Quote:
Originally Posted by bigdaddy  This past Friday, I was flying VFR just north of Houston, just over the edge of Class B airspace, at 11,500 heading north-east with Flight Following and an American Airlines jet was called as traffic 9 o'clock, 11,000 heading south-east.
As far as I could tell, I was where I was supposed to be and he was where he was supposed to be - our paths were about to cross with 500 feet between us.
But before I could call traffic in sight, the airliner notified ATC that he had a TCAS alert and that he was initiating a climb. Despite ATC's reply that we had 500 feet of separation, he still insisted on climbing. I watched as he began his climb up through and above my altitude.
I'm no TCAS expert, but it seems as if that could have caused a collision instead of avoiding one. I wonder what made him decide to climb instead of decend - besides ATC telling him, doesn't TCAS tell him what altitude the cause of the alert is at? |
TCAS is a pretty smart instrument these days with a bunch of algorithams that I can't begin to explain. Maybe you had 500 ft of seperation and maybe you didn't.....all it takes is either aircrafts instrumentation to be just a bit off (even if you do have the correct altimeter setting) for the TCAS to interrogate it as only 400 feet seperation. It also takes into account not only the 'intruder' aircraft but also other aicraft in the area.....was there someone below him that would have prevented a descent?? It's also possible that for whatever reason his TCAS picked up a slight descent from your transponder and that would also cause a climb command. It's also possible that even though he stated "initiating a climb" that he wasn't really level yet - he was just at the top of climb in which case the TCAS would have probably issued an increase in climb rate rather than going from a cluimb to commanding a descent. Every operator's (that I know of) flight operations manual is written that if you receive an RA (Resolution Advisory) you are required to respond and follow the TCAS guidance - generally it gives you a climb or descent and a minimum rate of climb/descent to maintain until it announces "Clear of conflict".
There are a ton of reasons his TCAS may have issued a climb.....who knows what it was.
Jason