The Eurocopter EC135: Melding Form & Function

In the EC135, Eurocopter has created an aircraft that?s at once powerful, capable and economical. Tom Benenson explains the evolution of the market leader.

0404_Lead2_1_F

0404_Lead2_1_F

Eurocopter EC135

When a manufacturer can successfully meld form and function in a product's design the results are invariably aesthetically and economically satisfying. In the mid-1980s, when MBB (Messerschmitt-Bolkow-Blohm) began development of its BO 108, it had no idea how successfully the helicopter's form would let it perform many missions. Initially, the BO 108 was intended as a flight test vehicle to investigate advanced systems. The flight test regime was designed to explore the technical and economic potential of advanced rotor technology, anti-resonance isolation systems, composite structures, cockpit installations and engine integration. Initially, the BO 108 was powered by a pair of Allison 250 C20-R engines.

A second BO 108, this one powered by a pair of Turbomeca TM319-1B Arrius engines, was introduced in 1991. At the time, the design featured a conventional tail rotor, but the BO 108 was soon fitted with a fenestron (a shrouded tail rotor) that had become a popular design feature on Aerospatiale's helicopters. The merging of MBB and Aerospatiale technology in the BO 108 was a result of major corporate shuffling that occurred when Germany's Daimler Chrysler Aerospace, which had acquired MBB, merged with Aerospatiale-Marta of France in 1992 to become Eurocopter, which in turn was a wholly owned subsidiary of EADS, the second largest aerospace and defense company in the world.

The BO 108, an adored stepchild of the corporate marriage, was refined and renamed the EC135 and eventually would become the first helicopter of the merged aerospace giant. In 1994, a pair of preproduction prototypes, one powered by Arrius 2B engines and the other by Pratt & Whitney of Canada PW206B engines, entered the flight test program. The following January, in 1995, the EC135 was introduced at the Helicopter Association International annual convention in Las Vegas.

The flight test program amassed more than 1,600 flight hours before European JAA certification was granted in June of 1996, an impressive short 18 months after its maiden flight; FAA approval followed by the end of that July, and deliveries began immediately afterward. That same year the EC135 was honored with the Flight Aerospace Industry Award for the most innovative helicopter. Within a year of certification, Eurocopter had sold 100 EC135s, and by the time the 100th EC135 was delivered, to the Bavarian police force, the fleet had amassed some 30,000 flight hours.

The EC135, an example of an advantageous combination of form and function, particularly with its large doors on either side of the cabin and the clamshell doors at the rear, immediately became a formidable challenger in the eight-seat, light-twin helicopter market. Its design and features let it carve a wide swath through the emergency medical service, police and corporate helicopter markets. The EC135 has captured some two-thirds of all new helicopter deliveries worldwide in its class of helicopters with a gross takeoff weight of some 6,250 pounds.

Over the years, Eurocopter continued upgrading the EC135. In late 2000, it began certification efforts for the EC135P2, powered by the Pratt & Whitney PW206B2, a version of the PW207 that improved single-engine performance and provided 30-second emergency power. The German certification approval for the new engine option was acquired in mid 2001, and the first EC135 with the Pratt engines was delivered to the Swedish National Police in August 2001. The PW206B2 engines deliver 621 shaft horsepower for takeoff and 562 for continuous power.

Another engine upgrade to create the EC135T2, powered by the Arrius 2B2, became available in September 2002 and also provided improved single-engine power. The Turbomeca Arrius 2B2 engines deliver 606 shp takeoff power and 571 shp max continuous power. Both engine choices, Pratt or Turbomeca, feature full authority digital engine control (FADEC) with manual engine backup as well as automatic start-up and shut-down. In single-engine situations, both engine options provide the same power: 816 shp for 30 seconds; 777 shp for two minutes and 708 max continuous power.

The engines, combined with the helicopter's four-bladed, fiber-reinforced composite bearingless main rotor system, provide impressive performance and power reserves even in single-engine operations. The rotor blades with "advanced tip geometry" in combination with the fenestron with "phase modulation" created by unequal spacing of the 10 blades are said to make the EC135, at 7 dBA below the ICAO limit, the quietest helicopter in its class.

In addition to its quiet, good neighbor qualities, the EC135 features a built-in anti-resonance isolation system (ARIS) that filters rotor-induced vibrations and smoothes out the ride for its passengers. The system keeps the vertical vibration level well below .1G at hover with no increase with speed.

The EC135, a popular choice for medevac and police missions, has a maximum cruise speed of 140 knots, an economical cruising speed of 120 knots and a range, without reserves and at economical cruise speed, of more than 350 nautical miles. Hover ceiling in ground effect at max weight is 10,000 feet; out of ground effect, the EC135 can hover at 7,200 feet.

The versatility of the helicopter is provided by a number of optional cockpit, cabin and cargo compartment configurations. The basic VIP package is a five-passenger arrangement with three rearward facing seats and two forward facing seats. The flight deck can be either fitted out in a conventional configuration or decked out with the "Avionique Novelle" glass cockpit with LCD multifunction displays.

The single-pilot IFR configuration consists of two Sextant SMD45 displays, plus a central panel display system (CPDS). The CPDS includes a vehicle and engine multifunctional display (VEMD) and a caution and advisory display (CAD). The avionics suite is the Honeywell Gold Crown. Additionally, the EC135 features Eurocopter's first limit indicator (FLI) that simplifies engine and torque monitoring so pilots can concentrate on the mission without missing vital information.

By October of 2002, Eurocopter was able to celebrate the occasion of the delivery of the 250th EC135. A year later, in September 2003, the company handed over the 300th EC135, to McAlpine Helicopters, Eurocopter's dealer in the United Kingdom. The 300th EC135 was the 26th to enter service in the United Kingdom, making it the best selling new light twin in the U.K. market.

In January, as a further indication of the EC135's multi-role capability and popularity, the Czech Police Aviation Department in Prague took delivery of the first of eight it ordered. Half of the eight helicopters will be used in the Czech Republic's Integrated Rescue System (emergency medical service, police, fire fighting, mountain rescue and search and rescue); three will be configured for police missions such as surveillance, anti-terrorist and crime fighting; and the last will be reserved for "flexible response, universal-mission" operations with quick-change interiors and equipment. By early this year Eurocopter had delivered 309 EC135s to more than 100 customers in 28 different countries and had a backlog of 45 aircraft.

This company's ability to increase its production rate is a result of the introduction of "station-based production" at the manufacturing plant at Eurocopter Deutschland (ECD) in Donauwörth. Under the system, final assembly of the EC135 is broken down into 13 stations at which dedicated teams complete the various assembly tasks. For example, different stations perform tasks such as mounting the landing skids, routing cables and mounting the engines. Combined with large-scale use of composites, the station-based production results in faster production times and more reliability in the assembly process.To meet the continuing growing customer demand, Eurocopter signed an agreement in November 2003 with Eurocopter-Romania (a joint venture with IAR, a Romanian helicopter manufacturer) for assembly of the EC135 in Brasov, Romania. According to the Joint Aviation Regulations, Eurocopter-Romania is also now an authorized maintenance facility for the EC135.

To further increase its maintenance and repair capability, American Eurocopter, the United States based marketing and support facility headquartered in Grand Prairie, Texas, has earned FAA repair station certification for its new facility at the Golden Triangle Airport in Columbus, Mississippi. Initially, the FAA certification will allow the maintenance and repair of AS350, AS355 and EC130B4 helicopters in the Columbus facility, but eventually the Mississippi plant will manufacture component parts for the Eurocopter production lines in Europe.

At the Helicopter Association International annual convention in Las Vegas in March, Eurocopter touted the EC135's impressive safety record (in 2003 the helicopter wasn't involved in any accidents) and provided details of the continued acceptance of the EC135 for VIP corporate, EMS, police and military missions. Its form fits many functions.