Flight Trials Research Articles

Evaluating ship superstructure aerodynamics for maritime helicopter operations through CFD and flight simulation

ABSTRACTThe unsteady air flow over and around the helicopter landing deck of a naval vessel is known to cause high pilot workload and to limit the helicopter's operational envelope for launch and recovery. Previous research has suggested that modifications to the ship's hangar edges can beneficially modify the flow over the deck. This paper examines the effectiveness of five hangar-edge modifications using computational fluid dynamics–generated airwakes and flight mechanics modelling, as well as piloted flight trials in a motion-base simulator. Results are presented, in terms of unsteady helicopter loads and pilot workload ratings, for modifications to the windward vertical rear edge of the hangar and with an oblique wind. The results demonstrate that while the airwake can be altered by superstructure modifications, the integrated effect of the altered airwake on the entire helicopter does not necessarily give the desired result; indeed of the five modifications tested, two were seen to be beneficial while three caused an increase in pilot workload compared with the unmodified hangar. Overall, the paper shows that the airwake can be modified by superstructure design changes, and that the effect on the helicopter can be measured through modelling and simulation. It is also demonstrated that making judgements on the severity of the airwake based on the aerodynamic flow field alone can be misleading. The benefit of these simulation tools is that they can be used during the ship design process to evaluate the effect of the superstructure aerodynamics, rather than wait until after the ship is built.

Medium-sized forest snails survive passage through birds' digestive tract and adhere strongly to birds' legs: more evidence for passive dispersal mechanisms

It is well known that land snails can be dispersed by birds, both by attachment to the body (ectozoochory) and by passing intact and alive through the bird’s digestive tract (endozoochory). Endozoochory has, however, only been recorded for very small species. We examined the possibility that larger species (up to c. 17 mm in maximum shell dimension) could survive passage through a bird’s digestive system. Live Alinda biplicata, Cochlodina laminata (both Clausiliidae) and Discus rotundatus (Discidae) were fed to 10 bird species (Corvidae, Turdidae, Sturnidae and Columbidae) in 14 experimental trials. Of 720 snails offered, 14 passed intact through the birds, of which nine were alive (eight clausiliids and one D. rotundatus); thus more than 1% of all snails offered survived ingestion. In an additional experiment, some A. biplicata and C. laminata remained attached to birds’ legs by pedal adhesion in simulated flight trials where the birds’ legs oscillated at the maximum rate achieved during flight.

Effects of ambient and preceding temperatures and metabolic genes on flight metabolism in the Glanville fritillary butterfly

Flight is essential for foraging, mate searching and dispersal in many insects, but flight metabolism in ectotherms is strongly constrained by temperature. Thermal conditions vary greatly in natural populations and may hence restrict fitness-related activities. Working on the Glanville fritillary butterfly (Melitaea cinxia), we studied the effects of temperature experienced during the first 2days of adult life on flight metabolism, genetic associations between flight metabolic rate and variation in candidate metabolic genes, and genotype–temperature interactions. The maximal flight performance was reduced by 17% by 2days of low ambient temperature (15°C) prior to the flight trial, mimicking conditions that butterflies commonly encounter in nature. A SNP in phosphoglucose isomerase (Pgi) had a significant association on flight metabolic rate in males and a SNP in triosephosphate isomerase (Tpi) was significantly associated with flight metabolic rate in females. In the Pgi SNP, AC heterozygotes had higher flight metabolic rate than AA homozygotes following low preceding temperature, but the trend was reversed following high preceding temperature, consistent with previous results on genotype–temperature interaction for this SNP. We suggest that these results on 2-day old butterflies reflect thermal effect on the maturation of flight muscles. These results highlight the consequences of variation in thermal conditions on the time scale of days, and they contribute to a better understanding of the complex dynamics of flight metabolism and flight-related activities under conditions that are relevant for natural populations living under variable thermal conditions.

Towards Autonomous MAV Soaring in Cities: CFD Simulation, EFD Measurement and Flight Trials

MAVs are increasingly being used in complex terrains, such as cities, despite challenges from the highly turbulent flow fields. We investigate the flow around a nominally cuboid building of height 40m both computationally and experimentally in a 1/100th scale wind-tunnel test. A relatively new computational technique, Improved Delayed Detached Eddy Simulation (IDDES), was used for computing the time-varying flow around the building and surrounding domain. The atmospheric boundary layer velocity and turbulent intensity profiles were replicated at the inlet boundary of the computational domain and wind tunnel. The spatial flow field from the CFD was investigated for locating suitable areas of lift, in order to see if soaring flight would be feasible. Good agreement was found with the wind-tunnel results. Flight trials of a small flying wing aircraft were conducted from the roof demonstrating the possibility of keeping aloft with no conventional power system. Soaring was achieved under piloted control and autonomously. The CFD results proved useful in locating the best lift areas and provided insights into path planning.

Archie the Daredevil Penguin by Andy Rash (review)

Reviewed by: Archie the Daredevil Penguin by Andy Rash Jeannette Hulick Rash, Andy Archie the Daredevil Penguin; written and illus. by Andy Rash. Viking, 2015 [40p] ISBN 978-0-451-47123-9 $16.99 Reviewed from galleys R 5-7 yrs Archie is the risk-taker of his penguin colony, whether climbing Mount Nosebleed, tobogganing through Craggy Pass, or, in his latest venture, attempting to fly via mechanical means to Iceberg Nine to partake in a fish fry. His flight attempts (a giant slingshot, Flap-O-Matic™ wings, and a rocket) are valiant efforts but each ultimately fails, and another penguin guesses what Archie is trying to hide: he is “afraid of the water and the strange creatures who lurk in the briny deep.” When his last flight trial lands him directly in the sea, Archie must confront his fears head on, but fortunately, the creatures he dreaded quickly and kindly surround him with helpful advice and encouragement to help him swim. While the ease with which Archie conquers his fears is more convenient than realistic, the consolation and support offered by the ocean dwellers is still satisfying. The text, presented entirely in speech bubbles, is snappy and straightforward with entertaining vocabulary (“Zounds!”) interspersed into the narrative. The humor is underscored by Rash’s high-contrast, slightly cartoonish digital illustrations in which big-beaked Archie, amusingly differentiated from the other penguins by his red safety helmet, intrepidly hurtles through the air and barrel-rolls under the sea. Kids who get a kick out of the penguins from Madagascar movies will find Archie’s stunts particularly diverting. Copyright © 2015 The Board of Trustees of the University of Illinois

Highly Accurate Attitude Estimation via Horizon Detection

Attitude pitch and roll angle estimation from visual information is necessary for GPS-free navigation of airborne vehicles. We propose a highly accurate method to estimate the attitude by horizon detection in fisheye images. A Canny edge detector and a probabilistic Hough voting scheme are used to compute an approximate attitude and the corresponding horizon line in the image. Horizon edge pixels are extracted in a band close to the approximate horizon line. The attitude estimates are refined through registration of the extracted edge pixels with the geometrical horizon from a digital elevation map DEM, in our case the SRTM3 database, extracted at a given approximate position. The proposed method has been evaluated using 1629 images from a flight trial with flight altitudes up to 600i¾?m in an area with ground elevations ranging from sea level up to 500i¾?m. Compared with the ground truth from a filtered inertial measurement unit IMU/GPS solution, the standard deviation for the pitch and roll angle errors obtained with 30 Mpixel images are 0.04i¾? and 0.05i¾?, respectively, with mean errors smaller than 0.02i¾?. To achieve the high-accuracy attitude estimates, the ray refraction in the earth's atmosphere has been taken into account. The attitude errors obtained on real images are less or equal to those achieved on synthetic images for previous methods with DEM refinement, and the errors are about one order of magnitude smaller than for any previous vision-based method without DEM refinement.

Differential pollen placement on an Old World nectar bat increases pollination efficiency.

Plant species that share pollinators are potentially subject to non-adaptive interspecific pollen transfer, resulting in reduced reproductive success. Mechanisms that increase pollination efficiency between conspecific individuals are therefore highly beneficial. Many nocturnally flowering plant species in Thailand are pollinated by the nectar bat Eonycteris spelaea (Pteropodidae). This study tested the hypothesis that plant species within a community reduce interspecific pollen movement by placing pollen on different areas of the bat's body. Using flight cage trials, pollen transfer by E. spelaea was compared between conspecific versus heterospecific flowers across four bat-pollinated plant genera. Pollen from four locations on the bat's body was also quantified to determine if pollen placement varies by plant species. It was found that E. spelaea transfers significantly more pollen between conspecific than heterospecific flowers, and that diverse floral designs produce significantly different patterns of pollen deposition on E. spelaea. In the Old World tropics, differential pollen placement is a mechanism that reduces competition among bat-pollinated plant species sharing a common pollinator.

Use of Custer Channel Wings–Wing Ducts on Small UAVs

The strong variations in lift that occur with changes in forward speed lead to one of the fundamental difficulties in aircraft design: how to provide sufficient lift at landing and take-off without having oversized wings for cruise conditions. This fundamental problem is generally tackled using two approaches. First, by providing flaps and other high-lift devices, extra lift can be generated during landing and take-off, albeit at the cost of extra drag and complexity. Second, by using long and smooth runways, higher landing and take-off speeds can be tolerated, closing the gap between these speeds and those of operational flight. Even so, it is common for aircraft flying in the cruise condition to be operating with rather small main wing angles of attack (AoAs) compared with those at stall, implying that smaller wings would be desirable if acceptable landing and take-off could be achieved. A number of designers have attempted to tackle this problem with various forms of powered lift augmentation. This paper re-examines the idea of the Custer wing duct, also known as a channel wing, here applied to small unmanned air vehicles (UAVs). Such aircraft are generally not operated from long smooth runways and rarely have complex high-lift systems in their wings. It is shown that by using suitable ducts around the propellers, startlingly good take-off and landing performance can be achieved, and that suitable ducts can be readily incorporated into small UAVs with the use of 3D printing (selective laser sintering) for their manufacture. Computational fluid dynamics (CFD) analysis, wind tunnel tests, and flight trials of a Custer channel wing UAV are described.

Global Maritime Surveillance by Airliner-Based AIS Detection: Preliminary Analysis

Demands on security, safety, and environmental protection in worldwide shipping are steadily increasing. Shipboard broadcast transponders based on the Automatic Identification System (AIS) can be easily detected close to coastal or waterway areas. Satellite-based AIS receivers detect globally but are limited in high-density traffic areas. This paper investigates the challenges and performance of AIS detection on aircraft at altitudes between 8 500 m and 10 000 m. During flight trials over sea and land, AIS signals were recorded. Post-processing of the recorded data allows the evaluation but also faces challenges due to the nature of overlapping AIS signals at the aircraft. A comparison of detected signals at the aircraft with received AIS signals on the ground is given, including the evaluation of the reception footprint of the aircraft. Finally, a concept for worldwide AIS detection via airliners is presented. The study shows the potential for global complementary surveillance coverage via airliner-based AIS detection.

Technology demonstrator of a novel software defined radio‐based aeronautical communications system

This study presents the architectural design, software implementation, the validation and flight trial results of an aeronautical communications system developed within the Seamless Aeronautical Networking through integration of Data links Radios and Antennas (SANDRA) project funded by the European 7th Framework Aeronautics and Transport Programme. Based on software defined radio (SDR) techniques, an integrated modular radio (IMR) platform was developed to accommodate several radio technologies. This can drastically reduce the size, weight and cost in avionics with respect to current radio systems implemented as standalone equipment. In addition, the modular approach ensures the possibility to dynamically reconfigure each radio element to operate on a specific type of radio link. A radio resource management (RRM) framework is developed in the IMR consisting of a communication manager for the resource allocation and management of the different radio links and a radio adaptation manager to ensure protocol convergence through IP. The IMR has been validated although flight trials held at Oberpfaffenhofen, Germany in June 2013. The results presented in the paper validate the flexibility and scalability of the IMR platform and demonstrate seamless service coverage across different airspace domains through interworking between the IMR and other components of the SANDRA network.

Towards an Optical Aircraft Navigation System

Navigation by means that are fully self contained, without the weight and cost of high performance inertial navigation units is highly desirable in many applications both military and civilian. In this paper we introduce a suite of sensors and behaviors that include: the means to reduce lateral drift due to wind using optical flow, detection of a constellation of landmarks using a machine vision system, and a polarization compass that is reliable at extreme latitudes based on polarization. In a series of flight trials and detailed simulations we have demonstrated that a combination of these functions achieves purely optical navigation with simplicity and robustness.

A rating scale for the subjective assessment of simulation fidelity

AbstractA new rating scale for capturing pilot subjective assessment of simulation fidelity is described in this paper. The scale has been developed through a series of flight and simulation trials using six test pilots from a variety of backgrounds, and is based on the methodology utilised with the Cooper-Harper Handling Qualities Rating scale and the concepts of transfer of training, comparative task performance and task strategy adaptation. The development of the new rating scale has been undertaken using simulations of rotary-wing aircraft on the University of Liverpool’s HELIFLIGHT-R research simulator, in conjunction with the Canadian Flight Research Laboratory’s Bell 412 ASRA in-flight simulator. The utility of the scale applied to locating fidelity boundaries for quantitative metrics is illustrated for an inter-axis coupling criterion. The work described in this paper is preliminary in nature, and research activities are on-going to continue the validation of the fidelity rating scale.

Taranis and beyond: inspiring aerodynamic capability

AbstractIn his 1916 book,Aircraft in Warfare, the Dawn of the Fourth Arm, F.W. Lanchester wrote:“The supremacy of British aircraft can only be maintained by the adoption of a thoroughly progressive constructional policy, guided constantly by the most recent scientific discovery and research, and by utilising to the full information and experience gained in the Services.”The recent successful flight trials of the Taranis low-observable unmanned demonstrator aircraft provide the latest evidence of the UK’s continued capacity for the entire design, development, manufacture, and flight testing of world-leading combat aircraft, particularly with regard to Aerodynamics. Taranis is both the culmination of many years’ research and development in the UK and a starting-point for the next generation of UK combat air systems.In this lecture, Taranis is reviewed, in such detail as current sensitivities will allow, in the wider context of UK combat aircraft aerodynamic capability, exemplified by the leading roles taken by the UK in the Tornado and Typhoon programmes and the important contribution made to the development of the F-35 Lightning II Joint Strike Fighter.The immediate technical challenges associated with the aerodynamic design and qualification of a low-observable air vehicle are considerable. In this instance they have been compounded by the balanced view taken within the project of trade-offs against many parameters. However, the UK aerodynamics community faces equally stringent challenges in terms of the identification and delivery of the most appropriate future systems; increasingly complex and demanding operational and functional requirements; and, perhaps most of all, maintaining an affordable and cost-effective capability in the face of strict budgetary pressures and austere economic conditions.Nevertheless, those challenges are accompanied by a wide range of opportunities, namely for national and international partnership; radically innovative engineering solutions and approaches; new thinking; and the engagement of the best minds and ideas in the UK academic community.Taranis represented a big integration task, requiring a particular set of skills to pull together the total package, resting on a bedrock of mastery of the technical issues. It has been an inspirational experience for those of us who have worked on it. It has demonstrated that the UK is capable of achieving the most demanding current and anticipated military aerodynamic requirements and has signposted the way to an exciting and nationally important future.

Flight trial demonstration of seamless aeronautical networking

This article presents the in-flight demonstration of a new integrated aircraft communications system combining legacy and future radio technologies. This system, developed and validated under real environmental conditions during flight trials, integrates all the aeronautical service domains within a common IPv6-based aeronautical network. The flight trials were held within the framework of the European SANDRA project at Oberpfaffenhofen, Germany, in June 2013. The presented outcomes emphasize the flexibility and scalability of the developed network and demonstrate the seamless service coverage of the given architecture across different airspace domains.

Update on Developing and Commercializing Oil Herders for In-Situ Burning

ABSTRACT Since the 2011 Conference (Buist et al. 2011 and Buist and Nedwed 2011), work on advancing oil herding agents for in-situ burning (ISB) has focused on three areas:Obtaining regulatory approvals for their use in North America;Developing an application system for use in a helicopter; and,Researching the effectiveness of herders for rapid-response ISB in open water. Desmi-AFTI worked in conjunction with S.L. Ross Environmental Research to get approval to use herders in North American waters. The proscribed test data from an accredited laboratory in Louisiana on three candidate herding agents (also called surface collecting agents) was submitted to the U.S. EPA for approval to list them on the National Contingency Plan (NCP) Product Schedule. Two herders have been placed on the list and are now commercially available. These two can be used, with the FOSC's concurrence, for spill response operations in U.S. waters. Samples of all three herders have been sent to Environment Canada, along with all the EPA test data, for their consideration. Quantities (200 L) of the two herders listed on the NCP Product Schedule have been produced and are stockpiled at Desmi-AFTI in Buffalo, NY. An application system, consisting of a pump, controls and reservoir has been designed to be placed inside an appropriate helicopter. It incorporates a reel-able hose that is used to lower the application nozzle to the correct height above the water for herder application. Dry land, static trials were conducted in September 2013 and helicopter flight trials are planned for summer and fall 2014. A back-pack sprayer system for herder application from a small vessel is available off-the-shelf, with only minor modifications required for cold-temperature use. The US Department of the Interior's Bureau of Safety and Environmental Enforcement sponsored a series of laboratory and Ohmsett experiments to see whether herders could contract oil slicks in wave conditions in open water. The results showed that the monolayer of each of the two best herders will survive for more than 45 minutes in a calm sea. The presence of breaking or cresting waves rapidly disrupts the herder monolayer and the oil slick resulting in the production of many small slicklets from the herded slick and the re-spreading of the oil to thin slicks. The monolayer survives for considerable periods of time in a swell condition, but the constant stretching and contracting of the herded slick results in elongating the oil slick and slowly breaking the slick into smaller segments. Testing of the helicopter application system with a herding agent on a 10 m3 experimental crude oil release in drift ice is planned for spring 2015. Further laboratory study of the approved herders is also planned with the goals of better understanding their toxicity and biodegradation and the window of opportunity for their effective use on weathered, emulsified and waxy oils.

Flow field velocity on the flight deck of a frigate

This paper presents the main results of the test campaign performed on a frigate ship model in a low-speed wind tunnel in order to investigate the ship superstructure airwake by means of particle image velocimetry (PIV). On board wind velocities measurements above the flight deck were carried out by a sonic anemometer and results were compared with these obtained in wind tunnel tests, providing information about the influence of the ship environment on the helicopter safe operational limitations during launch and recovery operations. The first step in the helicopter–ship qualification program is determine the wind limitations in order to build a candidate launch and recovery wind envelope. Thus subsequent steps of the program, additional effects produced by the helicopter rotor and ship motion must be evaluated, and finally flight trial on the ship must be performed to evaluate the pilot workload.

Use of night vision goggles for aerial forest fire detection

Night-time flight searches using night vision goggles have the potential to improve early aerial detection of forest fires, which could in turn improve suppression effectiveness and reduce costs. Two sets of flight trials explored this potential in an operational context. With a clear line of sight, fires could be seen from many kilometres away (on average 3584m for controlled point sources and 6678m for real fires). Observers needed to be nearer to identify a light as a potential source worthy of further investigation. The average discrimination distance, at which a source could be confidently determined to be a fire or other bright light source, was 1193m (95% CI: 944 to 1442m). The hit rate was 68% over the course of the controlled experiment, higher than expectations based on the use of small fire sources and novice observers. The hit rate showed improvement over time, likely because of observers becoming familiar with the task and terrain. Night vision goggles enable sensitive detection of small fires, including those that were very difficult to detect during daytime patrols. The results demonstrate that small fires can be detected and reliably discriminated at night using night vision goggles at distances comparable to those recorded for daytime aerial detection patrols.

Cockpit Visualization of Curved Approaches based on GBAS

The demand for fuel efficient flight paths which include shorter routes and routes adapted to the prevailing terrain as well as the aim to reduce the perceived noise on the ground in the terminal maneuvering area of airports lead to the development of curved approach procedures. In this paper, curved precision approach procedures solely based on a single receiver are evaluated and different means of presenting deviation information to the pilot are analyzed. The Terminal Area Path (TAP) functionality of a Ground Based Augmentation System (GBAS) is used as a technical enabler for curved approaches. Based on that, a simulation and flight trial assessment regarding the technical feasibility and the manual flyability of a descending curved approach was carried out. In addition, multiple display layouts and guidance cues were tested during the flight trials.

Model-Based Design of UAV Autopilot Software

This paper presents a Model-Based approach to develop UAV (Unmanned Aerial Vehicle) autopilot software. It employs Simulink to design the flight controller, Stateflow to implement control logic and Matlab coder to automatically generate embedded C code from the model developed. Software in the loop (SIL) and hardware in the loop (HIL) simulations are performed in the laboratory to validate the software developed. Flight trial cost and risks are minimized and the design cycles are greatly shortened. The feasibility and the effectiveness of the approach are verified through results from lab simulations and field trials.

Coning motion instability of spinning missiles induced by hinge moment

In the flight trials of a spinning missile, it was observed that an unexpected and unstable coning motion occurred after burnout. The missile was still in the free flight phase while the canards kept their original positions by servomechanisms. To address this unstable motion, the governing equation of the coning motion is derived and the dynamics of the fin actuators under the associated hinge moment is taken into account. The necessary and sufficient conditions of the coning motion stability are then analytically derived and further validated through nonlinear six degrees-of-freedom simulations for a representative scenario. It is demonstrated that the hinge moment may lead to the instability of spinning missiles under specific conditions. Finally, the effects of design parameters on the dynamic stability limit are discussed.