Date: 201602
Local time of day: 0601-1200
Location: ZDV.ARTCC, CO
Light: Night
Aircraft: Widebody; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach
Airspace: Class D CPR
ATC / advisory: Center ZDV
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness; Confusion
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: ATC Equipment / Nav Facility / Buildings; Airport; Airspace Structure; Chart Or Publication; Human Factors; Manuals; Weather; Procedure
Primary problem: Chart Or Publication

Narrative: I would like to start by saying that I believe several factors led to the development of this unsafe situation. The major contributing factor was the failure of the plow crew at the airport to advise ARTCC (by telephone in accordance with a written agreement) that they were plowing and also failed to publish a NOTAM regarding plowing operations or runway closure at the airport. The second factor that contributed to the situation was that I was fatigued and wasn't even aware of it. It was one of my first few midnight shifts this year and I am still getting accustomed to being awake between 2 and 6 in the morning. I only realized that I must have been fatigued when I heard the tapes because my reaction times to transmissions were slowed; my phraseology was unclear and indecisive; and my understanding of the potential situation was confused and not fully realized right away. There were other factors too; but not nearly as significant as the first couple I mentioned.Aircraft X checked on with a pilot's discretion descent to 16000 feet. I told them to advise when they had the current weather and the NOTAMs and the type of approach they were requesting. They stated that they had the weather and the NOTAMs and would like to do the ILS approach. I issued a clearance direct to the IAF; direct airport. I proceeded to review the NOTAMs and advised Aircraft X that there was a significant NOTAM for the runway 14 inches of snow. (This is where my confusion begins to set in. I thought that if it were really fourteen inches of snow that the runway would probably be closed. One Runway was currently NOTAMed closed so this one was open as far as I could tell.) I told the pilot that the NOTAM said fourteen inches of snow but potentially I was reading it wrong and it could be one quarter inch. I again mentioned the way it was written as one four I - N. Aircraft X responds 'Okay; uh; the word we got; uh; they were plowing the runway right now so uh; and uh; all the other NOTAMs we had showed less than; um; less than a quarter; just some patchy snow and ice. So; I; I can't believe it's fourteen. It's really kind of stopped snowing for a few hours now so.' (at this point I acknowledged the plowing; but may have been confused that it was the other runway). I responded; 'Aircraft X Roger... Sounds good; and if they are plowing that's better too and uh; just the way it reads; I didn't want to you know. I'm not too sure whether that means fourteen or one quarter you know I'm hoping for one quarter; so I just wanted to make sure you were aware. Thank you.' (Again; it didn't register in my mind that he could be talking about this runway and I feel that may have been a fatigue factor as well; because after the fact I didn't remember him even saying that they were plowing that early in our conversation.) Aircraft X responded and said the only thing that they read about deep snow with some snow drifts were observed earlier when they were taking MU readings and it wasn't on the runway. (I determined that the pilot seemed to know what he was talking about; was aware of current NOTAMs and that the runway did not have a NOTAM stating that it was closed. He seemed sure that there was enough information to land so I decided to continue to clear them in for the approach.After clearing Aircraft X for the ILS approach I told them to report their cancellation of IFR this frequency; if unable; through radio and change to advisory frequency is approved. Aircraft X responded; 'Okay; we'll switch over Aircraft X. We were just talking to the uh; field there and right now the runway's closed while they plow so; uh; we'll try to give you a heads up if there's going to be any delay.' (At this point I felt surprised that he actually was saying that they were plowing this runway and that it was closed because I didn't have any information on it other than what he was telling me. The following response I gave was because I was still confused about the whole situation and I thought maybe he wanted to overfly the airport and see what was really going on down there. Here was my response. 'Okay; uh; so right now I'm guessing you'll just head in and then uh execute a missed approach is that your plan?' Aircraft X responded that they would probably just hold at the outer marker. (At this point a full understanding of the potential danger of the situation had developed in my head and I did not think that I should let the pilot proceed any further.) I realized that the pilot was very near to crossing the Initial Approach fix and I tried to give him holding. I was very indecisive at this point and pretty much gave the pilot terrible holding instructions at 11000 feet which was higher than any terrain in the vicinity. The following exchange was uncoordinated and confusing; but the goal was to get them to stay high and hold at a fix I was familiar with. I eventually decided to have Aircraft X climb to 12;000 feet for some potential MIA (Minimum IFR Altitude) about 20 miles south.The airport needs to understand how to contact ARTCC for plowing operations. They need to understand how imperative it is to file a NOTAM well in advance of plowing the runway. I need to learn to recognize signs of fatigue and how to be clear and alert to unusual situations and to provide a safe and clear plan of action as soon as I realize something is amiss.




Synopsis: A ZDV ARTCC Controller cleared an aircraft for approach to a runway that was closed for snow plowing. A NOTAM had not been issued. Airport personnel did not advise the ATC facility of the closure.