Experimental evaluation of ice accretion on coaxial-rotor vehicles

Sihong Yan, Shawn Scroger, Jose Palacios

Research output: Contribution to conferencePaperpeer-review


Coaxial-rotor configurations are being implemented on large-scale helicopters and commercial unmanned aerial systems (UAS). The performance of coaxial-rotor configuration in icing condition is not fully understood and further evaluation is needed. . The goal of this research was to develop testing beds and methodologies to evaluate Two coaxial rotor test systems. Two test rigs were designed and fabricated in the Adverse Environment Rotor Test Stand at the Pennsylvania State University. One system has a coaxial configuration using 0.4 m diameter rotors, while the second one has a rotor diameter of 1.4 m. The power growth rate and thrust decline rate were quantified for both rotors. The average liquid water content of tests was 1.5 g/m3 and the median volume diameter was 20 µm. Tests were conducted under two temperatures, -5ºC and -10ºC. The upper rotor in the coaxial configuration worked as an icing shield for the lower rotor, as it collected a large majority of the incoming water droplets. At 3000 rpm, the power growth rate of the upper rotor was 23.4% greater than that of lower rotor. At 4000 rpm, the power growth rate of the upper rotor was 53.8% higher than that lower rotor in -5ºC. At -10ºC, the percentage difference of 4000 rpm was 48.3%. The shielding effect of the upper rotor is positively related to rotor speed. The thrust of the upper rotor also decreased in icing cloud and the thrust of the lower rotor was not affected by the ice accretion. The thrust decline rate of cases at 3000 rpm and -5ºC was 0.07 N/s. The decline rate of 4000 rpm at -5ºC and -10ºC were 0.08 N/s and 0.18 N/s. The difference in torque between the rotors leads to imbalances that negatively affect the maneuverability of a coaxial-rotor vehicle. The shedding event was observed on the dual-layer stand and introduced imbalanced loads to the system. The torque imbalance due to shedding could potentially be controlled by increasing rpm.

Original languageEnglish (US)
StatePublished - Jan 1 2019
EventVertical Flight Society's 75th Annual Forum and Technology Display - Philadelphia, United States
Duration: May 13 2019May 16 2019


ConferenceVertical Flight Society's 75th Annual Forum and Technology Display
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Control and Systems Engineering


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