Altitude deviation altitude excursion on TCASII RA triggered by same direction descending traffic.

Attributes
ACN	224288
Time
Date	199210
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : aco
State Reference	OH
Altitude	msl bound lower : 8500 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : pit
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6500 flight time type : 2000
ASRS Report	224288
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 17000 flight time type : 5500
ASRS Report	224195
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 0 vertical : 1500
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

We were level at 9000 ft. ATC advised us of overtaking aircraft behind and descending to 10000 ft. Shortly afterward we received a TCASII RA to descend. We did and the RA stopped at 8500 ft. We advised ATC and by this time saw the other aircraft passing overhead and we climbed back up to 9000 ft. The other aircraft did not bust his assigned altitude of 10000 ft but his descent rate must have set off the RA.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION ON TCASII RA TRIGGERED BY SAME DIRECTION DSNDING TFC.

Narrative: WE WERE LEVEL AT 9000 FT. ATC ADVISED US OF OVERTAKING ACFT BEHIND AND DSNDING TO 10000 FT. SHORTLY AFTERWARD WE RECEIVED A TCASII RA TO DSND. WE DID AND THE RA STOPPED AT 8500 FT. WE ADVISED ATC AND BY THIS TIME SAW THE OTHER ACFT PASSING OVERHEAD AND WE CLBED BACK UP TO 9000 FT. THE OTHER ACFT DID NOT BUST HIS ASSIGNED ALT OF 10000 FT BUT HIS DSCNT RATE MUST HAVE SET OFF THE RA.

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.