An air carrier medium large transport descended in response to a TCASII command.

Attributes
ACN	250436
Time
Date	199308
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ptw
State Reference	PA
Altitude	msl bound lower : 16500 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : iah
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute airway : zny
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
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 : 9000 flight time type : 3500
ASRS Report	250436
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	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 controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

ATC advised us of traffic at 12 O'clock and 10 mi at 17500 ft as we were leveling off at 17000 ft. As target got within 5 mi, TCASII was showing it at 400 ft above us and gave us an RA to descend. First officer followed advisory to approximately 16500 ft as I advised ATC. As TCASII was giving a 'clear of conflict,' ATC gave us climb clearance to higher altitude and had no comment about our TCASII procedure. Callback conversation with reporter revealed the following information: the reporter states that the intruding aircraft was never seen. The reporter's aircraft was climbing and leveling off. The reporter believes that TCASII cannot handle sits where aircraft are climbing or descending towards another aircraft.

Original NASA ASRS Text

Title: AN ACR MLG DSNDED IN RESPONSE TO A TCASII COMMAND.

Narrative: ATC ADVISED US OF TFC AT 12 O'CLOCK AND 10 MI AT 17500 FT AS WE WERE LEVELING OFF AT 17000 FT. AS TARGET GOT WITHIN 5 MI, TCASII WAS SHOWING IT AT 400 FT ABOVE US AND GAVE US AN RA TO DSND. FO FOLLOWED ADVISORY TO APPROX 16500 FT AS I ADVISED ATC. AS TCASII WAS GIVING A 'CLR OF CONFLICT,' ATC GAVE US CLB CLRNC TO HIGHER ALT AND HAD NO COMMENT ABOUT OUR TCASII PROC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THAT THE INTRUDING ACFT WAS NEVER SEEN. THE RPTR'S ACFT WAS CLBING AND LEVELING OFF. THE RPTR BELIEVES THAT TCASII CANNOT HANDLE SITS WHERE ACFT ARE CLBING OR DSNDING TOWARDS ANOTHER ACFT.

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.