Canada’s National Research Council has won a patent on “an active and adaptive rotor-blade control system called Smart Spring,” which is designed to reduce the noise and vibration when rotor blades interact with the vortices shed by the tip of the preceding blades. Previous engineering approaches, according to NRC, have attempted to alter the varying aerodynamic load on the blades to reduce the onset of this vibration. NRC took a different approach with Smart Spring.
The system consists of accelerometers, a signal-analysis processing computer and piezoelectric actuators used to exert forces in response to an applied voltage. The piezoelectric actuators are located near the blade root, where the loads are highest and damping forces have the greatest effect. A signal-processing computer analyzes the output from the sensors to measure the amplitude and mode of blade vibration, and it uses this information to control the piezoelectric actuators that change the blade torsion stiffness.
In another unique helicopter development, the Ottawa-based Institute for Aerospace Research (IAR) claims it made the first complete helicopter flight last month using only a helmet-mounted enhanced synthetic vision system (ESVS) to create a totally artificial environment. According to IAR, the flight, in a Bell 205, effectively turned zero-zero IMC into what it called Virtual VMC.
With Virtual VMC, the helmet-mounted sensors and vision system track head movements mechanically and fuse sensor imagery with a computer-generated virtual world to replicate the actual flight environment. The look-around capability of the helmet is said to be superior to existing head-up display systems and panel-mounted graphics by allowing the ESVS to display the virtual terrain on all sides of the aircraft. IAR expects an affordable product within five years.
Meanwhile, after eight years of “relatively conventional service” as a research helicopter, IAR’s Bell 412 advanced system research aircraft (ASRA) is now entering service as a fly-by-wire platform. Outfitted with four specialized control actuators, numerous sensors, parallel hydraulic systems, custom-designed control panels, advanced hardware and software systems and an impressive wiring array, the born-again 412 is touted by IAR as “the most flexible flying machine in the world.”
Carcinogenic Landing Gear
In other programs, the NRC is leading efforts to come up with an alternative to hexavalent chromium for providing landing gear with protective electroplating. The current coating has been found to be carcinogenic and can also cause perforated nasal passages and skin rashes, NRC representatives said. The Environmental Protection Agency is expected to impose stricter limits on its use, according to the council.
The National Research Council’s development is focused on a ceramic/metal composite coating, applied using a high-velocity oxy-fuel thermal spraying process.