Smyrna Air Center, a full-service FBO based at Smyrna/Rutherford County Airport near Nashville, Tenn., is showcasing its new GE H80 engine conversion option here at NBAA’12. While Smyrna (Booth No. 4304) has offered the Walter/GE M601E-11A turboprop engine as part of its Power90 conversion program since 2006, company representatives say that GE’s new H80–a redesigned version of the M601 series certified earlier this year–will provide even greater performance benefits to King Air 90 series owners.

“We’ve done some flight tests with an H80 on right side and [M601E] -11A on left side,” said Smyrna’s director of business development Dan Sigl, who has been involved with King Air engine upgrades since 2001. “At 34 degrees Celsius, the King Air C90 climbed from 532 feet field elevation to 28,000 feet in 21 minutes and was still capable of climbing at 800 feet per minute at that altitude.” According to Sigl, a typical King Air C90 with the original Pratt & Whitney PT6A-20 or -21 engines climbs about 50 fpm at 26,000 feet.

More power at altitude translates to better hot-and-high performance. While the PT6A-20/21 will produce its rated 550 shp near standard conditions, the 800-shp H80 can produce 550 shp at 10,000 feet at 105 deg F, allowing the pilot to take off with full power even in hot-and-high conditions.

The M601E-11A is rated at 705 shp. According to GE marketing materials, the difference in shaft horsepower between the M601 and H80 comes from a variety of new designs and materials, such as incorporating 3-D aerodynamic design and advanced materials into the compressor stages and turbine of the engine’s gas generator. The H80 replaces individually bladed compressor disks with an integrated blisk design in the axial compressor stages, and materials with higher temperature capabilities have been incorporated into the turbine nozzle guide vanes of both the gas generator and power turbine. In addition to boosting horsepower, these improvements over the original 1975 M601 design result in increased fuel efficiency indicated by the H80’s specific fuel consumption of 0.585 lb/shp/hr compared to the M601E-11A’s 0.65 lb/shp/hr.

Both the M601 and H80 engines share key characteristics that reduce maintenance costs compared to the PT6. The GE engines run fuel through diffuser “sling” rings on the center shaft, eliminating the need for recurrent fuel-nozzle maintenance and reducing susceptibility to flameout during flights in heavy moisture. Auto start and electronic limiter systems work together to eliminate hot starts, which means these engines do not require hot-section inspections during overhaul cycles.

“When you start a GE engine, you go: master on, boost pumps momentary on/off switch, put fuel selector in the detent and then it’s hands-off,” said Sigl. “The engine starts itself. The engine limiter is engaged when you hit the start switch. If it detects a spike in ITT [inter-turbine temperature], it will shut the fuel off, continue motoring to cool off and then shut the engine down. So you eliminate hot starts. There’s no more trying to get the fuel in at the right time and you don’t have to worry about the thing going up to 1,090 degrees. These engines will start at 560 or 570 degrees. [Normally] in a turbine, that’s making ice.”

A Conklin & de Decker financial analysis of the Power90 GE M601E-11A engine conversion prepared for GE Aviation in 2010 estimated nearly $300,000 in savings at overhaul compared to the PT6 based on no mid-life, nozzle or hot-section inspections required. The H80 would likely result in even more overhaul savings when calculated per hour since its TBO is 3,600 hours versus the M601E-11A TBO of 3,000 hours.

Smyrna holds the STCs to perform the M601 or H80 engine conversions on King Air A90, B90, C90 and E90 models. Initial cost of the twin-engine conversion is approximately $995,000 for H80 engines and $695,000 for M601 engines, but Sigl is quick to point out that this conversion list price doesn’t include rebates for current equipment. “The conversion kit includes two new engines with two-year warranty and five-bladed propellers,” said Sigl. “We will rebate the value of the replacement equipment, such as the engines and props, which could be as much as $350,000. PT6A-28s with some hours on them could fetch $300,000. So that reduces the actual outlay.”

Because the H80 is about four inches longer than the PT6, the conversion requires some cowl modification. Other modifications must be made to the fire shields, engine mounts, certain cockpit switches and the addition of the limiter annunciator.

Sigl predicts the H80 engine conversion will be popular with twin owners trading up from a Piper Cheyenne or Cessna 340 to the faster, roomier King Air. “You can take a 10- to 12-year-old airplane, put these engines on it and you’ll have a better performing aircraft than new,” Sigl said. “With these engines and GE’s [fixed-cost maintenance program], you can take someone who is coming out of a twin-engine piston and stick them in a King Air, and he knows exactly what his cost will be.”