Thursday, July 5, 2007
Pilot Error or Mechanical Failure? Brazil Midair Collision
Somewhere over the Amazon jungle in Brazil two modern, brand new aircraft crossed paths and one of them never landed. It is assumed that, at 37,000 feet, these two aircraft collided and the larger of the two, a Boeing 737-800, entered a descending spiral which culminated on the floor of the jungle. The jungle was so thick that rescuers had to parachute in and clear landing spaces for rescue helicopters. Of the 154 crew and passengers on the Boeing none survived.
Meanwhile, an Embraer Legacy 600 business jet experienced a slight jolt, described by a Times writer as a car hitting a pothole, landed at a nearby military base where they discovered damage to the left winglet and some damage to its tail. The wing had started to peel back, causing the Legacy passengers to fear they were going to crash, but the pilots were able to land safely.
What happened?
As with most aviation accidents the cause is not readily apparent. Each aircraft was under air traffic control (ATC), and each aircraft was equipped with TCAS (Traffic Collision Avoidance System) which should have warned them they were too close. To further complicate things, these aircraft were operating in a gray area of radar coverage where two different ATC facilities responsibilities overlap. It appears that the Legacy jet was following one airway at 37,000 feet and was supposed to descend to 36,000 feet upon reaching yet another airway. The Boeing was traversing the area at 37,000 feet.
The interesting part.
Brazilian authorities have detained the crew of the Legacy jet by taking their passports and not allowing them to leave the country. Further, officials have claimed that this crew purposely turned off their transponder (a device in the aircraft in which the crew sets a unique 4 digit code) in order to perform some pilot tricks in their aircraft. If the transponder was, indeed, turned off, or simply did not work, then the TCAS systems in both the Boeing and the Legacy jet would not work properly. As a pilot I can tell you that when the TCAS is working the warnings would be difficult, if not impossible, to ignore!
However, in another development it turns out that the manufacturer of the transponder, Honeywell, had problems with earlier versions of this model when the crew took longer than five (5) seconds to set a new code upon request of ATC. If it took longer than five (5) seconds the transponder would go into the standby mode, and would not be transmitting its proper signal.
Honeywell denies this particular transponder would have that problem, and insists that it had long ago advised operators of the problem and had issued a software upgrade to fix the problem. The pilots deny that they turned the transponder off, and it is hard to imagine anyone would do such a thing.
So while we are left to ponder the cause, the crew is left in limbo, trapped in Brazil, amongst a hostile population who want revenge for the deaths of 154 people.
Pilot error or mechanical failure?
We can only hope that the Brazilian authorities get this one right and that the proper, definitive cause of this accident is determined. As a fellow pilot I hope and believe the cause was not some cowboy activities, and that the pilots are returned home safely and soon.
Keep your wings level and fly straight.
Crusty Captain
