The Russian Helicopters management approved the Mi-8/17 heavy upgrade programme, initially dubbed Mi-171M, in March 2011. The new machine was derived from the Ulan-Ude Aviation Plant-made Mi-171A1 multipurpose medium transport/passenger helicopter certificated by the Aviation Registry of the Interstate Aviation Committee (IAC) and the Brazilian aviation authorities. Hence, the upgrade was designated as Mi-171A2. The upgrade programme's key objectives are a sharp improvement in operating characteristics and a reduction in its maintenance and flying cost per hour. The Mi-171A2 is expected to become the baseline production-standard commercial model of the most popular helicopter family further down the line.

Several components of the helicopter were upgraded at the same time. Firstly, the machine was given an advanced powerplant, rotor system and powertrain. The Mi-171A2 will be fitted with latest VK-2500PS-03 turboshaft engines from Klimov JSC in St. Petersburg (a subsidiary of the United Engine Corporation, itself a subsidiary of Oboronprom JSC that is part of the Rostec corporation). The VK-2500PS-03 features an emergency power rating of 2,400 hp for 30 min. and 2,700 hp for 2.5 min, as well as an extended service life.

The advanced rotor system of the Mi-171A2 includes an upgraded composite-blade main rotor, rotor hub and swash plate. The helicopter is furnished with a beefed-up powertrain and an X-shaped tail rotor. The novelties have increased the machine's cruising and maximum flight speed, improved its operability and extended the service lives of its units. In addition, provision has been made for the introduction of the up-to-date auxiliary power unit.

Another key line of the upgrade is a drastic reshuffle of the avionics suite. The Mi-171A2 will be equipped with the up-to-date KBO-17 avionics suite co-developed by the Ulyanovsk Instrument Manufacturing Design Bureau (UIMDB) and other subsidiaries of the Radio-Electronic Technologies Concern (Rostec company). This will expand the helicopter's operating envelope on scheduled long-distance and commuter passenger operations, with the machine complying with the airport arrival and departure standing operating procedures and present-day and future reduced vertical and lateral separation minimum requirements. In addition, this will enable the helicopter to perform aerial work, including hovering and flying on special flight paths, and will ensure a fuel consumption reduction by means of the optimal navigation calculations and adherence to the flight plan.

The KBO-17 will allow a reduction in the flying cost per hour through reducing the crew from three to two, slashing the weight of the airborne equipment, simplifying the pre-flight and post-flight checks and enhancing the diagnostic equipment effectiveness owing to the KBO-17 itself including the SUOVO-V1 general aircraft equipment control system and KSEIS-V1 integrated electronic display and warning system.

Finally, the helicopter operation system will be changed much too. The assigned life and time between overhauls of both the helicopter and its key systems are to be extended by far, with on-condition operation further down the road being an objective.

The Mi-171A2's maximum takeoff and landing weight is 13,000 kg and that with under-slung cargo stands at 13,500 kg. The weight of cabin cargo accounts for 4,000 kg and that of under-slung one equals 5,000 kg. The passenger version of the Mi-171A2 is equipped with 26 standard-issue or 18 shock-absorbing seats.

The maximal speed will increase from 250 km/h to 280 km/h, the cruising speed from 230 km/h to 260 km/h and the range on internal fuel from 715 km to 850 km. The directional control will improve much, and the permissible hover crosswind velocity will increase. The helicopter will be able to operate within the -50/+50°C temperature bracket in all climes.

Under the Mi-171A2 upgrade programme, prototype work involves three aircraft - the flying testbed derived from Mi-171 side number 987 and the OP-1 and OP-2 prototypes. The flight tests of the flying testbed fitted with the new rotor system including the upgraded composite-blade main rotor, upgraded hub, beefed-up powertrain and X-shaped tail rotor kicked off at the flight test facility of the National Helicopter Industry Centre in Tomilino (Moscow Region) in autumn 2012. The tests demonstrated a main rotor vibration reduction and a 700-kgf increase in the main rotor thrust with a simultaneous directional control stability increase owing to the advanced X-shaped tail rotor. During the trials, the flying testbed produced a maximum speed of 300 km/h (the max speed of the production-standard Mi-171 is 250 km/h).

Early in 2012, the prototype-making facility of the National Helicopter Industry Centre in Tomilino started manufacturing the first Mi-171A2 prototype (OP-1), using the airframe shipped by the Ulan-Ude Aviation Plant. The OP-1 made its debut in public in late August 2013 during the MAKS 2013 air show in Zhukovsky. This year it was used in the tests of the KBO-17 avionics suite.

The assembly of the second Mi-171A2 prototype, the OP-2, with the use of another UUAP-supplied airframe is nearing its end in Tomilino.

The Mi-171A2 certification test programme completion and IAC Aviation Registry type certificate release are slated for 2015. Then, UUAP is to launch Mi-171A2 full-rate production and delivery. Even now, major helicopter operators - both domestic and foreign - have displayed interest in the Mi-171A2.

(Photo: Russian Helicopters)