One would think that such a challenging application would warrant innovation and should be part of a system that encourages technological advances.

But thats not the way things are, at least as Michael Weigand sees them. According to the Vienna University of Technology professor, helicopters are built and marketed in a system that actually discourages innovation that could improve mechanical performance. Focus on safety breeds caution that keeps the industry from adopting new designs. In addition, operators make convenience a priority rather than using lubricants that are specifically tailored to the equipment. As a result, Weigand argues, helicopters are not built as well as they could be.

Now he and the universitys Mechanical Engineering Division are trying to loosen the reins. The school, in cooperation with industry, has launched an initiative to investigate a range of potential improvements in an effort to upgrade helicopter performance. Lubrication is among the elements being considered, and the project could lead to changes in the fluids that helicopter operators use.

Complex Machines

Weigand discussed the complexities of helicopter drive trains with LubesnGreases during a visit at the university last October and in an April telephone interview. Engines typically have a gearbox that requires lubrication. Transmissions translate the power from the engine to the main and tail rotors that provide lift and direction, though the exact configuration varies among different types of helicopters.

Numerous aspects make helicopters a tribological challenge. First of all, the European Aviation Safety Agency and the U.S. Federal Aviation Administration require that transmissions be able to continue performing for 30 minutes after a complete oil drain. The purpose of this requirement is to ensure that the machines can still be landed should an accident cause a total loss of lubricant.

Secondly, the output stages of the main transmission gearbox are highly loaded and move at relatively low speeds. These facts by themselves would call for a thick lubricant with extreme pressure additives. Meanwhile, the input stages for the gearbox are lightly loaded, turn at very high speeds and feature freewheeling clutch assemblies. These call for thin lubricants without EP additives.

Moreover, in an effort to minimize the number of different lubricants used, operators use, but Weigand asserted that this approach represents a compromise to the extent that transmissions are not filled with lubricants formulated solely and specifically for their needs.

Like other aircraft, there is so much emphasis on safety of helicopters that regulations require designs to be approved by the EASA or the FAA. To obtain Certification Specifications from these agencies requires extensive testing, including bench tests, tests on ground vehicles, in-service test flights and post-flight overhaul inspection.

According to Weigand, the cost for such tests presents a significant barrier to entry for new technologies. In addition, helicopter original equipment manufacturers are cautious about risking a machine for flight tests, sometimes creating another hurdle to testing.

Stifling Progress

Weigand believes the regulatory system, the expense of testing new developments, and caution about such tests have all conspired to stifle innovation in helicopter design. As a result, he contends that there is room for improvement in a variety of areas, several of which could reduce friction and reduce wear. Gears and bearings could be made with new materials, he said, or could be manufactured with super-finishing processes to make them harder and less susceptible to pitting or fractures. Low-friction coatings could help in the same way. He also thinks there is room to improve gear oils.

For one thing, if we develop oils that are used only in gearboxes, then they can be formulated specifically for that application, he said. In addition, if these lubricants are developed in tandem with the gears and gearboxes – which may have new designs – then it is possible to achieve some synergy and improve the performance of the entire system.

All of these areas are being studied as part of an initiative that began in January at Vienna University of Technology. The project is receiving some government support because Austrian officials are interested in the economic development that could result from the country becoming a hub for helicopter technology. Also cooperating are Austrian helicopter manufacturers, which see an opportunity to gain a competitive advantage.

Seeking Solutions

Weigand, who worked in the helicopter industry before joining the university, said the school is uniquely positioned to carry out such a project, thanks to its test laboratory. Located in the basement of a university building near the city center, the lab has a series of sound-proof rooms, the size of which can be adjusted to as large as 140 square meters. Equipment includes a helicopter transmission test stand, friction and wear bench tests and software to analyze results.

OEMs may have facilities like this, he said. But we do not know of any other academic institutions that are so equipped.

The project was designed for the lab work to yield recommendations for design changes and then to segue into field tests. The intent is that upon completion the project will have identified improvements that Austrian OEMs can adopt. The project is expected to last around a year and a half, Weigand said.

Weigand is careful not to predict what changes may come out of the project. The research division will test a variety of design alternatives and will follow the results where they lead. He did say there is a good chance of the project producing a formulation for gear oils that would be used only for transmissions, meaning a split between gear oil and engine oil functions.

Weigand believes the university can succeed in improving helicopter performance without compromising on safety. Any changes that emerge from the project will be subject to the same testing requirements that are now in effect, so they will be thoroughly vetted. Because of the way the initiative is structured, however, he believes it may help the industry adopt advances that will help these flying machines to last longer. To the extent that such changes cut down on wear and reduce breakdowns, they could improve safety.

Thats the kind of concerted effort that sophisticated machines like helicopters deserve.