Electrifying propellers with PROPCONEL
The propeller is a vital part of aircraft. It was probably the ancient Chinese who first came up with the concept – evidence suggests that Chinese children played with “helicopter toys” made from bamboo as far back as 400BC. Consisting of a pole with a propeller on top, it was a simple plaything – the children would spin the stick between their hands and the toy would take off into the air.
Today, most propellers on aircraft are controlled by hydraulic components driven by engine oil. The PROPCONEL project’s mission was to develop a new way of powering the propeller controls using electricity instead. Their propeller design will be integrated into the new turboprop engine Tech TP, a Clean Sky demonstrator which is being coordinated by SAFRAN.
The environmental advantages of an electronic system include better fuel efficiency, weight savings, and long-term engine health monitoring and diagnostics. PROPCONEL’s propeller also automatically protects the engine against out-of-tolerance operations, ensures better systems integration with engine and aircraft systems and is safer.
PROPCONEL investigated two different variants to achieve their goal, and finally the CS2 PROPCONEL Over Speed Governor was selected, which makes use of a hydromechanical flyweight and was considered safer than the other variation.
One advantage of an electrical PCU is that the inaccuracies of interventions and overall control, caused by mechanical transmissions, can be reduced. Current control systems, which are mainly based on lever, Bowden, articulated and mechanical transmissions, suffer from many disadvantages that operators and service organisations have to deal with. Electrical control eliminates many of these shortcomings, such as the need for individual adjustment. It also reduces the frequency of adjustment checks due to wear, and reduces the effect of thermal expansion.
Another advantage of eliminating lever, bowden and articulated mechanical transmissions is weight reduction. The use of electric control completely eliminated mechanical transmissions and replaced them with electrical cabling, which is significantly lighter than mechanical transmissions. The weight savings were taken into account during the construction itself too, especially within the body of the device and other structural node.
Time between overhauls (TBO) refers to the manufacturer's recommended number of running hours or calendar time before an aircraft component requires tuning. PROPCONEL successfully increased the TBO to 5000 hours, which will reduce operating maintenance costs. By prolonging the TBO and overall service rate, the number of times that the worn-out device will have to be replaced is reduced, also alleviating the environmental burden. The table shown below highlights the difference between a PCU with a standard Over Speed Governor and a PCU with a PROPCONEL Over Speed Governor in terms of weight, power consumption and TBO.
|Compared characteristics||PCU + OSG M-602||PCU + OSG PROPCONEL|
|Overall Dimensions /mm/||300x200x250||280x150x150|
|Power consumption /kW/||2,8-3,2||2,5|
One aspect of improvement not often talked about is how new innovations can lighten the pilot’s psychological load. Flying an aircraft is an immense responsibility and the simpler that it is for the pilot, the safer that it will be for all passengers involved.
PROPCONEL’s solution involves single-lever control of the propeller blades, as opposed to the more complicated system in operation today. This will reduce the number of parameters that a pilot has to monitor, thereby decreasing his mental load and reducing the risk of human error.
Finally, the results of the PROPCONEL project will be integrated into the TechTP demonstrator, and slight adjustments and modifications may be needed. The two beneficiaries who took part in PROPCONEL were JIHOSTROJ a.s. (JSV) and Czech Aerospace Research Centre (VZLU), and this project took four years in total.