Safran Microturbo’s new e-APU60 auxiliary power unit is set to enter service by year-end on AgustaWestland’s new AW189 helicopter. Currently, the company had delivered 10 production APUs to the rotorcraft manufacturer and now it is pursuing other business aircraft applications, including small- and medium-sized jets and other rotorcraft.
Developed to meet the needs of new-generation “more electric” and eventually “all-electric” aircraft, the compact unit promises to deliver a step change in power-to-weight ratio, improved reliability and lower cost of ownership. On May 31, the e-APU60 achieved certification by EASA under Category 1 rules for essential use (FAA TSO C77b) and it can be installed as part of any new aircraft program.
As part of an APU family delivering between 15 and 90 kW of electrical power, Microturbo has also started work on a bigger e-APU120 that will serve larger business aircraft and regional airliners. The company is part of French aerospace group Safran (Booth No. N5506), which also produces the Silvercrest turbofan.
Seven APUs were used for the certification tests and seven more units were involved in specific testing to integrate the powerplant with the AW189 twin. Collectively these totaled more than 1,000 hours and 5,000 cycles of testing. According to Microturbo CEO Pierre-Yves Morvan, the equipment has behaved exactly as it was designed to do with further maturation tests still under way. “We found very good [performance] results from the testing and there were no significant discoveries,” he explained. “It certified very easily.”
In addition to ground starting the AW189’s main engines, the e-APU60 supplies power to the helicopter’s electrical systems and runs the cabin air conditioning. Crucially for flight safety, it also can restart the main turboshafts in flight and provide backup electrical power throughout the flight envelope.
According to Morvan, one clear advantage of the e-APU technology is that the system does not require a lot of tubing to connect to the main engine (as is the case with conventional APUs). “There are not as many valves and not as much hot air, which overall means better reliability and weight, and the ability to achieve a much better power-to-weight ratio in a more compact unit, which all has a significant impact on the aircraft manufacturer,” he told AIN.
Microturbo is convinced that airframers will increasingly embrace the electrical APU technology embodied in e-APUs such as the Microturbo units. Boeing’s new 787 widebody airliner already uses an e-APU (provided by Pratt & Whitney) and Morvan believes others will follow suit as the expansion of electrical power for aircraft systems gathers pace.
“Some OEMs are very used to starting engines with air and so many of the design standards are built around this approach [as opposed to using electrical power],” said Morvan. “They need to see that there will be a significant gain for them and when they look at the weight and reliability improvements I think they will make the jump,” he said.
The e-APU also promises to contribute to reducing aviation’s environmental impact in terms of both engine emissions and noise. “APUs are used for a significant amount of time on the ground and operators want this to happen with far less fuel burn and noise,” concluded Morvan. “The e-APU is really quiet and this is a big breakthrough in noise levels. This is especially important for business jet operations because operators want their customers to be as comfortable as possible and not disturbed by engine noise.”