Baron 58/58TC
Flight Crew Private; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 25; Flight Crew Total 530; Flight Crew Type 230
Communication Breakdown; Situational Awareness; Workload; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Flight Cancelled / Delayed
Aircraft
I was flying on an IFR flight plan to ZZZ. Over far northwest Ohio I was handed off to Approach. Approach gave me a revised clearance into ZZZ1. When I keyed the mic to acknowledge; there was a pop and the smell of an electrical fire in the cockpit. I told [Approach] to standby; and shut down the avionics master. I simultaneously turned south toward several suitable landing fields; and began a descent. I cycled the avionics for several minutes and did not note any further burning smell. I was able to receive on COM 1 but I could not transmit. I tried to [advise ATC] but again this call was not heard. Given the possibility of an unextinguished fire; I proceeded direct to ZZZ2 and made an emergency landing. I called [Approach] immediately after landing to advise them that I was on the ground and OK. If I had switched to COM 2 I would have been able to transmit. However; with the workload at the time (including a possible fire; finding an alternate; managing the descent; and trying to isolate the failure); I didn't think of trying this.
BE58 pilot reported a loss of communication radio transmit capability and a burning smell in the cockpit led to a diversion.