Narrative:

The other day I had an occurrence that appears to be occurring with disturbing regularity. I was working flight dfw-cvg, dec/92. We took off and climbed to the normally assigned altitude of 10000 ft and leveled off. Subsequently, I acknowledged a climb clearance to 17000 ft. Passing 9500 ft both the captain and I noticed, on TCASII and visually, an aircraft on a course that would create a conflict with the climb to 17000 ft. I then requested a verification of the climb clearance. The controller responded that we were only cleared to 10000 and that the clearance to climb to 17000 had been for flight ebd not edd. As we were now at 10000 ft we leveled off and the flight continued without incident. The disturbing part of this is that many controllers have fallen onto the mode of issuing clrncs, waiting for a response but, not listening to the readback. Often this error occurs during a frequency change when the wrong frequency is read back. Many times the readback of the wrong frequency goes unnoticed, requiring a return to the previous one for verification. In our case, the conflicting traffic was inbound to dfw at 11000 ft. Had we continued on climb clearance only the TCASII would have alerted us to the conflict. One wonders what might have happened under instrument conditions without TCASII. Possible solutions for this problem are: make controllers and pilots aware that the problem exists. Place an increased emphasis during controller training on the necessity to listen for correct responses to clrncs. Create an awareness that it is very easy to relate voice sounds and tones. Just because the same tone of voice responds to a command, does not mean the voice is saying the correct thing.

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Original NASA ASRS Text

Title: MLG FLC RESPONDS TO WRONG CLRNC BUT SIGHTS SECOND ACFT ON TCASII. CTLR MISSES WRONG FLC RESPONSE.

Narrative: THE OTHER DAY I HAD AN OCCURRENCE THAT APPEARS TO BE OCCURRING WITH DISTURBING REGULARITY. I WAS WORKING FLT DFW-CVG, DEC/92. WE TOOK OFF AND CLBED TO THE NORMALLY ASSIGNED ALT OF 10000 FT AND LEVELED OFF. SUBSEQUENTLY, I ACKNOWLEDGED A CLB CLRNC TO 17000 FT. PASSING 9500 FT BOTH THE CAPT AND I NOTICED, ON TCASII AND VISUALLY, AN ACFT ON A COURSE THAT WOULD CREATE A CONFLICT WITH THE CLB TO 17000 FT. I THEN REQUESTED A VERIFICATION OF THE CLB CLRNC. THE CTLR RESPONDED THAT WE WERE ONLY CLRED TO 10000 AND THAT THE CLRNC TO CLB TO 17000 HAD BEEN FOR FLT EBD NOT EDD. AS WE WERE NOW AT 10000 FT WE LEVELED OFF AND THE FLT CONTINUED WITHOUT INCIDENT. THE DISTURBING PART OF THIS IS THAT MANY CTLRS HAVE FALLEN ONTO THE MODE OF ISSUING CLRNCS, WAITING FOR A RESPONSE BUT, NOT LISTENING TO THE READBACK. OFTEN THIS ERROR OCCURS DURING A FREQ CHANGE WHEN THE WRONG FREQ IS READ BACK. MANY TIMES THE READBACK OF THE WRONG FREQ GOES UNNOTICED, REQUIRING A RETURN TO THE PREVIOUS ONE FOR VERIFICATION. IN OUR CASE, THE CONFLICTING TFC WAS INBOUND TO DFW AT 11000 FT. HAD WE CONTINUED ON CLB CLRNC ONLY THE TCASII WOULD HAVE ALERTED US TO THE CONFLICT. ONE WONDERS WHAT MIGHT HAVE HAPPENED UNDER INST CONDITIONS WITHOUT TCASII. POSSIBLE SOLUTIONS FOR THIS PROB ARE: MAKE CTLRS AND PLTS AWARE THAT THE PROB EXISTS. PLACE AN INCREASED EMPHASIS DURING CTLR TRAINING ON THE NECESSITY TO LISTEN FOR CORRECT RESPONSES TO CLRNCS. CREATE AN AWARENESS THAT IT IS VERY EASY TO RELATE VOICE SOUNDS AND TONES. JUST BECAUSE THE SAME TONE OF VOICE RESPONDS TO A COMMAND, DOES NOT MEAN THE VOICE IS SAYING THE CORRECT THING.

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.