TCAS ii RA on descent at 19500' mandated a climb. Ras was resolved at 20500'. Flight returned to ass...

Attributes
ACN	173977
Time
Date	199103
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : eno
State Reference	DE
Altitude	msl bound lower : 19000 msl bound upper : 20500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 5000 flight time type : 1200
ASRS Report	173977
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flight cleared to FL190 by dca center. Descending out of 19500', TCAS ii TA was heard, followed shortly after by a climb command (RA by TCAS). Aircraft was then flown as dictated by TCAS ii which required a climb of about 2000 FPM. At about 20500' conflict was resolved and descent to FL190 was resumed. ATC was notified and indicated they were not aware of any conflict. They did speculate that an aircraft approximately 3000' below us may have triggered the alarm, due to his high rate of climb. There are some bugs with TCAS ii, but it works well. The aircraft below us was below FL180, and the local altimeter setting was 29.14. We were above FL180 and altimeter setting 29.92. He had a high rate of climb to 17000'. This probably triggered the conflict.

Original NASA ASRS Text

Title: TCAS II RA ON DESCENT AT 19500' MANDATED A CLIMB. RAS WAS RESOLVED AT 20500'. FLT RETURNED TO ASSIGNED 19000'.

Narrative: FLT CLRED TO FL190 BY DCA CTR. DSNDING OUT OF 19500', TCAS II TA WAS HEARD, FOLLOWED SHORTLY AFTER BY A CLB COMMAND (RA BY TCAS). ACFT WAS THEN FLOWN AS DICTATED BY TCAS II WHICH REQUIRED A CLB OF ABOUT 2000 FPM. AT ABOUT 20500' CONFLICT WAS RESOLVED AND DSNT TO FL190 WAS RESUMED. ATC WAS NOTIFIED AND INDICATED THEY WERE NOT AWARE OF ANY CONFLICT. THEY DID SPECULATE THAT AN ACFT APPROX 3000' BELOW US MAY HAVE TRIGGERED THE ALARM, DUE TO HIS HIGH RATE OF CLB. THERE ARE SOME BUGS WITH TCAS II, BUT IT WORKS WELL. THE ACFT BELOW US WAS BELOW FL180, AND THE LCL ALTIMETER SETTING WAS 29.14. WE WERE ABOVE FL180 AND ALTIMETER SETTING 29.92. HE HAD A HIGH RATE OF CLB TO 17000'. THIS PROBABLY TRIGGERED THE CONFLICT.

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.

TCAS ii RA on descent at 19500' mandated a climb. Ras was resolved at 20500'. Flight returned to assigned 19000'.