Incident at Gander FIR


1997-08-28: ACA630 A320 was cleared to descend to an altitude which was 1000 feet above opposite direction traffic TSKR11 C130 (reg130306). At approximately the same time these aircraft passed, ACA630 was observed descending below the cleared altitude resulting in less than minumum separation. Update: The TCAS equipment was removed from the aircraft and sent to the manufacturer for evaluation. The TCAS manufacturer completed unit testing with the TSB and Air Canada in attendance. It was concluded through unit testing and input data analysis (Radar/Comm data and flight crew reports) that the TCAS unit operated correclty. Data analysis indicates that the crew of ACA630 initially recieved a climb Resolution Advisory. The approaching TUSKR11 traffic altitude varied plus/minus 200 feet from FL140. This oscillating altitude caused the TCAS on ACA630 to sense an Resolution Advisory Reversal (ie an initial climb Resolution reverses to descend. The Aural command "Descend, Descend Now" reported by the crew only occurs with a reversal Resolution Advisory. TSB case closed.


CADORS Number 1997A0262
Occurrence Type Incident
Reported By NAV CANADA
Occurred At 1997-06-03 - 03:58
Day or Night?
Fatalities 0
Aerodrome ID
Aerodrome Name
Geographic Location Gander Oceanic, Atlantic Region, Gander FIR
TSB Occurrence Number
TSB Class of Investigation
AOR Number
Reported By NAV CANADA
Categories Airprox/TCAS alert/loss of separation/(near) midair collisions

Aircraft Details (1 aircraft)

Type Aeroplane
 Silhouette image of Aeroplane
Canadian Registration FDSN | Flightaware (Registration) | Flightaware (Tracking) | AvHerald
Foreign Registration
Country of Registration Canada
Occurrence Type Incident
Operator Commercial
Make  Silhouette image of AIRBUS
Model  Silhouette image of A320 211
A320 211
Year Built 1990
Engine Type Turbo fan
Engine Make
Engine Model
Gear Type Land
Private No
Amateur Built No
Flight Number
Flight Rule
CARS Subpart
Phase of Flight Cruise
Damage Unknown
Fatalities 0
Injuries 0
Events Conflict - loss of separation

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