Flight Test Program Research Articles

Parameter-Free Data Reduction for Short-Time Hypersonic Heat Flux Measurements

High-speed flows associated with hypersonics require significant, diverse, and successful ground-test campaigns before engaging in a flight test program. The present investigation focuses on demonstrating a new data reduction pathway for estimating the source heat flux using an elegant, though fragile, thin-film temperature gauge. The rapid response time of such sensors makes them well-suited for shock tunnel experiments. In such experiments, contaminated flow, composed of diaphragm debris, can often damage the sensing element. For the moment, the existence of an ideal coating (or even a hardened sensing element) is presumed that preserves the sensor’s survivability and accuracy over several test runs. A dynamic, physics-based data reduction methodology is proposed that accounts for the protective coating and that is applicable to millisecond testing times. This paper addresses three critical issues for acquiring the best estimate of the source heat flux. These issues include a) the formation of a baseline data reduction view that accounts for thin coatings; b) the development of a dynamic calibration method that removes the need for specifying thermophysical or geometrical properties; and c) the introduction of a time-scaling that allows for calibration to be performed in alternative and convenient time frames. This last point demonstrates the concept of the dimensionless time map and its novel consequences. The procedure is demonstrated on a reduced formulation, illustrating the merit of the concepts.

STAJe−: A Supersonic Flight Program STAJe− 1 Payload Design and System Study

The STAJe− flight program is the latest implementation of a university-based supersonic and hypersonic flight-test program. In the first flight, which is the subject of this study, the focus is on evaluating the suitability of commercial off-the-shelf electronic hardware, additively manufactured internal payload structures, and a long-range communications technique in the challenging environment presented by flight at high supersonic Mach numbers. These items can significantly reduce the cost of a flight experiment, and thus lower the threshold for flight experimentation. The scientific objectives of this flight are to collect pressure and temperature data on the whole trajectory to compare to numerical models, to optically measure the temperature of composite fins mounted on the payload, and to eject the flight module from the rocket assembly and track its location for subsequent recovery. Design calculations for the tracking system are presented alongside experimental results from ground tests demonstrating the suitability of the system. Furthermore, a one-dimensional calculation of the external wall temperatures over the trajectory is presented, which shows that internal systems are sufficiently protected from the harsh environment. Although the materials are shown to be appropriate for the flight, a layer of cork will be added to parts of the payload to further reduce the chance of structural failure. In addition, it is shown that a pneumatic ejection system is suited to overcoming the drag forces on the front of the rocket to initiate separation.

Automated information system for testing helicopters equipped with night vision systems based on diagnostics of the functional state of the crew

The subject of the study is the problem of ensuring optimal conditions for interaction between humans and aviation equipment in the interests of ensuring its safe operation, which has recently become more acute. Based on studies of the pilot's activity obtained during flight tests of helicopters equipped with night vision goggles, it is shown that the use of night vision goggles imposes special requirements on the organization of attention distribution, spatial orientation and is accompanied by an increase in the level of nervous and emotional tension. The main results of foreign developers on the improvement of night vision systems related to the introduction of technical vision systems on helicopters are described. It is proved that for an objective examination of such systems in flight tests, it is necessary to create a special automated information system. The developed automated information system provides the collection and processing of flight information during flight tests using intelligent sensors for monitoring and recording the biometrics of crew members and an image recognition system. It will allow recording, processing and accumulating flight and psychophysiological information in real test flights during the implementation of the entire flight test program, providing specialists in the field of aviation medicine and ergonomics with objective quantitative characteristics of the studied parameters when testing promising night vision systems of combat helicopters. It is shown that the introduction of modern information technologies into the process of testing aviation equipment allows objectively and with high accuracy to analyze and evaluate the content and psychophysiological structure of the pilot's activity based on a comparison of changes in flight parameters, the movement of controls, the direction of the pilot's gaze and his psychophysiological characteristics and recommend for practical use specific variants of night vision systems.

A simulation study of drone delivery of Automated External Defibrillator (AED) in Out of Hospital Cardiac Arrest (OHCA) in the UK.

BackgroundDrones are increasingly used in healthcare, and feasibility studies of deployment of Automated External Defibrillators (AED) in Out-of-hospital cardiac arrest (OHCA) have been conducted. Despite the potential contribution of drones to healthcare, regulatory barriers exist, including limits on flights beyond visual line-of-sight (BVLOS). The aim of this project was to deliver an AED BVLOS in Wales.MethodsWe developed of a Concept of Operations (CONOPS) to identify requirements, constraints, organisation and roles and responsibilities associated with deploying a drone to deliver an AED BVLOS. We equipped a Penguin B drone with satellite-enabled technology to enhance situational awareness and safety for the remote pilot. A BVLOS Operating Safety Case and three-week flight test programme was conducted with an AED attached directly to parachute for deployment to simulated OHCA.ResultsWe completed six flights totalling 92km, 1:02.5 hours of flight time and four successful parachute payload drops. We conducted a successful end-to-end flight demonstration of an AED delivered via BVLOS by drone to a simulated OHCA and resuscitation by lay responder’s in a remote location; the final delivery of 4.5km was completed in 2:50 minutes.ConclusionWe have delivered an AED by parachute, from fixed wing drone BVLOS in the UK in simulated OHCA. This project adds to the body of knowledge required for regulatory assurance on drone use BVLOS. Further research is needed before routine use of this technology.

Dynamic flight load measurements with MEMS pressure sensors

The determination of structural loads plays an important role in the certification process of new aircraft. Strain gauges are usually used to measure and monitor the structural loads encountered during the flight test program. However, a time-consuming wiring and calibration process is required to determine the forces and moments from the measured strains. Sensors based on MEMS provide an alternative way to determine loads from the measured aerodynamic pressure distribution around the structural component. Flight tests were performed with a research glider aircraft to investigate the flight loads determined with the strain based and the pressure based measurement technology. A wing glove equipped with 64 MEMS pressure sensors was developed for measuring the pressure distribution around a selected wing section. The wing shear force determined with both load determination methods were compared to each other. Several flight maneuvers with varying loads were performed during the flight test program. This paper concentrates on the evaluation of dynamic flight maneuvers including Stalls and Pull-Up Push-Over maneuvers. The effects of changes in the aerodynamic flow characteristics during the maneuver could be detected directly with the pressure sensors based on MEMS. Time histories of the measured pressure distributions and the wing shear forces are presented and discussed.

Advanced aeroelastic robust stability analysis with structural uncertainties

Robust flutter analysis described in this paper is based on the robust control theory framework. Therefore, a time-domain linear fractional transformation representation of the perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by means of the structured singular value mu, which is defined as an alternative measure of robustness. Robust flutter analysis deals with aeroelastic (or aeroservoelastic) stability analysis taking structural dynamics, aerodynamics and/or unmodeled system dynamics uncertainties into account. Flutter is a well-known dynamic aeroelastic instability phenomenon caused by an interaction between structural vibrations and unsteady aerodynamic forces, whereby the level of vibration may trigger large amplitudes, eventually leading to catastrophic failure of the structure. The primary motivation of the robust flutter analysis is that this method allows the computation of the worst-case flutter velocity which can support, for example, the flight test program by a valuable robust flutter boundary. This paper addresses the issue of an approach for aeroelastic robust stability analysis with structural uncertainties with respect to physical symmetric and asymmetric stiffness perturbations on the wing structure by means of tuning beams.

Computational fluid dynamics trimming of helicopter rotor in forward flight

A computational fluid dynamics (CFD) trimming method based on wind tunnel and flight test data is proposed. Aerodynamic coefficients obtained for a helicopter rotor using this method were compared with both experimental data from a test report and CFD results based on the control parameters that were reported in the same document. The method applies small disturbances to the collective pitch angle, the lateral cyclic pitch angle and the longitudinal cyclic pitch angle of the helicopter’s main rotor during forward flight to analyze the effects of each disturbance on the thrust coefficient, the pitching moment coefficient and the rolling moment coefficient of the rotor. Then, by solving a system of linear equations, the collective pitch angle, the lateral cyclic pitch angle and the longitudinal cyclic pitch angle of the main rotor in the CFD trim state are obtained. The AH-1G rotor is used in this paper. NASA has conducted a comprehensive flight test program on this model and has published detailed test reports. Using this method, the pitch moment and the roll moment can be corrected to almost zero and the calculated thrust coefficient is more consistent with the test data when compared with results from direct CFD simulations.

Performance of Isolated UAV Rotors at Low Reynolds Number

<div class="section abstract"><div class="htmlview paragraph">Vertical takeoff and landing vehicle platforms with many small rotors are gaining importance for small UAVs as well as distributed electric propulsion for larger vehicles. To predict vehicle performance, it must be possible to gauge interaction effects. These rotors operate in the less-known regime of low Reynolds number, with different blade geometry. As a first step, two identical commercial UAV rotors from a flight test program are studied in isolation, experimentally and computationally. Load measurements were performed in Georgia Tech’s 2.13 m × 2.74 m wind tunnel. Simulations were done using the RotCFD solver which uses a Navier-Stokes wake computation along with rotor-disc loads calculation using low-Reynolds number blade section data. It is found that in hover, small rotors available in the market vary noticeably in performance at low rotor speeds, the data converging at higher RPM and Reynolds number. This is indicative of the high sensitivity of low-Re rotor flows to minor geometrical differences/imperfections in the rotors. It requires proper handling in computations. CFD results show a higher deviation from the experimental thrust data at low rotor speeds. While thrust prediction comes close to the experiments at high rotor speed, matching torque prediction values within reasonable bounds is still a challenge.</div></div>

Low speed lateral-directional aerodynamic and static stability analysis of a hypersonic waverider

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing for lateral-directional cases was conducted in the University of Sydney 4 foot by 3 foot low speed facility. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between -5 and 15 degrees and angles of sideslip between -8 and 8 degrees. Throughout these ranges, aileron and rudder deflections up to 10 degrees are investigated. Results show that the vehicle aerodynamics are dominated by asymmetric wing and fin vortices, resulting in non-linear aerodynamic forces. At a centre of gravity location of 44.4% of the vehicle length the aircraft is stable directionally, but has lateral instability at angles of attack below -2 degrees. This is attributed to the low mounted wings with anhedral. The instability is minor and is not expected to result in an uncontrollable condition. Lowering the centre of gravity by approximately 2 centimetres, or 17% of the local fuselage height, can correct the instability. Lateral-directional dynamic stability was predicted using static derivatives and was found to be stable through the entire AoA range tested, with no dependence on mass moments of inertia. Both aileron and rudder controls are found to provide sufficient control authority, but the aircraft may benefit from increased rudder size. The results from this study, along with previous work on longitudinal stability and performance show the feasibility of moving to the flight test program, but aircraft dynamic stability must first be investigated.

Low-Cost and Aerodynamics-Aim Hypersonic Flight Experiment MF-1

For increasing understanding of fundamental hypersonic phenomena, the flight test program, named MF-1, is to gather fundamental scientific and engineering data on the physics and technologies critical to future operational hypersonic flight with low-cost flight test platform, which is built on the retrofitted rockets. The MF-1 program is a hypersonic flight test program executed by China Aerodynamic Research and Development Center (CARDC). The MF-1 flight flew in December 2015. The flight focuses primarily on integration of instrumentation on the test vehicle, with application to boundary layer transition and shock interaction experiments. The MF-1 payload consists of a blunted 7°half angle cone, a cylinder and 33° flare configuration. The payload was boosted to Mach 5.32 utilizing a solid-rocket booster without control for the whole flight. The flight was fully successful, and measured transition under supersonic and hypersonic conditions. The heat flux data were given by the three-dimensional thermal identification method to discriminate transition zone. The preliminary analysis shows that the real-time flight data obtained by MF-1 are reliable and can be used to validate the transition predicting model and software. The results show that the existing model is able to predict the transition location of cone at a small angle-of-attack for supersonic or hypersonic flow. This paper describes the MF-1 mission and some general conclusions derived from the experiment.

Dynamic methods for controlling the weight of the aircraft and helicopter

Despite the achieved level of development of methods and means of controlling the weight of aircraft, the number of emergencies associated with exceeding the allowable take-off weight of aircraft remains significant. Therefore, the question of the development of new methods for controlling the weight of aircraft, either immediately before take-off in the course of movement along the runway or immediately after take-off at the minimum flight height, remains relevant. This paper presents a scientific and technical substantiation of dynamic methods for controlling the mass of aircraft taking off and helicopters, based on introducing into the flight test program measurements of horizontal (for airplanes) and vertical (for helicopters) aircraft accelerations before take-off (for airplanes) and during take-off ( aircraft) with a maximum take-off weight, and their comparison with horizontal (for airplanes) and vertical (for helicopters) aircraft accelerations measured during operation takeoff (for airplanes) and during takeoff (for helicopters) with an unknown weight, respectively.

Aero pace

After a pause in the flight test program, A330-800 flying has resumed apace, building on the success of the larger -900 variant

Static and dynamic characterization of a flexible scaledjoined-wing flight test demonstrator

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing\'s ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.

First and Fifth Hypersonic International Flight Research Experimentation’s Flight and Ground Tests

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight-test program executed by the U.S. Air Force Research Laboratory and the Australian Defence Science and Technology Group, including flight, ground test, and computation. HIFiRE flights one and five (HIFiRE-1 and HIFiRE-5, respectively) were devoted to boundary-layer transition. The body of knowledge from the research campaigns showed a complex transition behavior. Axisymmetric flows and crossflow transition were strongly affected by wind-tunnel noise, with transition occurring at lower Reynolds numbers in the wind tunnel. Similarly, three-dimensional flows with inflected velocity profiles, such as the leeward side of HIFiRE-1 or the HIFiRE-5 centerline, exhibited much lower transition Reynolds numbers in ground tests as compared to flight. The disparity between flight and wind-tunnel transition Reynolds numbers was less pronounced for attachment-line transition. The supposition was that this transition mechanism was either less affected by wind-tunnel noise or was more susceptible to disparities in wall cooling between the wind tunnel and flight.

Aeroelastic analysis of a helicopter rotor in hover

The paper deals with the numerical analysis of a helicopter rotor in hover conditions, including aeroelastic effects. In existing literature the effects of an aircraft structural deformation on airloads distribution and performance are fairly well described but mainly for airplanes. The purpose of the presented work is to indicate the possible influence of blades elasticity on helicopter rotor loads and performance in hover. Additionally, it aims to validate a new computational method based on a set of experimental results for a UH-60A helicopter rotor. The method used combines a high fidelity Navier-Stokes aerodynamic model coupled with a low-order beam structural model. This approach made it possible to take into consideration blade deformations in simulations and revealed the high influence of aeroelastic effects on rotor loads and performance at hover conditions. To authenticate the results, the presented method was validated with experimental data from two different flight test programs, three small-scale wind tunnel tests and one full-scale wind tunnel test. They were conducted for the UH-60A helicopter rotor by different organizations. The comparison of results revealed that the created computational method has high accuracy.

G500 is Go

Having found additional range in its G500, Gulfstream extended the type's flight test program into 2018. With FAA certification is go awarded, the airframer is working toward certifying the closely related G600 this year

Where Data is King

Competing pressures and the need to innovate are just some of the factors shaping the instrumentation on Boeing's flight test programs

Hypersonic International Flight Research Experimentation-5b Flight Overview

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight-test program. The HIFiRE-5b flight flew in May 2016. The principle goal of this flight was to measure hypersonic boundary-layer transition on a three-dimensional body. The flight was fully successful, and measured leading edge, acreage, and centerline transition under supersonic and hypersonic conditions. This paper describes the HIFiRE-5b mission and some general conclusions derived from the experiment. This is one of five other companion papers that describe the experiment and postflight test and analysis in more detail.

The Comparison Of In-Flight Pitot Static Calibration Method By Using Radio Altimeter As Reference with GPS and Tower Fly By Methods On CN235-100 MPA

The new proposed In-Flight Pitot Static Calibration Method has been carried out during Development and Qualification of CN235-100 MPA (Military Patrol Aircraft). This method is expected to reduce flight hours, less human resources required, no additional special equipment, simple analysis calculation and finally by using this method it is expected to automatically minimized operational cost. At The Indonesian Aerospace (IAe) Flight Test Center Division, the development and updating of new flight test technique and data analysis method as specially for flight physics test subject are still continued to be developed as long as it safety for flight and give additional value for the industrial side. More than 30 years, Flight Test Data Engineers at The Flight Test center Division work together with the Air Crew (Test Pilots, Co-Pilots, and Flight Test Engineers) to execute the flight test activity with standard procedure for both the existance or development test techniques and test data analysis. In this paper the approximation of mathematical model, data reduction and flight test technique of The In-Flight Pitot Static Calibration by using Radio Altimeter as reference will be described and the test results had been compared with another methods ie. By using Global Position System (GPS) and the traditional method (Tower Fly By Method) which were used previously during this Flight Test Program (Ref. [10]). The flight test data case are using CN235-100 MPA flight test data during development and Qualification Flight Test Program at Cazaux Airport, France, in June-November 2009 (Ref. [2]).

Surface Heating and Boundary-Layer Transition on a Hypersonic Inflatable Aerodynamic Decelerator

The aerothermodynamic environment of a hypersonic inflatable aerodynamic decelerator with a flexible thermal protection system has been investigated through wind-tunnel testing. Boundary-layer transition onset locations and surface heating distributions were measured using global phosphor thermography on deflected, solid-surface models representative of a hypersonic inflatable aerodynamic decelerator aeroshell with a flexible surface. Data were obtained at Mach 6 for a wide range of surface deflection heights, angles of attack, and freestream Reynolds numbers. The surface deflections resulted in earlier boundary-layer transition onset and higher heating levels than for a smooth-wall surface, with the greatest effects occurring on the leeward side of the aeroshell. The heating augmentation and transition onset data were correlated using flowfield properties obtained from a complementary computational study. A method was developed to estimate flexible thermal protection system deflection effects using these correlations along with smooth-wall flowfield predictions. This method was validated through comparisons to the wind-tunnel data and then used to generate postflight predictions for aeroshell heating levels of the Inflatable Reentry Vehicle Experiment flight-test program. The results of this study provide a means for estimating flexible thermal protection system deflection effects for future flight tests as well as an experimental database for use in the development and validation of computational methods for simulations of hypersonic inflatable aerodynamic decelerator aerothermodynamic environments.