Date: 201812
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Weather elements / visibility: 10
Aircraft: PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Landing
Airspace: Class G ZZZ
ATC / advisory: CTAF ZZZ
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Private
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural FAR; Ground Event / Encounter Other / Unknown; Ground Incursion Runway
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airport; Human Factors
Primary problem: Human Factors

Narrative: About 20 miles out from ZZZ I observed on ADS-B another plane landing. 10 miles out I called a 10 mile straight-in. In response; a radio call asked me if I was five minutes out from landing. I responded that I was six and a half minutes out from landing; based on GPS ETE. The response to this was garbled and I did not hear any more calls from the area. I continued the approach; calling five mile and two mile finals; as well as the ETE since someone had asked for it earlier. I could see for several miles out that the runway was clear; so at first I thought someone had position and held and had wanted to know how much time they had; and had since taken off. At about a 1 mile final I also saw an airplane and a work truck on the parking ramp and some water ponded on the left edge of the runway. As I was on very short final; less than 50 AGL; I saw a yellow tarp X in the grass off the end of the runway. Since the X was not on the runway and I had seen another plane recently land and had been asked my ETA; I then thought that workers had gotten off the runway and moved the X off the runway to allow traffic to land; so I landed. I taxied to the parking area and turned around to file a flight plan for my third leg back. While I was filing the flight plan; the other plane that had been on the ramp next to the work truck took off from the same runway. I took off shortly after him without talking to anyone on the ground; and flew back to [to home airport] without incident.That evening at home I did a web search on runway closure markings and found AC150/5340-1L.In 5.7(a)(2) of this document I read that temporary closure markings can be placed just off the end of the runway if construction requires; which I did not know; and that is when I realized the runway was actually closed. Then I checked NOTAMs and saw the runway was NOTAMed closed. Contributing factors were that I assumed if a previous plane had landed recently and taken off just after I landed; that the runway was open. I also assumed that closure markings had to be over the numbers on the end of the runway; and did not know they could be just off the end of the runway. Since someone on the ground had talked to me and not told me the airport was closed (at least not in the initial transmission before it became garbled) I assumed that the airport was open. Finally since I only did a cursory check of the weather and did not fully brief the second leg of the flight; I did not see the NOTAM that the runway at ZZZ was closed.




Synopsis: PA-28 pilot reported not recognizing that a runway was closed and operated in and out of the airport.