Policy and Procedures for the use of ACAS (TCAS)

Policy and Procedures for the use of ACAS (TCAS)

Whenever Airborne Collision Avoidance System (ACAS) is installed and serviceable, it shall be used in flight. ACAS provides collision avoidance manoeuvre advice in the vertical plane, in either of two forms:

• Traffic Advisory (TA), which indicate the approximate position relative to the subject aeroplane, either in azimuth only, or azimuth and altitude, of nearby transponding aircraft which may become a threat;
• Resolution Advisory (RA), which recommend manoeuvres or manoeuvre restrictions in the vertical plane to resolve conflicts with other aircraft transponding SSR Mode C altitude. For specific operational procedures refer to OM Part B.

Traffic Advisory

A TA must be responded to by immediately attempting to establish visual contact with the intruder. If contact is established, safe separation shall be maintained. No avoiding action must be taken without visual contact. Pilots must be aware that an aeroplane sighted may not necessarily be the intruder or the sole intruder TCAS is responding to. TCAS is not able to provide RAs for intruders without altitude reporting capability. Therefore, TAs without relative altitude data on the display must be closely monitored.

Resolution Advisory

An RA is intended to advise flight crew on the manoeuvre they should carry out in order to achieve or maintain adequate separation from an established threat. It must be borne in mind that another aeroplane visually identified may not necessarily be the intruder or the only intruder causing the RA. Therefore PF shall immediately react to an RA observing following guidelines:

• Disengage the autopilot and manually apply positive and smooth control inputs in the direction and with the magnitude required by the RA;
• Manoeuvre shall never be made in a direction opposite to the one indicated by the RA;
• Manoeuvre’s magnitude shall not be greater than those demanded by an RA.

The PF must strictly follow the RA even when:

• ATC controller is issuing a contradicting ATC clearance;
• A conflict close to top of the operating envelope exists;
• Traffic information from the ATC controller is received;
• There is a visual acquisition of conflicting traffic.

Whenever ATC issues a clearance with which the pilot is unable to comply because of the presence of an RA, the PNF should inform the controller using phrase »UNABLE, TCAS RA« (pronounced: »UNABLE, TEE-CAS-ARAY«). The controller should acknowledge such a report or issue an alternative clearance.

In all other cases, ATC shall only be notified whenever a manoeuvre induced by an RA has led the pilot to deviate from the assigned clearance or instruction. The following phrase shall be used: e.g. »The Company 211, TCAS RA« (pronounced: »The Company 211, TEE-CAS-ARAY«). Whenever an RA requires »CLIMB« while the aeroplane is in landing configuration, a goaround procedure shall be initiated.

Clear of Conflict

After the ACAS has annunciated »CLEAR OF CONFLICT« and if, concurrently, no other traffic conflict exists, the PF shall return the aeroplane to the assigned level and clearance and shall report:

• e.g. »The Company 211, CLEAR OF CONFLICT, RETURNING TO (assigned clearance)«, or
• e.g. » The Company 211, CLEAR OF CONFLICT, (assigned clearance) RESUMED«.

The controller should acknowledge such a report and he may issue a revised clearance. Once an aeroplane in compliance with an RA, departs from an assigned ATC clearance, the controller ceases to be responsible for providing separation; however circumstances permitting, the controller should endeavour to provide traffic information to all aircraft affected by the manoeuvre. The controller’s responsibility resumes when:

• He acknowledges the report that the aeroplane has resumed its assigned clearance; or
• He acknowledges the report that the aeroplane is resuming its assigned clearance and issues an alternative clearance which is acknowledged by the flight crew member.

Internal Reporting

Whenever an aeroplane has departed from an ATC clearance in compliance with an RA, the pilot is to report the circumstances to the Company (via Air Safety Report), which further proceeds the report to the Authority.