Less than standard separation for two air carrier lgts on approach to dca.

Attributes
ACN	151604
Time
Date	199007
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dca
State Reference	DC
Altitude	msl bound lower : 3000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dca tower : chs
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 143 flight time total : 13300 flight time type : 9500
ASRS Report	151604
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot conflict : ground less severe
Independent Detector	other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 1000 vertical : 200
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

We were cleared to 3000' MSL and the river visibility approach to runway 18 at dca. Passing 3600', in a left turn to follow the river, approach control revised our clearance to maintain 4000'. I began an abrupt climb back to 4000', responding to the sound of urgency in the controllers voice. We were quickly told to again maintain 3000' and were advised of traffic at 3 O'clock and 4000'. We observed the head on view of an air carrier large transport Y at 3 0'clock and approximately 1000' distant. He appeared to be taking evasive action to the left and passed behind us. At the time of the incident we were still in a left turn descending through 3800'. We were unable to ascertain the nearest lateral sep as he passed behind us. I suspect the incident may have been caused by a breakdown in controller coordination since arrs from the east and west are handled on different frequencys. The other aircraft was not on our frequency so we were not aware that he was there. If one controller and frequency were used for final approach vector, both controller and flight crews would have the 'big picture'.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION FOR TWO ACR LGTS ON APCH TO DCA.

Narrative: WE WERE CLRED TO 3000' MSL AND THE RIVER VIS APCH TO RWY 18 AT DCA. PASSING 3600', IN A L TURN TO FOLLOW THE RIVER, APCH CTL REVISED OUR CLRNC TO MAINTAIN 4000'. I BEGAN AN ABRUPT CLB BACK TO 4000', RESPONDING TO THE SOUND OF URGENCY IN THE CTLRS VOICE. WE WERE QUICKLY TOLD TO AGAIN MAINTAIN 3000' AND WERE ADVISED OF TFC AT 3 O'CLOCK AND 4000'. WE OBSERVED THE HEAD ON VIEW OF AN ACR LGT Y AT 3 0'CLOCK AND APPROX 1000' DISTANT. HE APPEARED TO BE TAKING EVASIVE ACTION TO THE L AND PASSED BEHIND US. AT THE TIME OF THE INCIDENT WE WERE STILL IN A L TURN DSNDING THROUGH 3800'. WE WERE UNABLE TO ASCERTAIN THE NEAREST LATERAL SEP AS HE PASSED BEHIND US. I SUSPECT THE INCIDENT MAY HAVE BEEN CAUSED BY A BREAKDOWN IN CTLR COORD SINCE ARRS FROM THE E AND W ARE HANDLED ON DIFFERENT FREQS. THE OTHER ACFT WAS NOT ON OUR FREQ SO WE WERE NOT AWARE THAT HE WAS THERE. IF ONE CTLR AND FREQ WERE USED FOR FINAL APCH VECTOR, BOTH CTLR AND FLT CREWS WOULD HAVE THE 'BIG PICTURE'.

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.