Narrative:

During an instructional flight being conducted for the purpose of proficiency and recurrent training of a rated pilot, tpa approach control issued a clearance to descend to 2600 ft. This clearance was misinterp as being a clearance to descend to 2000 ft. The aircraft was on an IFR flight plan and was being flown with the pilot being trained in the left seat - he was also working the radios. As we were leaving 3000 ft I asked the pilot at the controls what altitude he was cleared to. He said 2000 ft. The controller advised that we should have stopped our descent at 2600 ft. We immediately climbed to the proper altitude. The PF later said he thought he had read back 2000 ft when cleared. Contributing factors included a ceiling of broken clouds at 3000 ft and the controller's inquiry as to our flight conditions. Also, the cockpit was noisy, making communications between the other pilot and myself difficult and making my microphone unusable for ATC communications (unreadable). Cockpit noise reduction, an intercom system and better attention to ATC instructions, despite distractions, will prevent future occurrences.

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Original NASA ASRS Text

Title: ATC FLC MISCOM ON ALT CLRNC. ATC INTERVENED WHEN FLC DSNDED BELOW ASSIGNED. PF SAID HE READ BACK THE ALT THAT HE HEARD AND ATC DIDN'T CORRECT THE ERROR.

Narrative: DURING AN INSTRUCTIONAL FLT BEING CONDUCTED FOR THE PURPOSE OF PROFICIENCY AND RECURRENT TRAINING OF A RATED PLT, TPA APCH CTL ISSUED A CLRNC TO DSND TO 2600 FT. THIS CLRNC WAS MISINTERP AS BEING A CLRNC TO DSND TO 2000 FT. THE ACFT WAS ON AN IFR FLT PLAN AND WAS BEING FLOWN WITH THE PLT BEING TRAINED IN THE L SEAT - HE WAS ALSO WORKING THE RADIOS. AS WE WERE LEAVING 3000 FT I ASKED THE PLT AT THE CTLS WHAT ALT HE WAS CLRED TO. HE SAID 2000 FT. THE CTLR ADVISED THAT WE SHOULD HAVE STOPPED OUR DSCNT AT 2600 FT. WE IMMEDIATELY CLBED TO THE PROPER ALT. THE PF LATER SAID HE THOUGHT HE HAD READ BACK 2000 FT WHEN CLRED. CONTRIBUTING FACTORS INCLUDED A CEILING OF BROKEN CLOUDS AT 3000 FT AND THE CTLR'S INQUIRY AS TO OUR FLT CONDITIONS. ALSO, THE COCKPIT WAS NOISY, MAKING COMS BTWN THE OTHER PLT AND MYSELF DIFFICULT AND MAKING MY MIKE UNUSABLE FOR ATC COMS (UNREADABLE). COCKPIT NOISE REDUCTION, AN INTERCOM SYS AND BETTER ATTN TO ATC INSTRUCTIONS, DESPITE DISTRACTIONS, WILL PREVENT FUTURE OCCURRENCES.

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.