Small aircraft X erroneous transponder mode C caused air carrier Y TCASII RA evasive action climb. S...

Attributes
ACN	265877
Time
Date	199403
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : far
State Reference	ND
Altitude	msl bound lower : 5500 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : far
Operator	general aviation : personal
Make Model Name	M-20 Series Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 5
ASRS Report	265877
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 500
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Small aircraft X, M020, sebound at 5500 ft MSL, VFR. Air carrier Y descending to 6000 ft MSL, inbound to fargo. X mode C indicated 5700 ft. I asked him to verify he was at 5500 ft. He said he was level at 5500 ft MSL. Y's TCASII told him to climb because X was indicating 200 ft below him, when Y was level at 6000 ft. Y climbed to satisfy TCASII. Separation never was lost.

Original NASA ASRS Text

Title: SMA X ERRONEOUS XPONDER MODE C CAUSED ACR Y TCASII RA EVASIVE ACTION CLB. SEE AND AVOID CONCEPT.

Narrative: SMA X, M020, SEBOUND AT 5500 FT MSL, VFR. ACR Y DSNDING TO 6000 FT MSL, INBOUND TO FARGO. X MODE C INDICATED 5700 FT. I ASKED HIM TO VERIFY HE WAS AT 5500 FT. HE SAID HE WAS LEVEL AT 5500 FT MSL. Y'S TCASII TOLD HIM TO CLB BECAUSE X WAS INDICATING 200 FT BELOW HIM, WHEN Y WAS LEVEL AT 6000 FT. Y CLBED TO SATISFY TCASII. SEPARATION NEVER WAS LOST.

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.

Small aircraft X erroneous transponder mode C caused air carrier Y TCASII RA evasive action climb. See and avoid concept.