Browse Topic: Test facilities
Future military missions for Agile Combat Employment (ACE) and next generation Special Operations Forces need an aircraft with effective hover and the ability to operate in transonic cruise. Hover requires significant power that can only be mitigated by larger diameter rotors, but large diameter rotors become a detriment to achieving transonic flight. The stop-fold rotor configuration can “make the rotor disappear” in cruise and stands out as the most viable option for meeting these next-generation air vehicle requirements. This paper discusses the progress Bell has made in developing enabling technologies for a practical and scalable high-speed VTOL (HSVTOL) based on the stop-fold configuration. To this end, a unique Track-Guided Test Vehicle (TGTV) was developed at Bell and tested at the 10-mile High Speed Test Track at Holloman Air Force Base. The test vehicle integrates all subsystems required to demonstrate the key technologies in a representative environment, including multi-mode
This study presents computational analyses of coaxial rotor hub flows and validation against experimental data obtained from the fifth Rotor Hub Flow Prediction Workshop. Experiments were conducted in a 12-inch diameter water tunnel at Pennsylvania State Applied Research Laboratory, employing tomographic particle-image velocimetry (Tomo-PIV) and precise hub drag measurements. Three CFD codes (UMD Mercury, CREATETM-AV Helios, and OVERFLOW) utilizing hybrid Reynolds-Averaged Navier-Stokes (RANS) / Large Eddy Simulation (LES) modeling based on Spalart–Allmaras turbulence model, were applied to replicate and analyze hub flows. Counter-rotating coaxial rotor hubs under free-air condition was simulated as the simplest case and the hub drags are compared between the three CFD codes. The full water tunnel configuration, consisting of two hubs, a fairing, and shafts, was also simulated and compared to experimental results, with a focus on hub drag, wake velocity fields, and turbulence
With recent advancements in the field of Advanced Air Mobility (AAM), including Electric Vertical Takeoff and Landing (eVTOL), Remotely Piloted Aircraft Systems (RPAS), and Unmanned Aerial System (UAS), it is beneficial to understand the impact of complex flow features on operations in urban and shipboard environments. Testing methods for studying these impacts, including simulated environments such as wind-tunnel flows and engineered equivalence tests, will need to be adapted to prepare for when the vehicles of interest are too large for the available testing facilities, and to permit low-cost alternatives for industry and government. This work demonstrates a development process that can be used to ensure the complex-flow-environment phenomena can be studied. First, this work illustrates the development of downdraft and turbulence flow types in a wind tunnel setting, and assesses the response of an M600 RPAS to these flows. Then, the same parameters are compared for a Mission Task
Helicopter pilots are exposed to a wide range of vibration frequencies, primarily generated by engine and rotor dynamics. These vibrations, particularly within the 0.5–80 Hz range, pose significant risks to pilot health, including musculoskeletal injuries and fatigue. To mitigate these effects, vibration isolators are employed, with passive and active isolation systems offering different advantages. This study investigates the initial design and performance of a novel metal additive manufactured vibration isolator, optimized for placement under the pilot's seat in a rotorcraft simulator. The isolator was designed with key structural parameters including stiffness, coil dimensions, and material properties while maintaining a lightweight and durable form, with a primary goal of validating the additive manufacturing of a metallic isolator. Experimental corroboration was conducted by incorporating modifications to the Gannon Biomechanics Flight Simulator test stand (GBFS), comparing the
This paper describes the methodology, involving testing and simulation activities, to assess malfunction conditions of complex systems installed on fly-by-wire vehicles, including the evaluation of their effects. This paper provides also a description about how the system malfunction tests are designed, driven by input requirements and systems capability and behavior. With respect to prior publications, this paper includes some practical test examples, based on systems monitoring, logics and alerting functions. The case study described here comes from a portion of multiple laboratory certification tests done for AW609 Tiltrotor, focused on Avionics System malfunctions. These tests and simulations are a valuable Means of Compliance with respect to applicable airworthiness rules, and a suitable means to verify the design safety requirements. Three relevant examples are presented, grouped by input requirement and safety conditions. The effect of such malfunctions is evaluated, with
A computational study is conducted on a coaxial rotor hub and sail fairing configuration to analyze hub surface forces and the characteristics of its downstream wake. The flow conditions and grids are based on experimental tests performed at the Penn State Applied Research Lab (ARL) Water Tunnel at a baseline Reynolds number. Grid development for the rotor hubs and sail fairing is done using Pointwise v18.04R1 and Chimera Grid Tools (version 2.2). Simulations are performed using NASA's OVERFLOW2.4b Reynolds Averaged Navier-Stokes solver. The drag forces on the rotor hubs are computed and compared to standalone drag data to analyze the effects of interactional aerodynamics. Flow features, frequency content and Reynolds stresses of the wake are analyzed. Frequency content and Reynolds stresses show clear spatial bias. The anisotropy of the Reynolds stresses is computed and used to determine the character of the wake turbulence.
This study models the interaction of a two-bladed 14" propeller with the ground under different configurations using actuator disk method (ADM) where the rotor is modeled using unsteady momentum sources distributed over the entire disk. While ADM has been extensively used for standard rotorcraft analysis, it's performance in unconventional operating conditions remains an open question. Exhaustive experiments conducted at DEVCOM Army Research Laboratory are compared with ADM to evaluate the inexpensive method's ability to predict rotor loads for parametric variations in rotor-ground interaction scenarios. Partial ground effect (part of the rotor operating IGE), side-by-side rotors in ground effect and variation in IGE pitch attitude are specifically considered in this study. ADM generally predicts the thrust increase in partial ground effect (PGE) as the rotor goes from OGE to IGE although the increase is somewhat earlier and milder than measured in experiments. Side-by-side rotors in
Design modifications to a 3lb variant of DEVCOM Army Research Laboratory's Common Research Configuration (CRC-3) are assessed using simulation tools. To identify areas for improvement, the baseline CRC-3 is analyzed in hover and forward flight, and contributors to overall power consumption are identified, with the rotor drag consuming the greatest amount of power, due to the high rotational speeds required to maintain thrust in the face of the freestream velocity. Potential areas for improvement are identified as: wing airfoil, rotor blade pitch, and rotor orientation. Changing the airfoil has little to no measurable effect on the overall power consumption. Increasing the blade pitch improves cruise performance considerably, but at the cost of hover efficiency, for an overall range improvement of up to 28%. Changing the rotor orientation improves rotor efficiency as well, without substantial cost to hover power consumption, increasing the range by 37% but will require a redesign of the
The paper presents recent and ongoing activities of the German Aerospace Center (DLR) focusing on experimental icing investigations within the nationally funded project InTEnt-H (2018-2022) and progressive activities in continuing internal DLR projects. The aim of InTEnt-H was to investigate innovative de-icing and anti-icing technologies for small and medium-weight helicopters, for which no rotor de-icing technologies exist to date, and to demonstrate the effectiveness of these systems in a suitable test facility. For this purpose, the whirl tower test facility of the DLR in Braunschweig has been converted into an icing test facility that is unique in Europe and will allow for the generation of atmospheric icing conditions. In this facility, de-icing and anti-icing systems for rotor blades can be tested under centrifugal loads and various icing conditions. The paper starts with a short presentation of the retrofitting works at the DLR whirl tower test facility and its major components
ABSTRACT Pressure Sensitive Paint (PSP) rotor hover predictions are obtained using computational fluid dynamics simulations. Laminar-turbulent transitional modeling predictions are made with the OVERFLOW 2.2 compressible flow solver on structured, overset grids. Solutions are generated based on a tip Mach number of 0.58 for varying collective pitch angles. In addition to isolated rotor predictions, results are generated for rotor-fuselage interactions using the PSP rotor and Rotor Body Interaction (ROBIN) fuselage. Hover performance is assessed and compared to available measurements obtained in the NASA Langley Research Center Rotor Test Cell (RTC). Grid generation techniques and computational methods for both cases are described. Rotor flow field behavior and transition locations are discussed for both cases along with the impact of transition modeling.
This paper presents activities performed in the frame of MOTUS, a DGAC-funded research project, to better understand and reduce annoyance of helicopter operations. It focuses on the operational context of La Réunion island where local authorities intend to define concrete measures to answer multiple complaints from the population. In parallel with ongoing research towards a better understanding of short- and long-term annoyance thanks to both laboratory and field studies, the paper presents an in-depth analysis of helicopter operations in the area. Furthermore, specific recommendations on low noise operations are proposed to local operators in order to reduce their noise footprint and improve helicopter acceptance.
Piloted simulation has been used for decades to support flight test activities at the Naval Air Warfare Center Aircraft Division located at Naval Air Station Patuxent River, MD. Conventional lab stations at the Manned Flight Simulator facility have been used effectively to support a wide range of flight test requirements. However, there were limitations with these conventional lab stations when the purpose was to assess handling qualities and pilot workload while landing rotorcraft aboard a ship. Two critical simulation elements were determined to be necessary: (1) an expanded field of view so the pilot could see the ship deck below the aircraft and (2) a motion system to provide the pilot with vital proprioceptive cueing in the turbulent ship environment. A new Virtual Reality Lab was developed at Patuxent River that included these key features. The primary components of the lab included virtual reality headsets, an Unreal Engine image generator, ocean and ship visual models, a six
ABSTRACT A full-scale Reynolds number water tunnel experiment was performed to generate a data set used to analyze the effects of helicopter rotor hub wake impingement on a canonical horizontal stabilizer. The experiment was designed and performed in the Pennsylvania State University Applied Research Laboratory Garfield Thomas Water Tunnel, where a 10.5 inch constant chord stabilizer was placed in the 48-inch diameter test section downstream of a 1/4 scale helicopter hub. Two rotor hubs were tested, a baseline configuration and a low-drag model. The stabilizer was mounted in the long-age wake. Lift, pitching moments, and unsteady pressures were measured on the horizontal stabilizer at a Reynolds number of 0:9x10⁶, 1:8x10⁶ and 2:7x10⁶, corresponding to hub diameter-based Reynolds numbers of 2:2x10⁶, 4:3x10⁶, 6:5x10⁶ and rotor advance ratios of 0.1, 0.2, and 0.3. The hub-wake interaction results were compared to a baseline airfoil test, which was performed without a hub upstream
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