What those Heli-Expo show attendees couldn’t have known but which they came to realize quickly enough was how quiet the EC 135 is in flight compared with many other helicopters. The remarkable reduction in noise footprint that today is an EC 135 hallmark was achieved in several ways, the most important being the technology incorporated into the helicopter’s fenestron tail. Sud Aviation, later bought by Aerospatiale, developed fenestron technology (like many aviation terms, the word fenestron comes from French — translated, it means “small window”). The EC 135 made use of an all-new type of shrouded tail rotor with 10 unevenly spaced anti-torque blades and additional fixed stators positioned in such a way that they reduced takeoff and overfly noise that can be measured in decibels. Eurocopter was able to achieve further gains by commanding the EC 135’s fadec to operate at variable main rotor speeds. The result is the quietest helicopter in its class, with a noise level that is 6.5 dba below current International Civil Aviation Organization standards.
In fact, when an EC 135 flies overhead, people on the ground barely take notice. The sound is a whisper compared with the window-rattling thrumming of some larger helicopters. Likewise, the acquisition and operating costs of the EC 135 compare favorably against the competition, and the exceptional handling qualities and single-pilot IFR capability contribute to a helicopter that, quite simply, can do everything it is supposed to do and more. These are the reasons Eurocopter has high hopes for a rebirth of sorts for the model in the United States as a powerful player in the VIP helicopter market, which traditionally has been dominated by bigger helicopters. It will be a tough market to crack: Of all the EC 135s produced to date, only about 17 percent of them have been outfitted with executive interiors. Of the 235 EC 135s operating in the United States, only a small percentage of them are configured for VIP use. But with the right marketing, Eurocopter believes this number can rise — perhaps significantly so — allowing the manufacturer to capture perhaps 30 percent or greater of the executive VIP market across its product line.
Flying the EC 135
During a recent demo flight around Manhattan, I came away impressed by the EC 135’s stability and maneuverability, both thanks to its Bolkow-inspired rigid main rotor. Eurocopter pilot Dave Burchill first took me through the engine start procedure, which is about as easy as pushing a button thanks to the fadec, which reduces the pilot’s primary job to monitoring the gauges while the computers do the rest. The main avionics suite is supplied by Thales, with GPS navcom receivers from Garmin and a three-axis autopilot with stability augmentation. On takeoff, Burchill demonstrated an interesting technology Eurocopter has incorporated into the EC 135. To enable the helicopter’s high useful load, the EC 135 includes a takeoff and landing mode called HI NR (for high rotor speed), which automatically raises the rotor rpm to 103 percent. To activate the HI NR capability, the pilot simply presses a button on the panel. When carrying a lot of weight, this faster rotor speed gives the fenestron more effectiveness by turning the tail rotor faster, allowing the pilot to maintain control at higher weights than would otherwise be possible. Above 50 knots, the HI NR system automatically shuts off. On approach to landing, it re-engages when speed drops below 50 knots.