Narrative:

We departed crw at XA24. There were numerous thunderstorms in the area. Tower had given us a northerly heading, but with a clearance to deviate around WX as necessary. We were in IMC and using the aircraft's WX radar to navigation around storm cells. During the climb, passing through 6500 ft, the captain asked me to speak with the flight attendant via the interphone to ensure that she remained seated until further notice due to the turbulence. While I was off frequency, the captain received a clearance to an assigned altitude. He did not hear the controller, and asked the controller to repeat. When I returned to communication #1, I heard the captain reading back '8000 ft direct pkb when able,' and watched as he dialed 8000 ft into the altitude selector. The controller made no response to my captain's readback, thus I had no reason to question the clearance or believe that there had been a mistake. At 7300 ft, we received a TCASII alert that prompted the captain to ask for verification of the assigned altitude of 8000 ft. The controller (different than the previous controller because of a controller change) said 'negative, descend and maintain 7000 ft.' even as the controller was speaking, we were in our descent because the TA had become an RA, commanding us to descend. The RA occurred at 7500 ft, and we were clear of conflict at 7000 ft. The controller notified us that there had been a possible pilot deviation and asked us to call the crw tower when we reached our destination. There were several contributing factors involved. Because of the severe WX in the area, there were multiple aircraft deviating to find a clear flight path. The effect is more aircraft and less usable airspace. Second, there was no redundancy in cockpit radio communications because I was using the interphone to tell the flight attendant to remain seated for her safety. One cannot hear radio communications when talking on the interphone. Third, there was a breakdown in pilot/controller radio communications. The captain did not hear the first assigned clearance from the controller and when he asked him to repeat it, the controller read back a hurried clearance. The captain read back what he thought he heard -- 8000 ft -- and the controller did not correct him. We later found out there was a controller change occurring at that time which is a possibility for why the breakdown occurred. Had it not been for TCASII alerting us, we would not have questioned the altitude. Though we were passing through 7300 ft, the controller did not initiate radio contact with us. There are several thoughts to keep this situation from occurring again. When one pilot is off frequency and a clearance is received by the other pilot, the clearance should be verified by the pilot returning to the frequency. During times of severe WX and deviations, extra vigilance should be taken by the controllers when changing stations or receiving one another. Some day I would like to see something like ACARS for ATC communications. That way, pilots could look at a computer screen and verify instructions visually as well as audibly.

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Original NASA ASRS Text

Title: SF340-A READBACK HEARBACK ERROR CAUSES LOSS OF SEPARATION.

Narrative: WE DEPARTED CRW AT XA24. THERE WERE NUMEROUS TSTMS IN THE AREA. TWR HAD GIVEN US A NORTHERLY HDG, BUT WITH A CLRNC TO DEVIATE AROUND WX AS NECESSARY. WE WERE IN IMC AND USING THE ACFT'S WX RADAR TO NAV AROUND STORM CELLS. DURING THE CLB, PASSING THROUGH 6500 FT, THE CAPT ASKED ME TO SPEAK WITH THE FLT ATTENDANT VIA THE INTERPHONE TO ENSURE THAT SHE REMAINED SEATED UNTIL FURTHER NOTICE DUE TO THE TURB. WHILE I WAS OFF FREQ, THE CAPT RECEIVED A CLRNC TO AN ASSIGNED ALT. HE DID NOT HEAR THE CTLR, AND ASKED THE CTLR TO REPEAT. WHEN I RETURNED TO COM #1, I HEARD THE CAPT READING BACK '8000 FT DIRECT PKB WHEN ABLE,' AND WATCHED AS HE DIALED 8000 FT INTO THE ALT SELECTOR. THE CTLR MADE NO RESPONSE TO MY CAPT'S READBACK, THUS I HAD NO REASON TO QUESTION THE CLRNC OR BELIEVE THAT THERE HAD BEEN A MISTAKE. AT 7300 FT, WE RECEIVED A TCASII ALERT THAT PROMPTED THE CAPT TO ASK FOR VERIFICATION OF THE ASSIGNED ALT OF 8000 FT. THE CTLR (DIFFERENT THAN THE PREVIOUS CTLR BECAUSE OF A CTLR CHANGE) SAID 'NEGATIVE, DSND AND MAINTAIN 7000 FT.' EVEN AS THE CTLR WAS SPEAKING, WE WERE IN OUR DSCNT BECAUSE THE TA HAD BECOME AN RA, COMMANDING US TO DSND. THE RA OCCURRED AT 7500 FT, AND WE WERE CLR OF CONFLICT AT 7000 FT. THE CTLR NOTIFIED US THAT THERE HAD BEEN A POSSIBLE PLTDEV AND ASKED US TO CALL THE CRW TWR WHEN WE REACHED OUR DEST. THERE WERE SEVERAL CONTRIBUTING FACTORS INVOLVED. BECAUSE OF THE SEVERE WX IN THE AREA, THERE WERE MULTIPLE ACFT DEVIATING TO FIND A CLR FLT PATH. THE EFFECT IS MORE ACFT AND LESS USABLE AIRSPACE. SECOND, THERE WAS NO REDUNDANCY IN COCKPIT RADIO COMS BECAUSE I WAS USING THE INTERPHONE TO TELL THE FLT ATTENDANT TO REMAIN SEATED FOR HER SAFETY. ONE CANNOT HEAR RADIO COMS WHEN TALKING ON THE INTERPHONE. THIRD, THERE WAS A BREAKDOWN IN PLT/CTLR RADIO COMS. THE CAPT DID NOT HEAR THE FIRST ASSIGNED CLRNC FROM THE CTLR AND WHEN HE ASKED HIM TO REPEAT IT, THE CTLR READ BACK A HURRIED CLRNC. THE CAPT READ BACK WHAT HE THOUGHT HE HEARD -- 8000 FT -- AND THE CTLR DID NOT CORRECT HIM. WE LATER FOUND OUT THERE WAS A CTLR CHANGE OCCURRING AT THAT TIME WHICH IS A POSSIBILITY FOR WHY THE BREAKDOWN OCCURRED. HAD IT NOT BEEN FOR TCASII ALERTING US, WE WOULD NOT HAVE QUESTIONED THE ALT. THOUGH WE WERE PASSING THROUGH 7300 FT, THE CTLR DID NOT INITIATE RADIO CONTACT WITH US. THERE ARE SEVERAL THOUGHTS TO KEEP THIS SIT FROM OCCURRING AGAIN. WHEN ONE PLT IS OFF FREQ AND A CLRNC IS RECEIVED BY THE OTHER PLT, THE CLRNC SHOULD BE VERIFIED BY THE PLT RETURNING TO THE FREQ. DURING TIMES OF SEVERE WX AND DEVS, EXTRA VIGILANCE SHOULD BE TAKEN BY THE CTLRS WHEN CHANGING STATIONS OR RECEIVING ONE ANOTHER. SOME DAY I WOULD LIKE TO SEE SOMETHING LIKE ACARS FOR ATC COMS. THAT WAY, PLTS COULD LOOK AT A COMPUTER SCREEN AND VERIFY INSTRUCTIONS VISUALLY AS WELL AS AUDIBLY.

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.