NRC Aerospace Announces Advancement In Icing Research

The National Research Council Canada Institute for Aerospace Research on Monday announced a significant advance in icing research. NRC Aerospace researchers have developed an isokinetic probe that can measure total water content when flying at altitude through clouds with ice crystals. This probe is the only fully functioning device of its kind in the world and represents a significant step forward in the effort to characterize and fully understand the total water content present in clouds with ice crystal conditions.

NRC Isokinetic Probe

Since the 1950s, ice crystal conditions have been identified as a potential problem for aircraft, but there has been no real understanding of this phenomenon occurring at high altitudes. Over the last few years, however, NRC Aerospace researchers have been building on past research capabilities and collaborating with research partners to gain a greater understanding of the effects of ice crystal ingestion on the safe operation of large aircraft engines. This effort included developing new and accurate sensors to fully characterize clouds containing ice crystals that are considered a threat for safe aircraft operations.

A wide variety of cloud liquid water content probes have already been developed, but none appear well suited to ice crystal conditions. In fact, existing probes typically underestimate cloud total water content. The NRC-designed and built probe, however, samples the cloud isokinetically and employs an NRC-designed evaporator that ensures an accurate total water content reading.

NRC Aerospace researchers have tested the probe extensively in NRC facilities, including the Research Altitude Test Facility under simulated flight conditions that included ice crystals in the range of 70 to 270 microns in concentrations up to 15 grams per cubic metre. Total water content readings are proving accurate. Flight testing of the probe in ice crystal conditions is planned for 2011.

Isokinetic Probe In Test Tunnel

This research builds on NRC Aerospace's capability demonstrated last year to create significant ice accretion in a simulated aircraft engine test rig with frozen ice crystals in air temperatures above 0ºC. This collaborative project with the Boeing Company to prove that ice crystals could form in an aircraft engine at temperatures above the melting point of ice represented a significant step forward in the understanding of how ice builds up in aircraft engines under ice crystal conditions.

Using the same rig as in the Boeing collaboration, NRC Aerospace researchers have also demonstrated that air data probes can accumulate ice under certain conditions. They have observed that these probes can handle conditions to a certain threshold, but fail once that threshold has been exceeded. Airworthiness authorities are currently reviewing the test procedures for these and may modify the regulations as required.

"We are attacking the ice crystal problem from all angles, building on past successes and moving into a new understanding of the problem," said NRC gas turbine laboratory director Dr. Ibrahim Yimer. "With these advances, we hope we can begin the process of modeling the phenomenon reasonably accurately at sea level in order to predict and develop mitigating solutions, thereby ensuring the safety of the traveling public."

FMI: www.nrc-cnrc.gc.ca