Date: 201706
Local time of day: 1201-1800
Location: ZKC.ARTCC, KS
Flight conditions: Marginal
Weather elements / visibility: Rain
Light: Daylight
Aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Descent
Airspace: Class E ZKC
ATC / advisory: Center ZKC
Second aircraft: Small Transport
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Other / Unknown; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; ATC Equipment / Nav Facility / Buildings; Company Policy
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: Aircraft X on western edge of ZKC 62's airspace; northbound; inbound to land at AVK. This airspace is usually operated by Vance approach control during the week; and only delegated back to ZKC at night and on the weekends. Our frequency coverage is not good; and has been logged as not good especially on the western portion of Sector 62 for some time now. There was weather building (moderate to heavy precip) just west of AVK and developing in clusters to the northwest. The radar controller advised Aircraft X of the weather and asked him about his approach request. He advised he'd take a look when he got closer. The radar controller subsequently descended Aircraft X to 4000; still above the MIA (Minimum IFR Altitude). Aircraft X descended below Sector 62's radio coverage and consequently made him NORDO to us. We were unable to communicate any further weather information to Aircraft X nor were we able to communicate his approach request. Fortunately; Aircraft Y was overhead at FL210 and advised he was able to hear Aircraft X and could relay to him. We spent the remainder of Aircraft X's flight relaying clearance and cancellation information through Aircraft Y overhead. This is an on-going frequency problem with ZKC 62. Apparently it is known that the frequency coverage is inadequate. The minimum IFR altitudes at AVK are 3600; and the missed approach altitude is 3300. Those are both WELL below our radio coverage. If Aircraft X had gotten into weather and declared an emergency or if he had gone missed approach; we would not ever have been able to talk to him. He would be completely blind by himself once he descends below about 4500 MSL because of inadequate frequency coverage. There are several other airports along the western and southwestern boundary with the same limitations. We had asked originally for Vance approach control to furnish one of their frequencies for better coverage when they are closed. That request was rumored to have been denied. We have also been told that Sector 62's frequency 127.8 cannot be tuned for better low altitude coverage without degrading its high altitude coverage. So it's a known problem with significant safety concerns that still exists; yet no solution has been offered yet.




Synopsis: ZKC Controller reported an aircraft in marginal weather went NORDO due to insufficient ATC radio coverage around AVK airport.