The collision avoidance system in the aircraft displays the position of the aircraft (in relation to your aircraft) the mode C altitude (if the other aircraft is equipped). Two type alerts are normally available to the pilot. The exact terminology may not be correct but the first is TA (traffic advisory or alert) this is oversimplifed an informational presentation. The second is an RA (Resolution alert) in the US the aircraft is mandated to follow the information presented. The onboard computer calulates the other aircrafts' position and issues a command (climb or descend, turn left or right) to avoid the other aircraft. So if the other aircraft is above you no matter how much the aircrafts' computer would instruct to to descend. If the other aircraft were transponder and Mode C (altitude reporting_ equipped it should have gotten a RA to climb. In this situation the conflict would be resolved. It would make no difference if the ground based conflict alert were operating or not. It is strictly an airborne based system. Now what bothers me is if the other aircraft was not TCAS equipped it would not have received an RA. The controller would have no way of knowing the actions of the TCAS equipped actions until the pilot told him what he was doing. So theoretically the controller could have issued a descent to one aircraft thinking this action would ensure separation and the TCAS equipment in the other aircraft could have issued a descent RA to the aircraft. Now both aircraft are executing the same evasive manuever. This is only hypothetical and doesn't mean that this is what happened. Being half way around the world and not having first hand knowledge a judgement of what actually happened is impossible. It amazes me that if this is what happened that it has taken this long for one to occur. Al ----- Original Message ----- From: "Dennis W Zeuch" <DZTOPS@aol.com> To: <AIRLINE@LISTSERV.CUNY.EDU> Sent: Friday, July 05, 2002 12:29 PM Subject: Re: Criminal investigation seeks answers in air collision >