Pilot Sensitivity to Simulator Flight Dynamics Model Formulation for Stall Training

Cunningham, Kevin; Shah, Gautam H.; Murphy, Patrick C.; Hill, Melissa A.; Pickering, Brent P.

doi:10.2514/6.2019-0717

Cited by 6 publications

(13 citation statements)

References 7 publications

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“…It is not possible to directly translate these frequency and amplitude dependencies into time simulation of free flights involving arbitrary motions. This can be partially resolved by replacing the dependence on the frequency 𝜔 with the dependence on the angular pitching velocity 𝑞, as was done in [17,19].…”

Section: Quasi-steady Modellingmentioning

confidence: 99%

“…As the name suggests, the GTT represents a generic mid-size regional jet airliner with a T-tail configuration. Its aerodynamic data were collected from a series of low-speed sub-scale wind tunnel and water tunnel tests, and some preliminary results have been reported in recent conferences [17][18][19]. Computational fluid dynamics was also deployed to estimate the influence of the Reynolds number on the measured aerodynamics data, allowing the pitching moment and pitch damping data to be adjusted to represent the equivalent full-scale aircraft.…”

Section: Gtt Implementation and Validationmentioning

confidence: 99%

“…The increase of frequency correlates with the increase of pitch rate amplitude 𝑞 𝑚𝑎𝑥 during forced oscillations executed at the same amplitude. This is why in [17,19], for example, the damping terms are the equivalent of equations (5)(6), where frequency was replaced with angular rate 𝑞. Such modification of the quasi-steady aerodynamic model allows only the delay process in flow separation to be represented, while the relaxation process is not accounted for.…”

Section: Gtt Implementation and Validationmentioning

confidence: 99%

“…We use both conventional bifurcation analysis and the nonlinear frequency response to examine the sensitivity of stall and post-stall behaviours to the choice of unsteady modelling method: quasi-steady or unsteady. The GTT uses wind tunnel test data by NASA and Boeing [17][18][19] from both static and forced oscillation tests, resulting in a nonlinear but conventional (quasi-steady) flight dynamics model. We then augment the quasisteady GTT model with unsteady aerodynamics effects using the state-space method (sometimes referred to as the Goman-Khrabrov model in the literature) [4], so as to compare the two aerodynamic modelling techniques and validate the capability of the state-space approach in matching the forced oscillation test results.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evaluation of Unsteady Aerodynamic Effects in Stall Region for a T-Tail Transport Model

Nguyen¹,

Goman

Lowenberg

et al. 2022

AIAA SCITECH 2022 Forum

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Although quasi-steady aerodynamic modelling is a widely used technique, its shortcomings in representing the stall and post-stall dynamics have been noted in the literature. Various methods to model the unsteady aerodynamics effects have been proposed as a result, but their direct implications on the aircraft's flight dynamics characteristics have not been widely studied. In this paper, we combine the state-space method for unsteady aerodynamic modelling with bifurcation analysis to examine the sensitivity of stall and post-stall behaviour to the choice of aerodynamic modelling method: quasi-steady or unsteady. It is found that quasi-steady modelling is adequate for the chosen example of a T-tailed transport aircraft that does not undergo rapid manoeuvring. The study is then expanded to investigate a hypothetical situation with highly unsteady aerodynamic characteristics resembling a delta wing configurationachieved by increasing the time delay constants in the unsteady model. This results in an aircraft with significantly lower flying qualities as indicated by bifurcation analysis. These findings highlight the need to implement unsteady aerodynamic modelling techniques in high-performance aircraft with significant vortex-related unsteady aerodynamics in order to sufficiently capture their stall and post-stall dynamics.

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Section: Quasi-steady Modellingmentioning

confidence: 99%

Section: Gtt Implementation and Validationmentioning

confidence: 99%

Section: Gtt Implementation and Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evaluation of Unsteady Aerodynamic Effects in Stall Region for a T-Tail Transport Model

Nguyen¹,

Goman

Lowenberg

et al. 2022

AIAA SCITECH 2022 Forum

View full text Add to dashboard Cite

show abstract

“…These developments emphasise the need to improve our understanding of the flight characteristics in the deep stall regime. Future studies on this topic can also benefit from recent data published by NASA [20][21][22], which provides highfidelity flight dynamics modelling of a hypothetical T-tail passenger aircraft as part of the global effort to reduce airliner loss-of-control incidents [23,24].…”

Section: Introductionmentioning

confidence: 99%

Analysing dynamic deep stall recovery using a nonlinear frequency approach

2022

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Based on bifurcation theory, nonlinear frequency response analysis is a recent development in the field of flight dynamics studies. Here, we consider how this method can be used to inform us on how to devise the control input such that the system transitions from an undesirable equilibrium solution—an aircraft deep stall solution in our case—to a desirable solution. We show that it is still possible to induce a large-amplitude oscillation via harmonic forcing of the pitch control device and escape the otherwise unrecoverable deep stall, despite very little control power available in such a high angle-of-attack flight condition. The forcing frequencies that excite these resonances are reflected as asymptotically unstable solutions using bifurcation analysis and Floquet theory. Due to the softening behaviour observed in the frequency response, these unstable (divergent) solutions have slightly lower frequencies than the value predicted using linear analysis. Subharmonic resonances are also detected, which are reflected in the time-domain unforced responses. These nonlinear phenomena show strong dependency on the forcing/perturbation amplitude and result in complex dynamics that can impede recovery if the existing procedures are followed. The proposed method is shown to be a useful tool for nonlinear flight dynamics analysis as well as to complement the rather thin literature on deep stall analysis—a topic of relevance for recent research on unconventional landing techniques in unmanned aerial vehicles. A full description of the aircraft model used, the unstable F-16 fighter jet, is provided in the appendix.

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Derivation of control inputs for deep stall recovery using nonlinear frequency analysis

2022

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Although the problem of locked-in deep stall is well documented over many years, there currently exists no consistent procedure that can guarantee recovery. Past studies have suggested that it might be possible to rock the aircraft in pitch to destabilise the statically stable deep stall trim point, thereby gaining enough momentum to push the nose down. However, the methods used in these studies are either of preliminary or empirical nature and cannot guarantee recovery. In this paper, we use bifurcation analysis to derive a recovery manoeuvre, specifically by assessing the aircraft’s nonlinear frequency response under an elevator forcing. The ensuing nonlinear Bode plot detects unstable (divergent) solutions near resonance that contribute to a successful deep stall recovery. Moreover, the nonlinear resonant frequency is slightly lower than the result obtained using linear analysis, and time simulation shows that relying on the linear result does not lead to a successful recovery. It is also found that at the high angles of attack associated with deep stall, the frequency separation between the short period and phugoid mode is significantly reduced, leading to only one visible peak in the frequency response. This feature is also reflected in the time-domain step response.

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Pilot Sensitivity to Simulator Flight Dynamics Model Formulation for Stall Training

Cited by 6 publications

References 7 publications

Evaluation of Unsteady Aerodynamic Effects in Stall Region for a T-Tail Transport Model

Evaluation of Unsteady Aerodynamic Effects in Stall Region for a T-Tail Transport Model

Analysing dynamic deep stall recovery using a nonlinear frequency approach

Derivation of control inputs for deep stall recovery using nonlinear frequency analysis

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