Carson Helicopters has kept blade planform but changed profile to make the tailrotor more efficient.

Perkasie, Pa.-based Carson Helicopters is developing a composite tailrotor upgrade for the Sikorsky S-61 medium twin. Thanks to a more efficient design, the new tailrotor should yield an increased payload at altitude. Testing is underway. Speaking in September at the European Rotorcraft Forum 2010 in Paris, company president Frank Carson said that the current five-blade tailrotor is not very efficient. Current blades are rectangular and not twisted. According to Carson, the first objective for the new blade is increased yaw control at high altitude. Second, it will use less power. Finally, no modification should be required to retrofit the new blades.

The first blade prototype led nowhere. It exhibited “very high control loads,” Carson said. One reason was a mismatch of the inertial properties of the new composite blade, when compared to the original metal blade. Another source of the problem was due to a small contour error in the blade mold.

What should be the final design now retains the current planform. Relative to the original design, airfoil profile has changed and Carson has introduced an eight-degree twist. Some ground tests have already shown that control loads are no longer an issue. Fatigue tests have been completed. Flight tests were due to begin this fall. Company engineers hope that, by requiring less power, the new tailrotor will add up to 300 pounds of lift to the main rotor.

Carson Helicopters is also developing an engine upgrade, from the CT-58-140-1/2 to the T58-GE-16. Engine power will increase from 1,400 to 1,870 hp, which makes a more efficient tailrotor all the more important. (From November 2010 Rotorcraft Report)