TCASII. Altitude deviation on descent.

Attributes
ACN	319453
Time
Date	199510
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : cew
State Reference	FL
Altitude	msl bound lower : 23800 msl bound upper : 24000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	artcc : zjx tower : cid
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise 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 : 180 flight time total : 14000 flight time type : 9500
ASRS Report	319453
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation 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	horizontal : 6000 vertical : 800
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were deviating around some thunderstorm activity. The autoplt had disconnected, so I was hand flying the aircraft. We were descending and assigned FL240. Center pointed out a commuter airline at FL230. I reconnected the autoplt, but we descended 200 ft. I then disconnected the autoplt and started to climb back to FL240. The TCASII then commanded a climb. We came within approximately 800 ft on the TCASII and about 1 mi of the aircraft. I probably should not have reconnected the autoplt as we passed near the traffic, since the autoplt had disconnected previously.

Original NASA ASRS Text

Title: TCASII. ALTDEV ON DSCNT.

Narrative: WE WERE DEVIATING AROUND SOME TSTM ACTIVITY. THE AUTOPLT HAD DISCONNECTED, SO I WAS HAND FLYING THE ACFT. WE WERE DSNDING AND ASSIGNED FL240. CTR POINTED OUT A COMMUTER AIRLINE AT FL230. I RECONNECTED THE AUTOPLT, BUT WE DSNDED 200 FT. I THEN DISCONNECTED THE AUTOPLT AND STARTED TO CLB BACK TO FL240. THE TCASII THEN COMMANDED A CLB. WE CAME WITHIN APPROX 800 FT ON THE TCASII AND ABOUT 1 MI OF THE ACFT. I PROBABLY SHOULD NOT HAVE RECONNECTED THE AUTOPLT AS WE PASSED NEAR THE TFC, SINCE THE AUTOPLT HAD DISCONNECTED PREVIOUSLY.

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.