Air carrier X TCASII RA with aircraft Y evasive action taken descent.

Attributes
ACN	201624
Time
Date	199202
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mkg
State Reference	MI
Altitude	msl bound lower : 24000 msl bound upper : 25000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 20 flight time total : 3000 flight time type : 20
ASRS Report	201624
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 2000 vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X cruising at FL240 center called out traffic, 1 O'clock descending to FL250. Shortly thereafter the TCASII directed a RA to descend at 1500-2000 FPM. I initiated the descent and thereafter obtained a visual on the traffic. I stopped the descent at FL238 and then climbed back to FL240. I didn't see the traffic until just after I initiated the descent. If I had seen the traffic beforehand I don't think the descent would have been necessary.

Original NASA ASRS Text

Title: ACR X TCASII RA WITH ACFT Y EVASIVE ACTION TAKEN DSCNT.

Narrative: ACR X CRUISING AT FL240 CTR CALLED OUT TFC, 1 O'CLOCK DSNDING TO FL250. SHORTLY THEREAFTER THE TCASII DIRECTED A RA TO DSND AT 1500-2000 FPM. I INITIATED THE DSCNT AND THEREAFTER OBTAINED A VISUAL ON THE TFC. I STOPPED THE DSCNT AT FL238 AND THEN CLBED BACK TO FL240. I DIDN'T SEE THE TFC UNTIL JUST AFTER I INITIATED THE DSCNT. IF I HAD SEEN THE TFC BEFOREHAND I DON'T THINK THE DSCNT WOULD HAVE BEEN NECESSARY.

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.