simulated icing flight tests were conducted on an advanced ice protection system as applied to an army uh-1h helicopter in the nrc spray rig at ottawa, canada. the system provides for electrothermal cyclic deicing of the main and tail rotor blades, electrically-heated windshield and stabilizer bar, and ice detectors. the aircraft had been tested previously in simulated icing conditions behind the ch-47 hiss. a total of 18.1 hours of testing were accomplished in 54 days at ottawa. test conditions ranged from 0 deg c to -20 c and liquid water contents equivalent to the recommended atmospheric icing criterion for continuous maximum. the deicing controller system demonstrated excellent functioning and reliability characteristics in general, the deicing of the rotor blades was considered to be good. test results were obtained to define recommended heater-on times for deicing as well as heater-off time between cycles. limited tail rotor icing and deicing were evaluated. natural icing flights were planned after system readiness was established but none were made due to the lack of proper weather conditions. it is recommended that further testing be accomplished under natural icing conditions to complete the evaluation. prior to this additional testing, another set of heated main rotor blades or modifications to existing blades, incorporating minor design and manufacturing changes, should be procured to preclude reoccurrence of the heater element-to-erosion shield short problem and other deficiencies noted from the experience to date. (author)