FAA certification of BLR Aerospace’s FastFin tailboom modification for the Airbus Helicopters H125 is imminent, with EASA approval to follow shortly after, the company said this week at Helitech 2016. It has already taken pre-certification deposits and has manufactured a number of kits that it will start delivering to customers as soon as authorities issue approvals.
The FastFin increases load and stability in the hover while reducing pilot workload. It provides easier control, especially in crosswinds, and increases right-pedal authority. In most conditions, the kit provides a 10-percent increase in right-pedal power, equating to an increase in useful load of up to 130 pounds in OGE (out of ground effect) hover. For hot-and-high operations, the kit can provide up to 85 pounds extra load in IGE (in ground effect) hovering.

FastFin include a new tailrotor drive shaft cover and a strake on the starboard side of the tailboom. Despite its name, it does not affect the vertical fin or tailrotor itself. In an unmodified helicopter, downward-travelling air from the main rotor creates lift in the hover as it passes on either side of the tailboom. This lift opposes the thrust from the tailrotor on the starboard side of the helicopter, reducing its effectiveness and adding to the effects of main rotor torque. The FastFin strake disrupts this airflow, eliminating the lift.

On the port side of the boom, the new driveshaft cover comes complete with an aerodynamic fairing that enhances the “good” lift that works in the same direction as the thrust of the tailrotor. The fairing provides a laminar airflow around the boom for maximum effectiveness. On the lower side of the fairing is a row of vortex generators that further smooths the airflow as it passes beneath the boom. The modification requires some some structural enhancement, but the kit uses existing rivet holes in the original tailboom. 

BLR delivered the 1,000th FastFin modification for Bell's medium helicopters earlier this year.