Honeywell will announce a new APU at the NBAA Convention this month aimed at turboprops, light jets and small helicopters. The company said the RE-50 is the first oilless and gearless APU with an integrated generator on the same shaft, and at 50 pounds it is about one-third the weight of Honeywell’s RE-150.
“It can be used by anybody flying into a remote airfield to run the air conditioner, assist in main engine start and anything to maintain the aircraft without having to hook up to a ground cart,” said Roger Wolfe, v-p and general manager of Honeywell’s airframe systems business. “Anybody who needs electrical output generation in the 250-amp range or less.”
Working with its automotive group, Honeywell has developed an “air bearing” for both turbocharger and APU applications. Therefore, these products do not require oil for lubrication and are designed to stay on-wing for three to four years before requiring any type of maintenance.
Because the generator is on the same shaft and spinning at the same speed as the APU, it also has no gears that would need a lubricant. The APU with the integrated generator will weigh about 55 pounds installed.
“We use a direct-drive shaft coupling that is a proprietary design that spins the generator and provides the electrical output,” Wolfe explained. “While it is rotating there is no friction except air. It needs to spin up to speed and then the air is generated as a function of its own speed, so there is virtually no contact.”
Although Honeywell has been working on an air bearing for many years, it hadn’t been able to introduce a practical version because of the load requirements. Wolfe said the newest design solves all of the temperature and load requirements. The company has also been developing gearless technology for “quite some time,” but the RE-50 is the first product launch.
Honeywell would not disclose the price of the RE-50 because it is working with several OEMs that “would not take too kindly to our releasing pricing information,” said Wolfe. “It’s going to be significantly below any of our current offerings. It’ll be very economical for an operator who wants to retrofit one. It certainly is going to be priced to be very attractive to all of the OEMs.”
In addition to current applications such as the King Air, Citation Encore and Citation Bravo and light helicopters, Wolfe said it could be used on the numerous very light jets now under development. And Honeywell continues to get requests for other uses, including military land-based applications. “We continue to be surprised where people want to put one of these,” Wolfe said.
The RE-50 initially will be offered for ground support and ground start. Later it will be adapted to support in-flight operations. It also produces a small amount of bleed air for other applications. Larger versions using some of the same technology and the resulting reduced parts count will be developed for the new Boeing 7E7.
“We do intend to scale this up in later models so that it brings the technology to the larger customers, per se,” Wolfe said.