Browse Topic: Data exchange
In this paper the time accurate coupling between the high fidelity CFD code FLOWer and the multi-body dynamics code SIMPACK is presented. To facilitate this coupling a socket-based data exchange was developed and used to exchange aerodynamic forces and kinematic data. Two flight states were investigated: a hover and a forward flight. To obtain a reasonable initial flight state a previously obtained, trimmed solution was taken as the base. This study shows the feasibility of the strong coupling approach with the direct influence of the helicopter motion on the flow field and vice-versa. As expected, the factor limiting the overall performance is the runtime of the CFD simulation. The effort of running the flight mechanics simulation and the data exchange necessary for the strong coupling is negligible compared to this runtime.
This paper investigates an output-based approach for predicting limit-cycle oscillations caused by freeplay, which can affect actuated structures of vertical lift vehicles. The proposed approach uses pre-critical time-history data to estimate the recovery rate to equilibrium following perturbations as a function of amplitude and a varying parameter. Recovery rate data points in the parameter-amplitude plane are fitted and extrapolated to predict limit-cycle oscillation solutions, corresponding to a recovery rate of zero. While previous work demonstrated this approach for systems with geometrical or polynomial stiffness nonlinearities, this study investigates its applicability to freeplay for the first time. The study uses time-history data from simulations of an analytical model of an idealized, elastically mounted tilting propeller in airplane mode, with freeplay in the tilting mechanism. The results highlight the promise of the proposed approach, paving the way for addressing more
We present our ongoing efforts towards the development of crash-tolerant rotorcraft airframe structures through topology optimization, with the goal of enhancing energy absorption and occupant survival during vertical impact events. A high strain rate explicit dynamics solver has been developed, fully accelerated on GPUs, to enable rapid and accurate simulation of impact events critical to crashworthiness evaluation. In parallel, we have built a scalable three-dimensional topology optimization framework that enforces stiffness, weight, and frequency constraints simultaneously, driving structurally efficient and vibration-resistant designs. Benchmarking results demonstrate significant GPU-enabled speedups, facilitating high-fidelity crash simulations and large-scale optimization at practical turnaround times. This work establishes a computational foundation for future integration of crash-centric objectives and constraints into the optimization framework.
A quantitative understanding of the perceptual elements of handling qualities rating brings us to the heart of pilot control. In previous work it was shown that pilot induced oscillation ratings (PIORs) were a strong linear function of the closed loop dominant mode decay rate of the modeled pilot-vehicle system. While PIORs are based solely on the degree that oscillation degrades the task, the handling qualities rating (HQR) scale employs aggregate performance criteria and three apparently distinct sensations: workload, compensation, and controllability. However, in practice the pilot must modulate control in real time based on an instantaneous sense of performance. It is incumbent to model these four perceptions if the objective is to reproduce the manner and resolution with which the pilot assigns HQRs. The current work examines the same offset landing task that was conducted in two separate piloted studies: 1) Flight, using the Calspan variable stability NT-33A aircraft, and 2
Rotorcraft continue to experience higher fatal accident rates compared to fixed-wing aircraft, primarily due to low altitude flight operations and reduced situational awareness in complex environments. A critical factor is the limited availability of accurate, up-to-date information on helipads and surrounding obstacles - such as trees, poles, and buildings - that pose significant risks during takeoff and landing. Existing resources, including the Federal Aviation Administration's heliport registry, are often outdated and incomplete, particularly for private or state-operated sites, and fail to report nearby obstacles. This lack of up-to-date data is largely due to privacy restrictions at certain locations and the high cost associated with comprehensive obstacle surveys. To address this challenge, we develop a deep learning (DL) framework that automatically detects helipads and nearby obstacles from high-resolution satellite imagery. Our approach combines Mask R-CNN for precise pixel
The Main Gearbox of a helicopter is a crucial component that delivers the desired performance and ensures the highest possible level of safety of the aircraft; it includes several gears and bearings, which require to be continuously lubricated by a pressurized oil flow. Undesired circumstances may cause the oil to leak from the main circuit, hence reducing its pressure and consequently the oil flow rate targeted towards the rotating components; this modifies their friction coefficient, and subsequently leads to an overheating of the parts with the risk of degenerating in a catastrophic failure. During the design of a helicopter drive system, engineers need to take proper precautions and make sure that the MGB is fully equipped with the proper features to cope with a loss of lubrication event; specifically, the drive system is supposed to be able to run at least 30 minutes after the oil pressure drops to zero. A lot of effort has been put over the years at Leonardo Helicopters to find
This research analyzes flight safety occurrences such as incidents and accidents in the vertical lift community over the last two decades. A study of civil vertical lift occurrence data was performed for flight occurrences from 2000 to 2024. Focusing on North America (Canada, United States), research data was acquired from the respective government Transportation Safety Board agency of either country. The study data set consisted of 4623 occurrences (occ.) or observations (i.e.; 861 for Canada and 3762 for the United States). The research methodology involved a 6-step process to analyze data quantitatively (descriptive statistics) and qualitatively (trends, mitigation projections). For the study period, quantitative findings indicated occurrence rates (4.53 occ. per 100k flight hours (Canada); 3.39 occ. per 100k flight hours (United States)), occurrence rates of change (declining Canadian and United States rates (-2.3%/yr. & -2.2%/yr.) respectively), and occurrence event types (in
A piloted simulation experiment was conducted in the NASA Ames Vertical Motion Simulator to investigate the effects of bandwidth, phase delay, attitude quickness, and maximum achievable rate on yaw-axis handling qualities in hover and forward flight. Two different aircraft were tested, representative of advanced scout-class rotorcraft. Five target acquisition and tracking Mission Task Elements were used in the study. Two of the tasks were modified versions of tasks used to determine the ADS-33E target acquisition and tracking yaw attitude quickness boundaries. Two of the tasks were modified versions of attitude capture and hold and sum-of-sines tracking previously used to evaluate pitch and roll axis handling qualities. The final task was a forward flight target acquisition task developed for this study based on a ground attack or strafing maneuver. Eight Army pilots participated in the study and evaluated 60 yaw-axis configurations. The results of the study suggest that the current
Maintenance of spatial orientation (SO) is achieved primarily through visual information where the horizon and celestial reference cues or flight instruments are used by pilots to infer aircraft orientation. However, cross checking the instruments in degraded visual environments can be complicated by factors such as workload, distraction, and situations where the vestibular and proprioceptive systems may provide false and competing orientation information. We describe experiments measuring pilot performance using a flight simulator under challenging conditions where the sensory information was controlled. Reducing available visual instruments increased the task difficulty. A wearable vibrotactile array could provide concurrent, additional orientation information. Increasing the flying task segment difficulty increased the perceived workload and also corresponded to an increase in accidents. Adding tactile orientation information reduced the accident rate.
A key objective of this work was to develop a quantitative rationale to explains some aspects of pilot rating variability, as this would point to the fundamental principles driving pilot response that may not be observable if averaged ratings are used as a handling qualities metric. This paper hypothesizes that the factors affecting a pilot's ability to stabilize and control an aircraft following abrupt control motion is neither the damping nor the frequency of the ensuing oscillation, but rather the length of time that the oscillation remains large enough to interfere with the task (i.e., the product of damping and frequency). A handling qualities metric is introduced called the decay rate parameter that reflects the decay rate of the closed loop dominant mode. Closed loop pilot-vehicle oscillation decay rates were generated by a pilot model employing pitch (visual channel) and pitch rate (vestibular channel) tracking strategies. These decay rates were used to predict minimum and
A Common Open Data Exchange format for rotorcraft Health and Usage Monitoring Systems (CODEX-HUMS) would offer a more affordable, capable and effective Integrated Vehicle Health Management System. The Society of Automotive Engineers (SAE) HM-1R committee is developing a standard definition for the CODEX-HUMS open data format produced or used by an on-board or off-board system, SAE Aerospace Standard AS7140. The standard format benefits end users (e.g., operators, developers, suppliers, integrators, and maintainers) with the capability to more rapidly operationalize HUMS data. This HUMS open data format meets the intent of a Modular Open System Approach (MOSA) and provides a foundation for rapid realization of operational benefits from the point of maintenance and from the exchange of HUMS data with external enterprise systems.
This paper documents the re-evaluation and updates to the previous Partial Regime Recognition Spectrum effort for the MH-47G using Structural Usage Monitoring System (SUMS). Further validation of the SUMS algorithm allowed for additions to the spectrum. These additions include more refined categorization of turn and partial power descent regimes based on angle of bank and descent rates, respectively; high load prorates for turns, partial power descents, level flight, and climbs based on the Cruise Guide Indicator; exceedances of maximum density altitude; and use of occurrences for Landing and Run-On Landing regimes. Additional years of flight data from 2013 to 2019 were included in this effort. The updated usage spectrum for the Army MH-47G aircraft has been delivered to the OEM (Original Equipment Manufacturer). The OEM calculated new fatigue lives and updated the "Fatigue Substantiation Report", which will soon be fielded.
This paper investigates a sliding-window matrix pencil method for predicting flutter points and limit-cycle oscillation amplitudes of nonlinear aeroelastic systems that experience whirl flutter. The approach applies the matrix pencil method to a short time window that slides along the free decay of a quantity of interest, quantifying the variation in the system's recovery rate to equilibrium with amplitude. The recovery rates at each amplitude and various forward speeds are extrapolated to predict the critical forward speed of zero recovery rate at those amplitudes. This process yields a set of limit-cycle oscillation solutions that can be visualized as a bifurcation diagram. The approach is demonstrated using output data from transient simulations of a propeller-nacelle test case with hardening structural nonlinearities. The impact of each parameter in the sliding-window matrix pencil method is first characterized via sensitivity analyses. Next, the bifurcation diagram is predicted
A state-of-the-art emerging progressive damage failure analysis tool CDMat has been successfully applied to multiple material systems on open-hole tension and compression, and double shear bearing laminate coupons under static and fatigue loading including simulation to ultimate failure. CDMat also successfully demonstrated component-level strength/fatigue analysis under the Air Force Composite Airframe Life Extension (CALE) and the Fail-Safe Technologies for Bonded and Unitized Composite Structures (FASTBUCs) Programs. Building on the success of CDMat an integrated software solution for certification and sustainment of rotorcraft primary composite structures is being developed. A method and an algorithm for fatigue crack growth simulation in laminated structures are proposed to improve the accuracy of CDMat fatigue predictions. The method is based on using cohesive material model, tracking material points at the crack front, and calculating the pointwise energy release rate employing
This paper investigates an output-based approach for tiltrotor whirl flutter bifurcation analysis. The approach uses free decay output data for a quantity of interest at various forward speeds to estimate the system's recovery rate to equilibrium while capturing its variation with amplitude. The recovery rate is then extrapolated to predict the bifurcation diagram, which gives the limit-cycle oscillation amplitude for the quantity of interest as a function of the forward speed. The approach is demonstrated using output data from transient simulations of a notional tiltrotor model with polynomial structural nonlinearities. The approach accurately predicts the tiltrotor whirl flutter speed and limitcycle oscillation amplitudes while only requiring two free decays. This approach can facilitate whirl flutter bifurcation analyses of tiltrotor systems exhibiting nonlinear dynamics.
Prior to 1950, use of the helicopter for evacuation was extremely limited, as military top brass often considered it a worthless contraption; thus, rescue was uncertain at best for downed pilots and wounded soldiers stranded behind enemy lines. However, this all changed in Korea, where twelve U.S. Army helicopters from three detachments, working in tandem with seven, newly created Mobile Army Surgical Hospital (MASH) units, would fundamentally change the Army's medical-evacuation doctrine forever. Using several models of the Bell H-13, the Hiller H-23, and the Sikorsky H-5 and H-19, this small band of courageous pilots pushed themselves and their aircraft to their limits, transporting 21,212 critically wounded soldiers for life-saving surgery to various MASH units, cutting the fatality rate from World War II in half. Adopting the 3rd Air Rescue Squadron's motto, "That Others May Live," these pilots and their helicopters were affectionately known to the wounded as "Angels of Mercy."
Safety professionals receive data from internal and external sources, then manually determine whether the issue constitutes a safety hazard. Many reports are received, and each report is reviewed, then investigated further, using a tedious, labor intensive, and possibly error prone process. In the course of reaching a decision, human bias is inevitable - any two humans could reach different conclusions, and the same individual human could draw different conclusions on different days. As technology has advanced, numerous approaches have been pursued, attempting to reduce human bias and improve both efficiency and effectiveness of the process. In recent years, moderate success was achieved, which provided accuracy rates near 85% but continued refinement did not achieve acceptable results. In early 2023, the challenge was given to a new team, and within a few months, state-of-the-art Artificial Intelligence/Machine Learning data analytics techniques were utilized to aid in safety data
The airframe digital twin analysis framework developed at the National Research of Canada is being transposed to safe life applications for rotorcraft components. A probabilistic safe life prediction approach, consisting of uncertain material property data and uncertain load spectra is used to calculate risk assessment metrics, such as the cumulative probability of failure, the hazard rate, and the average hazard rate as a function of time. A demonstration of this approach is presented for a CH-146 Griffon component, for which the uncertain loads are estimated from a model developed through machine learning. This preliminary assessment shows the feasibility of using digital twin concepts as a viable alternative to traditional deterministic life predictions, with the potential to reduce maintenance costs and increase aircraft availability.
Sealed electronic components are the basic components of aerospace equipment, but the issue of internal loose particles greatly increases the risk of aerospace equipment. Traditional material recognition technology has a low recognition rate and is difficult to be applied in practice. To address this issue, this article proposes transforming the problem of acquiring material information into the multi-category recognition problem. First, constructing an experimental platform for material recognition. Features for material identification are selected and extracted from the signals, forming a feature vector, and ultimately establishing material datasets. Then, the problem of material data imbalance is addressed through a newly designed direct artificial sample generation method. Finally, various identification algorithms are compared, and the optimal material identification model is integrated into the system for practical testing. The results show that the proposed material
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