Honeywell’s AS907 gets nod, production begins

 - April 23, 2008, 10:19 AM
Starting with its first “clean sheet” engine design since 1972, but minus one of the two original customers, Honeywell brought the new AS907 to dual FAA engine and production certification in June, just 44 months after the project was launched.
The sole current customer for the 7,000-lb-thrust-class turbofan is Bombardier for its Continental super-midsize business jet, scheduled to go into service in the middle of next year. But Mike Redenbaugh, Honeywell v-p and general manager of propulsion systems, said his company is “actively pursuing” additional applications.

Another version–the AS977–was to have gone on the four-engine Avro RJX85 regional airliner, but the program was abruptly canceled by BAE Systems last November. Honeywell said those engines are being returned and will be used for endurance testing and for parts.

The AS907 is flat rated to 6,500 lb of takeoff thrust for longer life, but Honeywell said the engine has growth potential of 20 to 25 percent to about 9,000 lb of thrust. The basic engine can be tweaked about 10 percent, but most of the additional power would come from more low-pressure compressor stages.

As for other business aircraft applications, Rob Wilson, v-p of the AS900 program, said Honeywell has had “quite a bit of discussion” with “all the normal cast of characters” about the same super-midsize class of airplane that the Continental is in.

“I can tell you that there is quite a bit of interest around the fact that the engine is certified, and we’ve demonstrated quite a high level of durability and reliability already,” he said. “There is a lot of interest around the economics that we can provide any platform–not only new platforms but re-engining existing ones.” He claimed there is “not a guy out there [we have] talked to” who has not expressed “quite a bit of interest” and taken the AS900 series into consideration in their product planning portfolio.

The AS900 program has accumulated more than 18,000 hr of test operation, and Honeywell expects to accumulate more than 20,000 test hours by the time the engine enters service next year. In addition to the flight testing at Bombardier, Honeywell has flight tested the engine on its Boeing 720 flying testbed.
Earlier this spring the AS907 passed bird ingestion, blade out and the 150-hr endurance tests. Honeywell said that in each of the key FAA tests the engine demonstrated its “robust power capability and design integrity.”

Disassembly and examinations after each test validated the AS907’s “simple design,” which includes compressor blisk manufacturing technologies and two-bearing sump layout, the company said. Under the new bird-ingestion standards, the engine must ingest the bird and still perform engine-out, go-around, power-up and power-down, Redenbaugh pointed out.

“We have 18 AS907 engines in test, and an additional 10 engines are in flight test at Bombardier, where they have accumulated more than 675 aircraft flight test hours–
or 1,350 engine flight test hours–on the Bombardier Continental,” said Redenbaugh.

Honeywell will begin building the first production AS907 engines next month, with deliveries to Bombardier planned in December. By 2004, the first full year of production, it expects to be churning out 60 engines a year. Bombardier has firm orders for 125 Continentals, including 25 from its Flexjet fractional operation.

Wilson said the company is also looking at applications outside the business jet community, such as unmanned aerial vehicles (UAVs). He also revealed there is “emerging discussion” with Japan and other countries about a twin-engine regional jet carrying about 30 passengers. He said the now-defunct Avro RJX program already proved that the design was deemed capable of meeting the rigors of regional service.

According to Honeywell v-p of engineering, technology and program management Peg Billson, in addition to expecting the engine to perform, customers now more than ever expect low-cost, excellent reliability and durability and simple maintenance, which have been design objectives since the AS900 program’s inception.

“To quote the FAA, ‘Honeywell has pushed the envelope for a thoroughly tested product during certification,’” she said. Along with the flight testing, Honeywell performed accelerated life testing on all the line-replaceable units (LRU), so that the engine will enter service with second- and third-generation hardware.

“And we all know that it is the LRUs that cause most of the reliability issues,” Billson added.

The AS900 was announced at the 1998 Farnborough Air Show and launched at the NBAA Convention later that year. At that time, Honeywell (then AlliedSignal Aerospace) had scheduled certification of both the AS977 and AS907 in the first quarter of 2001. Last May the company postponed the certifications of the two engine models to “harmonize” the approvals with those of the airframes; the AS977 was planned for certification in the first quarter of this year and the AS907 in the second. BAE systems subsequently canceled the RJX program on November 27 last year, making certification of the AS977 moot.

The engine design was driven by low cost of operation and low initial cost, said Wilson. He said the AS900 family of engines will be roughly 20 percent lower than current engine offerings in dollars per pound of thrust and 30 to 40 percent lower in maintenance costs per hour.

“So we’re talking 20 to 40 percent lower initial cost and operational cost,” he noted. “This recognizes a new paradigm of value for the customer, which has been our whole focus since day one.” The engines will be priced in the $850,000 to $1.1 million range; the development cost was $350 million.

Honeywell received FAR Part 33 certification for the engine alone. Because Honeywell and its major subcontractor–GKN of the UK–are supplying the entire nacelle and engine build unit, including the target-type thrust reverser, it is taking joint Part 25 certification with Bombardier.

With a bypass ratio of 4.2:1, the AS907 is configured with four axial compressor stages, including two variable-geometry stators, a single centrifugal compressor, an effusion-cooled combustor, a two-stage high-pressure turbine and a three-stage low-pressure turbine driving the high-efficiency, wide-chord, 34.2-in. damperless fan. Honeywell said that all discs in the AS907 are designed for a minimum durability of 15,000 cycles.

The axial compressor features integrally bladed rotors for lower parts count, simplified maintenance and improved performance, the company said, and the effusion-cooled combustor provides uniform temperature profiles and reduces the output of undesirable emissions.

The AS907 has a dual-channel Fadec and what Honeywell product line manager John Ricciardelli described as a “very user friendly” diagnostic and fault-detection system. He said the engine is designed for on-condition maintenance and maximum on-wing maintenance.