Reporter's aircraft X left assigned altitude in response to a TCASII RA.

Attributes
ACN	441507
Time
Date	199906
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : aml.vor
State Reference	VA
Altitude	msl bound lower : 8000 msl bound upper : 8300
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dca.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	441507
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne critical non adherence : clearance
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 0 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

During transition from dulles approach facility to dca approach, had a TCASII RA alert. I manually climbed the aircraft approximately 300 ft and noted the other aircraft was climbing in opposite direction to our flight path. The other aircraft passed under us by at least 500 ft. Iad and dca approach were both notified by us and were unaware of the other aircraft. The remainder of the flight continued under normal procedures.

Original NASA ASRS Text

Title: RPTR'S ACFT X LEFT ASSIGNED ALT IN RESPONSE TO A TCASII RA.

Narrative: DURING TRANSITION FROM DULLES APCH FACILITY TO DCA APCH, HAD A TCASII RA ALERT. I MANUALLY CLBED THE ACFT APPROX 300 FT AND NOTED THE OTHER ACFT WAS CLBING IN OPPOSITE DIRECTION TO OUR FLT PATH. THE OTHER ACFT PASSED UNDER US BY AT LEAST 500 FT. IAD AND DCA APCH WERE BOTH NOTIFIED BY US AND WERE UNAWARE OF THE OTHER ACFT. THE REMAINDER OF THE FLT CONTINUED UNDER NORMAL PROCS.

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.