Cpr HS125 responding to a TCASII RA may have caught a ZMP center controller off guard.

Attributes
ACN	428710
Time
Date	199902
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : lmn.vor
State Reference	IA
Altitude	msl single value : 29000
Environment
Flight Conditions	VMC
Weather Elements	Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp.artcc
Operator	general aviation : corporate
Make Model Name	HS 125 Series 700
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	BAe 146 Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 14
ASRS Report	428710
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 0 vertical : 1000

Narrative:

Pilot stated he had traffic on TCASII at minus 9 prior to RA. When TCASII changed to minus 8, an RA resulted advising him to climb. He started his climb, got a visual, and descended to clearance altitude. No problem, other than scaring the heck out of me. Callback conversation with reporter revealed the following information: the reporter stated that the two aircraft were both in level flight and properly separated. He believes an errant signal may have caused the TCASII RA. He said there have been other similar TCASII events occur with no apparent reason. The other aircraft did not take any action.

Original NASA ASRS Text

Title: CPR HS125 RESPONDING TO A TCASII RA MAY HAVE CAUGHT A ZMP CTR CTLR OFF GUARD.

Narrative: PLT STATED HE HAD TFC ON TCASII AT MINUS 9 PRIOR TO RA. WHEN TCASII CHANGED TO MINUS 8, AN RA RESULTED ADVISING HIM TO CLB. HE STARTED HIS CLB, GOT A VISUAL, AND DSNDED TO CLRNC ALT. NO PROB, OTHER THAN SCARING THE HECK OUT OF ME. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT THE TWO ACFT WERE BOTH IN LEVEL FLT AND PROPERLY SEPARATED. HE BELIEVES AN ERRANT SIGNAL MAY HAVE CAUSED THE TCASII RA. HE SAID THERE HAVE BEEN OTHER SIMILAR TCASII EVENTS OCCUR WITH NO APPARENT REASON. THE OTHER ACFT DID NOT TAKE ANY ACTION.

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.