Date: 201407
Local time of day: 1201-1800
Location: PDK.Airport, GA
Flight conditions: VMC
Light: Daylight
Aircraft: Skylane 182/RG Turbo Skylane/RG
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Initial Approach
Airspace: Class E A80
ATC / advisory: TRACON A80
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Aircraft component: Traffic Collision Avoidance System (TCAS)
Component problem: Design
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument
Human factors: Communication Breakdown; Confusion
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Equipment / Tooling; Human Factors; Airspace Structure
Primary problem: Equipment / Tooling

Narrative: Flying vector 220 on the initial approach to PDK. My Skywatch display showed a contact 300 FT low and climbing at 12 o'clock; inside 6 miles; but I didn't receive notification of this particular contact from TRACON (they had pointed out other traffic ahead; but I don't believe they mentioned this one). The contact seemed to level at my altitude and continued towards me; but I was unable to obtain a visual on it (Atlanta in the background may have made that difficult). When I got the audible warning from Skywatch about a potential collision I climbed about 200 FT and turned left while simultaneously notifying TRACON that I was taking evasive action. Their reply was along the lines of 'we just got a conflict alert here'. I continued turning left; to a heading of approximately 360; all the while scanning for the traffic (and asking my passenger to do the same). According to the Skywatch display; the traffic was very close for another 20-30 seconds but we were never able to make visual contact.(My estimate of estimated miss distance in the previous section is completely speculative; based on the fact that I never saw the other aircraft. It may have been much closer; or it could have been significantly further away.) After a short while; I was given instructions to descend to 3;000 and to turn inbound to PDK. The rest of the flight proceeded uneventfully.My diversion from an assigned vector and altitude was made without explicit ATC permission; and I did not declare an emergency when I notified TRACON of my actions. I believe these actions were justified as self-protection; especially in light of the fact that I seemed to have more timely information about the flight path of the other aircraft than did TRACON at the time.This incident occurred at the end of an almost 3 hour flight; but I don't believe there were any human performance considerations involved. I am IFR current; and was alert and well-rested.




Synopsis: A C182 pilot took evasive action from an unsighted aircraft to which he was alerted by a Skywatch CAS which does not provide Resolution Advisories.