A319
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Conflict Airborne Conflict
General None Reported / Taken
Procedure; Human Factors; Airspace Structure
While descending through 12;500 FT on the JCOBS 2 arrival; landing IWA; the aircraft generated a TA Alert for traffic in our 10-11 o'clock position; altitude not known. After checking and reducing the range on the ND; traffic was visually identified in our roughly 10 o'clock position. Visibility was somewhat reduced due to smoke from wildfires in the area or we may have been able to spot him sooner. But as it was; the other aircraft appeared to be in level flight below us; and approaching our descent path as we were on profile to make the crossing restriction at SWIRL Intersection at 11;000 FT. I queried ATC about the approaching target and they indicated that they only had a primary return from him. ATC had not advised us of the other aircraft at all; which turned out to be a C-130 flying westbound at approximately 11;500 FT; most likely over flying the PXR Class B without a Mode C transponder. At this time the First Officer correctly disengaged the autopilot; and stopped the descent until clear of the other aircraft and then continued with the descent to make the crossing restriction. We passed over the C-130; who seemed oblivious; at about 400 FT. ATC was notified; and they had assumed that the other aircraft was flying below the floor of Class B at or below 3;500 FT; at which time I advised them otherwise. While traffic avoidance is primarily the responsibility of the flight crew and ATC; it is possible; and likely; that a notation on the flight release from dispatch (if they are made aware) could increase pilot awareness and vigilance in traffic avoidance during times of wildfire fighting in the area with the associated increase of aerial fire patrol aircraft traveling to and from the area. The current ATIS broadcast at the time contained no mention of fire patrol activity either; which also would have been helpful.
IWA Air Carrier IFR arrival experienced a conflict event with traffic apparently engaged in fire fighting activities; the reporter suggesting this type of activity be briefed to crews flying in the area.