Air carrier medium large transport altitude deviation excursion from clearance altitude in response ...

Attributes
ACN	172855
Time
Date	199103
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : che
State Reference	CO
Altitude	msl bound lower : 20500 msl bound upper : 22000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv tower : hnl
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute airway : zdv
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 8000
ASRS Report	172855
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were at cruise altitude of FL220 when our TCAS showed a target at FL230. We received a traffic advisory at about 5-6 NM from the target and then an RA at about 2-3 NM commanding a descent. An immediate descent was commenced to approximately FL205. The clear of conflict was issued and we started a climb back to FL220 and communications with ATC initiated concerning our deviation. The other aircraft was an small transport. We were in light turbulence in the clouds with no visibility sighting. Is it possible to receive an RA in turbulence due to slight deviations in altitude. We thought we noticed at one time the other aircraft was only 600' above our altitude. The TCAS showed the small transport in a descent.

Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION EXCURSION FROM CLRNC ALT IN RESPONSE TO TCASII RA.

Narrative: WE WERE AT CRUISE ALT OF FL220 WHEN OUR TCAS SHOWED A TARGET AT FL230. WE RECEIVED A TFC ADVISORY AT ABOUT 5-6 NM FROM THE TARGET AND THEN AN RA AT ABOUT 2-3 NM COMMANDING A DSNT. AN IMMEDIATE DSNT WAS COMMENCED TO APPROX FL205. THE CLR OF CONFLICT WAS ISSUED AND WE STARTED A CLB BACK TO FL220 AND COMS WITH ATC INITIATED CONCERNING OUR DEVIATION. THE OTHER ACFT WAS AN SMT. WE WERE IN LIGHT TURB IN THE CLOUDS WITH NO VIS SIGHTING. IS IT POSSIBLE TO RECEIVE AN RA IN TURB DUE TO SLIGHT DEVIATIONS IN ALT. WE THOUGHT WE NOTICED AT ONE TIME THE OTHER ACFT WAS ONLY 600' ABOVE OUR ALT. THE TCAS SHOWED THE SMT IN A DSNT.

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.

Air carrier medium large transport altitude deviation excursion from clearance altitude in response to TCASII RA.