Narrative:

We were cleared for the profile of the eat VOR DME C approach and maintain 10000'. We were eastbound on V 120 when given this clearance. Just before intercepting the arc, which is the beginning of the approach, I changed frequencys on my side to talk to company. While I was talking to company, the captain turned on to the arc, dialed in a new altitude on the alerter and began a descent. Just after I changed back to center frequency, the controller stated to us with emphasis that we were to maintain 10000'. We were passing through 9100' at this time and immediately we climbed back to 10000'. After we got on the ground, we reviewed everything and realized the misunderstanding. When the controller stated that we were cleared for the profile of the approach and maintain 10000'. We thought he meant maintain 10000' until established and fly the profile. When you get your instrument rating and learn about approach plates the profile view of the approach deals with vertical descent and that is what we understood when the controller said cleared for the profile. What he actually meant was maintain 10000' and fly the horizontal profile of the approach or the radials of the approach. It was terminology that neither the captain or myself had ever heard before and since we associated profile with vertical we made an unintentional error. A different use in terminology would have prevented the error or if we had queried the controller the error would also have been prevented.

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Original NASA ASRS Text

Title: FLT CREW OF LTT COMMUTER ON ARC APCH TO EAT INSTRUCTED TO MAINTAIN 10000' STARTED DESCENT UPON ESTABLISHING THE ARC.

Narrative: WE WERE CLRED FOR THE PROFILE OF THE EAT VOR DME C APCH AND MAINTAIN 10000'. WE WERE EBND ON V 120 WHEN GIVEN THIS CLRNC. JUST BEFORE INTERCEPTING THE ARC, WHICH IS THE BEGINNING OF THE APCH, I CHANGED FREQS ON MY SIDE TO TALK TO COMPANY. WHILE I WAS TALKING TO COMPANY, THE CAPT TURNED ON TO THE ARC, DIALED IN A NEW ALT ON THE ALERTER AND BEGAN A DSNT. JUST AFTER I CHANGED BACK TO CTR FREQ, THE CTLR STATED TO US WITH EMPHASIS THAT WE WERE TO MAINTAIN 10000'. WE WERE PASSING THROUGH 9100' AT THIS TIME AND IMMEDIATELY WE CLBED BACK TO 10000'. AFTER WE GOT ON THE GND, WE REVIEWED EVERYTHING AND REALIZED THE MISUNDERSTANDING. WHEN THE CTLR STATED THAT WE WERE CLRED FOR THE PROFILE OF THE APCH AND MAINTAIN 10000'. WE THOUGHT HE MEANT MAINTAIN 10000' UNTIL ESTABLISHED AND FLY THE PROFILE. WHEN YOU GET YOUR INSTRUMENT RATING AND LEARN ABOUT APCH PLATES THE PROFILE VIEW OF THE APCH DEALS WITH VERT DSNT AND THAT IS WHAT WE UNDERSTOOD WHEN THE CTLR SAID CLRED FOR THE PROFILE. WHAT HE ACTUALLY MEANT WAS MAINTAIN 10000' AND FLY THE HORIZ PROFILE OF THE APCH OR THE RADIALS OF THE APCH. IT WAS TERMINOLOGY THAT NEITHER THE CAPT OR MYSELF HAD EVER HEARD BEFORE AND SINCE WE ASSOCIATED PROFILE WITH VERT WE MADE AN UNINTENTIONAL ERROR. A DIFFERENT USE IN TERMINOLOGY WOULD HAVE PREVENTED THE ERROR OR IF WE HAD QUERIED THE CTLR THE ERROR WOULD ALSO HAVE BEEN PREVENTED.

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.