Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 30; Flight Crew Total 2700; Flight Crew Type 1800
Communication Breakdown; Confusion
Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Ground Incursion Runway
Airport; Human Factors; Procedure
ZZZ was preparing for multiple taxiways being closed and aircraft back-taxiing to [Runway] X despite NOTAM prohibiting. Runway X was in use. It was the preferred calm wind runway and all aircraft were departing and landing 04. Taxi to X from the hangars requires crossing the approach end of [Runway] YY. I stopped at the hold-short line for YY; announced my intention to cross the runway; [and] turned on my strobes and checked for landing traffic in both directions. Not seeing any; I started to cross the runway and looked to my right; there was an aircraft on a takeoff roll on [Runway] Z. He did not announce he was taking off and did not have strobes or a landing light on. There was never any real chance of collision unless he aborted the takeoff and was going to run off the end of the runway; as the approach end of YY is at the very end of the runway.Several factors contributed to this chain of events. First; I scanned for landing traffic and did not consider an airplane taking off of Z as that runway is never used for takeoff. I've been at that airport for many years and never seen an aircraft take off on Z. Second; the pilot for some reason decided to use Z when all other aircraft and there were multiple aircraft flying; between coming and going for the airshow and high density of training on the field; were using X. Third; the pilot failed to broadcast he was departing Z; which he should have done multiple times just because all other aircraft were using X.I realize that a pilot is free to use any runway he chooses at an uncontrolled airport; but in this case with high density traffic and the favored runway being X; it was a poor choice. It does not excuse my failure to look both for landing and departing traffic. Perhaps the FAA should consider a rule change whereby airport management can actually designate an active runway at the field for given weather conditions.
GA pilot reported that while taxiing across the runway at a non-towered airport; an aircraft that did not communicate their intentions it was taking off using a different runway at the same time.