HS 125 Series
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Fatigue; Situational Awareness
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors
In cruise at FL390 we lost radio contact with ATC for an extended period of time. After a lengthy cockpit discussion on the arrival; weather; and reprogramming the FMS to reflect the NOTAM missed approach procedure for the ILS; I realized I was only hearing one side of the airborne communications. The non-flying pilot thought he had heard from the controller a short while ago. I immediately turned up the volume on the 121.5 standby and began to search the EFB for the communications box; while the non-flying pilot tried to hail someone on the primary radio.I eventually transmitted on 121.5 and was able to reach [another air carrier flight] to get a relay for a new frequency. I recognized the similar call sign from an earlier sector and considered our call sign could have been a contributing factor to our blackout. Shortly after I heard a Guard Controller trying to contact us. The non-flying pilot also was able to find a good frequency on the primary.It became very apparent to me that we had been out of radio contact for an extended period. I immediately removed myself from flight duty upon landing because I felt I had fallen to extreme task fixation due to chronic fatigue. We had been placed on the late night schedule with a transcontinental red eye followed by [late night] standby shifts for days until they flipped us to an AM show for this trip. To be candid; this lost communication event alarmed me. I had thought I could handle this type of situation better than I did; but it was insidious in how we thought we were on task; but in reality we had fixated on the arrival instead of alert to what was happening.
HS-125 Captain reported experiencing an extended period of no communications with ATC. Reporter cited chronic fatigue as a contributing factor.