Narrative:

Air carrier X check on our frequency and we reduced his airspeed to 250 KTS for spacing to dca. I observed air carrier X level FL270. I immediately quizzed him of his assigned altitude. He said FL240. I issued immediate clearance to FL270 for air carrier Y at FL260. He then reported level at FL270. Must listen much closer to pilots altitude when checking onto frequency and repeat all altitude in clrncs. Supplemental information from acn 279387: air carrier X checked on descending to FL240. I thought he said FL270. X left FL270 (26800 ft) and we asked what his altitude was. He said descending to FL240. We stopped him and told him to climb back to FL270 immediately. He had air carrier Y at FL260. He saw traffic and reported level at FL270. Need to listen more attentively. Supplemental information from acn 280549: air carrier X was cleared to cross 85 mi south of ric at FL270. He read back FL240 and I didn't catch the wrong altitude. Air carrier Y was wbound under X at FL260. Air carrier X descended into air carrier Y protected airspace. After conferring with the next controller that was now talking to X, I issued an immediate descent to FL250 for Y when it was clear the other controller told X to climb up to FL270. I gave a good clearance. X read it back wrong, and I missed it, so did the next controller when X checked on his frequency. Supplemental information from acn 279679: over fayetteville, nc, ZDC asked if we had read back a clearance to cross 85 south of richmond at FL240. We had not received that clearance, so I questioned if it was for us and that we would comply. Center acknowledged that I accepted that clearance. The descent from FL330 was started so we would reach FL240 85 NM south of ric. Center had us slow to 250 KTS during the descent. We changed frequencys to 122.75 and checked in that we were descending to FL240. Center then called traffic to us at 2 O'clock and 20 mi at FL260. The traffic showed up on the TCASII and I made a comment that it didn't look right. The captain slowed the descent and center then called and asked if we were level at FL270. (We were descending through about FL265). I told him we were descending to FL240. Center told us to climb immediately to FL270, and turn 40 degrees left. TCASII commanded a descent of approximately 2000 FPM. The captain started a left turn, but then we got a visual on the other aircraft and turned back to the right to avoid them. Supplemental information from acn 279975: orf- atl. In cruise flight FL260 ATC advised we had traffic at 11:00 O'clock 25 mi leveling at FL270. While showing TCASII to jumpseat passenger, we observed traffic continue through FL270 on down towards 260, TCASII gave an advisory to climb. (The captain took the aircraft and started a climb. During this I observed the TCASII altitude to show FL262 for the traffic. Soon after the climb was initiated center tells us to descend immediately to FL250. The captain uses idle thrust, full speed brakes and right bank to get the nose down and aircraft to FL250. During the descent I observed the traffic's altitude on TCASII to return from FL262 back to FL270.

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Original NASA ASRS Text

Title: ACR X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: ACR X CHK ON OUR FREQ AND WE REDUCED HIS AIRSPD TO 250 KTS FOR SPACING TO DCA. I OBSERVED ACR X LEVEL FL270. I IMMEDIATELY QUIZZED HIM OF HIS ASSIGNED ALT. HE SAID FL240. I ISSUED IMMEDIATE CLRNC TO FL270 FOR ACR Y AT FL260. HE THEN RPTED LEVEL AT FL270. MUST LISTEN MUCH CLOSER TO PLTS ALT WHEN CHKING ONTO FREQ AND REPEAT ALL ALT IN CLRNCS. SUPPLEMENTAL INFO FROM ACN 279387: ACR X CHKED ON DSNDING TO FL240. I THOUGHT HE SAID FL270. X LEFT FL270 (26800 FT) AND WE ASKED WHAT HIS ALT WAS. HE SAID DSNDING TO FL240. WE STOPPED HIM AND TOLD HIM TO CLB BACK TO FL270 IMMEDIATELY. HE HAD ACR Y AT FL260. HE SAW TFC AND RPTED LEVEL AT FL270. NEED TO LISTEN MORE ATTENTIVELY. SUPPLEMENTAL INFO FROM ACN 280549: ACR X WAS CLRED TO CROSS 85 MI S OF RIC AT FL270. HE READ BACK FL240 AND I DIDN'T CATCH THE WRONG ALT. ACR Y WAS WBOUND UNDER X AT FL260. ACR X DSNDED INTO ACR Y PROTECTED AIRSPACE. AFTER CONFERRING WITH THE NEXT CTLR THAT WAS NOW TALKING TO X, I ISSUED AN IMMEDIATE DSCNT TO FL250 FOR Y WHEN IT WAS CLR THE OTHER CTLR TOLD X TO CLB UP TO FL270. I GAVE A GOOD CLRNC. X READ IT BACK WRONG, AND I MISSED IT, SO DID THE NEXT CTLR WHEN X CHKED ON HIS FREQ. SUPPLEMENTAL INFO FROM ACN 279679: OVER FAYETTEVILLE, NC, ZDC ASKED IF WE HAD READ BACK A CLRNC TO CROSS 85 S OF RICHMOND AT FL240. WE HAD NOT RECEIVED THAT CLRNC, SO I QUESTIONED IF IT WAS FOR US AND THAT WE WOULD COMPLY. CTR ACKNOWLEDGED THAT I ACCEPTED THAT CLRNC. THE DSCNT FROM FL330 WAS STARTED SO WE WOULD REACH FL240 85 NM S OF RIC. CTR HAD US SLOW TO 250 KTS DURING THE DSCNT. WE CHANGED FREQS TO 122.75 AND CHKED IN THAT WE WERE DSNDING TO FL240. CTR THEN CALLED TFC TO US AT 2 O'CLOCK AND 20 MI AT FL260. THE TFC SHOWED UP ON THE TCASII AND I MADE A COMMENT THAT IT DIDN'T LOOK RIGHT. THE CAPT SLOWED THE DSCNT AND CTR THEN CALLED AND ASKED IF WE WERE LEVEL AT FL270. (WE WERE DSNDING THROUGH ABOUT FL265). I TOLD HIM WE WERE DSNDING TO FL240. CTR TOLD US TO CLB IMMEDIATELY TO FL270, AND TURN 40 DEGS L. TCASII COMMANDED A DSCNT OF APPROX 2000 FPM. THE CAPT STARTED A L TURN, BUT THEN WE GOT A VISUAL ON THE OTHER ACFT AND TURNED BACK TO THE R TO AVOID THEM. SUPPLEMENTAL INFO FROM ACN 279975: ORF- ATL. IN CRUISE FLT FL260 ATC ADVISED WE HAD TFC AT 11:00 O'CLOCK 25 MI LEVELING AT FL270. WHILE SHOWING TCASII TO JUMPSEAT PAX, WE OBSERVED TFC CONTINUE THROUGH FL270 ON DOWN TOWARDS 260, TCASII GAVE AN ADVISORY TO CLB. (THE CAPT TOOK THE ACFT AND STARTED A CLB. DURING THIS I OBSERVED THE TCASII ALT TO SHOW FL262 FOR THE TFC. SOON AFTER THE CLB WAS INITIATED CTR TELLS US TO DSND IMMEDIATELY TO FL250. THE CAPT USES IDLE THRUST, FULL SPD BRAKES AND R BANK TO GET THE NOSE DOWN AND ACFT TO FL250. DURING THE DSCNT I OBSERVED THE TFC'S ALT ON TCASII TO RETURN FROM FL262 BACK TO FL270.

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.