Date: 201707
Local time of day: 0601-1200
Location: HIO.Tower, OR
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class D HIO
ATC / advisory: Tower HIO
Second aircraft: Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Human-Machine Interface; Distraction; Situational Awareness
Second reporter function: Single Pilot
Anomaly: Airspace Violation All Types; Conflict NMAC; Deviation / Discrepancy - Procedural FAR
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: I was working Local 1. There were two GA aircraft on final for Runway 31L that were cleared to land. I had one GA aircraft extended on right downwind to follow the two aircraft on final; but then I received an inbound point-out from P80; the overlying TRACON; on Aircraft X from the southeast. I asked P80 to slow Aircraft X and direct him to fly over the fix INTLL. I told the GA aircraft extended in the right downwind that I was unable to accommodate his full stop on Runway 31L because of the faster Aircraft X traffic. I instructed the GA aircraft to extend right downwind and contact the Local 2 controller on 132.8 for a full stop landing on Runway 31R. Aircraft X checked on frequency and I cleared him to land number two behind the GA aircraft on short final. Additionally; I told Aircraft X that there would be traffic ahead and to his right on extended final for the north parallel. When Aircraft X was on about a five mile final; I observed an aircraft on what appeared to be a right base about four miles from the airport. I told Aircraft X to stop his descent and that it appeared that the aircraft for the north runway was overshooting final underneath Aircraft X at 1000 MSL. At that point Aircraft X indicated 1600 MSL. Aircraft X said that he saw the aircraft and was responding to a TCAS RA; but it didn't look like one of the high wing GA aircraft. Local 2 immediately advised that that was not his aircraft; and we determined that the southwest-bound aircraft was an airspace violator. I passed this information along to Aircraft X and asked if he would like to continue the approach. Aircraft X said he could; and I cleared him to land again on Runway 31L. I did not observe Aircraft X take any evasive maneuver to avoid the aircraft. I had both aircraft in sight the entire time; and Aircraft X appeared to cross over the violator between 400-600 feet. After Aircraft X landed the pilot called the tower and advised that the violator in question; Aircraft Y; landed at 7S3 shortly after. The pilot of Aircraft X also advised that they were reporting this incident as a near mid-air collision.On the FALCON replay; Aircraft Y could be seen violating the airspace from the northeast and then exiting the Delta airspace and skirt the edge of the airspace south bound. Aircraft Y re-entered the airspace from the southeast and made a turn southwest bound. This put him directly under final at about 1000 MSL. Had I noticed this violator earlier; I could have prepped Aircraft X sooner. But I am confident that my timely actions to stop Aircraft X's descent prevented this from becoming a collision.


Second narrative: After departing [north of SPB] to 7S3 and just setting cruise after climb out I realized that I was very close to HIO Class D. I immediately turned east toward PDX and flew between their airspace until clear to the south of HIO. I then continued on to 7S3 and landed there for fuel. After fueling I was told that I had entered the Class D airspace and that I would be hearing from ATC. I was not given a number to call; but was told that since I had installed ADSB they already had my information. I believe that a contributing factor was that in approaching from the north the Class D line is missing or obscured due to all of the printing. As soon as I realized how close I was I watched for other aircraft and diverted to an area I knew to be outside. Another factor was my inexperience with the area and the short duration of the flight. Had I prepared more I might have had their frequency dialed in but I had just set the radio to 7S3 frequency and changing to HIO freq. would have required more time than simply exiting.


Synopsis: HIO Tower Controller and pilot reported of a Class Delta airspace violation and a NMAC.