The growing use of Unmanned Aerial Vehicles (UAVs) demands higher reliability and safety. Propeller faults are a major risk for small UAVs, yet many studies do not calibrate severity or test early faults that preserve nominal flight. We investigate three propeller fault groups (edge cuts, cracks, surface unbalance), each introduced at three calibrated severity levels as small perturbations during normal flight without controller retuning. Severity levels are referenced to ISO 21940 balance-quality limits and quantified by measured residual unbalance and effective damaged area. We propose a physics-based residual detector that identifies a simple inner-loop model directly from flight dynamics data. A single residual state is tracked, with decisions based on a percentile threshold and a latency gate tuned on healthy data. Validation over 12 indoor flights (9 faulty and 3 healthy) shows perfect case-level precision and recall (no false alarms), while interval-level precision is 1.0 and recall is 0.48. Using two residual features, maximum margin and signature duration, the three fault groups occupy distinct regions of the feature space, showing clear separation for fault classification. A one-way ANOVA across fault types shows significant mean differences, and post-hoc tests confirm pairwise separations, indicating that the residual features provide discriminative power for fault type classification. Severity analysis reveals surface unbalance scales linearly with measured unbalance, while edge cuts and cracks show minimal variation due to aerodynamic stabilizing torques and persistent stiffness asymmetry. The study provides severity-calibrated evidence, a physics-based lightweight detector, and a consistent protocol for early propeller-fault assessment in real flight.

The goal of this study is to investigate the performance of a small horizontal axis wind turbine blade at wind speeds of lower than 5 m/sec numerically and experimentally. The rotor blade has a diameter of 0.7m and consists of two airfoils profile: the thin airfoil SD2030 selected at the outboard region, and the thick airfoil E231 at the inboard region. The former airfoil, SD2030, is highly recognized for aerodynamic performance as it is suitable for low Reynolds number (Re), while the latter airfoil E231 is likewise appropriate for low Re flow but has a higher thickness-to-chord ratio which acts as structural support and good strength at the hub. The selected airfoils were analyzed using QBlade software based on XFOIL and Blade Element Theory (BEM) for different Reynolds number. Using a low-speed wind tunnel and Reynolds number ranging from 1x105 to 5x105, experiments at pitch angles of 5ο were conducted to determine the variation in torque and predict blade performance. The results reveal that the turbine with two hybrid different airfoil profiles have achieved a better start-up response at low wind speed of 1.5 m/s and a high-power coefficient of 0.34 with 3.7 tip speed ratio. The turbine can be used to generate a power of 0.5W at 1.5 m/s and a maximum power harvest of up to 20W at a wind speed of 7m/sec. The turbine's performance compared to other small wind turbines from the literatures demonstrate good performance and the results obtained from wind tunnel data were found in satisfactory agreement with the results provided by the BEM code.

This note documents, at a preliminary stage, a propeller concept for small expendable interceptor UAVs cruising near 300 km/h (83 m/s). The concept derives from the DA4052 (9 × 6.75 in variant), an open-geometry small-scale propeller designed at the University of Illinois at Urbana-Champaign and characterised by wind-tunnel measurement in the UIUC Propeller Database. Four geometric modifications are proposed and have been implemented in CAD and realised as a three-blade fused-filament (PLA) article: truncation of both tip and root, giving a modified rotor diameter of 170 mm; an enlarged root chord in place of the parent’s root dip; replacement of the 12 % PROFOIL sections by the 14.6 % thick MH 113 propeller section; and a large increase in blade twist, raising pitch-to-diameter ratio from 0.75 to 2.23. A minimal cylindrical shroud, without lip contouring, diffuser or nozzle, is proposed as a subsequent noise-mitigation step. A single static bench run produced 6 N of thrust at an unrecorded rotational speed. The purpose of this note is to place the concept and its hypotheses on the public record. Computational, structural and experimental characterisation are ongoing. No validated performance claim is made here.

Aerial flight on Mars poses aerodynamic challenges due to its thin atmosphere, resulting in low Reynolds number (Re) conditions where conventional airfoils suffer from early separation and high drag. This study examines the performance of three airfoils: bio-inspired OWL, NASA’s CLF5605, and AS6097, at Re = 23000, representative of Martian rotorcraft operation. Two turbulence models, k–ω SST and SST Transition, were tested using steady RANS CFD in ANSYS Fluent with dynamic similarity applied for terrestrial conditions. The SST Transition model showed better agreement with experiments, particularly in capturing laminar separation bubbles. CLF5605 achieved the best aerodynamic efficiency, the OWL airfoil exhibited smooth trends and close validation agreement, while AS6097 produced the highest lift but inconsistent drag behavior.

Unmanned aerial vehicle (UAV) propeller noise is a primary barrier to drone operations in noise-sensitive urban areas. This short communication evaluates a hybrid concept in which a conventional APC 10×5 propeller is retrofitted with a profiled, closed-loop toroidal ring at the blade tips, with the aim of suppressing the tip vortex to augment static thrust and reduce tonal noise on an otherwise unmodified blade. The aerodynamic and aeroacoustic performance of the hybrid is benchmarked against the baseline propeller using a validated approach that couples Reynolds-averaged computational fluid dynamics (CFD) with the Ffowcs Williams–Hawkings (FW-H) acoustic analogy, complemented by static thrust measurements on a 3D-printed prototype. Relative to the baseline, the hybrid increases the static thrust coefficient by about 86% at the same rotational speed. Exploiting this margin to match a 5.6 N thrust at a reduced speed (5000 rpm versus 6700 rpm) lowers the sound pressure level (SPL) at the blade-passing frequency by 4.2 dB, with consistent harmonic suppression above 1 kHz. These gains come at the cost of a 100–120% rise in power coefficient at cruise advance ratios (advance ratio J = 0.2–0.4); the concept is therefore aimed at static- and low-speed-dominated operation rather than cruise. The toroidal ring offers a simple, low-cost retrofit for thrust-dominated, noise-sensitive missions such as tethered inspection or façade-cleaning drones, where acoustic signature outweighs power consumption.

This study analyses the aerodynamic and acoustic trade-offs of toroidal quadcopter propellers using variants derived from the APC 10×5 design to guide mission-specific adoption in next-generation quadcopters. Three configurations, namely a two-loop elliptical, a two-loop circular, and a three-loop circular design, were evaluated through CFD simulations. Static thrust tests on a thrust stand validated the CFD model, complementing wind-tunnel validation against published APC 10×5 data. Acoustic assessments used the Ffowcs Williams–Hawkings (FW-H) analogy. The results show that toroidal propellers achieve 38.8 to 59.2 % higher static thrust and significant noise reductions relative to the conventional benchmark, although efficiency is compromised by increased induced drag from vortex diffusion. Specifically, the three-loop circular variant reduced the peak tonal sound pressure level by approximately 26.8 dB (a factor of ≈22 in sound pressure) within the human-sensitive range, yet it suffered a ≈41 % lower thrust-to-weight ratio. The two-loop elliptical variant offered a practical balance with 38.8 % higher static thrust, a peak-tone reduction of ≈2.7 dB, and a maximum propulsive efficiency of 0.57 (vs. 0.69 for the benchmark). Propeller choice therefore dictates mission suitability: three-loop designs best serve noise-sensitive tasks such as surveillance, while elliptical designs better serve infrastructure inspection missions requiring a balance of efficiency and thrust.