Date: 201812
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 25
Light: Daylight
Aircraft: Citation Excel (C560XL)
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
ATC / advisory: UNICOM ZZZ
Reporter organization: Corporate
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Ground Incursion Runway
Detector: Person Flight Crew
When detected: In-flight
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: We were on the 4th leg of a round trip. We normally do not fly this many legs in a day and also do a very regimented sit down brief before a typical flight. On a day like [today]; we are taking off every couple of hours and we are out of our habit patterns in many ways. We filed an IFR flight plan from ZZZ to ZZZ1 Center handled our IFR flight across to ZZZ1. It was a short flight flown at 5;000 feet. Visibility was excellent and there were no flight hazards other than mid-air collision risk at low altitude. We got the field in sight about 20 miles out and cancelled IFR about 10 miles away from the airport. We maneuvered to about a 4-5 mile final using the RNAV approach for Runway 28 as a reference. The co-pilot (also a highly qualified Captain) made at least one radio call out on unicom as we were maneuvering and I remember distinctly him calling us on a 3 mile final because our foreflight gave us that call out and he parroted it almost verbatim. We got no response from anyone on this frequency. Just after that call at 3 miles; I saw something to the left of the runway that was hard to determine what it was and what it was doing. I could not tell if it was a plane or a mower. The closer I got down final I could see that it was a truck with a trailer behind it that was well clear of the runway on the left side. It is not uncommon to have mowers and bush hogs towed behind tractors cutting the grass right next to runways; so that is what I was thinking was happening. Using a truck to tow the bush hog seemed a little odd; but I dismissed it. The people operating the truck were not waving at us or acting in any way that seemed like something was not right about us landing there. I was very focused on trying to determine if this runway had a displaced threshold. All of our information on foreflight and fltplan.com showed a displaced threshold; but we were pretty sure it had been removed due to a massive clearing project for the approach path. We cannot purchase fuel at ZZZ1; so we have to ferry fuel into there which makes using the whole runway highly desirable. I was trying to determine the threshold displacement issue as we approached; watching this vehicle over to the left as well as handling the aircraft during this challenging phase of flight. I remember seeing some yellow around the numbers that was a little confusing to me; but I did not see any 'X' on the runway. The rest of the approach went fine and the runway was wide open; easily determinable to be in great shape and we landed. Upon de acceleration when turning into the ramp; we saw another white truck towing a trailer move off the taxiway to allow us to enter the ramp. That did not look right and I was getting a feeling something was amiss at this point. The ramp was empty and the FBO hangar doors were closed. We saw our company trucks waiting on our passengers which was normal; but there were quite a few other vehicles parked up there also - which was unusual. We shut down and before I left the cockpit; I pulled up the airfield diagram and noticed the red 'NOTAM' icon. I clicked it and saw the NOTAM saying the runway was closed [today] and would re-open [tomorrow] at [time]. I was somewhat confused; but also very upset as it appeared we landed on a closed runway. Upon exiting the aircraft; I met with the contractor supervisor who had a hand held radio capable of talking/listening on UNICOM. He was not mad; but said he wished we had called ahead so he could have alerted the contractors we were coming in. So; I asked him - So; it is not really closed - more like PPR? He said; yes. I asked him if we would be able to leave and he said 'Yes; no problem as long as we get out before dark.' Maybe this type of closure; is really more of a local airport controlled closure; but very confusing to me. They were working on edge lights and had the whole system turned off. I also spoke with the crews working down at the approach end and they did not feel like we came close to them orwere ignoring their markings. Ends up they had placed a yellow 'X' panel flat on the runway right over the numbers. They probably thought that would be where pilots would look. But; it would have been much easier to see had they placed those flat panel 'X' markers just pass the numbers by themselves. Even better-if they really wanted to close the runway; the vertical; and lighted X signs should be used. The panels probably work fine for planes flying an overhead pattern; but not for aircraft flying straight in approaches. When I debriefed with my co-pilot; he admitted he did in fact see the 'X' at the last second; but for some reason; did not call a go-around. I think his brain was overcome by all the positive things telling us the runway can't be closed and yellow X doesn't really look like runway is closed. Also; he (like me) had been focusing a lot of attention on trying to determine if we saw a displacement and trying to watch the 'mower' type vehicle. I think he was just to unsure of what he was seeing to call a very low altitude go-around - basically a balked landing - which is risky. Speaking of positive feelings about the runway status; one of the reasons I am writing this report is because I think there are some real lessons to be learned about NOTAMS and runway closures (are there different types?); who makes those decisions? Does having an operating tower make it a different matrix? When are contractors required to use raised; lighted 'X's? One of the other lessons to be learned is not to rely on fltplan.com to prompt you that a runway is closed to an airport you filed to . Many times; it will bring up a message saying 'This airport is closed' if you try to file there. Also; ATC will almost always help pilots make sure a critical NOTAM like this one is not missed. Most controllers will prompt the pilot by saying 'The ZZZ1 airport is NOTAM closed until [time/date]; what are your intentions?' In decades of flying; I have never seen ATC allow us as an IFR flight to proceed to and make a visual approach to a closed airport. The airport manager should have been 'On duty' also manning his radio to respond to any inbound flight or airborne inquiry about the runway. In the end; this all worked out OK. Nobody got hurt; nothing go damaged; the contractors work flow was not even affected much more than a few minutes. Two pilots got their egos a little bruised; but there truly are a lot of lessons to be learned here. I certainly have become complacent on using fltplan.com and counting on it to keep us out advised of these kind of critical NOTAMS. Also; we cannot count on ATC to help us check the NOTAMS either. They make mistakes just like we do. There are more issues that could be addressed that might be considered 'Contributing Factors' had we had a mishap; but what I have written already covers the majority of what I wanted to say. Suggestions: If a runway is to be closed at an airport without a tower; I would suggest this: Send a communique to the controlling facility advising them of the closure. ATC could have a hot list of short term closures that would be most likely to be missed. I would have the Airport Manager or some other person manning the unicom radio frequency at all times. Put the closure info on the AWOS if possible. Contractors working near runways should have red flags they could wave if they wanted to signal to an airplane to 'Go away'; 'Airport is closed'. The light gun could also easily be used for this purpose. Lastly; if you really want to close a runway; you must put the lighted X's standing up facing up the final approach.




Synopsis: GA pilot reported landing on a closed runway and some confusion relating to if it was a PPR or actually closed.