Less than standard separation between 2 air carrier. Operational error.

Attributes
ACN	97512
Time
Date	198810
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bna
State Reference	TN
Altitude	msl bound lower : 3600 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bna
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 4000 flight time type : 1800
ASRS Report	97512
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac non adherence : required legal separation other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 0 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Intra Facility Coordination Failure

Narrative:

We were cleared by tower to depart runway 31, after takeoff turn left to 280 degrees and climb to 3000'. After takeoff we turned left to 280 degrees and contacted departure control on 119.35. Departure control responded 'radar contact climb to 4000'.' we set 4000' in the altitude alert window in the cockpit and continued to climb and accelerate to 250 KTS. Passing 3500' I noticed air carrier Y in our 10 O'clock position less than 1 mi that appeared to be at 4000'. His flight path was converging with ours. I pushed the nose down gently to stop our climb and actually descended to about 3000' as air carrier Y passed directly overhead. We asked the departure controller what altitude air carrier Y was assigned. He responded '4000'.' we answered that he had just given us 4000' clearance a few mins prior. He paused and then said he was sorry, that he meant to clear us to 3000'. Nothing further was said about the incident. I believe the controller may have thought he said 3000' to us, but he actually said 4000'. He never did call out air carrier Y as traffic to us either.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 ACR. OPERATIONAL ERROR.

Narrative: WE WERE CLRED BY TWR TO DEPART RWY 31, AFTER TKOF TURN LEFT TO 280 DEGS AND CLB TO 3000'. AFTER TKOF WE TURNED LEFT TO 280 DEGS AND CONTACTED DEP CTL ON 119.35. DEP CTL RESPONDED 'RADAR CONTACT CLB TO 4000'.' WE SET 4000' IN THE ALT ALERT WINDOW IN THE COCKPIT AND CONTINUED TO CLB AND ACCELERATE TO 250 KTS. PASSING 3500' I NOTICED ACR Y IN OUR 10 O'CLOCK POS LESS THAN 1 MI THAT APPEARED TO BE AT 4000'. HIS FLT PATH WAS CONVERGING WITH OURS. I PUSHED THE NOSE DOWN GENTLY TO STOP OUR CLB AND ACTUALLY DSNDED TO ABOUT 3000' AS ACR Y PASSED DIRECTLY OVERHEAD. WE ASKED THE DEP CTLR WHAT ALT ACR Y WAS ASSIGNED. HE RESPONDED '4000'.' WE ANSWERED THAT HE HAD JUST GIVEN US 4000' CLRNC A FEW MINS PRIOR. HE PAUSED AND THEN SAID HE WAS SORRY, THAT HE MEANT TO CLR US TO 3000'. NOTHING FURTHER WAS SAID ABOUT THE INCIDENT. I BELIEVE THE CTLR MAY HAVE THOUGHT HE SAID 3000' TO US, BUT HE ACTUALLY SAID 4000'. HE NEVER DID CALL OUT ACR Y AS TFC TO US EITHER.

Data retrieved from NASA's ASRS site as of August 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.