I was in Managua Nicaragua beside a 124, I wanted to head over and check out te aircraft and crew but as time fell short they were closing up. Seemed like forever for them to get all engines started for taxi. Thrust up for taxi I saw a large spark and a security shack crumble a far distance behind. On the runway for takeoff I whitnessed the same long power up to set thrust. It was early dawn seemed like they clipped the fence dissapearing at a very low altitude.