Flight crew of 2 DC9 aircraft responded to their TCASII RA warnings by climbing above assigned altitude when one was descending to an altitude of 1000 ft above the cruising altitude of the other.

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Attributes
ACN	332797
Time
Date	199604
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : rst
State Reference	MN
Altitude	msl bound lower : 27000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 11 controller radar : 11 flight time total : 120
ASRS Report	332797
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	other other : other pilot : atp pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 180 flight time total : 12000 flight time type : 9000
ASRS Report	333502
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 20000 vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X was level at cruise altitude of FL270. Air carrier Y was opposite direction traffic descending to FL280. Traffic had been called to both aircraft. Air carrier Y called questioning the traffic's altitude. I observed air carrier X mode C at FL274 and climbing. I asked air carrier X to verify level at FL270 and he responded that he was climbing due to a TCASII advisory. Air carrier Y then also climbed due to a TCASII advisory. Although separation was not lost and the aircraft acquired each other visually, the situation caused enough distraction to degrade several other traffic sits I had, causing other turns to aircraft. This was an unnecessary TCASII advisory. Traffic separation had been established, and both aircraft knew what the other had been cleared to. Blind faith in TCASII almost caused a serious accident.

Original NASA ASRS Text

Title: FLC OF 2 DC9 ACFT RESPONDED TO THEIR TCASII RA WARNINGS BY CLBING ABOVE ASSIGNED ALT WHEN ONE WAS DSNDING TO AN ALT OF 1000 FT ABOVE THE CRUISING ALT OF THE OTHER.

Narrative: ACR X WAS LEVEL AT CRUISE ALT OF FL270. ACR Y WAS OPPOSITE DIRECTION TFC DSNDING TO FL280. TFC HAD BEEN CALLED TO BOTH ACFT. ACR Y CALLED QUESTIONING THE TFC'S ALT. I OBSERVED ACR X MODE C AT FL274 AND CLBING. I ASKED ACR X TO VERIFY LEVEL AT FL270 AND HE RESPONDED THAT HE WAS CLBING DUE TO A TCASII ADVISORY. ACR Y THEN ALSO CLBED DUE TO A TCASII ADVISORY. ALTHOUGH SEPARATION WAS NOT LOST AND THE ACFT ACQUIRED EACH OTHER VISUALLY, THE SIT CAUSED ENOUGH DISTR TO DEGRADE SEVERAL OTHER TFC SITS I HAD, CAUSING OTHER TURNS TO ACFT. THIS WAS AN UNNECESSARY TCASII ADVISORY. TFC SEPARATION HAD BEEN ESTABLISHED, AND BOTH ACFT KNEW WHAT THE OTHER HAD BEEN CLRED TO. BLIND FAITH IN TCASII ALMOST CAUSED A SERIOUS ACCIDENT.

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.