Paragliders Stability Characteristics

Benedetti, Diego Muniz; Pinto, Rafaela da Silveira; Ferreira, Ricardo

doi:10.4271/2013-36-0355

Cited by 2 publications

(5 citation statements)

References 2 publications

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“…The CL-Alpha curve plotted in Figure 8, presenting an average lift slope of 0.024 per degree, is fully compatible with the results obtained by previous researchers [27]. Further, the resulting wing load range from 30 Pa to 50 Pa corresponds precisely to the expected range previously calculated [8]. Therefore, parallel observations seem to lead to consistent results, reinforcing the usefulness of the differential pressure measurement approach, and the relevance of the inner flow.…”

Section: Pressure Coefficient (Cp) Distribution and Lift Estimationsupporting

confidence: 88%

“…These results support computational predictions from which the C p distribution follows the baseline airfoil pattern, with a relevant modification limited to the air intake region [6,18,27]. Considering a steady glide speed of 10 m/s, typical of inflatable wings [8], a differential pressure range of 0-150 Pa is expected throughout the surface.…”

Section: Differential Pressure Measurement Standardssupporting

confidence: 82%

“…None of these values correspond to the final wing load, which requires integration throughout the surface, but they are a fair indicative based on local evaluations. Considering that common paragliders and parafoils present wing-loads around 40 Pa [8], the collected data show that the average reading at operational speed (9 m/s) is substantially above this value, whereas, at inflation speed (6 m/s), the average differential pressure is much lower. Consequently, a calibrated system can dynamically monitor wing stiffness using the average differential pressure, and its time derivative sign, to provide an alert preventing further reductions in speed.…”

Section: Collapse Triggers and Shape Stabilitymentioning

confidence: 90%

“…The flight dynamics of most inflatable wing systems are based on the pendulum mechanism [8], which is obtained by positioning the center of gravity (CG) of the system far below and after the aerodynamic center (AC). Such a construction provides mechanical and aerodynamic stability through the dynamic balance between the wing's relative airspeed and incidence.…”

Section: Structural Aspectsmentioning

confidence: 99%

“…Dynamic excursions, at low and high speeds, were executed by varying AOA to evaluate the system's capability to capture dynamic changes in pressure distributions during maneuvers and to evaluate instrumentation integrity. It is worth clarifying that the operational range concept is related to normal flight conditions, which is limited to speeds between 9 to 12 m/s and AOA from 0 • to 10 • [8]. For most paragliders and parafoils, the steady glide is maintained at speeds near 10 m/s and AOA around 5 • .…”

Section: Wind-tunnel Test Proceduresmentioning

confidence: 99%

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Wind-Tunnel Measurement of Differential Pressure on the Surface of a Dynamically Inflatable Wing Cell

Benedetti

Veras

2021

Aerospace

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An instrumentation system for in-situ measurement of the inner-outer pressure differential at the upper and lower surfaces of dynamically inflatable wings is designed and tested, revealing important insights into the aerodynamic characteristics of inflatable airfoils. Wind tunnel tests demonstrated full capability of low-pressure differential readings in the range of 1.0–120 Pa, covering speeds from 3 to 10 m/s at angles of attack from −20 to +25°. Readings were stable, presenting coefficients of variation from 2% to 7% over the operational flight envelope. The experimental data confirmed the occurrence of a bottom leading-edge recirculation bubble, linked to the low Reynolds regime and the presence of an air intake. It supported the proposition of a novel approach to aerodynamic characterization based on local pressure differentials, which takes in account the confined airflow structure and provides lift forces estimations compatible with practical observation. The results were also compatible with data previously obtained following different strategies and were shown to be effective for parameterizing the inflation and stall phenomena. Overall, the instrumentation may be applied straightforwardly as a flight-test equipment, and it can be further converted into collapse alert and prevention systems.

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Section: Pressure Coefficient (Cp) Distribution and Lift Estimationsupporting

confidence: 88%