The Airbus Helicopters H135M is a military market form of its successful H135 light utility helicopter product. The H135 was born during the 1970s under the brand label of Messerschmitt-Bolkow-Blohm (MBB) (with support from French-based Aerospatiale) as the "Bo 108". A twin-engine arrangement (digitally-controlled through FADEC) was selected with features taken from the preceding Bo 105 helicopter and the aircraft, in prototype form using a conventional, open tail rotor unit, achieved a first-flight on October 17th, 1988. The Bo 108 was only intended as a technology demonstrator but its evolution meant that it became something more.
In the latter part of the 1990s, the Fenestron tail unit was installed and more composite construction introduced. Two pre-production prototypes then followed and, with MBB now under the Eurocopter brand label, the product emerged as the "EC135". The helicopter was recorded another first-flight on February 15th, 1994 and the design was debuted publically during January of 1995. Following Type Certification, service entry occurred in 1996 and production has been ongoing since 1995. Over 1,220 units have been produced to date (2017) with global operators covering both military and civilian markets. In the former, the product became the EC635 with service entry coming in May of 1998.
With the introduction of Airbus Helicopters, the EC135 product graduated to become the "H135" and, in turn, the EC635 has evolved to become the "H135M".
Like the H135 before it, the H135M relies on a fixed, four-point landing skid undercarriage and features a Fenestron-shrouded tail rotor. The main rotor assembly is made up of a low-mounted, four-bladed system. The forward section of the fuselage is heavily windowed allowing for excellent vision out-of-the-cockpit. The helicopter is operated by one pilot and can seat up to eight passengers or two patient litters / two support staff for the MEDEVAC role.
Airbus Helicopters champions the H135 for its versatility in "hot and high" environments, an atmospheric condition where there is low air density caused by high elevation and high ambient temperatures. This presents a challenge to both aircraft and engines and thusly deserves attention by engineers to formulate a product capable of operating in such an environment. With this quality, the H135 has become one of Airbus Helicopters more popular products and certainly one of the more popular light utility types in service - the aircraft capable of undertaking a vast array of mission types both civilian and military in nature. The Fenestron tail rotor unit also aids in suppressing noise signatures which is an important quality to consider for urban operations.
Power for the H135M is from 2 x Pratt & Whitney Canada PW206B2 turboshaft engines developing 817 horsepower (each) and driving a two-bladed main rotor and a Fenestron-shrouded tail rotor. Performance includes a maximum speed of 161 mph, a cruising speed of 158 mph and a range out to 405 miles. The aircraft's service ceiling is listed at 20,000 feet. Rate-of-climb is 2,150 feet-per-minute.
Variants of the line include the H135MT1/P2/T2 and the H135MP2+/T2+. The former were introduced from 2001 onward while the latter pair saw introduction in 2006 with refinements including strengthening. All models share two engine options - either Pratt & Whitney or Turbomeca types - to suit customer / mission performance needs.
Military operators of the H135M are few to date (January 2017) and include Iraq (Army), Jordan (Air Force), and Switzerland (Air Force).