The present Paper investigates the ditching characteristics of a helicopter model by means of an in-house-developed smoothed-particle-hydrodynamics solver coupled with a six degree-of-freedom motion equation. Verification and validation have confirmed the feasibility and accuracy of the developed solver in predicting hydrodynamic problems. In view of the inherent importance, the effect of initial pitching

In this Paper, the wake dynamics of coaxial rotors are studied using the high-wake-resolution method. The high-wake-resolution method is a novel combination of the truncated vortex tube model for initial and boundary conditions and the wave-number-extended finite-volume interpolation scheme. The wake resolution of this method is verified by comparison with other general computational fluid dynamics

Air traffic controller workload is considered to be a limiting factor for further air traffic growth. To reduce workload, increased automation levels and novel decision-support tools are being investigated. This Paper describes the adaptation and evaluation of a previously developed interface, called the Solution Space Diagram, in a route merging task. It portrays both constrained and unconstrained

Some of the existing challenges of fixed-wing micro aerial vehicle designs at low Reynolds number are low lift and reduced aerodynamic efficiency. Delta wings, despite their characteristic maneuverability, are rarely used for micro aerial vehicles, perhaps due to the limited lifting capacity because of the reduced aspect ratio. Corrugations on insect wings are ubiquitous and augment the aerodynamic

Droplet deformation and breakup in the continuously accelerated flowfield generated by an incoming airfoil have been studied. The upper limit of droplet deformation and the minimum distance to the airfoil model at which the breakup onset takes place have been modeled. Three analytical equations have been developed based on the combination of two models: a droplet deformation and trajectory model for

A 10%-scale high-lift version of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested. The main objective of the test was to develop an AFC system that can provide the necessary lift recovery on a simple-hinged flap high-lift system while minimizing its pneumatic power requirement. The tests were performed in the

A simple, accurate, reduced-order model is developed for predicting the maximum available thrust performance of subsonic ring-wing propulsors varying in shroud airfoil length, thickness, camber, and/or angle of attack relative to the centerline. The method, applicable to drones, aircraft, ships, and more, identifies the potential upper limit to the thrust augmentation available from hover to cruise

Recent aircraft noise calculation methods separate engine and airframe noise components to provide accurate single-flight noise predictions. General noise mapping, such as legal compliance calculations, usually relies on position data as the only available input. Therefore, more advanced input variables of engine and airframe noise models require estimation based on position data. This paper presents

Regime recognition (RR) is an important aspect of condition-based maintenance for modern helicopters. RR involves the postflight classification of flight data into regime categories. These classifications are then used to predict fatigue damage and vehicle usage spectra. Although several RR algorithms have been proposed to date, many suffer from an overreliance on training data or poor accuracy when

Because of the large domestic civil aircraft projects started in China a decade ago, there is a greater need to control the accuracy of the Mach number in aerodynamic tests, especially near the designed cruise point of large commercial aircraft. Nowadays the control accuracy of China Aerodynamics Research and Development Center 2.4-meter transonic wind tunnel Mach number is in the range of ±0.002 to

This paper presents a thorough evaluation of three flutter prediction techniques based on the well-understood autoregressive moving-average (ARMA) parametric model. Other than the original stability parameter Fz that is derived from the identified autoregressive coefficients, the flutter margin and the Houbolt–Rainey (H-R) method are also presented and adjusted to provide alternative flutter predictions

In this Paper, the integrated propeller–wing system design space is investigated to gain insight into the influence of propeller diameter, location, and rotation direction. To conduct this investigation, a methodology is developed that uses the propeller power required during steady-level flight as a metric for efficiency. Full mutual interaction between the propeller and wing are taken into account

This work presents the aeromechanics analysis and evaluation of an ultralight counter-rotating coaxial rotorcraft using a combined numerical and experimental approach with a focus on turn, climb, and descent flight conditions. The helicopter features a 2-by-2 bladed coaxial rotor system with teeter hinges, 6.5 m in diameter and uniform airfoil sections of the linearly twisted blades. Hover and forward-flight

An advanced potential flow method is used to study the aerodynamic interactions between small rotors of quadrotor configurations and the impact on the overall flight performance. The aerodynamic analysis method is validated by comparing the thrust and power predictions of isolated rotors in hover and forward flight with experimental results. The aerodynamic model was next extended to consider the interactions

We discuss the requirements of a predictive microburst flight trajectory guidance system, and analyze the trajectories of low thrust-to-weight ratio airplanes passing through a microburst downdraft and vortex ring along the approach glideslope. The simulation results reveal that it is possible to fly through such a microburst using 5–20 deg pitch angle and maximum thrust. T tests and one-way analysis

Control surface reversal is a classical aeroelastic phenomenon commonly investigated during aircraft development. It occurs under static equilibrium between the elastic restoring torque and the aerodynamic moment on the system. Besides the equilibrium, it depends on an additional condition defined through the lift force. As discussed in the literature, this second condition can be considered by two

Boundary-layer ingestion (BLI) promises increased aircraft efficiency, but excessive inlet distortion must be avoided to prevent fans that are too heavy or structurally infeasible. We propose a new approach to study the effect of distortion on BLI propulsors via an aeropropulsive design optimization with a constraint on inlet distortion using highly efficient gradient-based methods with analytic derivatives

An experimental remotely piloted aircraft named X-HALE was designed and built at the University of Michigan to collect experimental data for the flight dynamics of vehicles with very flexible wings. Similar aircraft with a wing span of 4 and 6 m were later developed and built at the Aeronautics Institute of Technology, Brazil, to study the flight dynamics and control of highly flexible aircraft. In

The hinge clearance and rotation axis deviation of aircraft landing-gear retraction mechanism are unavoidable due to factors, such as manufacture, assembly, wear, and wing deformation. Such negative factors affect the dynamic response of the mechanism itself, which is more serious for spatial mechanisms. To study this effect, both numerical and experimental investigations on a spatial landing-gear

This paper studies the influence of flared-hinge folding wingtips on the aerodynamic derivatives and flight dynamics of a narrow-body transport aircraft. In addition, the influence of fold angle, hinge-line angle (flare angle), and wingtip size on wing loading is assessed. The Tornado vortex lattice method is used for aerodynamic predictions and to estimate the stability and control derivatives. First

Journal of Aircraft, Ahead of Print.

The mean flowfield in the aft region of cargo aircraft configurations is analyzed using large-eddy simulations. A simplified surrogate fuselage is considered, consisting of a cylinder with axis parallel to the flow and a slanted (upswept) base. Emphasis is placed on understanding the major changes that occur in the flow as the upsweep angle of the base is increased in a broad 20°–45° range. Qualitative

This paper conducts improved delayed detached eddy simulation (IDDES) to numerically investigate the performance of a three-dimensional (3D) aircraft control surface using coflow jet (CFJ) active flow control. For the numerical validation with the baseline control surface that has a large flow separation, the predicted lift coefficient CL and drag coefficient CD achieve a very good agreement with the

A key challenge in the design of hybrid-electric propulsion systems (HEPSs) for aircraft is the complexity involved in handling efficient sizing of the components as well as control synergy between multiple power sources. To handle this challenge effectively, combined optimal design and control (codesign) methods that enable the integration of energy management optimization along with vehicle sizing

Journal of Aircraft, Ahead of Print.

The pursuit of greener aviation led to the investigation of new aircraft concepts. Disruptive aircraft configurations show great potential in reducing the ground noise impact, but extensive research is required before they can be manufactured. Tube-and-wing aircraft with over-the-wing engines, benefiting from noise shielding, are a more feasible option for midterm noise reduction targets. This work

Journal of Aircraft, Ahead of Print.

By using a computational-fluid-dynamics-based numerical virtual flight (NVF) simulator, a simplified quasi-Cobra maneuver of a typical third-generation fighter is simulated and the unsteady aerodynamics, such as the dynamic forces and moments and the flow separation, are analyzed preliminarily. The NVF simulator integrates an unsteady Reynolds-averaged Navier–Stokes (RANS) solver on dynamic unstructured/hybrid

Journal of Aircraft, Ahead of Print.

The quad tilt rotor (QTR) has complex aerodynamic characteristics and strong aerodynamic interference. The flight dynamic model is the basis of control. To effectively account for the aerodynamic interference between the multiple aerodynamic surfaces of the QTR unmanned aerial vehicle, a hybrid optimization trimming analysis method based on Immune Algorithm/Levenberg–Marquardt (IA/LM) and lattice Boltzmann

The rotor blade double-swept-tip geometry can effectively improve the aerodynamic and aeroacoustic behaviors of a rotor. However, the aeroelastic or aeromechanical behaviors of a double-swept rotor helicopter are a challenge to helicopter flight safety and need to be investigated. In this paper, the aeromechanical stability of a bearingless rotor helicopter with double-swept blades is studied. The

As multirotor vehicles become integrated into the national airspace for applications such as package delivery and videography, it is important that the inner-loop control system be robust and able to meet ever-demanding performance constraints. To achieve high bandwidth control designs, it is necessary to have accurate and high bandwidth open-loop models. In this Paper, a linear state-space model of

Recent research on flight-deck interval management technology, including the findings of a flight-test demonstration conducted by NASA, led to the development of an alternative control logic for flight-deck interval management, termed as “interval management–speed planning.” As this logic demonstrated promising results in numerical simulations, for the first time, test pilots and airline pilots were

Journal of Aircraft, Ahead of Print.

Journal of Aircraft, Ahead of Print.

This Paper describes a new method of correcting the wind tunnel wall interference of permeable Kevlar test section walls. The classical three-dimensional panel method is extended to flows in a Kevlar-walled test section and modified to improve its general predictability. The results computed using this enhanced panel method are in good agreement with experimental results with regard to the pressure

Journal of Aircraft, Ahead of Print.

Earlier work did not find any static stiffness nonlinearities in the F-16 wing structure, but suggested that dynamic nonlinearities may be present. Computational studies have demonstrated that small amounts of nonlinear structural damping are sufficient to change a diverging flutter oscillation into a limited amplitude oscillation. Experimental damping measurements of a fixture-mounted F-16 wing were

Journal of Aircraft, Ahead of Print.

A computational investigation of the drag and heat transfer experienced by multiple trailing (following) vehicles in hypersonic flight is presented. Linear arrays of vehicles in flight at Mach 10 are modeled. Results are presented for both parametric two-dimensional cases and for a three-dimensional case. Drag and heat transfer on trailing vehicles in two-dimensional (five vehicle) arrays, for both

This Paper describes how flight simulation has been used to investigate helicopter recovery operations to the deck of HMS Queen Elizabeth, the United Kingdom’s new aircraft carrier. A helicopter flight simulation environment has been developed in which the unsteady airflow over the ship has been created using full-scale computational fluid dynamics. A six-degree-of-freedom motion flight simulator has

Hybrid-electric aircraft are a potential way to reduce the environmental footprint of aviation. Research aimed at this subject has been pursued over the last decade; nevertheless, at this stage, a full overall aircraft design procedure is still an open issue. This work proposes to enrich the procedure for the conceptual design of hybrid aircraft found in literature through the definition of a multidisciplinary

A generic framework for the simulation of transient dynamics in nonlinear aeroelasticity is presented that is suitable for flexible aircraft maneuver optimization. Aircraft are modeled using a flexible multibody dynamics approach built on geometrically nonlinear composite beam elements, and the unsteady aerodynamics on their lifting surfaces is modeled using vortex lattices with free or prescribed

Journal of Aircraft, Ahead of Print.

Journal of Aircraft, Ahead of Print.

Reliable prediction of aircraft poststalled dynamics is entirely dependent on the adequacy of the aerodynamic model. A mathematical model of aerodynamic characteristics of a light aircraft is developed for a wide range of angles of attack, sideslip, and angular rates. It is augmented by a model of uncertainties based on a set of repeated measurements of static aerodynamic characteristics. The effect

A multidisciplinary gradient-based sensitivity-analysis methodology is evaluated for optimization of rotorcraft configurations. The tightly coupled discipline models include physics-based fluid dynamics and rotorcraft comprehensive analysis. A discretely consistent adjoint method accounts for sensitivities of the unsteady flow and unstructured, dynamic, overset grids; whereas sensitivities of structural

It has been shown experimentally that local nonlinear stores attached to the wings of a model airplane enhance overall energy dissipation through global nonlinear modal energy exchanges. Here, a computational model is developed to investigate this effect. The dynamics of the airplane–store system is studied under impulse loading with both stores locked (L-L configuration), left-wing store unlocked

It is investigated whether a nonrotating lifting fan remaining uncovered during cruise flight, as opposed to being covered by a shutter system, can be realized with limited additional drag and loss of lift during cruise flight. A wind-tunnel study of a wing-embedded lifting fan has been conducted at the Side Wind Test Facility Göttingen of DLR, German Aerospace Center in Göttingen using force, pressure

Formal experiment design and analysis techniques featuring design of experiments were applied to a Mars parachute wind tunnel test. The experiments were part of an extensive study conducted in 2014 by the NASA Engineering and Safety Center to evaluate the performance of two candidate parachute systems. Reduced scale models of the legacy Disk-Gap-Band (DGB) parachute and new Supersonic Ringsail (SSRS)

Journal of Aircraft, Ahead of Print.

The increased number of daily flights in the last decades has led to the densification of major airports and the proliferation of air traffic delays. The approach phase is inherently complex and labor extensive for flight crews, whose mission is to follow a stabilized approach. Current flight management systems do not provide much help in situations of high energy, where crews apply challenging energy

An aeroelastic modeling capability of a flexible aircraft with gas turbine engines is developed using a computational fluid dynamics tool as an integration platform. The new modeling capability allows for the typical aeroelastic analysis to include a nonlinear dynamic model of the turbomachinery that is capable of capturing relevant gas dynamics. An example case of the aero-propulso-elastic (APE) modeling

Journal of Aircraft, Ahead of Print.

Carbon fiber reinforced polymer composites are widely used in aircraft structures due to their excellent mechanical properties, light weight, and corrosion resistance compared to conventional metallic materials. However, the low electrical conductivity in the composite’s thickness direction makes them susceptible to lightning strike damage. An all-polymeric lightning strike protection (LSP) system

Until electric energy storage systems are ready to allow fully electric aircraft, the combination of combustion engine and electric motor as a hybrid-electric propulsion system seems to be a promising intermediate solution. Consequently, the design space for future aircraft is expanded considerably, as serial hybrid-electric, parallel hybrid-electric, fully electric, and conventional propulsion systems

Journal of Aircraft, Ahead of Print.

Folding wingtips have begun to feature on recent aircraft designs, as a solution for compliance with existing airport gate width regulations while enabling high-aspect-ratio wings for lower induced drag and better overall fuel efficiency. Recent studies have suggested that by allowing folding of the wingtip during flight, additional gust load alleviation can be achieved. This paper describes the first

This paper presents the development of a simulation framework, SIMSHOL, which has a predictive capability to inform and support real-world ship–helicopter operating limit trials for a range of helicopter–ship combinations. SIMSHOL is a desktop-based predictive simulation tool that presents an objectively optimized human pilot modeling technique within an integrated pilot–vehicle–environment that represents

Journal of Aircraft, Ahead of Print.