A CL65 first officer reported a readback error with ZID which caused a track deviation.

Attributes
ACN	581699
Time
Date	200304
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : zid.artcc
State Reference	IN
Altitude	msl single value : 23300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : vacating altitude climbout : intermediate altitude cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 3500 flight time type : 625
ASRS Report	581699
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	non adherence : far non adherence : clearance non adherence : company policies other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : returned to intended or assigned course
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

While on an assigned heading, we were cleared to climb to FL270, passing FL230 direct etg, which I read back. Passing FL230, we initiated the turn (left) direct. At FL234 the controller asked if we started an early turn. I stated we started the turn at FL230 as directed. He told us he had cleared us direct through FL240 vice FL230 and gave us a turn back to the right (approximately 20 degrees). As we rolled out on the new heading we were reclred direct etg and handed off to the next sector. Both the captain and I heard the original clearance as 'climb and maintain FL270, leaving FL230, cleared direct etg.'

Original NASA ASRS Text

Title: A CL65 FO RPTED A READBACK ERROR WITH ZID WHICH CAUSED A TRACK DEV.

Narrative: WHILE ON AN ASSIGNED HEADING, WE WERE CLRED TO CLB TO FL270, PASSING FL230 DIRECT ETG, WHICH I READ BACK. PASSING FL230, WE INITIATED THE TURN (L) DIRECT. AT FL234 THE CTLR ASKED IF WE STARTED AN EARLY TURN. I STATED WE STARTED THE TURN AT FL230 AS DIRECTED. HE TOLD US HE HAD CLRED US DIRECT THROUGH FL240 VICE FL230 AND GAVE US A TURN BACK TO THE R (APPROX 20 DEGS). AS WE ROLLED OUT ON THE NEW HEADING WE WERE RECLRED DIRECT ETG AND HANDED OFF TO THE NEXT SECTOR. BOTH THE CAPT AND I HEARD THE ORIGINAL CLRNC AS 'CLB AND MAINTAIN FL270, LEAVING FL230, CLRED DIRECT ETG.'

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.