On August 21, 2000, at 1300 eastern daylight time, a Douglas DC-3, N79MA, collided with a parked Beech 18, N697Q, while taxiing to the parking ramp after landing at the Key West International Airport in Key West, Florida. The airplane was operated by Missionair, Inc., under the provisions of Title 14, CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed and an Instrument Flight Rules (IFR) flight plan was filed. The pilot and co-pilot were not injured and the airplane sustained substantial damage. The flight had originated from La Ceiba, Hondurus at 0830. According to the pilot, after exiting the runway, he taxied normally to the U.S. Customs service ramp. Upon attempting to turn right at the Customs Ramp, no right brake function was available. The pilot said that due to the close proximity of other aircraft, differential power was not an option. The pilot stated that he cut the magnetos and tried to gently brake with the left brake. He said the left wing struck a parked Beech-18, damaging the upper engine nacelle and propeller. He said that the impact caused the airplane to continue to the left until the right propeller not rotating struck the left wing of the same Beech-18. Examination of the right brake found that the right expander tube had failed. As a result, the pilot was unable to stop the airplane before colliding with a parked and unoccupied Beech 18.