Augustine k Jose
What is TCAS
TCAS, and pronounced tee-kas) is an aircraft collision avoidance system designed
to reduce the incidence of mid-air collisions between aircraft. International Civil
Aviation Organization to be fitted to all aircraft with a maximum take-off mass
(MTOM) of over 5,700 kg .
It uses transponder mode c and mode s.
Interrogates 1030 MHZ Receives reply via 1090 MHZ.
This interrogation-and-response cycle may occur several times per second.
The TCAS builds a 3d map of airspace near aircraft ,
incorporating their range (garnered from the interrogation and response round trip
time), altitude (as reported by the interrogated aircraft), and bearing (by the
directional antenna from the response).
2 types of alerts:
TA which is a threat advisory that alerts the pilot that another aircraft is close
enough to be a potential threat
RA is a resolution advisory that means the other aircraft IS a threat (30 seconds to
a possible collision) and issues commands to evade a collision.
7 TCAS Basics
TCAS I - Aircraft with 10 to 30 seats
Traffic Advisory Only
TCAS II - Aircraft with more than 30 passenger
Mode S – Detailed flight parameter information
ATC Ground Based Radars
Other Mode S equipped aircraft
Provides coordinated RAs
8 Traffic Advisory
A TA indicates that an aircraft
is a potential threat
RA may be necessary w/in, approx, the next 25 sec
most commonly displayed as a yellow circle
9 Resolution Advisory
An RA indicates that an aircraft
Is a threat
displayed as a red square
accompanied by a recommended vertical maneuver.
TCAS on Vertical Speed Indicator
The red arc indicates the area to avoid, the pilot always
shoots for the green arc.
In this example, the airplane is descending at about 3000
feet per minute.
Textbook page 149
14 AFI 11-202 Vol 3
Response to TCAS Alerts.
If a TCAS RA requires maneuvering contrary to ATC instructions, right-
of-way rules, cloud clearance requirements, or other VFR/IFR flight
rules, pilots are expected to follow the TCAS RA.
15 Ten Fundamental Dos and Don’ts
1. TCAS must be operated in RA mode to provide full safety benefit
2. Pilots must follow all RAs promptly and accurately
3. Pilots must never maneuver in the opposite sense of an RA
4. Pilots must report RAs to controllers as soon as possible
5. Controllers must not interfere with pilots’ reactions to RAs
6. Vertical speed must be reduced in response to “Adjust Vert Spd”
7. TCAS traffic displays must not be used for self-separation
8. Vertical speed must be reduced when approaching cleared FL
9. VFR pilots must operate their altitude reporting transponder
10. Pilots and controllers must be recurrently trained on TCAS ops