The National Research Council (NRC) of Canada has for the first time conducted biofuel test flights using chase aircraft to measure the emissions. The campaign is among a number of different projects which the government research and development body is presenting at Farnborough this year.

The biofuel test flights were completed in May and June 2012 using a Canadian-gown feedstock based on brassica carinata. NRC's flight research laboratory employed its Dassault Falcon 20 to test the fuel and a Lockheed T-33 vintage jet trainer to trail the business aircraft and measure its emissions in real time.

Stewart Baillie, director of the institute's flight research laboratory, says the Falcon crew was able to switch back and forth between standard Jet A1 and the biofuel blend with Jet A1. This showed that the biofuel emissions comprised "significantly less" particulate matter, such as black carbon and sulphate, than Jet A1, he says. The results are preliminary and a full assessment is underway before NRC publishes its final report.

The Canadian institute was the first to use biofuel beyond a 50:50 blend ratio, which is currently the maximum-certified limit by the American Society for Testing and Materials (ASTM). While NRC conducted some flights with a standard 50:50 mixture, it also employed a 60:40 blend.

No difference was detected by the pilots when they changed between conventional Jet A1 and biofuel. Bailey says that the crew reported that the aircraft's performance was "indistinguishable" during a range of ground and flight operations, including engine restarts at altitude.

The biofuel - named "Resonance" - has been newly developed by Canada-based Agrisoma Bioscience. The crops used for the NRC tests were grown in the Saskatchewan prairie province in 2011. But this year, Agrisoma says, this has commercially been contracted on a "significant" scale in western Canada. The biotechnology company adds that brassica carinata is ideally suited as a non-food industrial oilseed, because it grows it in semi-arid areas unsuitable for food production with "reduced overall crop input requirements".

Among NRC's other projects is the development of a stochastic model to predict ice build-up on airframe structures more accurately. This has now been licensed to the Montreal-based icing simulation specialist Newmerical Technologies.

The work focussed in particular on the melting and refreezing of water droplets as they move across aircraft structures, for example, wings downstream from the anti-ice systems. "It's all about better characterising the randomness of water in the atmosphere and how it interacts with the surfaces in the aerodynamic flow," says Baillie.

The model allows simulating the formation of rough and discontinuous, three-dimensional ice structures and to predict the density and surface quality of accreted ice.

Ice can build up in unexpected areas, namely the engine core, and this was the focus in another recent project that NRC conducted together with Boeing. Following 46 reported power-loss cases at high altitude since 1990, the researchers proved in wind tunnel tests that ice can build up in the low-pressure compressor (LPC) of gas turbine engines.

The incidents, which included uncommanded thrust roll-backs, flaming-out, stalling and LPC damage through shed ice took place at altitudes above 23,000ft (7,000m), which is usually considered to be the upper limit where liquid water droplets exist. However, they all happened in the vicinity of thunder clouds in tropical regions.

The researchers proved that ingested ice-crystals can partially melt and refreeze on internal components in areas such as ducts, where airflow changes can cause sudden temperature variations. Baillie says this kind of analysis had not been done before but will be useful for regulators in North America and Europe as they begin certifying commercial gas turbine engines against this type of ice build-up this year.

Source: Flight Daily News