Gulfstream IV / G350 / G450
Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
ATC Issue All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors
We were in cruise at FL450 in VMC conditions when we noticed that we were no longer hearing radio transmission from ATC though we were hearing other aircraft on the radio. I had gone to the lavatory 20 to 30 minutes earlier and had turned on the cockpit speakers so that I could hear radio conversations when not in my seat. This also allows flight attendants and other personnel who might be in the cockpit to hear the radio. There is no cockpit door on the Gulfstream IV and this is our standard procedure. When I returned to the cockpit all was normal and; up until the point where we realized that we no longer had two way communications; we had been monitoring a series of radio transmissions regarding turbulence at cruise altitudes. These were two way communications and we could hear both ATC and the aircraft. As we were starting to experience turbulence at our altitude; I asked my co-pilot to ask Center if they had any ride reports at our altitude. When; after several radio transmissions; we could not raise center; we attempted to contact other aircraft on the frequency for a relay. This did not produce immediate results; so I called Chicago Center on 121.5; but received no response. We finally got a response from [another aircraft]; who relayed our frequency request to Center. This took several transmissions to establish our position over OBK and get a frequency. We were on 132.65 and the frequency 125.72 was finally relayed by [another aircraft]. This frequency proved to be in error and was an ATIS frequency; several more radio transmissions failed to resolve the issue. We finally received an ACARS message to contact Chicago on 132.625. We established communication on that frequency and were rapidly switched through four frequencies before resuming normal flight. Subsequently we were given a phone number to call for Chicago Center for possible pilot action.When I contacted Chicago Center via phone; I relayed to them what we had done and experienced. I was also advised that we had been out of radio contact for 34 minutes. The controller expressed personal and institutional concerns that something untoward had happened in the aircraft. I fully understand this as I have been flying for over four decades. I'm not sure why we lost contact with the appropriate ATC facility; did we miss a frequency change; or were we not given one? However my concern is how we were allowed to fly for that long before ATC contacted Dispatch; our flight plan and flight following provider; using the phone number on our flight plan. Dispatch is manned 24/7 and when they receive a call from Center for lost comm they; immediately and without further deliberation or phone calls; data link the new frequency to the aircraft. The instant we realized we no longer had two way communications; we initiated the process to re-establish contact. How did we get that far without an ACARS message?I am in no way minimizing this incident as two way communication is essential to flight operations. However; frequency changes are missed on a routine basis; on any given day flying across the country you will hear numerous transmissions to all types of aircraft attempting to get them on the right frequency. My concern is the delayed use of a tool that provides virtually immediate; verifiable efficacy in restoring lost radio communications.
G-IV Captain at FL450 reported lost communication with ATC and attempted to regain contact. Eventually a frequency was relayed via ACARS and the crew was informed they were out of contact for a while.