Date: 201710
Local time of day: 1201-1800
Location: PWK.Airport, IL
Flight conditions: VMC
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Takeoff / Launch
ATC / advisory: Tower PWK
Second aircraft: Light Transport
Reporter organization: Personal
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; Flight Crew Rejected Takeoff
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: I was cleared for departure on Runway 24 at Chicago Executive airport. Runway 16 and 24 were being used for departures. I commenced my takeoff roll and was approximately 25-30% down the runway at approximately 50-60 knots; accelerating rapidly when over the Tower frequency controller called 'STOP! [Call sign] STOP; STOP RIGHT NOW!' I immediately applied full brakes; initially thinking that I had misunderstood my takeoff clearance; or that I was not actually on a runway; but was on a taxiway (more on that later.) A fraction of a second later I saw Aircraft Y taxiing on Taxiway Echo from left to right toward Runway 16; and crossing over the hold short line onto Runway 24; directly in front of me. I estimate that he was 100 feet directly in front of me with my speed down to probably less than 20 knots. I could clearly see the copilot in the cockpit as he was looking forward; I don't think he even saw me. The Tower Controller then had me turn behind him onto Taxiway Charlie back to the departure end of Runway 24. The controller apologized for what had happened; then again cleared me for takeoff which was uneventful as was the rest of the flight.Since I was on Tower frequency and not Ground; I do not know what taxi clearance was given to the Aircraft Y pilots. Whether the Ground Controller cleared him to taxi to 16 without holding at Runway 24; or he was instructed to hold at 24; but did not; the mistake was potentially catastrophic. Had the controller not called out when he did; or even a fraction of a second later; I would have not seen Aircraft Y until it was too late for me to stop in time to avoid hitting him. I would have been very close to rotation speed and it would have been impossible to fly over him. By the grace of God an accident did not occur which no doubt would have resulted in fatalities.Because I do not know the instructions given to the Aircraft Y; it is impossible for me to know why he was on the runway; but Runway 24 is quite narrow and the painted white markings are extremely faded. I initially mistook it for a taxiway when I was cleared on to Runway 24; and taxied north onto taxiway Charlie so had to make a 180 degree turn on Charlie and taxi back to the runway. This despite me having SafeTaxi diagrams on my Garmin 750; which I was using at the time. That portion of the runway has a displaced threshold so the markings are not typical white lines; but are the arrows pointing to the threshold; again these were very faded and nearly imperceptible. If the markings for Runway 24 at Taxiway Echo were similarly faded (likely) I could see how a taxiing airplane could mistake it for just another taxiway. This location is listed as a 'hot spot' on the airport diagram; and clearly that designation is justified; but just listing it as such doesn't make it any less dangerous.




Synopsis: GA pilot reported aggressive aborted takeoff when alerted by ATC; as another aircraft taxied onto the runway.