Commuter mdt altitude deviation excursion from clearance altitude in response to TCASII RA.

Attributes
ACN	189265
Time
Date	199109
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 7750 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 10000 flight time type : 1800
ASRS Report	189265
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	horizontal : 6000 vertical : 400
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Observed TA which turned in RA. Descended aircraft 250 ft as per TCASII command and alerted ATC. Observed traffic in descent and it was a light twin operating VFR in the chicago TCA. TCASII in this situation did help avert a midair. My only complaint is the aural TCASII warnings are too loud.

Original NASA ASRS Text

Title: COMMUTER MDT ALT DEV EXCURSION FROM CLRNC ALT IN RESPONSE TO TCASII RA.

Narrative: OBSERVED TA WHICH TURNED IN RA. DSNDED ACFT 250 FT AS PER TCASII COMMAND AND ALERTED ATC. OBSERVED TFC IN DSCNT AND IT WAS A LIGHT TWIN OPERATING VFR IN THE CHICAGO TCA. TCASII IN THIS SITUATION DID HELP AVERT A MIDAIR. MY ONLY COMPLAINT IS THE AURAL TCASII WARNINGS ARE TOO LOUD.

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.