Eurocopter designs all of its helicopters with fenestrons, which are tail rotors enclosed in ducts in line with the fuselage, to make their tail rotors quieter and safer. The tail rotors of most other manufacturers' helicopters are mounted on the side of the rear fuselage and so represent more of a safety hazard. The fenestron on this Eurocopter EC 155B1 medium-sized civil helicopter can clearly be seen. The aircraft is pictured flying over the Mediterranean Sea at Menton on the border of Provence in southern France and Liguria in Italy.
Credit: Eurocopter/JÃ©rome DEULIN
Many people have never flown in a helicopter and consider them playthings of the rich. But these vertical-takeoff, vertical-landing aircraft impact our lives in many surprising ways.
"The public isn?t aware of all the things helicopters do that affect their lives on a daily basis," said Matt Zuccaro, president of the Helicopter Association International (HAI).
Anyone living in a big U.S. city is used to the sight of news and police helicopters buzzing around and knows helicopters are used in search-and-rescue operations at sea and on mountains. But fewer people, perhaps, are aware of the major part helicopters play in providing pemergency medical services and in fighting forest fires.
People know that top executives often fly in helicopters, but they may not realize the significant economic benefits that helicopters create by improving business productivity, said Zuccaro.
Intensive use of helicopters by the offshore oil community also benefits the public. "Helicopters provide a major contribution to the oil industry in producing and delivering in a timely manner the petroleum products that we use every day," said Zuccaro.
They can have a positive environmental impact. The U.S. timber industry often uses large helicopters such as the Boeing 234 Chinook to lift logs from remote sites, "obviating the need for cutting logging roads," he said.
But their ability to take off and land vertically in city centers or inaccessible places comes at a price. Helicopters are noisy, relatively slow and fuel-hungry. They are expensive to operate and haven't yet proved suitable for city-to-city service.
However, the helicopter industry is working on new technologies and operational procedures to make its aircraft more community-friendly and efficient.
HAI's "Fly Neighborly" program, used successfully in New York for years, ensures that helicopter operators consult with communities to locate heliports and develop routes in ways that minimize the environmental impact of their aircraft.
One area in which manufacturers are concentrating their technological development efforts is in reducing the aerodynamic noise made by helicopters' main and tail rotors. Aerodynamic noise is responsible for most helicopter noise that people on the ground hear.
Manufacturers are now designing new helicopters with four or more main rotor blades. This avoids the distinctive chopping noise that the older, twin-bladed Bell UH-1 "Huey" helicopter makes, which can be heard miles away.
Meanwhile, Eurocopter uses a technology called the "fenestron" to reduce the noise made by tail rotors. The tail rotor produces a small portion of a helicopter's lift, but its main roles are to prevent the helicopter's fuselage from spinning around (by counteracting the torque produced by the main rotors) and to provide side-to-side control of the aircraft.
The fenestron is a tail rotor enclosed within a duct and positioned in line with the fuselage. This reduces noise and improves safety. Eurocopter also spaces its helicopters' tail-rotor blades unevenly, reducing "phase modulation" effects to make the tail rotors quieter and more pleasant-sounding.
Manufacturers are now using composite materials in helicopter fuselages and rotor blades to make their aircraft lighter and more fuel-efficient. But what prevents helicopters from going faster is "retreating blade stall."
In a traditional helicopter, the main rotor blades revolve horizontally around a central point and move forward and backward during each revolution. They produce most of the lift and all of the thrust that moves the aircraft.
When the helicopter reaches a certain speed, its forward movement negates the lift produced by the backward movement of each rotor blade, causing the blade to stall. That speed -- which varies depending by helicopter model but usually is less than 200 mph -- represents a speed barrier.
However, in a tilt-rotor aircraft such as the Bell/Agusta 609, the main rotors become propellers. The retreating blade problem disappears and the aircraft can fly much faster.
Active blade control is also being studied closely. This technology seeks to control individually the angle at which each rotor blade meets the air during each part of the rotation cycle, rather than controlling the angle communally by means of a "swash plate" attached to the rotor hub, as happens now.
Another approach, being flown experimentally by Piasecki Aircraft on the X-49A (a modified Sikorsky UH-60 helicopter) is to make the tail rotor a "vectored thrust ducted propeller" that faces aft and drives air past a rudder and tailplanes.
This air provides thrust to move the helicopter, provide vertical lift, counteract the main-rotor torque and allow the rudder and tailplanes to control directional stability.
Most U.S. helicopter flying is performed at altitudes below 5,000 feet and outside the National Airspace System. HAI is working closely with the FAA to install new ADS-B navigational and traffic/terrain-avoidance equipment in all oil-support helicopters operating in the Gulf of Mexico, an area in which most airspace is not radar-controlled.
Similar initiatives will follow in Alaska and Hawaii. By means of this and other initiatives, HAI hopes to reduce the worldwide helicopter accident rate by 80 percent within a decade.
Increasingly, organizations are realizing the benefits helicopters can offer. At the recent Heli-Expo show in Orlando, nearly $700 million of orders were placed. "The industry is extremely healthy," said Zuccaro.