Honeywell's AS907 Heading for New Applications

Honeywell's new AS907 turbofan engine that powers Bombardier's Continental may be heading for new applications.

The "usual cast of characters" among business jet manufacturers is studying the AS900 family for new programs and potential re-engining of existing models, Honeywell AS900 program manager Rob Wilson recently told Show News. It might also find an application on unmanned aerial vehicles (UAVs), he said.

Interest centers on the fact the engine is now certified, and on the low cost, greater reliability and low operating economics the engine offers.

The 8,000-pound-thrust class engine is flat-rated to 6,500 pounds takeoff rating for the Continental. It is set to enter service on that aircraft by summer 2003.

The simultaneous award by the FAA in June of the AS907's type and production certifications "is a phenomenal achievement," according to Peg Billson, vp for engineering, technology and program management, coming just 44 months after the program was launched. The event marked a significant milestone in engine development for business aircraft-and the culmination of a $350 million investment by the Phoenix-based company. But the significance goes deeper than that.

Honeywell set hitherto unattainable targets for the AS907: It had to show a 30- to 40-percent improvement in cost of operation, cost 20 percent less in dollars per pound of thrust, and enter service with on condition maintenance, 3,500 hours to first inspection, and 7,000 hours to overhaul-about 14 years in the life of a typical corporate business jet. It would also have 30 percent fewer parts than comparable engines, and every line replaceable unit (LRU) could be removed and replaced in less than 15 minutes.

The engine will enter service with an unprecedented 20,000 hours of testing and 50,000 mission cycles under its belt. Flight test hours now total more than 4,000, and one engine has over 3,500 hours in "severe" test conditions.

For the first time the LRUs supplied by outside vendors were subjected to the same severe testing. "We put them through a process called shake and bake," said Wilson. "We subjected them to two to three times what they would experience in service, shaking them, putting them through thermal cycles of minus 75 degrees to 200 degrees, and then activating them.

"We broke 10 components in 24 different ways, and the electronic control unit eight times. We will continue testing through October," Wilson said. Ironically the ECU was a Honeywell component.

Most of the 38 LRUs on the AS907 are now second generation, shake-and-bake-proof units, redesigned to not let the engine down in service, he added.

Honeywell believes the AS907 is the first business jet engine to pass the new FAA bird ingestion tests. Conducted in December and March, respectively, these involved shooting a four-pound bird into the engine at a speed of 220 knots, and shooting two one-and-one-half-pound birds into the engine at 170 knots to simulate an airborne encounter with a flock of smaller birds.

FAA certification standards require the engine to be able to shut down safely after the four-pound bird strike, but the small-bird encounter is more challenging. In addition to continuing to produce at least 75 percent thrust, the engine must respond to throttle transients after the small-bird strike, simulating an aircraft go-around after ingesting birds. The AS907 continued to produce 75 percent thrust and responded well to throttle movements.

Not the least of Honeywell's hurdles was preparing the final paperwork for the FAA-certifying the AS907 required 350,000 double-sided pages of documentation.

Honeywell is now working on expanding the AS900 family. Already running is a core demonstrator for the AS903/4/5 in the 4,000- to 6,000-pound-thrust range.

By John Morris