BendixKing CAS 66A - Manual (Page 49)

NOTES (CON'T)
It is possible to see an aircraft flying the same course and direc-
tion as your own aircraft, yet TCAS may not consider it a threat.
TCAS calculates the closure rate of the Intruder, and derives the
time to the Closest Point of Approach (CPA). If there is no closure
rate, no advisory will be issued, unless the Intruder is very close
(within approximately 0.2 mile). Conversely, traffic at the same
altitude very far ahead (about 10 miles) may be shown as a TA by
TCAS because of a very rapid closure rate.
System Considerations CAS 66A Pilot's Guide
Effective Date 5/99 006-08746-0000 Rev 5 45
TCAS I Pilots Guide 2/8/06 3:52 PM Page 45