TCASII induced altitude deviation while aircraft on downwind for runway 26 at iah.

Attributes
ACN	435547
Time
Date	199904
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : iah.airport
State Reference	TX
Altitude	msl bound lower : 6000 msl bound upper : 6800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : i90.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : visual arrival : vfr
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : i90.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 13000 flight time type : 6000
ASRS Report	435547
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : nmac non adherence : clearance
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : returned to original clearance
Miss Distance	horizontal : 100 vertical : 500
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous
Air Traffic Incident	Operational Error Pilot Deviation

Narrative:

While on downwind for runway 26 at iah, we were level at 6000 ft and received a TCASII RA from a climbing aircraft moving right to left at 5000 ft and still climbing. TCASII advised us to climb and although we had the aircraft in sight we did climb to about 6800 ft to remain clear of this traffic. At one point TCASII showed us to be only 500 ft above the traffic as he passed closely behind us. We advised approach control of the deviation then returned to 6000 ft when clear. The remainder of the flight was normal.

Original NASA ASRS Text

Title: TCASII INDUCED ALTDEV WHILE ACFT ON DOWNWIND FOR RWY 26 AT IAH.

Narrative: WHILE ON DOWNWIND FOR RWY 26 AT IAH, WE WERE LEVEL AT 6000 FT AND RECEIVED A TCASII RA FROM A CLBING ACFT MOVING R TO L AT 5000 FT AND STILL CLBING. TCASII ADVISED US TO CLB AND ALTHOUGH WE HAD THE ACFT IN SIGHT WE DID CLB TO ABOUT 6800 FT TO REMAIN CLR OF THIS TFC. AT ONE POINT TCASII SHOWED US TO BE ONLY 500 FT ABOVE THE TFC AS HE PASSED CLOSELY BEHIND US. WE ADVISED APCH CTL OF THE DEV THEN RETURNED TO 6000 FT WHEN CLR. THE REMAINDER OF THE FLT WAS NORMAL.

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.