A foreign cargo B747-400 received a TCASII alert on a cargo MD11 who was 2000 ft below. The B747 responded to an RA with a climb and then a descent and caused less than standard separation to occur. The MD11 had visual contact with the B747 and the ARTCC controller descended the MD11 further below the B747 to eliminate any further false TCASII alerts.

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Attributes
ACN	384762
Time
Date	199710
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sya
State Reference	AK
Altitude	msl bound lower : 33000 msl bound upper : 35500
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : pacific enroute : other oceanic enroute airway : zan
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : other oceanic enroute : pacific
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 14 controller radar : 15
ASRS Report	384762
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : developmental
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	controller : issued new clearance flight crew : took evasive action flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 300
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

I was training a radar trainee on anchorage ARTCC's oceanic sectors. All sectors were combined together and traffic was busy. Air carrier X (B747) was inbound to anc at FL350. There was also a non TCASII equipped air carrier Y (MD11) underneath air carrier X at FL330. The air carrier X aircraft broadcast 'air carrier X RA, RA.' we had no traffic other than the air carrier Y, MD11, underneath him. The air carrier Y, MD11, was in level flight with a valid mode C of FL330. The air carrier X aircraft climbed to FL355 then descended rapidly to FL336-FL333. Air carrier X was advised of the air carrier Y traffic and air carrier Y advised he had air carrier X in sight. Air carrier X then climbed back to FL344 and experienced in his language 'momentary loss of control' and descended again to FL336. Air carrier Y was descended to FL310 and advised of the problem with air carrier X. I believe the air carrier X, B747, had a false TCASII alert from his own transponder and that if air carrier Y had been equipped with TCASII the aircraft would not have gotten so close. Conflict alert only works for ATC if you have an idea of what the problem is. 2 level aircraft going into conflict alert with no other traffic just indicates a 'normal' flow in the system.

Original NASA ASRS Text

Title: A FOREIGN CARGO B747-400 RECEIVED A TCASII ALERT ON A CARGO MD11 WHO WAS 2000 FT BELOW. THE B747 RESPONDED TO AN RA WITH A CLB AND THEN A DSCNT AND CAUSED LTSS TO OCCUR. THE MD11 HAD VISUAL CONTACT WITH THE B747 AND THE ARTCC CTLR DSNDED THE MD11 FURTHER BELOW THE B747 TO ELIMINATE ANY FURTHER FALSE TCASII ALERTS.

Narrative: I WAS TRAINING A RADAR TRAINEE ON ANCHORAGE ARTCC'S OCEANIC SECTORS. ALL SECTORS WERE COMBINED TOGETHER AND TFC WAS BUSY. ACR X (B747) WAS INBOUND TO ANC AT FL350. THERE WAS ALSO A NON TCASII EQUIPPED ACR Y (MD11) UNDERNEATH ACR X AT FL330. THE ACR X ACFT BROADCAST 'ACR X RA, RA.' WE HAD NO TFC OTHER THAN THE ACR Y, MD11, UNDERNEATH HIM. THE ACR Y, MD11, WAS IN LEVEL FLT WITH A VALID MODE C OF FL330. THE ACR X ACFT CLBED TO FL355 THEN DSNDED RAPIDLY TO FL336-FL333. ACR X WAS ADVISED OF THE ACR Y TFC AND ACR Y ADVISED HE HAD ACR X IN SIGHT. ACR X THEN CLBED BACK TO FL344 AND EXPERIENCED IN HIS LANGUAGE 'MOMENTARY LOSS OF CTL' AND DSNDED AGAIN TO FL336. ACR Y WAS DSNDED TO FL310 AND ADVISED OF THE PROB WITH ACR X. I BELIEVE THE ACR X, B747, HAD A FALSE TCASII ALERT FROM HIS OWN XPONDER AND THAT IF ACR Y HAD BEEN EQUIPPED WITH TCASII THE ACFT WOULD NOT HAVE GOTTEN SO CLOSE. CONFLICT ALERT ONLY WORKS FOR ATC IF YOU HAVE AN IDEA OF WHAT THE PROB IS. 2 LEVEL ACFT GOING INTO CONFLICT ALERT WITH NO OTHER TFC JUST INDICATES A 'NORMAL' FLOW IN THE SYS.

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.