ALTDEV.

Narrative

THE JETSTREAM 3100 HAS A DME READOUT WITH 4 BUTTONS (DME; KTS; TIME; TIMER) THE BUTTONS DO NOT REMAIN DEPRESSED WHEN A SPECIFIC MODE IS SELECTED AND THE READOUT DOES NOT INDICATE WHETHER YOU ARE IN DISTANCE; TIME; OR KTS. THE ONLY WAY TO KNOW THE MODE BEING DISPLAYED IS TO PUSH THE BUTTON ESPECIALLY BTWN 'DME' AND 'TIME' MODES. I WAS THE PF. MY COPLT PUSHED 'TIME' TO ASSURE THAT HIS CALL TO OUR BASE OPS WAS ACCURATE. HE NEVER PUSHED IT BACK TO THE DME MODE. I BEGAN A VOR DME 14 APCH TO ARCATA. THINKING THAT I WAS INSIDE 'WHEEL' INTXN; I STARTED MY DSCNT BASED ON WHAT I THOUGHT I WAS AN INDICATION OF LESS THAN 10.8 DME. HOWEVER; THE READOUT WAS ACTUALLY INDICATING 'MIN TO THE STATION.' I WAS ACTUALLY OVER 22 NM OUT AND STARTED DOWN WAY TOO EARLY. ZSE CAUGHT OUR MISTAKE BEFORE WE DID. CHAIN OF EVENTS: HOW THE PROB AROSE: SWITCHOLOGY. CONTRIBUTING FACTORS: DECEIVING TO THE POINT OF DECEPTIVE READOUT DISPLAY. HOW IT WAS DISCOVERED: ZSE QUERY. CORRECTIVE ACTIONS: PART OF MY INST APCH BRIEF FROM NOW ON. HUMAN FACTORS: DUE TO DIRECT RTING AND COMPLACENCY BOTH MY COPLT AND MYSELF FAILED TO PERCEIVE THE PROPER DISTANCE FROM ARCATA DURING A CRUCIAL PHASE OF FLT (IE; POOR SITUATIONAL AWARENESS).