Microturbo is ground testing its e-APU, a new auxiliary power unit designed for new-generation business aircraft that are expected to need more electrical power. The company projects certification and first deliveries in early 2012.

The test program started in Toulouse, France, in December. Trials have focused on control of the APU and its thermal and dynamic performance. According to Microturbo commercial director Jean-Baptiste Jarin, dynamic characteristics are meeting design expectations. The e-APU has already supplied up to 60 kWe (kilowatt-electric) in electrical power on the test bench.

“The e-APU’s high-pressure cycle is based on proven technologies that bring remarkable reliability and performance,” Jarin told AIN. The turbomachinery is made of a single-stage centrifugal compressor and a two-stage turbine. According to the French company, the compressor and turbine are similar to those of the Arrius turboshaft engine for helicopters produced by its Safran group sibling Turbomeca. 

Further tests this year will focus on the e-APU’s combustor, blade-out retention, noise and endurance. The company plans to demonstrate a 41,000-foot start-up, but the operational ceiling will be 51,000 feet. By 2012, Microturbo plans to log several thousand test hours and cycles.

For five-ton-plus business aircraft, including helicopters, the e-APU will offer an electric power output of 15 to 90 kWe. The core engine will be unchanged for the various power settings, but the electrical equipment and the gearbox  will be adapted to the power requirement. Microturbo claims the e-APU has already been selected for two aircraft programs, which it did not name.

According to Jarin, the e-APU will be better than conventional APUs in both reliability and power-to-weight ratio. The service life of its parts is also expected to be longer, extending its durability.