Airdrop Operations Research Articles

Functional Assumptions “Helicopter Simulator for Polish Police Aviation”

The analysis of the training needs for the crews of police multi-purpose Black Hawk S70i helicopters serving in Polish Police Forces has been an impulse to attempt the construction of the simulation system within the research and development project financed by the National Centre for Research and Development entitled “Helicopter Simulator for Police Aviation” consisting of three components, i.e. a training stand for a pilot (cockpit), a stand for a cargo handler, a training stand for the police officers practicing the air drop operations. The simulator is supposed to provide an opportunity to drill various emergency situations, which consequently will allow to prepare the crews and technical personnel in the full range to perform the tasks as far as theoretical knowledge and practical skills are concerned. Replacing real exercises by the training held in virtual environment will contribute to the decreased costs to be incurred by Police and increased safety for any persons participating in the actions remaining the subject matters of the said trainings. The article presents the designing assumptions resulting, among other things, from multidisciplinary research performed over the determination of the detailed training needs and equipment requirements with regards to the Full Flight Simulator. The said research was conducted in collaboration with the officers of the Police Aviation Board in the High Command of the Police Headquarters as well as the operators of the counter terrorism sub-units of Polish Police Forces.

Role of Geographic Information Systems in analysing the selection of cichociemni drop zones based on a case study of the “Mewa 1” drop zone

Abstract The article discusses the possible use of GIS tools in detailed spatial analysis of materials and old maps showing the activities of Polish soldiers during World War II. The research was based on information regarding the military operations of the “Silent and Unseen” paratroopers (in Polish: cichociemni) in the General Government (GG), available in the archives of the Polish Underground Movement Study Trust (in Polish: Studium Polski Podziemnej) in London, as well as on prewar maps of the Polish Military Geographical Institute (in Polish: Wojskowy Instytut Geograficzny – WIG). The authors present the historical background to, and important details of the cichociemni airdrops. They also describe how these operations were organised and suitable airdrop sites selected. The main part of the article is devoted to an analysis and assessment of the extent to which selected drop sites of the cichociemni complied with the criteria contained in the instructions of the Staff of the Commander-in-Chief in London (in Polish: Sztab Naczelnego Wodza w Londynie). The article presents a case study of the “Mewa 1” drop zone located in the GG. The authors used calibrated WIG maps, which they then converted into vector versions. They also made use of modern DTM and a slope map created on its basis. All the criteria for selecting drop zones included in the historical instructions were analysed. Based on the example of the drop zone in question, as well as on the authors’ own spatial analyses, it was concluded that this particular drop zone met some of the criteria formulated in the guidelines of the Commander-in-Chief’s Staff, but only partially met others or failed to meet them at all. In addition, the authors noted a number of limitations regarding these criteria. For example, they did not take into account the locations of the occupiers’ garrisons or anti-aircraft positions, which are particularly important for the success of airdrop operations. The analyses and the results thereof constitute the first study of the armed operations of the cichociemni in GG areas using digital maps and spatial analyses based on GIS.

FUNCTIONAL ASSUMPTIONS FOR THE “HELICOPTER SIMULATOR FOR POLICE AVIATION”

An analysis of training needs for the crews of police multi-purpose Black Hawk S70i helicopters serving in Polish Police Forces has been an impulse to attempt the construction of the simulation system within the research and development project financed by the National Centre for Research and Development entitled “Helicopter Simulator for Police Aviation” consisting of three components, i.e. a training stand for a pilot (cockpit), a stand for a cargo handler, a training stand for the police officers practicing the air drop operations. The simulator is supposed to provide an opportunity to drill various emergency situations, which consequently will allow preparing the crews and technical personnel in the full range to perform the tasks as far as theoretical knowledge and practical skills are concerned. Replacing real exercises by training held in a virtual environment is expected to contribute to a decrease in costs to be incurred by Police and enhanced safety for any persons participating in the actions remaining the subject of the said trainings. The article presents the design assumptions that arise, among other things, from multidisciplinary research performed over the determination of the detailed training needs and equipment requirements with regards to the Full Flight Simulator. The said research was conducted in collaboration with the officers of the Police Aviation Board in the High Command of the Police Headquarters as well as the operators of the counter terrorism sub-units of Polish Police Forces.

A paratrooper model sensitivity analysis for personnel airdrop

Personnel airdrop operations are subject to the unsteady flow around aircraft and variations in the paratrooper's exit orientation, body, weight, and balance. This could lead to non-repeatable airdrop operations including the possibilities of the paratrooper colliding with the aircraft or, after parachute deployment, another paratrooper leaving the opposite side. An exit trajectory sensitivity analysis addressing variations in mass distributions, exit velocity, initial position, and initial orientation is, therefore, an essential tool to increase aircrew and soldier safety. The goal of this study is to conduct time accurate simulations of two high-fidelity paratrooper models with different weight and balance data exiting the left- and right-side troop/exit doors of a C-130 after an initial prescribed motion. The aircraft model has an open troop door with fully-opened air deflector and extended flaps flying at 1,000 ft and 130 kn, and without propeller blades. Upon completing an initial prescribed motion, the paratrooper model is permitted to respond to the influence of the aircraft flow field and gravity. Solutions are calculated using HPCMP CREATETM-AV Kestrel software. In these simulations, the initial exit motion, position, and orientation are fixed. Trajectory data are extracted and compared. A normalized parameter of distance to the paratrooper diameter is defined to measure the trajectory translation deviations from a baseline exit case. The results show that trajectory data are more sensitive to the weight and balance data than aerodynamic forces/moments, which are functions of body profiles. For all tested right exits, the maximum deviations measure about three paratrooper body reference diameters, and all follow similar trajectory paths. Cases with small moments of inertia around the z-axis and a small side-force can lead to a negative yaw turn at initial exit times and a possible contact of main canopy container with the aircraft. The results show that left and right exit trajectories are very different mainly due to the asymmetries of paratrooper models. The results of these simulations document and characterize the associated strong moments, and the final states of the trajectories will serve as initial conditions for the subsequent parachute deployment.

Aircraft Mass Properties Estimation During Airdrop Maneuver: A Nonlinear Filtering Approach

Unlike a single-body approach, modeling based on a two-body approach has been employed to prepare the required system dynamic model as a time update equation in the applied filtering technology and measurement data for the estimation process. This more precise mathematical model enabled better understanding about the dynamics of the change in the aircraft mass properties during the airdropping operation. The problem is defined as estimation of the optimal mass properties parameters for the best possible fit of the model output to the real data. The parameter estimation problem is investigated by a nonlinear filtering methodology in two sequential steps. In the first step, the single extended Kalman filter is used to estimate the aircraft total mass and moment of inertia before entering an airdrop maneuver. In the second step, both the aircraft dynamic states and mass parameters are estimated during an airdrop maneuver using a joint extended Kalman filter. Monte Carlo simulations have then been performed to assess the performance of the algorithm in the presence of measurement errors and model uncertainties. The results indicate that time-varying aircraft mass properties estimation, as a technological requirement for the aircraft adaptive flight control system to reduce the risks involved with the airdrop operation, is satisfactorily possible.

이중 무인항공기 고공 비행전개 및 자율귀환 실험

이중 무인항공기 고공 비행전개 및 자율귀환 실험

Active disturbance rejection control for heavy cargo airdrop operations

In view of the strong nonlinear and coupling characteristics of the airdrop operations, a novel control method is proposed based on the active disturbance rejection control (ADRC) for decoupling control strategy of the pitch angle and airspeed. The unknown disturbances, including aerodynamic uncertainty and nonlinear coupling effect between the aircraft and cargo dynamics, are estimated and compensated with the extended state observer (ESO). Meanwhile, the nonlinear law state error feedback (NLSEF) is adopted to restrain the compensation residual. Simulation and flight quality evaluation shows the satisfactory capacity and strong robustness of the proposed control method in guaranteeing the airdrop task and flight safety.

Simulation of C-130 H/J troop doors and cargo ramp flow fields

This article presents the results of a continuing computational effort to understand the flow field characteristics of a C-130 Hercules aircraft configured for personnel airdrop operations. Flight operations with either the troop door or cargo open lead to vortical structures and unsteady flows which can adversely affect airdrop operations. Simulation results using the CFD solver Kestrel, developed within the High Performance Computing Modernization Program CREATETM-AV program, show vorticity generated behind the open cargo door and with the flaps extended, a relatively strong vortex forms along the fuselage which traverses above the troop door into the upsweep section of the aircraft tail. Open troop door simulations capture large velocity gradients and unsteadiness for configurations with and without actuator disk propeller models and with and without sideslip. Simulations are computed on both converged hybrid meshes on the order of 100 × 106 cells and near-body/Cartesian off-body grids, and these results reconfirm that vortex modeling is dependent on mesh resolution around troop door or cargo ramp. The addition of a refined mesh near the troop door, in conjunction with using a delayed detached-eddy turbulence model, provided highly resolved flow physics in this region of interest.

Numerical Simulation of Wake Flowfield Behind the C-130 with Cargo Ramp Open

Simulation results are presented for a C-130 aircraft configured to perform cargo airdrop operations. Flight operations with the cargo ramp open lead to strong vortical flow structures and unsteady flows, which can adversely affect airdrop operations and parachute deployments. The results document complex wake structures formed behind the C-130 with the cargo ramp open at 0 and 50% flap settings. In particular, the wake contains two asymmetric counter-rotating vortices formed between the open ramp and the upsweep section of the aircraft and near the rear edges of the ramp. The flow separates along these edges because of the sharp turn that flow makes as it enters the cargo compartment. The separated flow then rolls up into two vortices. These vortices move outward and upward, and then they pass very near the lower surface of the horizontal stabilizer. These vortical flows lead to unsteady airloads on the horizontal stabilizer, and thus the aircraft. The wake effects are larger behind the upper upsweep section and are minimum at the lower positions. Grid and time sensitivity studies are performed for several geometries to ensure numerical simulations are accurate for the separated and vortical flows. The results show that, as the grid becomes more refined in the region behind the upsweep section of the aircraft, the localized wake structures and unsteady effects are better captured by the flow solver.

Probabilistic Algorithm for Ballistic Parachute Transition Altitude Optimization

A probabilistic algorithm for the optimization of drogue-to-main parachute transition altitude is proposed for high-altitude, low-opening ballistic airdrop. In light of the significant effects of wind and model uncertainty on impact-point dispersion, the algorithm makes use of explicit nonlinear uncertainty propagation techniques to provide a probabilistically optimal transition altitude. The algorithm begins by the specification of a desired impact-point distribution, which is propagated backward in time through the nonlinear main parachute dynamics using the stochastic Liouville equation. This spatially varying probability density is uploaded to the package before release from the aircraft. During drogue descent, the package descent trajectory through these probability densities is predicted, and an optimal drogue-to-main parachute transition altitude is identified. A key aspect of the proposed algorithm is that the desired impact-point distribution is an input to the algorithm, enabling novel capabilities to shape the resulting dispersion pattern and avoid obstacles in the target area. Furthermore, the algorithm explicitly accounts for primary sources of uncertainty affecting ballistic airdrop operations. Results demonstrate that the proposed optimization algorithm has the ability to reduce dispersion, improve accuracy, and shape impact distributions around obstacles and among multiple drop zones.

Modeling and active disturbance rejection control for sequential airdrop operations

With the assumption t at the motion acceleration of the cargo is unknown, the dynamic model that accords with the engineering practice of sequential cargo airdrop operations is derived by using the separation body method, which can describe the impact of the sequential moving cargos on the flight safety and airdrop-mission capacity. On this basis, a novel flight control method is designed based on the active disturbance rejection control (ADRC) theory. the system is decoupled and linearized through the nonlinear state error feedback; the total unknown disturbances, including unmolded dynamics and uncertainty, are estimated and compensated real-timely by the extended state observer. Moreover, with the consideration of the time-delay system, the ADRC is improved to enhance the accuracy and rapidity of the control system. Simulations are carried out under the condition that one transport aircraft performs sequential airdrop operations. The results verify that the desirable performance and robustness have been achieved and the proposed control method is quite competent for the sequential airdrop operations.

Adaptive backstepping sliding mode control for heavy-weight airdrop operations

This paper proposes an adaptive backstepping sliding mode flight control method that is compatible with heavyweight cargo airdrop. The goal is to maintain the plane states during cargo extraction process, in the presence of uncertainties of both constant and time-varying types, as well as matched and unmatched types. A backstepping sliding mode flight control law with parameter adaptation is presented based on the plane-cargo dynamics in strict-feedback form. The control approach consists in having an adaptation law that approximates the disturbance and uncertain aerodynamic function, which is separated from the complex nonlinearities. Also, the adaptation algorithm with projection can bound the estimated function. This ensures the robustness of the controller against time-varying disturbance and uncertainty. The convergence performance and robustness property of the control law are proved by the Lyapunov theory. The control effect is evaluated on a transport plane performing a maximum load airdrop task in a number of simulation scenarios.

Finite-time adaptive sliding mode control for heavyweight airdrop operations

Finite-time adaptive sliding mode control for heavyweight airdrop operations

Flight controller design for aircraft low altitude airdrop

Purpose During low altitude airdrop operations, the heavy cargo moving inside and the sudden dropping out exert serious threats on the aircraft safety and mission performance. This paper aims to propose an efficient flight control method for the airdrop operations. Design/methodology/approach A novel controller which combines feedback linearization with nonlinear integral sliding mode control is proposed. The aircraft airdrop model is decoupled and linearized by using the feedback linearization technique. On this basis, an integral sliding mode controller is designed to stabilize the speed and pitch attitude of the aircraft. In the sliding manifold, one class of nonlinear functions with the property of “smaller errors correspond to bigger gains and bigger errors correspond to saturated gains” is introduced to form the integral term; thus, the overcompensation of the integral term to big errors is omitted, and the dynamic response performance is improved. Lyapunov-based stability analysis shows that the controller could completely reject model uncertainties by choosing proper controller parameters. Findings The flight control system with strong robustness could meet the low altitude airdrop indexes in the maximum weight cargo airdrop task. Originality/value This paper fulfils an urgent need to study how to control the aircraft to guarantee mission performance and flight safety during the low altitude airdrop operations.

Application of Satellite- and NWP-Derived Wind Profiles to Military Airdrop Operations

AbstractThe Joint Precision Airdrop System (JPADS) has revolutionized military high-altitude airdrop capability, allowing delivery of equipment and supplies to smaller drop zones from higher altitudes than was previously possible. This capability relies on accurate wind data, currently provided by GPS dropsondes released in the vicinity of the drop zone shortly before the airdrop. This research investigates the potential for a wind-profiling algorithm to generate the required wind data from passive IR and microwave satellite soundings, eliminating the requirement for a hazardous dropsonde pass near the drop zone. The Atmospheric Infrared Sounder (AIRS) provides a 3D temperature field and determines the heights of 100 standard levels. From these data, the slopes of the isobaric pressure surfaces and temperature gradients are used to calculate wind speed and direction using the thermal wind relationship. The accuracy of these satellite-derived wind profiles is evaluated through comparison with rawinsonde measurements near the coordinates and time of the AIRS sounding. Further investigation of the wind profile accuracy is made by a comparison with numerical weather prediction (NWP) data worldwide, and the effect of cloud cover in the vicinity of the target coordinates is analyzed. The AIRS-derived winds are found to be less accurate than short-term NWP winds for the JPADS application, but the technique developed may be applied to alternate applications, such as use in the stratosphere, where NWP winds are not widely available. The agreement between satellite-retrieved temperatures and measurements at altitudes above 30 km indicates the AIRS data could be used to create accurate, 3D fields of optical turbulence strengths for directed-energy applications.

Heavyweight airdrop flight control design using feedback linearization and adaptive sliding mode

This paper investigates the problem of designing a novel adaptive sliding-mode controller for heavyweight airdrop operations. The design objective is to guarantee asymptotic tracking performance of the aircraft states, in the presence of bounded nonlinear uncertainties without prior knowledge of the bounds. On the basis of feedback linearization of the aircraft–cargo model, a sliding-mode control method with projection-based adaptive function approximation is proposed. This method uses an adaptation strategy to achieve robustness against model uncertainties, and a knowledge of the bounds on the complex uncertainties is not required. Notably, the adaptation law with projection can bound the estimated function, and this avoids singularity of the control signal. Simulations are conducted under the condition that one transport aircraft performs a maximum load airdrop mission at a height of 25 m, using single-row single-platform mode. The results verify the good properties of the control method, which can meet the airdrop mission performance indexes well in the presence of ±20% aerodynamic data uncertainty and 20% actuator fault.

Projection-Based Adaptive Backstepping Control of a Transport Aircraft for Heavyweight Airdrop

An autopilot inner loop that combines backstepping control with adaptive function approximation is developed for airdrop operations. The complex nonlinear uncertainty of the aircraft-cargo model is factorized into a known matrix and an uncertainty function, and a projection-based adaptive approach is proposed to estimate this function. Using projection in the adaptation law bounds the estimated function and guarantees the robustness of the controller against time-varying external disturbances and uncertainties. The convergence properties and robustness of the control method are proved via Lyapunov theory. Simulations are conducted under the condition that one transport aircraft performs a maximum load airdrop task at a height of 82 ft, using single row single platform mode. The results show good performance and robust operation of the controller, and the airdrop mission performance indexes are satisfied, even in the presence of ±15% uncertainty in the aerodynamic coefficients, ±0.01 rad/s pitch rate disturbance, and 20% actuators faults.

Sensitivity Analysis of Airdrop Condition Parameters Based on Response Surface Method

The airborne vehicle would suffer from impact at landing. The magnitude of impact and stability of airborne vehicle are constraint parameters of successful landing. There was a lack of scientific explanation on the sensitivity of landing condition parameters. For overcoming the deficiency of classical sensitivity analysis, this paper describes the application of new technology for the sensitivity analysis. Based on the Finite Element and Response Surface method, the research on sensitivity analysis of landing condition parameters was proposed. The results have important significance in the design and optimization of airborne vehicle and airbags system. It can be also provide guidance for airdrop operation.

Sliding mode disturbance observer-based backstepping control for a transport aircraft

This paper presents a novel control method by integrating the sliding mode disturbance observer-based control and the backstepping control technique, and successfully applies it to a flight control system for heavy cargo airdrop operations. The super-twisting second order sliding mode disturbance observer (SOSMDO) is employed to estimate bounded but otherwise arbitrary disturbances, thus ensuring asymptotic convergence of the estimation error to zero in a finite time. Besides, the integrated controller can significantly improve the robustness of the flight control system to modeling uncertainty and external disturbance in the presence of state/control constraints. The closed-loop stability is guaranteed in the sense of Lyapunov. In addition, the proposed approach can considerably reduce design cycles. The performance of the proposed control method is demonstrated in a very low altitude extraction airdrop simulation with a high-fidelity six-degree-of-freedom transport aircraft model.

Experimental investigation of the vortical activity in the close wake of a simplified military transport aircraft

This paper focuses on the experimental characterization of the vortex structures that develop in the aft fuselage region and in the wake of a simplified geometry of a military transport aircraft. It comes within the framework of the military applications of airflow influence on airdrop operations. This work relies on particle image velocimetry measurements combined with a vortex-tracking approach. Complex vortex dynamics is revealed, in terms of vortex positions, intensities, sizes, shapes and fluctuation levels, for both closed and opened cargo-door and ramp airdrop configurations.