Narrative:

While executing GPS runway 8 approach to ZZZ; I misread the chart and began first step-down at abc should have waited until ZZZ. While descending; GPWS issued 'caution -- terrain' aural warning. Immediately leveled off; checked chart and discovered error; climbed to correct altitude. Rest of approach and landing were normal. I'm not sure what factors led to selecting the wrong step-down. But one was that the waypoint ZZZ was displayed as such on the mfd display by the FMS; but on the instrument chart the waypoint is labeled by '7.0 NM' in large bold type with ZZZ in light italicized type surrounded by brackets and very difficult to read. I remember on passing abc a moment of confusion trying to reconcile the two; and having been focused on that waypoint and noticing it as a step-down point; I must have subconsciously thought I was passing the waypoint prematurely. Lessons learned -- when flying approached with multiple step-downs; it is essential to verify and re-verify each step-down; where it begins; how you will identify it; and what the associated minimum altitude is. Also; taws is a hugh safety factor when executing instrument approachs.

Google
 

Original NASA ASRS Text

Title: A C560 IN MOUNTAINOUS TERRAIN STEPPED DOWN TO AN APCH FIX EARLY ACTIVATING GPWS TERRAIN WARNING. THE PILOT CONFUSED THE MFD WAY PT WITH THE CHART FIX.

Narrative: WHILE EXECUTING GPS RWY 8 APCH TO ZZZ; I MISREAD THE CHART AND BEGAN FIRST STEP-DOWN AT ABC SHOULD HAVE WAITED UNTIL ZZZ. WHILE DSNDING; GPWS ISSUED 'CAUTION -- TERRAIN' AURAL WARNING. IMMEDIATELY LEVELED OFF; CHKED CHART AND DISCOVERED ERROR; CLBED TO CORRECT ALT. REST OF APCH AND LNDG WERE NORMAL. I'M NOT SURE WHAT FACTORS LED TO SELECTING THE WRONG STEP-DOWN. BUT ONE WAS THAT THE WAYPOINT ZZZ WAS DISPLAYED AS SUCH ON THE MFD DISPLAY BY THE FMS; BUT ON THE INST CHART THE WAYPOINT IS LABELED BY '7.0 NM' IN LARGE BOLD TYPE WITH ZZZ IN LIGHT ITALICIZED TYPE SURROUNDED BY BRACKETS AND VERY DIFFICULT TO READ. I REMEMBER ON PASSING ABC A MOMENT OF CONFUSION TRYING TO RECONCILE THE TWO; AND HAVING BEEN FOCUSED ON THAT WAYPOINT AND NOTICING IT AS A STEP-DOWN POINT; I MUST HAVE SUBCONSCIOUSLY THOUGHT I WAS PASSING THE WAYPOINT PREMATURELY. LESSONS LEARNED -- WHEN FLYING APCHED WITH MULTIPLE STEP-DOWNS; IT IS ESSENTIAL TO VERIFY AND RE-VERIFY EACH STEP-DOWN; WHERE IT BEGINS; HOW YOU WILL IDENT IT; AND WHAT THE ASSOCIATED MINIMUM ALT IS. ALSO; TAWS IS A HUGH SAFETY FACTOR WHEN EXECUTING INST APCHS.

Data retrieved from NASA's ASRS site as of May 2009 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.