Research Publications/Outputs

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Aerodynamic design of an electronics pod to maximise its carriage envelope on a fast-jet aircraft
(2024-12) Du Rand, R; Jamison, Kevin A; Huyssen, Barbara
The purpose of this paper is to reshape a fast-jet electronics pod’s external geometry to ensure compliance with aircraft pylon load limits across its carriage envelope while adhering to onboard system constraints and fitment specifications. Initial geometric layout determination used empirical methods. Performance approximation on the aircraft with added fairings and stabilising fin configurations was conducted using a panel code. Verification of loads was done using a full steady Reynolds-averaged Navier–Stokes solver, validated against published wind tunnel test data. Acceptable load envelope for the aircraft pylon was defined using two already-certified stores with known flight envelopes. Re-lofting the pod’s geometry enabled meeting all geometric and pylon load constraints. However, due to the pod's large size, re-lofting alone was not adequate to respect aircraft/pylon load limitations. A flight restriction was imposed on the aircraft’s roll rate to reduce yaw and roll moments within allowable limits. The geometry of an electronics pod was redesigned to maximise the permissible flight envelope on its carriage aircraft while respecting the safe carriage load limits determined for its store pylon. Aircraft carriage load constraints must be determined upfront when considering the design of fast-jet electronic pods. A process for determining the unknown load constraints of a carriage aircraft by analogy is presented, along with the process of tailoring the geometry of an electronics pod to respect aerodynamic load and geometric constraints.
Evaluation of guidance, navigation, and control algorithms for hydrogen-powered multi-aircraft systems
(2025-09) Makhubo, Mamokete; Ndebele, Bright B; Ragimana, Phumudzo
This paper presents a modular digital-twin framework to compare inner-loop attitude controllers: geometric PD (“PID”), discrete Linear-Quadratic Regulator (LQR), and a movepenalized linear Model Predictive Controller (MPC), for a heavy-lift T30-class quadcopter intended for hydrogen propulsion study. The twin couples 6-DoF rigid-body dynamics, actuator mixing, motor/ESC lag, a bus-level electrical model, and stochastic wind (OrnsteinUhlenbeck) with look-ahead guidance on a sharp lawnmower survey. To isolate controller effects, task difficulty is equalized by autotuning a single scalar so that the achieved cross-track Root-Mean-Squared Error (RMSE) lies in a 2.6 ± 0.25 m band. The tuned controllers then run identical 600 s simulations under the same wind seed and retimed speeds. On the equalized run, PID and LQR achieve 2.45 m and 2.55 m RMSE, respectively, while MPC settles at 3.13 m due to its move penalty and finite horizon. All three deliver survey-class performance with mean bus power ≈ 4.8 kW and peaks in the 7–8 kW range, but MPC reduces energy per meter by approximately 2.3% at the cost of relaxed lateral accuracy. A 10-seed Monte Carlo confirms this trade: PID/LQR remain in-band for 90%/80% of seeds, while MPC consistently lowers energy per meter with similar mean power but gentler peaks. For hydrogen-electric UAVs, these metrics map directly to propulsion co-design, where energy per meter informs hydrogen mass and range, peak power sets stack/buffer sizing, and actuator smoothness affects balanceof-plant transients. The results show that controller selection is not only a matter of tracking accuracy but also an energy-management lever: PID/LQR suit survey tolerance, while MPCstyle penalization favours endurance and balance-of-plant stability.
Flutter clearance techniques and tools for gliders
(2024-08) Van Zyl, Louwrens H
The flutter clearance of gliders pose some special challenges. Modal frequencies are low, making suspension of the glider for ground vibration testing challenging. The low frequencies also make large amplitudes of excitation desirable. In flutter flight testing space for excitation systems and telemetry systems is limited.
Internal aircraft cavity bay tests in the medium speed wind tunnel (MSWT)
(2024-08) Mashilangwako, Kgoane J
Continuous improvements in the wind tunnel facility capability gives a corresponding improvement and expansion on the types of tests that can be performed, and the accuracy, precision and quality of the data one can get from a wind tunnel test.
On the existence of a family of ideal aircraft configurations
(2024-09) Huyssen, Reinhard J; Spedding, GR
The bulk of fossil fuel in aviation is consumed in the domain of fixed-wing subsonic flight. Environmental concerns put strong incentives on the industry to improve flight efficiency. Best flight efficiency can only be attained if an aircraft design is based on its ideal configuration. Already since the middle of the previous century, the industry became entrenched in the tube-and-wings configuration, here referred to as the Current Dominant Configuration (CDC). It is widely speculated that better arrangements of wings and bodies exist, and many research initiatives are dedicated to the exploration of alternatives. These are typically done for specific types of aircraft, mostly for the airline industry. Yet, new aircraft developments keep employing the CDC as if proposed alternatives are ignored. Here a hypothesis is tested which suggests that a single family of aircraft configurations exists which is ideal for the majority of economically significant flight objectives within this domain. To organise the aircraft design space into families of configurations, a hypothetical Ideal Wing is introduced as a common basis from which all configurations evolve by inflation to provide practical flyers with volume for their payload. While the most prominent configurations, including the CDC, appear to disqualify as candidates for the proposed ideal configuration, the one which qualifies, has not been seriously examined in human aviation, although it is familiar. Termed the Natural Dominant Configuration, as it appears in natural flyers, it certainly merits further exploration.
Projected changes in daily temperature extremes for selected locations over South Africa
(2025-03) McBride, CM; Kruger, AC; Johnston, Charmaine M; Dyson, L
Extreme events, particularly very high temperatures, are expected to increase because of climate change. It is thus essential that localised studies be done to quantify the magnitude of potential changes so that proper planning, especially effective adaptation measures, can be affected. This study analysed annual extreme daily maximum temperatures for future climate change scenarios at 22 locations in South Africa, through analysis of a subset of the Coordinated Regional Downscaling Experiment (CORDEX) model ensemble datasets. The multi-model simulations were validated against observational data obtained from the South African Weather Service for the period 1976–2005. Two study periods of mid- (2036–2065) and far-future (2066–2095) were analysed for two Representative Concentration Pathways, i.e., RCP4.5 and RCP8.5. Bias correction was done on the model data to correct simulated historical climate data, to be more characteristic of observed measurements. While the method included adjustment for variance, systematic underestimations of extremes were still evident. The Generalized Extreme Value distributions were fitted to the bias-corrected projections, and 10-, 50- to 100-year return periods quantile values were estimated. The return period quantile values are likely to increase under both Representative Concentration Pathways in the mid- and far-future periods, with the largest increase in return period quantile values set to occur towards the end of the century under the highest emission scenario. All stations showed an increase in the frequency of days with maximum temperatures above specific critical thresholds, with some stations under the RCP8.5 scenario projected to experience temperatures of greater than 32°C (35°C) for more than 200 (100) days per year by the end of the century, an increase from a baseline of approximately 70 to 150 (14 to 83). For the same scenario, Return periods for 38°C for most stations are projected to be shorter than a year. From the above and considering the likely underestimation in the severity of the projected changes, i.e. too low return period quantile values, the general implication is a strong likelihood that most places in South Africa is likely to experience a strong increase in the intensity, duration, and frequency of very hot extremes in future, with potentially dire consequences to relevant socio-economic sectors. We suggest that future research, comprised of the full set of CORDEX data be conducted to optimise the results of this study.
The benefits of replacing the traditional dimensional calibration system with the Laser Measurement Technology in the CSIR Wind Tunnel Facilities
(2024-09) Ragimana, Phumudzo; Mabeko, Philimon K; Dikgale, Moyahabo S
Calibrations in any aerodynamic metrology field require patience as it is time-consuming. The Council for Scientific and Industrial Research has wind tunnel facilities with a wind tunnel model support system of 6 degrees of freedom. These degrees of freedom are three translations and rotations, which must be calibrated per project-specific requirements and the facilities maintenance management schedule. This paper addresses the impact of introducing advanced laser measurement technology instead of traditional dimensional instrumentation calibration systems at the CSIR Wind Tunnel Facilities. Conventional calibration methods typically entail extensive manual processes and significant downtime, resulting in higher operational costs and slower instrumentation calibration and wind tunnel testing cycles. The advantage of implementing the laser tracker system is that it enhances the calibration accuracy in the CSIR Wind Tunnel facilities. Therefore, the laser tracker system addresses these challenges and offers an efficient alternative. By enhancing precision and speed, the new technology improves the wind tunnel facilities’ dimensional instrumentation maintenance processes and aerodynamic testing while delivering substantial cost and time savings. Manual and time-intensive traditional methods incur higher costs, slower calibration processes, and limited precision and human errors. Laser measurement technology simplifies these tasks, producing faster and more precise calibrations. Through several calibration activities and data collection, it is evident that this replacement enhances instrumentation calibration efficiency and decreases operational expenses, representing a valuable improvement for future aerospace research and development.
The benefits of replacing the traditional dimensional calibration system with the Laser Measurement Technology in the CSIR Wind Tunnel Facilities
(2024-09) Ragimana, Phumudzo; Mabeko, Philimon K; Dikgale, Moyahabo S
Calibrations in any aerodynamic metrology field require patience as it is time-consuming. The Council for Scientific and Industrial Research has wind tunnel facilities with a wind tunnel model support system of 6 degrees of freedom. These degrees of freedom are three translations and rotations, which must be calibrated per project-specific requirements and the facilities maintenance management schedule. This paper addresses the impact of introducing advanced laser measurement technology instead of traditional dimensional instrumentation calibration systems at the CSIR Wind Tunnel Facilities. Conventional calibration methods typically entail extensive manual processes and significant downtime, resulting in higher operational costs and slower instrumentation calibration and wind tunnel testing cycles. The advantage of implementing the laser tracker system is that it enhances the calibration accuracy in the CSIR Wind Tunnel facilities. Therefore, the laser tracker system addresses these challenges and offers an efficient alternative. By enhancing precision and speed, the new technology improves the wind tunnel facilities’ dimensional instrumentation maintenance processes and aerodynamic testing while delivering substantial cost and time savings. Manual and time-intensive traditional methods incur higher costs, slower calibration processes, and limited precision and human errors. Laser measurement technology simplifies these tasks, producing faster and more precise calibrations. Through several calibration activities and data collection, it is evident that this replacement enhances instrumentation calibration efficiency and decreases operational expenses, representing a valuable improvement for future aerospace research and development.
The effect of combustor hole-set arrangement when comparing two different hole-set design methods
(2024-07) Meyers, Bronwyn C; Grobler, Jan-Hendrik
This presentation focuses on the effect of combustor hole-set arrangement when comparing two different hole-set design methods.
Urban Air Mobility: Regulatory Pathways and Readiness for Integration in South Africa
(2025-07) Ndlovu, Hlamulo P; Niken, Adrian; Madonsela, N; Teane, Tshegofatso O; Moodley, Theolan
Urban Air Mobility (UAM) refers to the use of small, electric or hybrid-electric aircraft, often highly automated, designed to transport passengers or goods at low altitudes within urban and suburban environments, which has been developed in response to traffic congestion in the cities. This presentation highlights work that forms part of the International Forum for Aviation Research (IFAR) project titled “Navigating the Skies: A Guide to Certification for Urban Air Mobility”.

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