OSTIV Congress Day 4
Development of a module data acquisition system for flight testing; R. Starke
After power outages during the morning, the congress finally reconvened after launch if the field in the afternoon. The first speaker, Richard Starke, who is a crewmember of the South African team, presented a talk on the development of a flight-test data acquisition system at the North-West University/Potchetstroom, South Africa. The data acquisition system that is suitable for sailplanes is meant to reduce the workload of a pilot during test flights for research, development, and certification purposes. It is a small, lightweight device that can easily be integrated in the aircraft during tests. The system logs up to 8 analog signals, aircraft attitude and states, as well as two video signals with voice over. The post-flight analysis program allows reliving the flight and recorded parameter for a detailed indebt analysis as demonstrated by the speaker with the example of stall and spin entry tests.
Modeling thermal; G. Waibel
The second talk of the day was given by G. Waibel about the nature and characteristics of thermal models that the sailplane designer can use for average cross-country speed predictions. Waibel reviewed existing models, such one of the earlier one by Bruce Carmichael. The Carmichael thermal model assumed relatively tight thermals, which tended to result in relatively light wing loadings. Latter models, for example by Horstmann and Quast, tried to account for different weather model. The speaker believes in the greater prevalence of “hat-like” thermals than assumed until now. According to his interpretation and observations of thermal developments occur much more frequently than assumed so far, and need to be considered more with future sailplane designs that have heavier wing loadings.
Spline mapping to maximize energy exploitation of non-uniform thermals; J. Bird, J.W. Langelaan
The first talk after the break was given by John Bird, who is a graduate student at Penn State. As part of his research, he is exploring autonomous, that is automated soaring, in order to improve the performance of small unmanned aerial vehicles. The speaker elaborated his approach that uses splines in order to map a random thermal and, based on that thermal model, adjust the flight path for maximum climb rate. In simulations, he explored the effectiveness of this approach in comparison to other thermal-centering methods that are quite commonly used in soaring. Especially for complex thermal shapes this approach appears to have merits. Nevertheless, the thermaling strategy described by Reichmann, decreasing bank angle in stronger lift and increasing bank in lesser lift, appears to be similarly effective to a limited degree.
Is it time for practical dynamic maneuvering in soaring?; G. Osoba
G. Osoba discussed the use of “dynamic maneuvering” to improve the energy exploitation of small structured turbulences. Unlike dynamics soaring, dynamic maneuvering takes advantage of constant maneuvering and varying load factors to use the energy that is present in a turbulent atmosphere. An example is are the micro gusts that sailplanes with very light wing loadings utilize on a regular basis, for example the Carbon Dragon. The successful use of those small-scale structures, however, requires constant maneuvering through a series of little localized events. In order to support this theory, the speaker showed several flight logs where those strategies were employed.
Experimental Comparison: Integrating Wake Rake and Wake Survey: G. Bramesfeld, E. Pifer, B. Vierra, A. Premi
The last paper of the day was given by Götz Bramesfeld about an integrating wake, which can be used to predict profile drag coefficients. In general, drag measurements are made by using traversing total pressure probes to determine the momentum deficit that exists in the wake. The deficit is directly related to the profile drag of an airfoil. An integrating wake rake uses a number of total-pressure probes that span the wake behind a wing section. The pressures from these probes are all feed into a plenum, and the pressure in the plenum is a pneumatically “integrated.” The pressure losses in the wake are a measure of the profile drag. The fact that traversing is not necessary makes an integrating rake very attractive for rapid drag measurements and flight testing. The theory of the wake rake was presented ,and a calibration of the device in a wind tunnel were discussed. The comparison between the traversing wake probe drag data and that obtained with the integrating rake are in reasonable agreement. The system shows promise for future flight test and drag measurements.
The senior authors have been requested to submit their papers to OSTIV’s quarterly, peer-reviewed, print and on-line journal Technical Soaring. The contact is Chief Editor Dr. Judah Milgram. Thus, soon you will be able to study the complete papers.