Flight crew of large transport is cleared to 31000 ft from 35000 ft. Traffic is called at the altitu...

Attributes
ACN	381225
Time
Date	199709
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : spa
State Reference	SC
Altitude	msl bound lower : 31000 msl bound upper : 31400
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl tower : mci
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : cfi pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 209 flight time total : 12367 flight time type : 1137
ASRS Report	381225
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 9000 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

We were cleared to descend to FL310 from FL350. The first officer read back FL310, set the altitude alert at 31000 ft and I confirmed the altitude by pointing at the set altitude and speaking '310' as per our SOP. During the descent and just below FL330, ATC called traffic for us at 12 O'clock position and FL310. They concluded their transmission with, 'when clear of this traffic, you'll be cleared to a lower altitude.' I immediately asked the first officer to ask ATC to confirm the traffic was at FL310, because that was our cleared altitude and it didn't make sense. At that time, one of our flight attendants knocked and entered the cockpit. The first officer was distracted momentarily by the flight attendant beginning to talk, but ATC had been too busy for him to ask the controller about the traffic anyway. I again asked him to confirm the traffic. Descending through FL319 and before the first officer was able to ask ATC about the traffic, the controller asked us to verify our altitude and to climb to FL330 because we had traffic at FL310. Within several seconds, the following transpired: TCASII called 'traffic' (we never received an RA). I disconnected the autoplt and began a climb. The conflicting traffic was told to turn left 20 degrees. The conflicting traffic told ATC they were following a 'descend' RA. We were told to turn left 20 degrees. ATC told the conflicting traffic to disregard the 'descend' RA as their traffic conflict (us) was now climbing. We reset the altitude alert and climbed to FL330. I didn't get a good look at the TCASII during the final seconds of this event, but I believe the vertical separation between us and the other aircraft was 400 ft and the horizontal separation was about 1-2 mi. After we landed, I called ATC and spoke with the supervisor about the conflict. He said that after the event occurred, they pulled the tape and we had indeed been erroneously cleared to FL310 instead of FL330.

Original NASA ASRS Text

Title: FLC OF LGT IS CLRED TO 31000 FT FROM 35000 FT. TFC IS CALLED AT THE ALT TO WHICH THEY ARE CLRED. PRIOR TO QUERYING ATC TCASII ISSUES ALERT. CTLR ALSO VECTORS BOTH ACFT. TAPE REPLAY INDICATES CTLR ERROR.

Narrative: WE WERE CLRED TO DSND TO FL310 FROM FL350. THE FO READ BACK FL310, SET THE ALT ALERT AT 31000 FT AND I CONFIRMED THE ALT BY POINTING AT THE SET ALT AND SPEAKING '310' AS PER OUR SOP. DURING THE DSCNT AND JUST BELOW FL330, ATC CALLED TFC FOR US AT 12 O'CLOCK POS AND FL310. THEY CONCLUDED THEIR XMISSION WITH, 'WHEN CLR OF THIS TFC, YOU'LL BE CLRED TO A LOWER ALT.' I IMMEDIATELY ASKED THE FO TO ASK ATC TO CONFIRM THE TFC WAS AT FL310, BECAUSE THAT WAS OUR CLRED ALT AND IT DIDN'T MAKE SENSE. AT THAT TIME, ONE OF OUR FLT ATTENDANTS KNOCKED AND ENTERED THE COCKPIT. THE FO WAS DISTRACTED MOMENTARILY BY THE FLT ATTENDANT BEGINNING TO TALK, BUT ATC HAD BEEN TOO BUSY FOR HIM TO ASK THE CTLR ABOUT THE TFC ANYWAY. I AGAIN ASKED HIM TO CONFIRM THE TFC. DSNDING THROUGH FL319 AND BEFORE THE FO WAS ABLE TO ASK ATC ABOUT THE TFC, THE CTLR ASKED US TO VERIFY OUR ALT AND TO CLB TO FL330 BECAUSE WE HAD TFC AT FL310. WITHIN SEVERAL SECONDS, THE FOLLOWING TRANSPIRED: TCASII CALLED 'TFC' (WE NEVER RECEIVED AN RA). I DISCONNECTED THE AUTOPLT AND BEGAN A CLB. THE CONFLICTING TFC WAS TOLD TO TURN L 20 DEGS. THE CONFLICTING TFC TOLD ATC THEY WERE FOLLOWING A 'DSND' RA. WE WERE TOLD TO TURN L 20 DEGS. ATC TOLD THE CONFLICTING TFC TO DISREGARD THE 'DSND' RA AS THEIR TFC CONFLICT (US) WAS NOW CLBING. WE RESET THE ALT ALERT AND CLBED TO FL330. I DIDN'T GET A GOOD LOOK AT THE TCASII DURING THE FINAL SECONDS OF THIS EVENT, BUT I BELIEVE THE VERT SEPARATION BTWN US AND THE OTHER ACFT WAS 400 FT AND THE HORIZ SEPARATION WAS ABOUT 1-2 MI. AFTER WE LANDED, I CALLED ATC AND SPOKE WITH THE SUPVR ABOUT THE CONFLICT. HE SAID THAT AFTER THE EVENT OCCURRED, THEY PULLED THE TAPE AND WE HAD INDEED BEEN ERRONEOUSLY CLRED TO FL310 INSTEAD OF FL330.

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.

Flight crew of large transport is cleared to 31000 ft from 35000 ft. Traffic is called at the altitude to which they are cleared. Prior to querying ATC TCASII issues alert. Controller also vectors both aircraft. Tape replay indicates controller error.