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When helicopters are to fly in icing conditions, it is necessary to consider the possibility of ice shed from the rotor blades. In 2013, a series of tests were conducted on a heated tail rotor at NASA Glenn's Icing Research Tunnel (IRT). The tests produced several shed events that were captured on camera. Three of these shed events were captured at a sufficiently high frame rate to obtain multiple images of the shed ice in flight that had a sufficiently long section of shed ice for analysis. Analysis of these shed events is presented and compared to an analytical Shedding Trajectory Model (STM). The STM is developed and assumes that the ice breaks off instantly as it reaches the end of the blade, while frictional and viscous forces are used as parameters to fit the STM. The trajectory of each shed is compared to that predicted by the STM, where the STM provides information of the shed group of ice as a whole. The limitations of the model's underlying assumptions are discussed in comparison to experimental shed events..

A new design for a droplet generator capable of producing single droplets is presented. The design relies on thermoelectric heating to vaporize water at the interface between a droplet and a blunt syringe tip. While other designs require careful tuning to produce drops of varying size, this technique enables the simple creation of droplets of any size within a range. The design is of simple construction and can be completed with off-the-shelf components, and relies on resistive heating to vaporize water at or near the droplet-nozzle interface and release the droplets. We demonstrated that the design can be used to produce droplets as small as 110 µm or as large as 2 mm. Drop size is limited by the geometry of the nozzle since water must wet the tip of the nozzle and hang under gravity. Our experiments showed that released droplets have relatively small disturbances introduced by the release mechanism when compared to competing techniques. These disturbances were intermittently observed as the voltage, pulse width, and drop size were changed, and optimal settings were determined for the smallest drop sizes produced.

The formation of ice on aircraft is a highly dynamic process during which ice will expand and contract upon freezing and undergoing changes in temperature. Finite element analysis (FEA) simulations were performed investigating the stress/strain response of an idealized ice sample bonded to an acrylic substrate subjected to a uniform temperature change. The FEA predictions were used to guide the placement of strain gages on custom-built acrylic and aluminum specimens. Tee rosettes were placed in two configurations adjacent to thermocouple sensors. The specimens were then placed in icing conditions such that ice was grown on top of the specimen. It was hypothesized that the ice would expand on freezing and contract as the temperature of the interface returned to the equilibrium conditions. While results from the aluminum specimens matched this hypothesis, results from the acrylic specimens show a short period of contraction followed by a much larger expansion at the interface, indicating more complex ice growth thermodynamics than anticipated. Some samples were observed to delaminate, suggesting that the residual strain is significant to the shedding of ice for inflight applications.