Helicopter Engines and Concept

Helicopter Engine

The number, size and type of engine(s) used on a helicopter determines the size, function and capability of that helicopter design. The earliest helicopter engines were simple mechanical devices, such as rubber bands or spindles, which relegated the size of helicopters to toys and small models. For a half century before the first airplane flight, steam engines were used to forward the development of the understanding of helicopter aerodynamics, but the limited power did not allow for manned flight. The introduction of the internal combustion engine at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.

Early helicopter designs utilized custom-built engines or rotary engines designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. The single, most-limiting factor of helicopter development during the first half of the 20th century was that the amount of power produced by an engine was not able to overcome the engine's weight in vertical flight. This was overcome in early successful helicopters by using the smallest engines available. When the compact, flat engine was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for larger helicopters.

                                 MD Helicopters 520N NOTAR

Turbine engines revolutionized the aviation industry, and the turboshaft engine finally gave helicopters an engine with a large amount of power and a low weight penalty. Turboshafts are also more reliable than piston engines, especially when producing the sustained high levels of power required by a helicopter. The turboshaft engine was able to be scaled to the size of the helicopter being designed, so that all but the lightest of helicopter models are powered by turbine engines today.

Special jet engines developed to drive the rotor from the rotor tips are referred to as tip jets. Tip jets powered by a remote compressor are referred to as cold tip jets, while those powered by combustion exhaust are referred to as hot tip jets. An example of a cold jet helicopter is the Sud-Ouest Djinn, and an example of the hot tip jet helicopter is the YH-32 Hornet.

Some radio-controlled helicopters and smaller, helicopter-type unmanned aerial vehicles, use electric motors. Radio-controlled helicopters may also have piston engines that use fuels other than gasoline, such as Nitromethane. Some turbine engines commonly used in helicopters can also use biodiesel instead of jet fuel.

Control System

A helicopter has four flight control inputs. These are the cyclic, the collective, the anti-torque pedals, and the throttle. The cyclic control is usually located between the pilot's legs and is commonly called the cyclic stick or just cyclic. On most helicopters, the cyclic is similar to a joystick. However, the Robinson R22 and Robinson R44 have a unique teetering bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead.

The control is called the cyclic because it changes the pitch of the rotor blades cyclically. The result is to tilt the rotor disk in a particular direction, resulting in the helicopter moving in that direction. If the pilot pushes the cyclic forward, the rotor disk tilts forward, and the rotor produces a thrust in the forward direction. If the pilot pushes the cyclic to the side, the rotor disk tilts to that side and produces thrust in that direction, causing the helicopter to hover sideways.

The collective pitch control or collective is located on the left side of the pilot's seat with a settable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively (i.e. all at the same time) and independently of their position. Therefore, if a collective input is made, all the blades change equally, and the result is the helicopter increasing or decreasing in altitude.

The anti-torque pedals are located in the same position as the rudder pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the direction in which the nose of the aircraft is pointed. Application of the pedal in a given direction changes the pitch of the tail rotor blades, increasing or reducing the thrust produced by the tail rotor and causing the nose to yaw in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor altering the amount of thrust produced.

Helicopter rotors are designed to operate in a narrow range of RPM.The throttle controls the power produced by the engine, which is connected to the rotor by a fixed ratio transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor RPM within allowable limits so that the rotor produces enough lift for flight. In single-engine helicopters, the throttle control is a motorcycle-style twist grip mounted on the collective control, while dual-engine helicopters have a power lever for each engine.

A Swashplate transmits the pilot commands to the main rotor blades for articulated rotors.

Turbomeca

Turbomeca is a world leader in the market of civil and parapublic helicopters (EMS, police, etc.) and holds a predominant position in the market of military helicopters. Turbomeca offers the largest engine power range, from 450 to 3000 shp, and powers the most famous names in the helicopter manufacturing industry, including : Agusta, Boeing, Denel, Eurocopter, Hindustan Aeronautics Ltd, Sikorsky. Turbomeca S.A. also has 2,000 operators. Turbomeca designs, develops and produces the Arrius, Arriel, TM 333, Ardiden, Makila engine families, plus the MTR390 and RTM 322 engines in cooperation with partner manufacturers. Turbomeca engines are modular turboshaft powerplants which facilitate maintenance operations. Turbomeca engines are designed with high power growth potential (up to 20%) for a broad array of applications. Today, Turbomeca offers  two engine families - Arrius and Arriel - for the single or twin-engine light and medium helicopter segment. These engine families, including their derived versions, power a wide range of civil helicopters from Eurocopter (Ecureuil, Dauphin, EC135, etc.), Agusta (A109 Power) and Sikorsky (S76), but also the Eurocopter Fennec and Panther or Agusta A109 Power military helicopters. In the medium helicopter segment, from 5 to 7 tons, Turbomeca is also present in the military market for combat helicopters. It provides the MTR390 for Eurocopter's Tiger and the TM 333 for HAL's (Hindustan Aeronautics Ltd) Dhruv. Turbomeca developed the Ardiden for civil and military applications in this helicopter class. In the heavy helicopter market, the Makila and RTM 322 turboshaft engines power helicopters built by Eurocopter (EC 225/725, Super Puma, NH90), Agusta Westland (EH101) and Boeing (WAH-64).