Narrative:

On climb out; approaching 3;000; we were cleared to climb to 7;000. The next clearance I heard was; cross loulu at or below 7;000; climb to 17;000. On hearing the new altitude I reached up and rolled the MCP altitude knob to 17;000 and planned to put '7000B' at the loulu fix in the FMC. The controller called back to correct my hear back read back error to confirm clearance; cross loulu at or below 7;000; climb and maintain 10;000. My first officer; seeing my error; quickly returned the MCP to 7;000 and disconnected the autopilot to prevent us from climbing through 7;000. As the result of the combination of the 'unusual and unexpected' altitude clearance; our rate of climb and my attempt to keep VNAV working smoothly; my error caused us to exceed the at or below part of our clearance even though my first officer made a valiant attempt to level our aircraft 7;000 as soon as possible. Contributing factors: when one is climbing in VNAV one is often prepped to stay ahead of the aircraft by being ready to set the next altitude to prevent the aircraft going into altitude cap so as to continue a smooth; uninterrupted climb; then updating the FMC to match the clearance. I have never had a clearance at or below climbing out of iad and it caught me off guard. I have had at or below type clearances at other airports but those restrictions have also been published on the SID's and; therefore; were not unexpected. My not hearing the correct clearance; 17;000 vs. 10;000; caused an added distraction and delay; which contributed to the altitude deviation.

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Original NASA ASRS Text

Title: The delay caused by a readback error on an unexpected 'at or below 7;000 at LOULU' clearance departing IAD resulted in an altitude deviation for a B757-200 flight crew.

Narrative: On climb out; approaching 3;000; we were cleared to climb to 7;000. The next clearance I heard was; cross LOULU at or below 7;000; climb to 17;000. On hearing the new altitude I reached up and rolled the MCP ALT knob to 17;000 and planned to put '7000B' at the LOULU fix in the FMC. The Controller called back to correct my hear back read back error to confirm clearance; cross LOULU at or below 7;000; climb and maintain 10;000. My First Officer; seeing my error; quickly returned the MCP to 7;000 and disconnected the autopilot to prevent us from climbing through 7;000. As the result of the combination of the 'unusual and unexpected' altitude clearance; our rate of climb and my attempt to keep VNAV working smoothly; my error caused us to exceed the at or below part of our clearance even though my First Officer made a valiant attempt to level our aircraft 7;000 ASAP. Contributing factors: When one is climbing in VNAV one is often prepped to stay ahead of the aircraft by being ready to set the next altitude to prevent the aircraft going into ALT CAP so as to continue a smooth; uninterrupted climb; then updating the FMC to match the clearance. I have never had a clearance at or below climbing out of IAD and it caught me off guard. I have had at or below type clearances at other airports but those restrictions have also been published on the SID's and; therefore; were not unexpected. My not hearing the correct clearance; 17;000 vs. 10;000; caused an added distraction and delay; which contributed to the altitude deviation.

Data retrieved from NASA's ASRS site as of July 2013 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.