Effect on surface pressures of trapezoidal holes in a T-38 stabilator

Westkaemper, J. C.; Chandrasekharan, Reuben

doi:10.2514/3.44746

Cited by 5 publications

(4 citation statements)

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“…This may have first been observed in the late 1970s in wind-tunnel studies on the damaged T-38 stabilator in the low-speed wind-tunnel shown in Fig. 4b [2]. Figure 5 shows the extent of the through hole geometries investigated in this T-38 left stabilator during this wind-tunnel test.…”

Section: Aerodynamic Damage Modelmentioning

confidence: 75%

“…This was first identified by us as shown in Fig. 6, which illustrates the spanwise lift distribution determined from the integration of the measured chordwise pressure distributions on the one T-38 stabilator wind-tunnel model equipped with pressure taps [1,2].…”

Section: Aerodynamic Damage Modelmentioning

confidence: 99%

“…Flow through this damaged hole, in turn, creates a jet spoiler effect and significant unsteady lift, moment, and drag forces resulting from a separated unsteady wake flow localized at this damage site. Our earlier Air Force wind-tunnel studies on damaged lifting surfaces illustrated that the perturbation air loads due to this localized damage remains confined to this local damage site for the lower angles of attack of the lifting surface [1,2]. At the higher angles of attack of approximately 6 deg through stall, however, the effect of the localized damage propagates significantly over the lifting surface and its controls.…”

Section: Introductionmentioning

confidence: 99%

“…Localization of aerodynamic damage spanwise load distributions at small angles of attack and propagation of perturbation loads at the higher angles of attack[1,2].…”

mentioning

confidence: 99%

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Wind Tunnel Studies of Damaged-Wing-Induced Limit Cycle Oscillations

Park

Stearman

Kim

et al. 2008

Journal of Aircraft

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The influence of damage on the performance of the lifting surface of an aircraft has been an area of interest to the military for over half a century. Some of the earlier studies of this subject focused on the impact that structural damage resulting in the loss of lifting surface structural strength, stiffness, and mass might have on imparting catastrophic aeroelastic failures to the lifting surface. Discouraging mixed results arose over the next 30 years in these investigations that employed only structural damage models. As time passed, it was finally noticed that if the often neglected, usually second-order, drag term was now included (as aerodynamic damage often creates a high, unsteady, localized drag rise) in the earlier aeroelastic damaged-wing analyses, more encouraging results were obtained. That is, the realistic asymmetric damaged lifting surfaces flutter and divergence analysis did show lowered, and not raised, flutter and divergence speeds over that of the undamaged lifting surface. This occurred both in the presence of or in the absence of structural damage as in the case of icing or external wing stores. In essence, it was determined at this time that the resulting high and unsteady drag rise caused by the damage could do more than just cause an energy deficiency in the aircraft mission. It could, in fact, cause shorter term catastrophic or stiffness failure events in terms of reduced flutter and divergence speeds as well as give rise to limit cycle oscillations embedded within what was shown to be that part of the damaged-aircraft flight envelope free from classic flutter and divergence. The present experimental wind-tunnel study was carried out to confirm these past theoretical findings by employing a one-twelfth-scale F-111 aeroelastic model and (third-order) higher-order statistical signal processing to identify the frequency ordering that occurs in these additional damaged-induced limit cycle oscillations. These limit cycle oscillations were also found to exhibit the classic lock-in/lock-out phenomenon that occurs in the well-known F/A-16 and F/A-18 wing store induced limit cycle oscillations. Nomenclature C = modal damping matrix Ft = classical forcing function H C i; j; l = cubic frequency-domain Volterra transfer function H L k = linear frequency-domain Volterra transfer function H Q i; j = quadratic frequency-domain Volterra transfer function Kt = modal stiffness matrix which may vary with time M = modal mass matrix P C k = output of the cubic component of the Volterra model P L k = output of the linear component of the Volterra model P Q k = output of the quadratic component of the Volterra model P Y k = true observed response power spectrum PŶk = estimated response power spectrum of the Volterra model q = set of generalized coordinates S XX = power Spectrum of Xl S XXX = bispectrum of Xl S XXXX = trispectrum of Xl Xl = calculated value of the discrete Fourier transform of xn xn = nth sampled value of a digital time series Yl = calculated value of the discrete Fourier transform of yn yn= ...

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Section: Aerodynamic Damage Modelmentioning

confidence: 75%

Section: Aerodynamic Damage Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Localization of aerodynamic damage spanwise load distributions at small angles of attack and propagation of perturbation loads at the higher angles of attack[1,2].…”

mentioning

confidence: 99%

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