MUTR – Multipurpose test rig for transmission gearboxes

Jun 7, 2021


Multipurpose test rig for transmissions gearboxes (MUTR)


The project is focused on the design of the gearbox test system of the newly created RACER helicopter demonstrator. The project is solved within the Clean Sky Joint Technology Initiative 2 – IADP Fast Rotorcraft section. Two new propeller concepts for rotorcraft are being solved within IADP FR. It is based on a tilt wing (tilt motor / tilt wing) and a second concept for choosing from a new RACER helicopter configuration Airbus Helicopters other with many other European partners and research organizations.

The subject of the project “Multipurpose Test Rig” (MUTR) is the design and implementation of an auxiliary (adaptive) gearbox, which will be part of a multipurpose testing device intended for testing newly designed helicopter reducers. Special gear-reducers are developed for a new type of high-speed side-rotor helicopter. This main gearbox is a key helicopter drive device as it transmits power from two turbo shaft motors to the main rotor and side rotors. The gearbox must meet a number of conditions based on applicable aeronautical regulations for certification. In addition, such new equipment must comply with a mixture of regulations, some of which meet the requirements for aircraft, others for helicopters.

During the development of the RACER project, the performance requirements for the gearbox gradually increased, which was also reflected in the test bench concept. Finally, it is a massive device allowing to test not only the normal travel modes of the machine, but also all emergency and overload conditions to which the main reducer can be exposed in operation.

The proposed test mode consists of four parts, the main gearbox plate, side load groups, adaptive gearbox and support mechanisms. Placing the main reducer on the board has the same characteristics as on the actual machine, so the measured values ​​are applicable to the property verification and certification process. Side load units simulating load from the side rotors are also mounted on the main gearbox plate. The load is performed by an energy-efficient hydraulic torquers. The power transmitted by the shafts representing the drive units is conducted from the adapter gearbox to the main gearbox. In this gearbox, it branches into two side rotor branches and one main rotor branch. From the main rotor branch, the power goes through the viscoterm hydraulic units to the top of the adapter, from the side branches to the front of the adapter. This layout creates three power loops in which the power flow can be independently changed. Simultaneously, it is possible to simulate running in single engine inoperative mode and in different flight modes of the machine.

In addition to two pairs of gears, a unique torquer and torque meter are located in the gearbox. This arrangement makes it possible to perform load tests and calibrate the torquer. The concept allows the torque to be loaded and calibrated up to 3600 rpm or up to 7000 Nm of torque. The hydraulic system not only loads the torsion, but also solves the cooling of gearing and gearbox bearings. The cooling system has a capacity of up to 120kW, which is sufficient to cool the energy losses incurred during plant operation. The control system sets and performs the torquer loading and calibration at the advanced level of automation as directed by the operator. VZLU considers to include innovative torquer solutions under the patent protection.

The project workflow as of 11/2019: At this stage of the project, the 3D model of the test state is fixed and all documentation for the production of the designed parts is prepared. This will be followed by assembly and testing of the entire test stand, or its subsequent modification. Testing a torquer based on an innovative solution will be essential.

The results of the MUTR project fall into the field of hydraulic states for testing of aircraft gearboxes. It is assumed that VZLU outputs will be used not only within the CS2 Racer project, but that some or at least a part of the outputs will be used by VZLU in development work with others, such as domestic manufacturers of aircraft power units.


 VZLU, Topic Manager – Airbus Helicopters


CS2 – 717199


9/2016 – 6/2020


Ing. Petr Pick, PhD.