Computer glitch causes erroneous ground speed readout for ARTCC rdp.

Attributes
ACN	296260
Time
Date	199502
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : tas
State Reference	NM
Altitude	msl bound lower : 25000 msl bound upper : 25000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	other
Make Model Name	Intruder (A6)
Operating Under FAR Part	other : other
Flight Phase	cruise other cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	other personnel other
Qualification	controller : non radar
Experience	controller military : 3 controller non radar : 12 controller radar : 12
ASRS Report	296260
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : unable
Consequence	faa : investigated
Miss Distance	horizontal : 27000 vertical : 600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

ZDV handed off an MD80 to my sector. The MD80 was level at FL240. My stratum was FL270 to FL999. ZDV handed off the A6 at FL250 to the sector below me. The MD80 was requesting FL330. Both aircraft had rtes ultimately converging from a northwest direction to a southeast direction. All involved sectors were fully aware of the traffic and situation. I was training on the radar side and the MD80 was in front by 6 or 7 mi at an airspeed of 450 KTS. The A-6 was indicating an increasing speed from 320-380 KTS. At approximately 6.8 mi I double-checked the aircraft speeds, even checking the filed flight plans. The A-6 filed 420 KTS, the MD80 filed 437 KTS winds were out of the northwest at 50 KTS. I deemed separation sufficient and climbed the MD80 to FL330. My instructor still was not comfortable so I turned the MD80 15 degrees right away from the A-6 still in-tail. The A-6 continued in speed ultimately to 500 KTS and caught the MD80. Investigation showed the A-6 was flying at 490-500 KTS all the way. Our computer 'glitched' when the ZDV controller started a 'track message' on the A-6 prior to handoff. The ZAB computer therefore began 'searching' for the 'new track.' in doing so, it lost the actual speed of the A-6 and then began tracking and building up to the actual speed. The computer history showed ZAB speed readout going from 420 KTS to 120 KTS, 140 KTS, etc, until reaching 500 KTS. I climbed the MD80 when the speed indicated 380 KTS.

Original NASA ASRS Text

Title: COMPUTER GLITCH CAUSES ERRONEOUS GND SPD READOUT FOR ARTCC RDP.

Narrative: ZDV HANDED OFF AN MD80 TO MY SECTOR. THE MD80 WAS LEVEL AT FL240. MY STRATUM WAS FL270 TO FL999. ZDV HANDED OFF THE A6 AT FL250 TO THE SECTOR BELOW ME. THE MD80 WAS REQUESTING FL330. BOTH ACFT HAD RTES ULTIMATELY CONVERGING FROM A NW DIRECTION TO A SE DIRECTION. ALL INVOLVED SECTORS WERE FULLY AWARE OF THE TFC AND SIT. I WAS TRAINING ON THE RADAR SIDE AND THE MD80 WAS IN FRONT BY 6 OR 7 MI AT AN AIRSPD OF 450 KTS. THE A-6 WAS INDICATING AN INCREASING SPD FROM 320-380 KTS. AT APPROX 6.8 MI I DOUBLE-CHKED THE ACFT SPDS, EVEN CHKING THE FILED FLT PLANS. THE A-6 FILED 420 KTS, THE MD80 FILED 437 KTS WINDS WERE OUT OF THE NW AT 50 KTS. I DEEMED SEPARATION SUFFICIENT AND CLBED THE MD80 TO FL330. MY INSTRUCTOR STILL WAS NOT COMFORTABLE SO I TURNED THE MD80 15 DEGS R AWAY FROM THE A-6 STILL IN-TAIL. THE A-6 CONTINUED IN SPD ULTIMATELY TO 500 KTS AND CAUGHT THE MD80. INVESTIGATION SHOWED THE A-6 WAS FLYING AT 490-500 KTS ALL THE WAY. OUR COMPUTER 'GLITCHED' WHEN THE ZDV CTLR STARTED A 'TRACK MESSAGE' ON THE A-6 PRIOR TO HDOF. THE ZAB COMPUTER THEREFORE BEGAN 'SEARCHING' FOR THE 'NEW TRACK.' IN DOING SO, IT LOST THE ACTUAL SPD OF THE A-6 AND THEN BEGAN TRACKING AND BUILDING UP TO THE ACTUAL SPD. THE COMPUTER HISTORY SHOWED ZAB SPD READOUT GOING FROM 420 KTS TO 120 KTS, 140 KTS, ETC, UNTIL REACHING 500 KTS. I CLBED THE MD80 WHEN THE SPD INDICATED 380 KTS.

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.