This Enstrom F-28A was built in 1966 as an F-28 and was the second production helicopter built by Enstrom. It was flown to Detroit, Michigan and exhibited in a trade show where it won an award for best product design in Michigan, beating out the Ford Mustang. In September 1967, ownership was transferred to AiResearch Corp. where it had an Allison turboshaft engine installed and was operated as a test bed called the T-28 Prototype. In 1973 the aircraft was returned to Enstrom and was remanufactured as an F-28A, its present configuration.