Sometimes odd is, well, better. That is certainly true when it comes to propellers, if you ask Dave Marone, vice president of sales and marketing for mod-specialist BLR Aerospace (Booth N4916), which holds a supplemental type certificate (STC) for winglets for the Beechcraft King Air. He is here at NBAA 2015 to show attendees precisely how productive the company’s partnership with European propeller manufacturer MT-Propeller has been this past year.

“BLR went shopping for prop technology as a practical complement to our winglet system,” Marone told AIN. “What we wanted was to marry a low-vibration, low-noise prop to our winglet STC, and really make the King Air more comfortable for passengers, and a more efficient short field performer for operators.”

MT-Propeller (Booth C13010) is no novice when it comes to building propellers for turboprop engines. The company has provided a capable propeller for the PC-12 and has 10 years of research invested in marrying its propellers to turbine engines. “The King Air series was, in my mind, the next logical step,” said Marone.

The five-blade, scimitar-shape Whisper Prop that MT provided to BLR Aerospace is unique in composition, shape and size. “It has a laminated hard-wood [natural composite] core that dampens vibration,” explained Marone. “The swept-blade scimitar design is more efficient because, as your blade velocity approaches the speed of sound, the swept design allows the undesirable build-up of air pressure in front of the blade to shed easier than it would with a constant-chord design.”

As for the five blades, an odd number reduces harmonic resonance between the blades, as compared to a four-blade or two-blade propeller. It also means blades can be shorter and still have enough surface area to absorb the horsepower coming out of the engine. Total amount of thrust divided by five (as opposed to four or three) means that as each blade passes near the ground it is creating less vacuum; the propellers are less likely to suck up foreign objects on a rough field with more blades on the prop. Beyond that, the Whisper Prop’s smaller propeller diameter provides more ground clearance. It is also quieter than longer-blade propellers because it allows for a slower blade-tip velocity.

Now that BLR has sold the first 10 Whisper Prop/winglet systems and five are flying, it can validate real-world performance with confidence.

“The customers are getting what they were looking for. An excellent performing prop with superior ergonomics and improving ride quality,” Marone told AIN. “The combination of the winglets and Whisper Props on the Beech King Air C90 is a reduction of 30 to 50 percent of measurable noise/vibration in the aircraft cabin [in decibels, when compared to the standard King Air C90GTx propeller], bringing it down to jet-like levels. The King Air 350 lapse time from brake release to Vr is reduced significantly, making it an even better performing short-field aircraft,” he said. Performance numbers in the field show that the winglet/Whisper Prop combination reduced takeoff ground roll in the King Air 350 by as much as 10 percent.

In other news BLR announced that its FastFin tail rotor enhancement and stability system is now FAA certified (EASA certification is imminent) on the AgustaWestland AB412 helicopter, the license-built version of the Bell 412, for which BLR already had a FastFin STC. The FastFin upgrade, made up of two parallel stall strips (Dual Tailboom Strakes) and a reshaped vertical fin, improves tail rotor authority and wind azimuth tolerance. Nearly 900 FastFin systems are installed on Bell 204, 205, UH-1, 212 and 412 models, and the system is factory standard on new Bell 412EP and EPI helicopters.

The company’s FastFin kit is also being designed for use on the Cobra AH-1 attack helicopter as part of a performance improvement suite that should increase hover loads on the helicopter by as much as 1,000 pounds, according to Marone. It will be available as a commercial off-the-shelf package. Also being tested with the system is the AS350 helicopter. The company expects FAA Part 29 certification for both aircraft in late 2016.