A DEHAVILLAND DASH 8 WAS DISPATCHED IN NON COMPLIANCE WITH AN UPPER WING ROOT PANEL NOT SECURED. PANEL DEPARTED THE ACFT.

Narrative

I WAS TROUBLESHOOTING THE ROLL SPOILER CIRCUIT BREAKER POPPING ON ACFT X. I GOT AVIONICS TO CHANGE OUT DIODE CR4 FOR THE LIFT DUMP VALVE IN THE #1 NACELLE. TO DOUBLE CHK THE WIRING; PANEL 261 DT WAS LIFTED FOR ACCESS TO THE WING ROOT CANNON PLUG. WHILE AVIONICS WAS CHKING CR4. I MOVED TO THE R-HAND WING ROOT CANNON PLUG UNDER PANEL 261 NT TO CHK THE WIRE (M) ON 2700-2P. I FOUND A SHORT. AROUND THAT TIME; AVIONICS WAS DONE IN 261 DT. I WAS THERE WHEN THE CANNON PLUG WAS INSTALLED. AVIONICS GRABBED PANEL 261 DT AND PUT IT IN PLACE. I TURNED BACK TO THE R-HAND WING ROOT AND THE SHORTED WIRE (I ASSUMED THEY PUT THE PANEL DOWN). WHEN THE TEMPORARY WIRE WAS INSTALLED; I TY-WRAPPED THE WIRE BUNDLES IN THE WING ROOT AND DID AN AREA SAFETY CHK AND CLOSED PANEL 261 NT. WHEN I WAS FINISHED I LOOKED OVER AT 261 DT AND DID NOT SEE ANY CAM LOCKS STICKING UP; SO I THOUGHT IT WAS DOWN AND INSTALLED. SINCE BOTH PANELS WERE ON THE SAME JOB CARD; I SIGNED IT OFF SINCE I WAS THERE AND LOCKED. I SHOULD HAVE VERBALLY ACKNOWLEDGED THE PANEL WITH AVIONICS. THE SECOND FLT CREW NOTICED PANEL 261 DT WAS NOT INSTALLED.