Helicopter Operations Research Articles

A Maneuvering Flight Noise Model for Helicopter Mission Planning

A new model for estimating the noise radiation during maneuvering flight is developed in this paper. The model applies the quasi-static acoustic mapping (Q-SAM) method to a database of acoustic spheres generated using the fundamental rotorcraft acoustics modeling from experiments (FRAME) technique. A method is developed to generate a realistic flight trajectory from a limited set of waypoints and is used to calculate the quasi-static operating condition and corresponding acoustic sphere for the vehicle throughout the maneuver. By using a previously computed database of acoustic spheres, the acoustic impact of proposed helicopter operations can be rapidly predicted for use in mission planning. The resulting FRAME-QS model is applied to near-horizon noise measurements collected for the Bell 430 helicopter undergoing transient pitch-up and roll maneuvers, with good agreement between the measured data and the FRAME-QS model.

Simulation model of loads created by a hingeless helicopter rotor

This work proposes a technique for simulation of integral loads created by a hingeless helicopter rotor, which is based on implementing neural network algorithms. A method, which accounts for variation of angular speeds of the main rotor in the simulation model is proposed. Feasibility of the proposed model is justified on an example of computation and simulation of a helicopter operating in steady flight conditions.

Numerical modeling of turbulence above offshore helideck – Comparison of different turbulence models

The turbulent flow over an offshore oil-rig helideck has been simulated by a commercial engineering CFD code, Star-CCM+, with nine different turbulence models: two Reynolds-stress transport equation (RSE) models, six k–ε models and one k–ω model. Simulations by the same code and models were compared to experimental data for simpler test cases, including flows over a backward-facing step and a surface-mounted cube. The primary aim was to compare RSE models to two-equation models on the background of a new industry standard for helicopter operation with requirements on the vertical velocity variance over the helideck. It was found that RSE models do not outperform two-equation models for separated flows and wakes. The RSE models seem to underpredict the turbulence energy more than the two-equation models and hence, also the vertical velocity variance. Among the two-equation models, the realizable k–ε model and Menter׳s k–ω model performed better than the standard k–ε model, while a cubic k–ε model predicted unphysical, negative normal Reynolds stresses. Attempts on adjusting the coefficients of the k–ε model, as promoted by some authors, worked fine for undisturbed atmospheric flow but quite poor for more complex flows.

Minimizing takeoff and landing risk in helicopter pickup and delivery operations

The problem of minimizing total helicopter passenger risk caused by takeoffs and landings is studied. There are passenger pickup and delivery demands to be satisfied at given points by flights starting and ending in the same heliport and visiting several points. For each point, the delivery demand is the number of passengers to be transported from the heliport to this point and the pickup demand is the number of different passengers to be transported from this point to the heliport. Each pickup and delivery demand must be satisfied in full by one flight. There are an upper bound on the number of flights and an upper bound on the helicopter passenger capacity. The objective function is a linear combination of the numbers of passengers involved in takeoffs and landings at visited points. A solution is characterized by the number of flights, sets of visited points and their sequences for all flights. Properties of optimal solutions are established. Several cases are proved NP-hard. A quadratic boolean programming formulation and two dynamic programming algorithms are suggested for the general case. Computer experiments demonstrated that they are able to solve real-life instances. Polynomial time algorithms are presented for special cases. Implementation of the suggested solutions into the real helicopter operations should decrease the number of fatalities.

Generalized Prognostics Algorithm Using Kalman Smoother

The ability to prognosticate the future state of a mechanical component can greatly improve the ability of a helicopter operator to manage their assets. Fundamentally, prognostics can change the logistics support of a helicopter by: reducing spares, improving the likelihood of a deployment meeting its mission requirements, and reducing unscheduled maintenance events. A successful prognosis is based on applying a fault model and usage of metrics (torque) to a diagnostic. This paper addresses a generalized fault and usage model through simplification of Paris’ Law and the use of a Kalman Smoother. This state observer technique is a backward/forward filtering technique that has no phase delay. This allows a generalized, zero tuning model that provides an improved component health trend, and a better estimate of the current remaining useful life (RUL).

Method for Lightweight Optimization for Aerospace Milled Parts – Case Study for a Helicopter Pilot Lightweight Crashworthy Seat Side Struts

Abstract As a follow up of the light weight design policies, topology optimization of aerospace milled parts is on the focus of development teams from many years. In the last period (especially after Airbus A380 roll up) there were presented methods to save weight and even parts on airplanes manufactured this way. Emerged form an aerospace structures design team, paper presents a method to combine the 2D topological optimization with classic 3D static stress design iterations, leading to significant weight savings. The results will be implemented on a future helicopter operator seat under development for a multirole helicopter.

Target Detection with Helmet-mounted Displays in Low Visibility Helicopter Operations

Poor visibility can pose a serious safety hazard in helicopter flight, leading to a loss of situation awareness, spatial disorientation, and high pilot workload. Therefore, the use of helmet-mounted displays recently became increasingly important for rotary-wing aircraft. To assist pilots in degraded visual environment, new HMD symbology designs were developed at the DLR Institute of Flight Guidance. They were tested in a simulator study with 18 civil and military helicopter pilots and compared to a state-of-the art PFD/ND test condition. Concurrent task performance was investigated, which included the detection and identification of targets in the environment. Hit rate was analyzed as a function of display type, visibility, target type, and the presence or absence of cueing. Moreover, differences between pilot experience and operational area were assessed. Results revealed a significant HMD detection cost for un-cued targets compared to when no symbology was presented. In contrast, cueing significantly increased hit rate, resulting in substantial HMD benefits when proper attentional guidance was provided.

Flow in the near air wake of a modified frigate

Current naval ships were designed without considerations for the air wake encountered on the flight deck. Naval frigates superstructures design has resulted in a sharp-edges box type that generates a wake dominated by highly turbulent recirculating flows. These flows can affect the safety of the helicopter during the takeoff and landing maneuvers. This paper presents wind tunnel tests performed in order to obtain a more complete insight and understanding of the typical flow on a simple frigate shape. Moreover, a solution to reduce the influence of the wake flow above the flight deck and a risk reduction for on-board helicopter operations is proposed by modifying the usual frigate geometry. Four simple frigate shape hangar roof configurations were investigated by wind tunnel testing. Measurements of the velocity and pressure fields on the flow above the flight deck were performed and results compared in order to evaluate the effectiveness of the modified hangar roof design.

Low Cost Helicopter Training Simulator: A Software Case Study from the Brazilian Military Police

This work describes a computer based training system to assist the crew members to learn the ground school of helicopter AS350-B2, manufactured by HELIBRAS, a Brazilian helicopter company and widely used by the Armed Forces, Civil and Military Policies and by companies of executive transportation and load lifting. The training system consists of a 1:1 scale aircraft cabin simulator, a system software and a MS Flight Simulator interface. The project is in advanced phase of development and it already possesses positive declarations of interest from company training divisions and helicopter's operators. A case software used by Brazilian Military Police is presented.

군용헬기 결빙 감항인증을 위한 국내 기상환경에 관한 연구

Based on atmosphere weather data by balloon in Osan and Gwangju area, if icing condition occurs in weather environment of altitude range where helicopter is operated was analyzed in quantitative way. Yearly icing occurrence frequency for daytime during recent three years was average 102 days in Osan, average 91 days in Gwangju. Icing weather environment to highly affect operation of helicopter varies a little according to analysis methods but icing intensity at MDT level was calculated in all the methods, and 14.5~38 times was suggested in Osan; 2.5~30 times in Gwangju. Icing at MDT level was calculated in common in all the analysis methods through wide periods such as Jan., Feb., Mar., and Nov. in Osan. In Gwangju, icing at MDT level was suggested focusing on Jan. only. Therefore, military helicopter developed in Korea is required to strive obtaining certificate of airworthiness about icing condition at MDT level for implementation of perfect operational mission and safe operation.

Detection and identification of helicopter noise in beach environments

Noise generation by helicopters has been studied extensively as has auditory perception of helicopter noise—both in terms of detection and identification and in terms of annoyance. Recent work [Hoglund et al., J. Acoust. Soc. Am. 128, 164–171 (2010)] has identified the importance of accounting for the specific soundscape when modeling detection performance, suggesting that empirically derived signal-specific detection thresholds must be further adapted to account for differences between real-world ambient environments. Beaches and other coastal environments are an interesting case study for evaluating real-world performance of detection and identification models. In addition to a presenting an unusual and highly dynamic propagation environment for helicopter noise, the natural soundscape resulting from wind and breaking waves has unique spectral and temporal properties that influence how it masks the acoustic signature of helicopters. Here, measurements of a helicopter operating in a beach environment are compared with theoretical and empirical models including models of airborne noise from breaking waves [Bolin and Abom, J. Acoust. Soc. Am. 127, 2771–2779 (2010)]. Detection and identification performance are compared with predictions of models for rotorcraft noise—developed in other ambient environments—and models for wind-turbine noise—developed for similar coastal environments.

야간산불진화 헬기 운영과 항공안전

Not only in Korea, but also in other countries, most helicopter accidents occur at low altitude. Analysis on accidents data collected both in Korea and other countries has brought two conclusions. Firstly, helicopter operations during the night hours carries a high risk. Secondly, the most common cause of night hour operations is loss of control due to the flight illusion. As an operation relying on a night vision in particular has a very high accident hazard, accompanying instruments such as NVG are ought to be provided. Hence, a thorough preparation and inspection on missions for night forest fire extinguishing should be required and perfect guidelines/road maps and enough training programs for the operation should be provided before the engagement in missions.

Study on the Vortex Ring State of Helicopter and Flight Training Operation

Vortex ring state (VRS) is an inherently unsteady aerodynamic phenomenon. For rotor operations in the VRS, an inherent unsteadiness is a characteristic of the flow state, which is reflected by the waves and knots produced on the tip vortex filaments. Operationally, entry into the VRS manifests as rotor thrust fluctuations and also an increase in the average rotor shaft torque, the latter which is necessary to overcome the higher induced aerodynamic losses associated with rotor operations inside its own wake. Arming to the flight safety, the VRS development is discussed, the VRS models are summarized, and the operations for flight out VRS are given at the end of this paper. It is helpful to helicopter flight and training.

Do oil and gas risk owners understand real-world helicopter winch rescue hazards?

Helicopter search and rescue (SAR) for oil and gas operations in the northwest of WA is undertaken by helicopters and crews contracted to support oil and gas operations. The capability of these crews and aircraft varies and is described by helicopter operators as either limited or restricted SAR. This differs to similar oil and gas regions of Australia and globally, where full or dedicated SAR is available to respond to pre-identified rescue events. Key differences between full and restricted SAR equate to WA operations being unable to conduct winch rescue at night from the water, limited capability to winch from vessels and lack or search technology such as night vision and heat signature equipment considered essential elsewhere. The type of oil and gas operations undertaken in the northwest of WA are no different to other parts of the world, especially in terms of identified accident event potential. However, despite the need for full SAR as a preparedness measure for oil and gas emergencies overseas, northwest WA still operates to a lesser capability. There is much discussion as to the rational for this situation, but regardless of opinion logic would suggest, at the very least, opportunity exists to review northwest oil and gas risk management process for this specific field as development of increasingly complex and distant offshore operations continues. Therefore, this report, its supporting training materials and supplementary reports, seek to both clarify and reinforce hazards associated with helicopter SAR to enable more robust risk management going forward.

Experimental Investigation of the Flow on a Simple Frigate Shape (SFS)

Helicopters operations on board ships require special procedures introducing additional limitations known as ship helicopter operational limitations (SHOLs) which are a priority for all navies. This paper presents the main results obtained from the experimental investigation of a simple frigate shape (SFS) which is a typical case of study in experimental and computational aerodynamics. The results obtained in this investigation are used to make an assessment of the flow predicted by the SFS geometry in comparison with experimental data obtained testing a ship model (reduced scale) in the wind tunnel and on board (full scale) measurements performed on a real frigate type ship geometry.

2A2-F03 マルチロータヘリコプタ運用システムの開発(飛行ロボット・メカトロニクス(2))

2A2-F03 マルチロータヘリコプタ運用システムの開発(飛行ロボット・メカトロニクス(2))

The virtual AirDyn: a simulation technique for evaluating the aerodynamic impact of ship superstructures on helicopter operations

AbstractThis paper describes a simulation technique that has been developed to quantify the unsteady forces and moments that are imposed onto a maritime helicopter by a ship’s airwake during a deck landing. An unsteady CFD-generated airwake, created using a CAD model of the ship, is integrated with a flight dynamics model of a helicopter. By holding the helicopter at a fixed position in the airwake it is possible to quantify the unsteady forces and moments imposed on the aircraft. The technique is therefore a software-based airwake dynamometer, and has been called the virtual AirDyn. As well as determining the mean loads, from consideration of the unsteady loads in the closed-loop pilot response frequency range of 0·2-2Hz it is also possible to quantify the magnitude of the unsteady disturbance in each axis. The loads are also indicators of the control activity the pilot would have to exert to maintain aircraft position and attitude. By placing the virtual AirDyn at different positions around the landing deck in different wind conditions, it is able to quantify the effect of the airwake on the mean and unsteady loads. The quantified loads can be explained by examining the CFD-generated flow field, and the geometric features on the ship’s superstructure that gave rise to them can be identified. The virtual AirDyn is therefore a tool that can be used to evaluate and inform ship design for maritime helicopter operations.

2013 Aircrew, Avionics, and Operations Survey, Part 2

In this second half of a 2-part series, chief/lead pilots were invited to complete a 40-question survey modeled on the AirMed 2000 Helicopter Avionics and Operations Survey via an online survey. The survey was available to rotor-wing (RW) and fixed-wing air medical transport services in the United States, although year 2000 comparative data are RW only. Topics surveyed include flight hours, aircraft models, avionics, interiors, staffing, weather minimums, and maintenance facilities.

Helicopter Accident Analysis

Analysis of helicopter accidents is fundamental to the development of effective mitigation measures. However, there are significant weaknesses in the current methods. This paper proposes a new structured framework for the analysis of accidents in helicopter operations, which includes the determination of the appropriate timeframe for analysis, establishment of terminological definitions, identification of the relevant accident variables and data sources, and the execution of a three-fold statistical analysis strategy. It is implemented in the context of worldwide offshore helicopter operations, enabling the identification of a number of areas for priority intervention including the need for a global harmonisation of accident data capture and dissemination, causal factor-based metrics for the calculation of accident rates, better pilot support for night-time and arrival operations, and a new safety paradigm to mitigate rare accidents. The framework is recommended for the analysis of helicopter accidents and incidents to support safety improvement.

Effects of visual and motion cues in flight simulation of ship-borne helicopter operations

Good visual cues are necessary in the flight simulation of ship-borne helicopter operations. Operating in a degraded visual environment cues has a negative impact on pilot workload and task performance. However, the need for motion cues in piloted flight simulation is still a widely debated issue. This paper describes a preliminary piloted flight simulation study into the effects of visual and motion cues on the operation of ship-borne helicopters and pilot workload. Unsteady CFD airwakes have been computed and integrated into the FLIGHTLAB modelling and simulation environment with a simulated rotorcraft model, configured to be representative of an SH-60B helicopter. A series of ship-deck landing and hover manoeuvres have been conducted using the University of Liverpool’s HELIFLIGHT-R motion-base flight simulator representing different visual and motion cues, for a range of ship airwakes and sea states (ship deck motions). The usable cue environment (UCE), handling quality and pilot workload ratings were assessed using visual cue ratings, handling quality rating and the Bedford workload rating scale and Deck Interface Pilot Effort Scale. This paper presents the results from simulation trials with two test pilots examining the effect of the simulation cueing on task performance and workload. Visual cues were found to have a significant impact both on the UCE ratings and pilot workload ratings. In degraded visual environments, the pilot’s ability to make corrections in attitude and translational rates was reduced. Pilots experienced higher workload in terms of compensatory control inputs to complete the same mission task as compared to operations in a good visual environment. Analysis of the pilots’ workload ratings and control activity show that motion cueing can cause differences in pilot perceived workload. For the simulation of ship-borne operations, the impacts of motion cueing are dependent on other simulation conditions, which include visual environments, airwake, sea states and ship deck motion. The effect of motion cueing on pilot workload and control activity was found to be more significant when the visual cueing was degraded. The variations in pilot workload ratings and control activities under different motion and visual cues indicate that the Ship Helicopter Operating Limits can be affected by the simulation cueing fidelity.