Russian Helicopters is preparing to restart flight-test activities with the Kamov Ka-62 medium-twin having been forced to alter the design of the rotorcraft to address an unspecified issue.

The manufacturer says changes have been made to the Ka-62's shrouded tail rotor and empennage, which have been "modified and reinforced". In addition, the prototype has had a production-standard transmission fitted.

Detailing the alterations in the latest issue of its in-house magazine, Russian Helicopters says vibration testing of the first prototype was conducted in July "and the results showed that the changes had solved the problem".

The manufacturer expects to complete preliminary testing of the 6.5t helicopter and begin the certification effort by the end of 2018.

Development of the Ka-62, which is powered by twin Safran Helicopter Engines Ardiden 3Gs, began in 2012, with an initial aim of validation and service entry within three years.

However, the programme has been beset by multiple, unspecified delays; first flight of the helicopter – a short 15min sortie – only took place in May 2017, after making a brief hover the previous April.

Two further flight-test articles have been assembled, with the first of these now undergoing electrical and systems evaluations.

"The high level of interest in [the] Ka-62 has required us to look long and hard at the operational specifications of each and every element of the helicopter," says Yuriy Denisenko, managing director of the Progress Arsenyev Aviation Company, which builds the rotorcraft.

"In accordance with the plan agreed with Russian Helicopters, the company should complete the certification of the helicopter in 2018-2019 and start serial production."

Most recently, Russian Helicopters had given 2020 as the likely date for service entry.

Meanwhile, windtunnel testing of the company's newest product – the VR Technologies VRT500 light-single – is under way at Moscow's Central Aerohydrodynamic Institute. Structural evaluations of the type's three-blade, co-axial main rotors have also begun.

With a maximum take-off weight of 1.6t, the VRT500 will be the airframer's first sub-2t helicopter. However, no details of the rotorcraft's specification have so far been released.