Descending visual approach to dca, reporter and air carrier Y commanded erroneously by TCASII RA.

Attributes
ACN	279718
Time
Date	199408
Day	Tue
Local Time Of Day	0601 To 1200
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
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	arrival other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	arrival 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 : 200 flight time total : 10000 flight time type : 6000
ASRS Report	279718
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 500
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

Air carrier X flight 0001 arriving from aml VOR on 070 degree heading, descending to 4000 ft to intercept potomac river visually. Air carrier Y flight 0002 arriving from balance 255 degree radial descending from 6000 ft to 3000 ft to intercept potomac river visually. Both aircraft were to turn south and follow river to dca. While descending through approximately 4500 ft, we got an RA to descend at 2000 FPM. Meanwhile, air carrier Y got RA to climb. My first officer sighted the air carrier Y B-737 and instructed me to level off. The air carrier Y first officer sighted us and instructed his captain to increase descent rate to avoid a collision. After discussion with all pilots involved and dca area manager working radar, it was agreed that, if both aircraft followed the commanded RA, there would have been a midair collision. Initial RA came when air carrier Y was 100 ft below us as we were both descending. Our rate of descent was 1000 FPM. B-737 was descending at 2500 FPM with gear, flaps, and speed brakes deployed. They would have been unable to climb in that confign. In this instance, the TCASII RA was wrong. Jet arrs from balance VOR should be level prior to intercepting the potomac river at 3000 ft if we are to intercept at 4000 ft.

Original NASA ASRS Text

Title: DSNDING VISUAL APCH TO DCA, RPTR AND ACR Y COMMANDED ERRONEOUSLY BY TCASII RA.

Narrative: ACR X FLT 0001 ARRIVING FROM AML VOR ON 070 DEG HDG, DSNDING TO 4000 FT TO INTERCEPT POTOMAC RIVER VISUALLY. ACR Y FLT 0002 ARRIVING FROM BAL 255 DEG RADIAL DSNDING FROM 6000 FT TO 3000 FT TO INTERCEPT POTOMAC RIVER VISUALLY. BOTH ACFT WERE TO TURN S AND FOLLOW RIVER TO DCA. WHILE DSNDING THROUGH APPROX 4500 FT, WE GOT AN RA TO DSND AT 2000 FPM. MEANWHILE, ACR Y GOT RA TO CLB. MY FO SIGHTED THE ACR Y B-737 AND INSTRUCTED ME TO LEVEL OFF. THE ACR Y FO SIGHTED US AND INSTRUCTED HIS CAPT TO INCREASE DSCNT RATE TO AVOID A COLLISION. AFTER DISCUSSION WITH ALL PLTS INVOLVED AND DCA AREA MGR WORKING RADAR, IT WAS AGREED THAT, IF BOTH ACFT FOLLOWED THE COMMANDED RA, THERE WOULD HAVE BEEN A MIDAIR COLLISION. INITIAL RA CAME WHEN ACR Y WAS 100 FT BELOW US AS WE WERE BOTH DSNDING. OUR RATE OF DSCNT WAS 1000 FPM. B-737 WAS DSNDING AT 2500 FPM WITH GEAR, FLAPS, AND SPD BRAKES DEPLOYED. THEY WOULD HAVE BEEN UNABLE TO CLB IN THAT CONFIGN. IN THIS INSTANCE, THE TCASII RA WAS WRONG. JET ARRS FROM BAL VOR SHOULD BE LEVEL PRIOR TO INTERCEPTING THE POTOMAC RIVER AT 3000 FT IF WE ARE TO INTERCEPT AT 4000 FT.

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.