The CoE is a unique UK facility that along with Cascina Costa’s Transmission CoE, makes Leonardo a world leader in this core technology. Helicopter transmissions are an integral element of any helicopter. The transmission is a complex assembly of gears and components that convert high speed, low torque input power from the helicopter’s turbine engines into low speed, high torque power that will turn the helicopter’s main rotors.
In addition, an intermediate gearbox at the rear of the helicopter changes the angle of the drive towards a tail rotor gearbox, which will then transfer the engine power to a perpendicular angle for the tail rotor, all of which is achieved via a series of drive shafts.
The transmission system plays a central role in platform efficiency, reliability, comfort level, and, most critically, safety. Ensuring that the transmission systems are designed, tested, manufactured and serviced correctly is paramount for all helicopter operators, whether they are military, civil or parapublic. At the same time, it is also critical that the parts are precision machined and hardened to handle the significant loads that will be experienced.
A state-of-the-art helicopter gearbox manufacturer
Only a handful of companies in the world are able to design, develop, test and manufacture highly complex transmissions for large helicopters, including main rotor, intermediate and tail rotor gearboxes. Leonardo Helicopters in Yeovil is one of these select few and it is the only company in the UK with this capability, which makes it the sole OEM capable of end-to-end helicopter production in the UK.
Leonardo has a dedicated helicopter transmissions Centre of Excellence that specialises in the full product lifecycle of rotorcraft gearboxes, from initial concept and design, to testing, serial production and ongoing in-service support.
“The Centre of Excellence has gone through a phase of enormous growth and success in the last few years,” says Stuart McCabe, Head of Transmissions at Leonardo Helicopters UK.
In recent years, the Centre of Excellence has seen a number of strategic investments that positions it as a leader in rotorcraft transmissions not just in the UK, but globally.
The team of highly skilled engineers in Yeovil are able to take transmissions from initial concept, all the way through to full-scale manufacturing, with testing and certification playing a key role.
Central to this is a cutting-edge piece of test and engineering equipment known as the Flexible Transmission Test Rig (FTTR), which is the result of a multimillion-pound investment by Leonardo in the UK’s manufacturing capabilities.
The FTTR is a unique capability that allows both development testing and production testing on the same platform.
“Anyone that sees the test rig in the flesh will be in awe of the size and obvious complexity of it; you can’t just set it up anywhere in the world,” explains McCabe, who has over 30 years’ experience at Leonardo in transmissions. “The FTTR is also essential for UK sovereign capability and ensuring that transmission testing and delivery for critical frontline military assets remained onshore, which could have strategic consequences in times of conflict.”
FTTR – a modular and flexible transmission testing solution
The FTTR allows Leonardo to test developmental transmissions and components in all kinds of scenarios, including failure testing, overpowering, oil loss, and testing in different environments. It can also carry out test runs that are 200 hours long, which are required for certification.
The FTTR additionally allows Leonardo to test multiple types of gearboxes with just one test rig.
“Most of our test rigs can only test a particular type of gearbox, but the investment was made in a core rig facility with different interchangeable pallets so that we could have multiple gearboxes that could be tested on the same rig,” explains Angus Morgan, Transmission Test Facility Manager at Leonardo’s site in Yeovil.
This allows every transmission system that is manufactured by Leonardo to be tested through the FTTR, simulating start up, ground runs, take off, cruise flight and landing.
“We are checking areas like pressures, temperatures, flow rates and temperature of bearings. We then take the gearbox apart and visually inspect it to make sure it is running correctly and then we run it again to ensure there are no leaks,” adds Morgan. “It ensures that they are in the best condition they can possibly be before they are delivered.”
The FTTR is computer-controlled and has been used to test the main gearboxes for the AW159 Wildcat, Lynx and Apache AH1 helicopters, as well as tail and intermediate gearboxes for the AW139 and AW149. In recent years, the FTTR has also been used extensively to support testing gearboxes for the AW101 programme.
Notably, the FTTR only draws 15% of the energy it needs from the electricity grid, which has a positive environmental impact. The energy recovered from braking the tail and main rotor outputs is recycled back into the system, reducing overall power requirements.
More investment in the transmission Centre of Excellence
As part of continued investment in Yeovil and the transmission CoE, the FTTR has gone through a process of obsolescence management and key upgrades have been carried out this year to the test rig’s computer systems to future proof them, including the introduction of new hardware and software. This critical investment in the FTTR ensures that Yeovil retains the capability to manufacture and test complex helicopter components for many years to come, and as a result the UK retains a full end-to-end capability to manufacture helicopters.
By upgrading the FTTR, Leonardo is also unlocking its potential as a development asset for new products. As part of its investment in the CoE, Leonardo is purchasing a brand-new test rig pallet for a future development gearbox type that will begin testing next year as a product demonstrator.
“Without the software upgrade we wouldn’t have been able to use the flexibility of the rig, which means for a relatively small cost in comparison to a dedicated rig, we can purchase an adapting pallet that can test pretty much any type of helicopter gearbox on the market,” said Morgan.
In addition, further investment at the transmission CoE will see the delivery of a new state-of-the-art production and inspection machines, which will help engineers manufacture and check gears to the latest demanding standards, this will enhance areas such as vibrations and reliability.
Conclusion
Yeovil is the Home of British helicopters and its capability to design, test and build complex helicopter transmission systems is unmatched in the UK market. The transmission CoE provides the UK with highly skilled engineering jobs, aerospace technology that competes on a global scale, and a critical sovereign capability for the UK armed forces and its future requirements.
