Captain of an medium large transport air carrier aircraft took over the controls from the first officer to respond to a TCASII RA resulting in an excursion from assigned descent altitude.

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Attributes
ACN	261731
Time
Date	199401
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : abb
State Reference	IN
Altitude	msl bound lower : 20300 msl bound upper : 20500
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 100 flight time total : 15000 flight time type : 80
ASRS Report	261731
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
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 : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent to 20000 ft with clearance to 14000 ft at pilot's discretion, TCASII RA occurred at approximately 20300 ft. Due to high cockpit noise level (high airspeed) and copying of cvg ATIS, actual voice command was not intelligible. First officer had received TA from ATC and had traffic in sight but it did not know this. When RA occurred and first officer did not react, I took control of aircraft, disconnected autoplt and leveled airplane. In the process airplane climbed to approximately 20500 ft. Airplane then descended to 20000 ft. RA occurred again, but by this time first officer had told me of TA and said that had traffic in sight. No further action was required and visual indication was 1000 ft separation. ATC controller advised. I was informed that while we were cleared for descent, the other aircraft was cleared to climb to 19000 ft. Apparently our closure rate caused the RA. In retrospect, at no time was there any real threat of collision or near miss.

Original NASA ASRS Text

Title: CAPT OF AN MLG ACR ACFT TOOK OVER THE CTLS FROM THE FO TO RESPOND TO A TCASII RA RESULTING IN AN EXCURSION FROM ASSIGNED DSCNT ALT.

Narrative: DURING DSCNT TO 20000 FT WITH CLRNC TO 14000 FT AT PLT'S DISCRETION, TCASII RA OCCURRED AT APPROX 20300 FT. DUE TO HIGH COCKPIT NOISE LEVEL (HIGH AIRSPD) AND COPYING OF CVG ATIS, ACTUAL VOICE COMMAND WAS NOT INTELLIGIBLE. FO HAD RECEIVED TA FROM ATC AND HAD TFC IN SIGHT BUT IT DID NOT KNOW THIS. WHEN RA OCCURRED AND FO DID NOT REACT, I TOOK CTL OF ACFT, DISCONNECTED AUTOPLT AND LEVELED AIRPLANE. IN THE PROCESS AIRPLANE CLBED TO APPROX 20500 FT. AIRPLANE THEN DSNDED TO 20000 FT. RA OCCURRED AGAIN, BUT BY THIS TIME FO HAD TOLD ME OF TA AND SAID THAT HAD TFC IN SIGHT. NO FURTHER ACTION WAS REQUIRED AND VISUAL INDICATION WAS 1000 FT SEPARATION. ATC CTLR ADVISED. I WAS INFORMED THAT WHILE WE WERE CLRED FOR DSCNT, THE OTHER ACFT WAS CLRED TO CLB TO 19000 FT. APPARENTLY OUR CLOSURE RATE CAUSED THE RA. IN RETROSPECT, AT NO TIME WAS THERE ANY REAL THREAT OF COLLISION OR NEAR MISS.

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.