For one GE engineer, the experience of sailing between the islands of the Gulf of Naples or the spectacular Cyclades in the Aegean proved valuable in an environment that is the polar opposite. An expert sailor, it turns out that the Senior Engineer for Inclement Weather, Paolo Vanacore, was able to lean into his meteorology experience for ice testing the GE Catalyst.
“During my first job interview at the beginning of my career in aviation, they asked me about meteorology and I answered according to my sailor’s skills. So they assigned me to inclement weather,” says Paolo Vanacore, a Senior Engineer for Inclement Weather at GE Aviation in Munich.
“Icing and other atmospheric threats may cause detrimental effects to aero engine performance and ultimately on safety, resulting in a reduction of thrust or lack of engine controllability,” explained Vanacore, a mechanical engineer.
He and the team were able to leverage the global expertise of many of GE’s staff and partners, starting from the core European team with Avio Aero, GE Aviation Czech and the Engineering Design Center (EDC) in Warsaw, up to GEIQ in Mexico and the GE Engineering Centre in Bangalore.
The team started preparing two years in advanced of the first test, defining the extensive protocol called CPA, or Icing Critical Point Analysis. They also included work on other inclement weather tests and analyses such as rain, hail, snow, ice crystals and mixed conditions, such as freezing rain, freezing drizzle and ice slab ingestion.
“These were, in a way, unprecedented tests for a turboprop. CPA has not been used on a clean-sheet general aviation engine several decades,” Vanacore noted.
After the first trip to Canada in 2017, Vanacore found himself back at the National Research Council (NRC) in Ottawa in January 2020 after the Catalyst had been installed on the flying test bed.
The Ottawa test room at the NRC is connected to the outside environment through a small wind tunnel about 10 meters long. From here, the freezing Canadian winter air is drawn-in and mixed with supercooled liquid droplets sprayed throughout the tunnel. Thus, atmospheric conditions and in-flight temperatures are generated and conveyed to the engine in the form of clouds consisting of small drops at sub-zero temperatures.
“The droplets in these uniform clouds range in size from about 15 microns to a few millimeters, and temperatures range from -20 to 0 degrees Celsius, simulating the variability of altitude, from ground level up to about 30 thousand feet (9 Km),” explains Vanacore. “When they fall below -20 °C, reaching -40 °C for example, ice crystals begin to form in the clouds. Especially at high altitudes, at certain speeds, they become like stones. We conducted tests that led these clouds to flow against the engine at extended vertical or horizontal trajectories. This simulated flight maneuvers with variable density and consistency, depending on the temperatures but also on the speed or angle of impact.”
That environment may sound daunting, but it’s the reality of what happens in the air. Passengers often don’t notice these harsh elements thanks to such robust engine and airframe testing.
“Airborne droplets may remain liquid in nature. But, as soon as an airplane flies through the cloud, they immediately freeze on the impact with cold metal surfaces, such as the fuselage, propeller blades and engine compressor inlet components, unless those parts are sufficiently ice-resistant,” Vanacore continued.
But like many activities, the outbreak of COVID-19 caused some unforeseen challenges. The team was required to head back to Europe in early March 2020, and the engineers had to reorganize their work amid an unprecedented global crisis.
“We didn’t lose heart,” he said. “Although we could not get to Canada, we coordinated with the NRC team in Canada. And we also benefited from the support of two test engineers at GE Aviation in Evendale, who were much closer,” says Vanacore.
Despite the distance, teams were able to follow the testing activities in real time, thanks to cameras both outside and inside the engine. Eight non-intrusive micro-cameras monitored the engine components to achieve the main objective of the tests, which was to verify that accretion of or even shedding of ice did not damage the mechanics or threaten the operation and performance. Such clear, direct communication has been key also for the [Organization Designation Authorization] delegated engineer, who was able to remotely track and oversee compliance on behalf of the FAA.
During hundreds of hours simulating all these flight conditions, data were analyzed and stored, helping to prove and optimize the capability and reliability of the materials as well as the design. Ultimately, all the testing contributes to better safety.
“The results were excellent,” says Vanacore. “We even simulated the restart after long inactivity at polar temperatures. The engine’s responses have exceeded expectations. And its anti-ice system demonstrated a high level of reliability even under such extreme weather conditions where an aircraft in service is rarely found.”
According to Vanacore, this experience is a best practice due to the multidisciplinary nature of the analyses and tests performed. To be successful, it was necessary to plan and adapt according to the local weather conditions, allowing the right amount and temperature of air to be conveyed into the tunnel for each specific test.
“It was a bit like seeking the wind while sailing at sea with your crew. Well, here a team of 20 aviation professionals were seeking the cold and ice. But the level of teamwork, and above all cohesion, during this long and cold race rewarded us with a great success.”
After completing ice testing, the GE Catalyst is entering the home stretch toward installation on Textron Aviation’s Cessna Denali. Read the full story in Aviation Week.