The US Coast Guard is to flight-test tailboom strakes developed by Boundary Layer Research (BLR) to increase tail-rotor control margin on its Eurocopter HH-65 Dolphin helicopters. The strakes promise to overcome an uncommanded left yaw condition that has caused several aircraft mishaps, as well as provide additional tail rotor control authority to cope with a planned uprating of the helicopter's twin Honeywell LTS101 turboshafts.
Uncommanded left yaw can occur when low pressure on the right side of the tailboom, caused by main rotor downwash, overpowers the helicopter's fenestron tail rotor. BLR's dual strakes, running along the top and bottom of the boom, destroy the low-pressure region, increasing anti-torque control margin and reducing pilot workload. The NASA-developed technology has previously been applied to the Bell 205, 212, 412 and UH-1 family.
The HH-65 programme is in three phases over 12 months, says Dave George, BLR's rotorcraft division manager. The USCG has supplied a tailboom for ground tests leading to flight trials this year. The company will then supply five strake kits for extended evaluation.
Source: Flight International
