Effects of turbulence

ACAS II can issue two types of advisory

· TRAFFIC ADVISORY (TA), warns the flight crew to be ready for a potential Resolution Advisory and helps the crew in the visual search for the intruder aircraft. The TA is triggered between 20 and 48 seconds before the Closest Point of Approach (CPA)

· RESOLUTION ADVISORY (RA), an advisory to the flight crew to execute avoidance manoeuvres in the vertical plane. The RA is activated between 15 and 35 seconds before the CPA

* Airborne Collision Avoidance System ** Traffic Alert and Collision Avoidance System

Communication of TA or RA

The TA or RA is communicated to the flight crew by means of both a visual display and an aural alert message.

The following can be expected:

· Climb or descent without prior warning

· No emergency squawk

· Two aircraft or more involved

· Notification from pilot of "TCAS climb" or "TCAS descent"

Effects of turbulence

If an aircraft experiences severe turbulence that makes it deviate very suddenly towards another aircraft, the altitude varies with an important acceleration.

TCAS II computes a high vertical speed and an advisory may be triggered.

Even though these are rare events, TAs or RAs may be triggered between aircraft on adjacent flight levels because of turbulance.

In event of a pilot reporting a manoeuvre induced by an RA, REMEMBER:

· The controller shall not attempt to modify the aircraft flight path

· The controller shall provide traffic information as appropriate

· Pilots very busy

· TCAS II altitude data is more accurate than radar data

NB: Once an aircraft departs from its clearance in compliance with an RA, the controller ceases to be responsible for providing separation between that aircraft and any other aircraft affected as a direct consequence of the manoeuvre induced by the RA

The controller shall resume responsibility for providing separation for all the affected aircraft when:

1. The controller acknowledges a report from the flight crew that the aircraft has resumed the current clearance
OR

2. The controller acknowledges a report from the flight crew that the aircraft is resuming the current clearance and issues an alternative clearance which is acknowledged by the flight crew

Following an RA event, or other significant ACAS event, pilots and controllers should complete an air traffic incident report.

An aircraft hitting a bird may create an emergency situation, known as Birdstrike.
	The seriousness of this emergency depends on: · the size of the bird · the speed of the aircraft at impact · where it hits the aircraft. Its effects may be very severe. The most dangerous strikes are to the · windshield · engine A strike of this nature may lead to the ultimate loss of the aircraft.
Strikes other than windshield and engine may impair the flying characteristics of the aircraft, making levels and headings difficult to maintain and safe landings difficult. THey may ultimately lead to loss of control, or even structural failure.