This study aims to encourage the idea of utilizing unmanned aerial vehicles in the fire-fighting application. In this paper, we present a remote-controlled rotary-wing unmanned aerial vehicle made from metal alloys. This unmanned aerial vehicle, using a payload drop mechanism, can carry fire-extinguishing balls and release them to combat fires, especially in places not easily accessible by humans. The payload drop mechanism is a novel design that has an advantage of dropping two (maximum four) fire-extinguishing balls one at a time using one servo motor. Hence, the servo motor is controlled by one radio channel of the remote controller. Besides, comparing it to our (mechanism A) first designed mechanism, this payload drop mechanism shows smaller horizontal area for fitting most of the drones as well as less effect of vibrations during flight. The whole system is designed using Solidworks platform and manufactured with computer numerical control machining and three-dimensional printing. Thus, the potential use of unmanned aerial vehicles to carry out fire-fighting operations using the proposed payload drop mechanism is successfully examined.