Date: 201202
Local time of day: 1201-1800
Location: STS.Airport, CA
Flight conditions: VMC
Light: Dusk
Aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight plan: VFR
Flight phase: Taxi
ATC / advisory: Ground STS
Second aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Ground
Anomaly: Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Contributing factors: Airport; Environment - Non Weather Related; Human Factors
Primary problem: Airport

Narrative: I had 2 [of the same aircraft type] holding short of Runway 14; one at Taxiway A and the other in the run-up area. Aircraft X called ready to go as aircraft Y crossed over the hold short line at 'A' and proceeded onto the runway. I thought the aircraft that called was the one moving and asked if he was already on the runway. Then aircraft Y on the runway called ready to depart as he taxied down Runway 14 to Runway 19. I told aircraft Y to cross Runway 14 back to run-up area and contact Ground for a possible pilot deviation. The taxiway markings and runway signs at the field are very confusing and lead to many mistakes. I do not know if that would have stopped this incident; but better signage would certainly help to avoid mistakes by pilots not familiar with this airport.


Second narrative: An incident occurred in which an aircraft taxied onto an active runway. Five minutes before the incident; the aircraft called me on Ground Control for taxi instructions. I gave the instructions to taxi to the active runway; Runway 14; via Taxiway Yankee. The pilot replied; '[Aircraft X]; Yankee to one four.' I watched him taxi to the runway and due to lack of signage he began to turn at Taxiway Alpha just short of the run-up area. He stopped short of the hold bars for Runway 14. A few minutes later; an aircraft that just arrived turned off at Taxiway Bravo to contact me. He called me and said; 'Ground; aircraft Z for [parking].' One second later; before I could reply to aircraft Z; aircraft X called and said; 'Aircraft X ready for departure one four; I think I'm on the little short thing just for the other runway.' I did not catch him say that; but I knew it was him who called. Just before I talked to him; I scanned and he was still holding short of Runway 14 at Taxiway Alpha. I then replied to aircraft Z to taxi to Runway 14 via Yankee; then corrected myself realizing he was not a taxi back; and instructed him to taxi to [parking] via Yankee. Then; before I could reach out to aircraft X; he contacted me a second time with; 'Aircraft X ready for departure one four.' Again; I scanned; saw him at Alpha holding short of Runway 14; and replied; 'Aircraft X contact Tower;' since he thought he was on the Tower frequency. I then scanned to make sure aircraft Z was taxiing as instructed and that's when I heard the Local Controller say; 'Hey; hey!' pointing at aircraft X; who was crossing the hold bars and taxing onto Runway 14 without a clearance to do so. I told the Local Controller his aircraft ID and he tried to reach aircraft X with nil results. So; I reached out and said; 'Aircraft X contact Tower!' He replied; 'Roger; contacting Tower.' Local Control established contact and instructed the pilot to exit the runway and contact the Tower via phone for a pilot deviation. Santa Rosa Sonoma County Airport has a lack of signage. There have been many complaints regarding this. Better signage on the taxiways [is needed].


Synopsis: Two STS controllers report a Runway 14 incursion at Taxiway A because of poor taxiway and runway signage.