Narrative:

Cleared to 6000' by chicago departure. Captain was flying aircraft. ATC asked flight for WX report on a 180 degree heading. Captain deviated from 'sterile cockpit' procedure below 10000' by calling F/a's on intercom to warn them of possible turbulence. Altitude alert device was functioning normally at this time. Captain continued climbing past 6000' until first officer noticed altitude (8600') when he finished WX report to ATC. Captain made rapid descent back down to 6000'. ATC switched flight to ZAU and no mention was made by ATC of flight's altitude deviation. Situation could have been avoided if strict adherence to 'sterile cockpit' procedure was followed. Also the altitude alert system has an aural warning advising crew of climb or descent to within 1000' of assigned altitude. The same aural warning goes off approximately 300' from altitude to indicate a deviation. The 'deviation' aural warning should be a louder aural warning in order to really get the flight crew's attention. We continued 2300' beyond the 'deviation' warning. Flight crews hear the aural warnings from the altitude alert about 10-30 times per flight so it becomes too common to be used as a useful warning device. Apparently the ATC controller never noticed our deviation from assigned altitude.

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Original NASA ASRS Text

Title: FLT CREW OF ACR MLG ALLOWS ACFT TO CLIMB TO 8600' WHEN ONLY CLEARED TO 6000' DUE TO COCKPIT DISTR.

Narrative: CLRED TO 6000' BY CHICAGO DEP. CAPT WAS FLYING ACFT. ATC ASKED FLT FOR WX RPT ON A 180 DEG HDG. CAPT DEVIATED FROM 'STERILE COCKPIT' PROC BELOW 10000' BY CALLING F/A'S ON INTERCOM TO WARN THEM OF POSSIBLE TURB. ALT ALERT DEVICE WAS FUNCTIONING NORMALLY AT THIS TIME. CAPT CONTINUED CLBING PAST 6000' UNTIL F/O NOTICED ALT (8600') WHEN HE FINISHED WX RPT TO ATC. CAPT MADE RAPID DSCNT BACK DOWN TO 6000'. ATC SWITCHED FLT TO ZAU AND NO MENTION WAS MADE BY ATC OF FLT'S ALT DEVIATION. SITUATION COULD HAVE BEEN AVOIDED IF STRICT ADHERENCE TO 'STERILE COCKPIT' PROC WAS FOLLOWED. ALSO THE ALT ALERT SYS HAS AN AURAL WARNING ADVISING CREW OF CLB OR DSCNT TO WITHIN 1000' OF ASSIGNED ALT. THE SAME AURAL WARNING GOES OFF APPROX 300' FROM ALT TO INDICATE A DEVIATION. THE 'DEVIATION' AURAL WARNING SHOULD BE A LOUDER AURAL WARNING IN ORDER TO REALLY GET THE FLT CREW'S ATTN. WE CONTINUED 2300' BEYOND THE 'DEVIATION' WARNING. FLT CREWS HEAR THE AURAL WARNINGS FROM THE ALT ALERT ABOUT 10-30 TIMES PER FLT SO IT BECOMES TOO COMMON TO BE USED AS A USEFUL WARNING DEVICE. APPARENTLY THE ATC CTLR NEVER NOTICED OUR DEVIATION FROM ASSIGNED ALT.

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.