Given how critical the tail rotor is to basic helicopter flight, it is difficult to believe that ground-breaking NASA research on tail-rotor effectiveness (and the loss thereof) could languish in a filing cabinet at the Langley research center for nearly two decades. But it happened.
The Vietnam War was the impetus for the project, where Bell UH-1 Hueys were found lacking tail-rotor effectiveness at critical moments, and the U.S. military tasked NASA with finding a solution. Yet when the war ended, the military's urgency to find a solution to loss of tail rotor effectiveness (LTE) went away and the research sat dormant in a folder.
The material was unearthed in 1998 by Robert Desroche, founder and owner of BLR Aerospace of Everett, Wash., an aerodynamicist and a pilot. And that's how BLR's Fastfin STC was developed. Desroche, whose company holds numerous patents, read a paper written by Henry Kelley, principal researcher on the tail-rotor augmentation project and decided that the research was worth pursuing.
“NASA has a privatization program whereby technologies originally patented by NASA can be made available to U.S. taxpayers through a licensing agreement,” explained Dave Marone, vice president, sales and marketing for BLR. “What BLR did was take the product as conceptualized by Henry Kelley and his team at NASA and put it through extensive flight testing and refinement to make it into a product that could be commercialized and STC'd for aircraft.”
That's how Fastfin was developed. The dual tailboom strakes originally patented by Kelley were mated to a unique, sculpted vertical fin designed by Desroche, which allows for the sail area necessary for weathercock stability of the aircraft without having an undesirable physical impediment to the airflow.
Now, regardless of what direction the wind is coming from, the pilot gets a managed laminar flow over the tailboom, instead of a disrupted, inefficient flow. “The Fastfin-equipped helicopter's off-wind performance compared to a stock Bell 412, for instance, is a night and day experience,” explained Marone. Fastfin is STC'd for Bell 204, 205, UH-1, 212 and 412 aircraft.
The safety enhancements of Fastfin would be reason enough to apply the STC, but with better aerodynamic performance come other desirable results, namely, increased performance. “Depending on the weight of the aircraft and the operating altitude, the fuel savings will be 2.5 to 6.5 percent while in the hover [not in forward flight],” said Marone, referring to the Bell 412 with the Fastfin mod.
“Along with that we can increase useable operational loads,” he said. In this case we are improving yaw control [permitting an increase in useful load] in the neighborhood of 12 percent and 12 percent of 11,900 lbs is about 91 percent of its [previous] operationally useful load at that altitude. That is the logic.”
Marone reported at Heli-Expo 2012 that the company has sold nearly 100 Fastfin mods for the Bell helicopters since it was certified in December of 2010. Those who would like to learn more about the engineering technology that went into the STC can meet Henry Kelley at the BLR Aerospace booth (No. 8846) in Exhibit Hall F.