STARTED THE ENGS; I TURNED ON THE ROTATING BEACON; STROBES AND NAV (POS) LIGHTS. BEING PARKED NEXT TO A BUILDING AND WITH OTHER PEOPLE NEARBY ON THE RAMP I TURNED OFF THE FLASHING STROBES TO PREVENT BLINDING THEM. ALSO; IN THE SMA; AS WITH MANY MANUFACTURERS; WITH THE NAV LIGHTS ON; THE INTERIOR LNDG GEAR INDICATOR LIGHTS ARE EITHER DIMMED OR EXTINGUISHED ALTOGETHER. BEING MORE CONCERNED WITH MY GEAR DOWN INDICATION LIGHTS; I TURNED OFF THE NAV LIGHTS. BEFORE TAXIING TO THE RUNUP AREA I TURNED ON THE 2 LNDG/TAXI LIGHTS TO GUIDE ME OUT. IN THE PROCESS I DID NOT HIT THE THIRD SWITCH; TURNING ON THE NAV LIGHTS. I DID; HOWEVER; AFTER THE PREFLT RUNUP AND CHKLIST PROC AND BEFORE DEP TURN ON THE STROBES; BUT AGAIN I WAS MORE CONCERNED WITH SEEING MY GEAR INDICATOR LIGHTS AND FAILED TO TURN ON THE NAV LIGHTS. I DEPARTED WITHOUT NAV LIGHTS (XA05 AM) ALTHOUGH TWR MADE NO MENTION OF THE FACT. I LANDED IN OMAHA IN DAYLIGHT AT XA35 AM WITHOUT GIVING IT ANY THOUGHT. APPARENTLY A GADO OFFICER WAS ON THE RAMP AND WITNESSED THE DEP WITHOUT LIGHTS AND SPOKE TO THE FBO ABOUT THE PROBLEM AFTER MY DEP. IN CONCLUSION; CARE MUST BE TAKEN TO BE SURE THAT THE NAV LIGHTS ARE ON IN THIS SERIES PLANES BEFORE A NIGHT OR TWILIGHT DEP EVEN THOUGH THEIR BEING ON MAY DIM OR EXTINGUISH THE LNDG GEAR INDICATOR LIGHTS. FAILURE TO CHK MAY RESULT IN A DEP WITHOUT NAV LIGHTS.