Rotorcraft
Detailed Description
Back in 1943 in an article of LIFE magazine (June 21) about the helicopter it was featured that “After the war is over …the helicopter may well become the average man’s fling machine to be used – not right away but inevitably – much as the average man uses his automobile”. A bright future was foreseen for the helicopter as at the end of the war it was felt by many persons and by many helicopter developers that the helicopter would surely be the supplement to, if not a replacement for, the average man’s automobile. More than fifty years have passed since these affirmations were made and we hardly can see the helicopter in personal transportation. Thus, the question is why aren’t personal helicopters in every garage and instead of this automobiles? The answer at this question is that rotorcraft (helicopter and tiltrotors) perhaps more than any other vehicle, through its complex nature, requires a multi-disciplinary integration of a variety of aeronautical engineering disciplines. DAR group performs multi-disciplinary research in the field of aerodynamics, simulation, control and handling qualities for helicopters developing multi-disciplinary tools for the designer capable of predicting helicopter behaviour under different conditions. Some examples of research activities include the following fields:
Rotor aerodynamics
Perhaps the key element in understanding and predicting helicopter characteristics is knowing the behaviour of rotor inflow and wakes. DAR group has developed in the past new concepts for the lifting line theory and applied it to helicopters (see Holten [1977], Holten [1996]). More recent research in the rotor aerodynamics refer for example at studying the so-called “apparent mass” effects. This relates to the dynamics of the air volume flowing through the rotor disc. Unique effects of apparent mass flow passing through the rotor have being tested in the wind tunnel (see figure from Jessurun, Pavel and Toet [2001]). It was showed that although load factors of order 2.5 are usually considered as maximum load factors attainable for the helicopters, when a pilot performs rapid control movements the chance exists to achieve much larger values (up to 4 g, especially at high speeds) and can result in loss of control.
Helicopter Flight Mechanics and Simulation Modelling
In the field of simulation modelling new guidelines were defined for predicting the necessary rotor dynamics to be considered in simulation models (see dissertation Pavel [2001], paper of Aalst and Pavel 2002]).
Recent research on helicopter simulation modelling has been performed within the GARTEUR Action Group HQ/AG 12 and relates to validation criteria for real-time simulation models. See simulation fidelity
. The research performed in the project on validation criteria for simulators supplied the helicopter manufacturers with criteria, rules and procedures for simulator development and acceptance (see Padfield, Pavel, Casolaro, Roth, Hamers and Taghizad [2004], Padfield et, al. [2005]).Research is being performed at the moment in collaboration with TNO and Royal Netherlands Air Force on Chinook concerns the behaviour of the Chinook helicopter transporting a slung load after the premature breakdown of one of its cables. See the Chinook project.
Rotorcraft Handling Qualities
Nowadays helicopters are still more difficult and tiring to fly than fixed-wing aircraft. The reasons are those mentioned 40 year ago: the existence of an additional vertical control (collective pitch lever); excessive cross-coupling; inadequate dynamic instability; alertness required to ensure conversion to autorotation in the case of engine failure. In collaboration with the Group of Flight Science and Technology Research Group at the University of Liverpool DAR group is performing research in the area of improving the handling qualities of rotorcraft. In this sense, we defined new sets of complementary handling qualities criteria for performance/vibratory analysis. In this way the designer can decide from the beginning how manoeuvrability and agility characteristics can be “designed-in”, rather than treating them as fall-outs as currently done in more traditional design approaches. See the Handling Qualities Project.
Another recent project performed within the GARTEUR group relates to research on pilot induced oscillations and aims to assess the needs of industry for analytical and experimental tools addressing the problem of pilot induced/ assisted oscillations. See the PIO Project
Helicopter design
In helicopter design a revolutionary concept of a helicopter without reaction torque is under development. More on the Ornicopter Project. (see Holten [2002], Mols [2003], [Korteweg84 [2004], [Holten and Heiligers79 [2004], [Holten and Heiligers80 [2004], [Holten and Heiligers81 [2004], [Holten et. al.82 [2004])
Related Projects
- Developing new rotorcraft handling qualities criteria for agility enhancement and structural load alleviation in collaboration with University of Liverpool
- Contributions to the “GARTEUR Action Group HC/AG12 on “Validation Criteria for Helicopter Real-Time Simulation Models” on new criteria for qualification and validation of helicopter training and research simulators
- contributions to the “GARTEUR Exploratory Group EG22 on pilot activated oscillations on new criteria for identification of pilot induced oscillations for helicopters
- investigations on helicopter operations on board of ships
- investigations on the Chinook operations with an external sling load after cable failures together with The Royal Netherlands Air Force and TNO.
- Furthermore, a revolutionary concept of a helicopter without reaction torque is under development
Related Courses
Other
For students interested in doing their final thesis project on a rotorcraft related subject, this document may be interesting to read.
