Air carrier climbed to an occupied altitude due to readback hearback error.

Attributes
ACN	152730
Time
Date	199008
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : txf
State Reference	AR
Altitude	msl bound lower : 23000 msl bound upper : 33000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zfw
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 17000 flight time type : 3500
ASRS Report	152730
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 300 flight time total : 3600 flight time type : 225
ASRS Report	152899
Events
Anomaly	non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 9000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Ftw center cleared us to FL330. All 3 crew members and jump seat occupant heard this. FL330 was read back by first officer. Due to thunderstorms in area there was lots of voice traffic on center frequency. As we went through FL240 an air carrier large transport was seen ahead. No evasive action was required. We asked ftw center about the traffic and he replied that we were only cleared to FL230. He may have been blocked by other traffic. Center then cleared us back to FL230 and within 20 second reclred us to FL330. The cause was too much traffic on the frequency and many thunderstorms on departure route. Supplemental information from acn 152899. ZFW was very busy. Thunderstorms were causing numerous deviations. Passing through 23000' we noticed an air carrier large transport passing from our 1 O'clock position right to left and heading toward us. He passed off the left side of the aircraft at about 1 NM. We called back to ATC to inform them and ask what he was doing there. The controller said that we had only been cleared to FL230, and to descend immediately to FL230. After leveling off he came back and said his indications were that we came within 700' of the other jet.

Original NASA ASRS Text

Title: ACR CLIMBED TO AN OCCUPIED ALT DUE TO READBACK HEARBACK ERROR.

Narrative: FTW CTR CLRED US TO FL330. ALL 3 CREW MEMBERS AND JUMP SEAT OCCUPANT HEARD THIS. FL330 WAS READ BACK BY F/O. DUE TO TSTMS IN AREA THERE WAS LOTS OF VOICE TFC ON CTR FREQ. AS WE WENT THROUGH FL240 AN ACR LGT WAS SEEN AHEAD. NO EVASIVE ACTION WAS REQUIRED. WE ASKED FTW CTR ABOUT THE TFC AND HE REPLIED THAT WE WERE ONLY CLRED TO FL230. HE MAY HAVE BEEN BLOCKED BY OTHER TFC. CTR THEN CLRED US BACK TO FL230 AND WITHIN 20 SEC RECLRED US TO FL330. THE CAUSE WAS TOO MUCH TFC ON THE FREQ AND MANY TSTMS ON DEP RTE. SUPPLEMENTAL INFO FROM ACN 152899. ZFW WAS VERY BUSY. TSTMS WERE CAUSING NUMEROUS DEVS. PASSING THROUGH 23000' WE NOTICED AN ACR LGT PASSING FROM OUR 1 O'CLOCK POS R TO L AND HDG TOWARD US. HE PASSED OFF THE L SIDE OF THE ACFT AT ABOUT 1 NM. WE CALLED BACK TO ATC TO INFORM THEM AND ASK WHAT HE WAS DOING THERE. THE CTLR SAID THAT WE HAD ONLY BEEN CLRED TO FL230, AND TO DSND IMMEDIATELY TO FL230. AFTER LEVELING OFF HE CAME BACK AND SAID HIS INDICATIONS WERE THAT WE CAME WITHIN 700' OF THE OTHER JET.

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.