DC9-40 crew had a false TCASII RA descending into msp.

Attributes
ACN	553841
Time
Date	200208
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : gep.vortac
State Reference	MN
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : m98.tracon
Operator	common carrier : air carrier
Make Model Name	DC-9 40
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : m98.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 20000 flight time type : 10000
ASRS Report	553841
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe cabin event : passenger misconduct non adherence : company policies other anomaly other
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : issued advisory none taken : detected after the fact other
Miss Distance	horizontal : 3000 vertical : 100
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

While on descent into msp, we had just received a descent from 7000 ft to 6000 ft when a target appeared suddenly on TCASII at 11:30 O'clock position at -200 ft and well inside the inner ring. Immediately TCASII commanded a climbing RA at 2000 FPM. I disconnected the autoplt and began an aggressive climb and scanned forward for traffic. I did not see any traffic and neither did the first officer. The TCASII RA went away without announcing 'clear of conflict.' there was an A320 traffic visible 12:30 O'clock position and 5 mi on final for runway 12R but this couldn't have been the traffic at issue. In point of fact, I am convinced there was no traffic and that this was another case of passenger electronic device interference causing a false TCASII RA. Suspecting this, I made a PA announcement directing that 'all electronic devices including cell phones and pagers be depwred.' I also had the first officer ask the lead flight attendant to do a passenger electronic device walk. He reported back in a couple of mins 'no passenger electronic devices observed in use.' we resumed our descent to 6000 ft and the TCASII functioned normally the rest of the flight and tested normally at the gate. The otherwise normal function of TCASII and the abrupt appearance of the TCASII target and equally abrupt disappearance and the abject lack of a visual target in the depicted location convinces me that this was a false RA and that paper operation in the cabin is the most likely explanation.

Original NASA ASRS Text

Title: DC9-40 CREW HAD A FALSE TCASII RA DSNDING INTO MSP.

Narrative: WHILE ON DSCNT INTO MSP, WE HAD JUST RECEIVED A DSCNT FROM 7000 FT TO 6000 FT WHEN A TARGET APPEARED SUDDENLY ON TCASII AT 11:30 O'CLOCK POS AT -200 FT AND WELL INSIDE THE INNER RING. IMMEDIATELY TCASII COMMANDED A CLBING RA AT 2000 FPM. I DISCONNECTED THE AUTOPLT AND BEGAN AN AGGRESSIVE CLB AND SCANNED FORWARD FOR TFC. I DID NOT SEE ANY TFC AND NEITHER DID THE FO. THE TCASII RA WENT AWAY WITHOUT ANNOUNCING 'CLR OF CONFLICT.' THERE WAS AN A320 TFC VISIBLE 12:30 O'CLOCK POS AND 5 MI ON FINAL FOR RWY 12R BUT THIS COULDN'T HAVE BEEN THE TFC AT ISSUE. IN POINT OF FACT, I AM CONVINCED THERE WAS NO TFC AND THAT THIS WAS ANOTHER CASE OF PAX ELECTRONIC DEVICE INTERFERENCE CAUSING A FALSE TCASII RA. SUSPECTING THIS, I MADE A PA ANNOUNCEMENT DIRECTING THAT 'ALL ELECTRONIC DEVICES INCLUDING CELL PHONES AND PAGERS BE DEPWRED.' I ALSO HAD THE FO ASK THE LEAD FLT ATTENDANT TO DO A PAX ELECTRONIC DEVICE WALK. HE RPTED BACK IN A COUPLE OF MINS 'NO PAX ELECTRONIC DEVICES OBSERVED IN USE.' WE RESUMED OUR DSCNT TO 6000 FT AND THE TCASII FUNCTIONED NORMALLY THE REST OF THE FLT AND TESTED NORMALLY AT THE GATE. THE OTHERWISE NORMAL FUNCTION OF TCASII AND THE ABRUPT APPEARANCE OF THE TCASII TARGET AND EQUALLY ABRUPT DISAPPEARANCE AND THE ABJECT LACK OF A VISUAL TARGET IN THE DEPICTED LOCATION CONVINCES ME THAT THIS WAS A FALSE RA AND THAT PAPER OP IN THE CABIN IS THE MOST LIKELY EXPLANATION.

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.