Flight crew climbed from FL280 to FL310 on the basis of a similar call sign aircraft clearance from ...

Attributes
ACN	329720
Time
Date	199603
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : dsm
State Reference	IA
Altitude	msl bound lower : 28000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zkc tower : mia
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 260 flight time total : 16000 flight time type : 4000
ASRS Report	329720
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : took evasive action other
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 12000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were at 28000 ft. Checked in with ZKC. On a direct FMS flight to zuni VORTAC. Heard an air carrier X jet checking on our frequency and even though we were aware of it, ATC didn't notify us of similar call signs. FL280 was getting turbulent and as I was flying this leg I asked copilot to request FL310. We both heard our clearance to FL310, copilot read it back over the radio and then I put 31000 ft in the altitude window and in the FMS to let autoplt climb aircraft. Center didn't come back and say we were wrong or got the wrong clearance so we climbed to FL310. Usually if you deviate by 300-500 ft from your assigned altitude ATC will ask you what you're doing. We were going through 30000 ft and I was monitoring the TCASII when I saw a possible conflict with an aircraft at our 12 O'clock at FL300 heading toward us. I immediately started a left turn to avoid aircraft and had first officer call ATC to inform them of aircraft conflict and turn. That's when ATC came on and asked us our altitude and he said we should be at FL280. Not sure of conflicting aircraft, but it was either air carrier Y airline flight or air carrier X jet. Due to my quick turn to avoid aircraft, never got a TCASII TA or RA. Lateral separation was about 2 mi, but they say vertical was 500-1000 ft. Controller said he never gave us clearance to FL310, didn't hear the first officer acknowledge clearance to FL310, but says he gave air carrier X jet clearance from FL350 to FL310. Trying to figure this out I think we asked for FL310 at the same time that air carrier X jet got FL310. There was no standby or we have your clearance from center. But we got a clearance to FL310 right after we requested it. The first officer spoke into the microphone and confirmed clearance, I saw him do it, but ATC says controller didn't hear it and it's not on tape. Similar call signs, asking for the same altitude all at the same time, that's a one in a million, and ATC never heard or challenged us until we were through 30000 ft. Fate.

Original NASA ASRS Text

Title: FLC CLBED FROM FL280 TO FL310 ON THE BASIS OF A SIMILAR CALL SIGN ACFT CLRNC FROM FL350 TO FL310. THE FO ACKNOWLEDGED THE CLRNC TO FL310, BUT THE CTLR DID NOT HEAR IT.

Narrative: WE WERE AT 28000 FT. CHKED IN WITH ZKC. ON A DIRECT FMS FLT TO ZUNI VORTAC. HEARD AN ACR X JET CHKING ON OUR FREQ AND EVEN THOUGH WE WERE AWARE OF IT, ATC DIDN'T NOTIFY US OF SIMILAR CALL SIGNS. FL280 WAS GETTING TURBULENT AND AS I WAS FLYING THIS LEG I ASKED COPLT TO REQUEST FL310. WE BOTH HEARD OUR CLRNC TO FL310, COPLT READ IT BACK OVER THE RADIO AND THEN I PUT 31000 FT IN THE ALT WINDOW AND IN THE FMS TO LET AUTOPLT CLB ACFT. CTR DIDN'T COME BACK AND SAY WE WERE WRONG OR GOT THE WRONG CLRNC SO WE CLBED TO FL310. USUALLY IF YOU DEVIATE BY 300-500 FT FROM YOUR ASSIGNED ALT ATC WILL ASK YOU WHAT YOU'RE DOING. WE WERE GOING THROUGH 30000 FT AND I WAS MONITORING THE TCASII WHEN I SAW A POSSIBLE CONFLICT WITH AN ACFT AT OUR 12 O'CLOCK AT FL300 HEADING TOWARD US. I IMMEDIATELY STARTED A L TURN TO AVOID ACFT AND HAD FO CALL ATC TO INFORM THEM OF ACFT CONFLICT AND TURN. THAT'S WHEN ATC CAME ON AND ASKED US OUR ALT AND HE SAID WE SHOULD BE AT FL280. NOT SURE OF CONFLICTING ACFT, BUT IT WAS EITHER ACR Y AIRLINE FLT OR ACR X JET. DUE TO MY QUICK TURN TO AVOID ACFT, NEVER GOT A TCASII TA OR RA. LATERAL SEPARATION WAS ABOUT 2 MI, BUT THEY SAY VERT WAS 500-1000 FT. CTLR SAID HE NEVER GAVE US CLRNC TO FL310, DIDN'T HEAR THE FO ACKNOWLEDGE CLRNC TO FL310, BUT SAYS HE GAVE ACR X JET CLRNC FROM FL350 TO FL310. TRYING TO FIGURE THIS OUT I THINK WE ASKED FOR FL310 AT THE SAME TIME THAT ACR X JET GOT FL310. THERE WAS NO STANDBY OR WE HAVE YOUR CLRNC FROM CTR. BUT WE GOT A CLRNC TO FL310 RIGHT AFTER WE REQUESTED IT. THE FO SPOKE INTO THE MIKE AND CONFIRMED CLRNC, I SAW HIM DO IT, BUT ATC SAYS CTLR DIDN'T HEAR IT AND IT'S NOT ON TAPE. SIMILAR CALL SIGNS, ASKING FOR THE SAME ALT ALL AT THE SAME TIME, THAT'S A ONE IN A MILLION, AND ATC NEVER HEARD OR CHALLENGED US UNTIL WE WERE THROUGH 30000 FT. FATE.

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 climbed from FL280 to FL310 on the basis of a similar call sign aircraft clearance from FL350 to FL310. The first officer acknowledged the clearance to FL310, but the controller did not hear it.