B747 flight crew misinterprted an ATC heading assignment of 340 degrees as clearance to a final alti...

Attributes
ACN	982516
Time
Date	201112
Local Time Of Day	1201-1800
Place
Locale Reference	MWH.Airport
State Reference	WA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Widebody Low Wing 4 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 5200 Flight Crew Type 1000
Events
Anomaly	Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

Climbing out; seattle center cleared us to FL230 and issued a heading of 340. My first officer and I misinterpreted the clearance as climb to FL230 and expect your final altitude to be FL340. Since the assigned heading of 340 would have been about 80 degrees off from our on-course heading; and since our original flight plan was filed for FL340 we both mistakenly interpreted the digits 3..4..0.. As pertaining to an expected altitude rather than a severe heading change. We ended up maintaining our on course heading of about 260 degrees and climbed to FL230 until the controller asked why we had not changed heading and assigned us a different vector. We should have listened more carefully; questioned any clearance or information that was not clearly understood; and confirmed the clearance.

Original NASA ASRS Text

Title: B747 flight crew misinterprted an ATC heading assignment of 340 degrees as clearance to a final altitude of FL340.

Narrative: Climbing out; Seattle center cleared us to FL230 and issued a heading of 340. My First Officer and I misinterpreted the clearance as climb to FL230 and expect your final altitude to be FL340. Since the assigned heading of 340 would have been about 80 degrees off from our on-course heading; and since our original flight plan was filed for FL340 we both mistakenly interpreted the digits 3..4..0.. as pertaining to an expected altitude rather than a severe heading change. We ended up maintaining our on course heading of about 260 degrees and climbed to FL230 until the controller asked why we had not changed heading and assigned us a different vector. We should have listened more carefully; questioned any clearance or information that was not clearly understood; and confirmed the clearance.

Data retrieved from NASA's ASRS site as of April 2012 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.