Small Transport; Low Wing; 2 Turboprop Eng
Flight Crew Flight Instructor; Flight Crew Flight Engineer; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 70; Flight Crew Total 16000; Flight Crew Type 100
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Less Severe; Airspace Violation All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors
I arrived at the ZZZ around XA:30. The flight was going to be a VFR flight back to ZZZ1. I listened to ATIS on comm 2. There was has no letter present on the information. I selected to comm 1 and called Ground for taxi. There was no response. I switched to Tower frequency and had no response. There was no traffic on the airport that I observed. I wrongly assumed the Tower was not operating. I assumed it was closed or opening late for COVID-19. There was no NOTAM filed. This was a faulty and bad assumption. I checked again for traffic and called on CTAF frequency that I was taxiing out to Runway XX. I taxied and completed my run up. The radio was still quiet. I checked for traffic and announced I was taking the runway and departing for a left crosswind departure. I took off and climbed out. About 20 minutes after departing the area; I tuned in ZZZ2 ATIS on comm 1. There was no ATIS. I tried comm 2 and got the ATIS. I immediately realized there was a problem with comm 1. I immediately was concerned I had left ZZZ without clearance. I asked ZZZ2 for the phone number to ZZZ Tower. I landed immediately and called ZZZ Tower. ZZZ Tower said that my radio transmissions were not received and they had seen me taxi and takeoff without clearance. They said there was no traffic conflict. ZZZ said they were concerned I was NORDO and didn't know it. ZZZ Tower said they were glad I called and figured it out. I immediately had my comm system checked by an A&P. The comm panel was found to be sticking and comm 1 would not engage. The comm panel was removed; cleaned; checked and reinstalled in proper working order. COVID-19 has caused many disruptions to the aviation system. I was flying the night that ZZZ2 Tower was closed for COVID. I assumed this was the probable cause of not being able to contact the Tower. I had checked the NOTAMs and Tower operation times for ZZZ before my flight. My assumption was incorrect that due to a lack of traffic and radio chatter that the Tower was closed. I should have investigated my radio system further for a failure. I should not have assumed the tower was closed.
Pilot reported thinking the Tower was closed due to no response on the radio and departed airport.  While airborne pilot realized the radio was not functioning correctly therefore had taken off without a clearance.