Icing Investigations and Product Development on MU-2B Airplanes

Mitsubishi Heavy Industries, Ltd (MHI) produced over 704 MU-2B airplanes from 1965 through 1986, and all were approved for flight into known icing conditions. With the ATR 72 accident at Roselawn, Indiana, all turboprop airplanes were subjected to additional scrutiny concerning operation in icing and, in particular, SLD conditions. MHI sponsored extensive ground and flight test programs to verify MU-2B flight characteristics in both FAR Part 25 Appendix C and SLD conditions. As a result of this test program several product improvements and operational procedures were developed. These were offered to the field to aid pilots in recognizing and exiting both normal and severe icing conditions. This paper details results of this testing and recommendations for increased pilot awareness of icing conditions. Results and conclusions have broad application to turbopropeller driven aircraft.