Sustained Flight Research Articles

Consumption of arthropods by hummingbirds in the Sierra Madre de Chiapas, Mexico

An organism's morphological features can determine the type of prey they consume due to adaptive advantages in capturing them, for example, the shape and length of the bill in birds. Hummingbirds have been considered specialists in nectar consumption. However, they have been documented to also be important insectivores in ecosystems. In this study, we evaluated arthropod consumption by hummingbirds in relation to their bill and capture strategies. We theorized that hummingbirds with short-medium bills (9-11 bill length to body mass cube root ratio) capture a higher proportion of non-flying arthropods, as they have a lower linear speed of closure of the bill tip relative to the base, while species with long bills (13-14) capture mainly flying arthropods. The study was conducted in El Triunfo Biosphere Reserve, Chiapas, southeastern Mexico from 2015 to 2016, where seven hummingbird species that captured arthropods, their strategies of capture, and the type of prey consumed were recorded. We also analyzed the stomach contents (n = 72 stomachs) collected in the Sierra Madre de Chiapas. We calculated the frequency of occurrence of arthropods and their diversity, as well as the breadth of the feeding niche and the bill-prey relationship of 15 hummingbird species. The Green-throated Mountain-gem ( Lampornis viridipallens) and Rivoli's Hummingbird ( Eugenes fulgens) presented the highest richness of arthropod consumption. Arthropod prey belonged to eight orders, where Hymenoptera and Diptera were the most frequent. The most recorded capture strategies were on the substrate in sustained flight (37.5%) and hovering in sustained flight (33.3%). A positive association was found between the type of arthropods consumed and the morphological traits of the hummingbirds, non-flying arthropods were captured by hummingbirds with short-medium bills, while hummingbirds with long bills captured flying arthropods. Morphological adaptations for food resource use are a trait that determines food selection, capture, and handling success.

Biomechanics of avian flight

Throughout recorded human history, birds have fascinated and inspired humans to dream of flying. The Greek myth of Daedalus and his son Icarus, who flew too close to the sun and fell to his death, first written by Diodorus (60-30 B.C.E.) and later poetically revised by Ovid (8 C.E.), evokes the dangers of hubris. Many indigenous peoples invoke spiritual qualities and protection ascribed to birds that were symbols of freedom and viewed as sacred messengers of the gods. As a student of bird flight, Leonardo da Vinci (1452-1519) was the first to document dynamic soaring by birds. And, subsequently, the flight of birds inspired human engineered pursuit of powered aircraft design, with the Wright Brothers being the first to design and achieve sustained flight at Kitty Hawk, NC, USA in 1903.

Parametric Study on Aerodynamic Performance of a Flapping Wing Rotor MAV Capable of Sustained Flight

By combining the flapping and rotary motion, a flapping wing rotor (FWR) shows unique kinematics of motion. It can produce a significantly higher aerodynamic efficiency and lift coefficient than insect-like flapping wings. However, due to the lack of controllable FWR aerial vehicles, the effect of different flapping parameters of the FWR on aerodynamic characteristics and efficiency remains to be evaluated experimentally. In this work, we conduct experimental studies to investigate the FWR’s lift performance based on our previous vehicle design, which has demonstrated sustained stable hover and maneuver. In particular, by using such flyable FWR as the test platform, the changes in attack angle of the wing, the torsion of wings, different neutral positions, different up and down flapping angles, and different flapping amplitudes, were studied respectively. CFD simulation was used as an auxiliary and supplementary means for validation. As a result, design essentials to lift maximization of the FWR are proposed. The result proves that changing the attack angle and the torsion of the wing will have a certain impact on the lift. In addition, the ideal lift force can be generated when the neutral position tend to zero degrees and the up and down flapping angles tend to be equal. With the growth of the flapping amplitude, the lift force increases continuously. These experimental results provide important design cues for maximizing lift and payload capability of FWR-MAVs.

Non-canonical function of an Hif-1α splice variant contributes to the sustained flight of locusts.

The hypoxia inducible factor (Hif) pathway is functionally conserved across metazoans in modulating cellular adaptations to hypoxia. However, the functions of this pathway under aerobic physiological conditions are rarely investigated. Here, we show that Hif-1α2, a locust Hif-1α isoform, does not induce canonical hypoxic responses but functions as a specific regulator of locust flight, which is a completely aerobic physiological process. Two Hif-1α splice variants were identified in locusts, a ubiquitously expressed Hif-1α1 and a muscle-predominantly expressed Hif-1α2. Hif-1α1 that induces typical hypoxic responses upon hypoxia exposure remains inactive during flight. By contrast, the expression of Hif-1α2, which lacks C-terminal transactivation domain, is less sensitive to oxygen tension but induced extensively by flying. Hif-1α2 regulates physiological processes involved in glucose metabolism and antioxidation during flight and sustains flight endurance by maintaining redox homeostasis through upregulating the production of a reactive oxygen species (ROS) quencher, DJ-1. Overall, this study reveals a novel Hif-mediated mechanism underlying prolonged aerobic physiological activity.

Ambrosia Beetle Occurrence and Phenology of Xylosandrus spp. (Coleoptera: Curculionidae: Scolytinae) in Ornamental Nurseries, Tree Fruit, and Pecan Orchards in Georgia.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae, Platypodinae) in the genus Xylosandrus are problematic in ornamental nurseries and are emerging as serious pests in orchard crops. An updated survey of ambrosia beetles focusing on these damaging species, and their corresponding phenology was conducted in Georgia to aid in refining management practices for these beetles. Ambrosia beetles were monitored across nine sites in 2019 and seven sites 2020 at ornamental nurseries, tree fruit, and pecan orchards in Georgia. At each site, six ethanol-baited bottle traps were deployed; with three traps along the edge of a wood-line and three traps placed 30 m from the edge of the nurseries and orchards. Traps were deployed from mid-January through July or August depending on site and year. All captured ambrosia beetles were counted and identified. Captures of X. crassiusculus, X. germanus, and X. compactus, were analyzed further to investigate spatial distribution and seasonal flight activity. At high population sites, more beetles were captured along adjacent wood lines than in the orchard or nursery interior. At most sites, flight activity began in February and March continued until the termination of the study in July or August. At most sites, sustained flight activities with multiple peaks were observed in March, April, and May, corresponding to average weekly temperatures reaching ≥15.5°C. These results have important implications on temporally and spatially precise management for these beetles across three important agricultural production systems in the southeastern US.

Experimental Validation of an Effective Control Mechanism to Enable Flapping Wing Rotor Stable Flight

Design and implementation of an effective control mechanism is the key to enable the controlled flight of flapping wing rotor micro aerial vehicles (FWR-MAVs). In order to address this open challenge, in this paper, a triple-wing FWR-MAV with its particular control system is proposed. The corresponding experimental study of the vehicle is conducted. As a result, the triple-wing propulsion system demonstrates advantages in both lift generation and flight stability based on the force measurement. The control torques of the proposed FWR-MAV are generated by a particular slip flow rudder mechanism. The effectiveness of such a design combination has been validated experimentally. A series of flight tests are conducted, including sustained hovering and forward-backward maneuvering. To the best of our knowledge, such a design yields the world’s first FWR-MAV capable of sustained controlled flight.

Membrane muscles tension bat wings for faster flight

Watching a bat flit through the night sky, you might think that the delicate membrane stretched between the animal's elbow, long splayed digit bones and down its side to the hind limbs is no more than an inert flexible surface that catches air passively like fabric covering the struts of a kite. Yet, the elegant wing membrane is spanned by thin thread-like muscles. Could the muscles, known as plagiopatagiales proprii, tense and relax the membrane to fine-tune how the structure bows and catches the air as the animals swoop and flutter? Jorn Cheney, Jeremy Rehm, Sharon Swartz and Kenny Breuer from Brown University, USA, decided to find out.But first, the team need to know how Jamaican fruit bats (Artibeus jamaicensis) fly when they had full use of the wing membrane muscles. Cheney and Rehm tempted the animals with guava juice to fly through still air in a wind tunnel and into a 5 m s−1 head wind, filming the animals with six high-speed cameras to reconstruct the wing shape during their distinctive wingbeats to find out how much the membrane bowed as the animals propelled themselves forward. Then the pair painstakingly paralysed all 25 of the fine muscles in each wing by individually injecting botulism toxin into each, inactivating them temporarily. ‘We use tiny, microliter amounts of dilute Botox, much less than would be used in a cosmetic procedure to minimize a single forehead wrinkle’, says Swartz. Once the animals had recovered, Cheney and Rehm then encouraged the bats to fly again in the still air and headwind, to find out how loss of muscle control affected the animals. The animals with the paralysed wing membrane muscles struggled to remain aloft in the motionless air. Even though they could still fly at 6.2 m s−1 into the head wind – which was 1 m s−1 slower than they had managed with full use of the wing membrane muscles – the animals struggled when there was no headwind, descending rapidly to the ground as they tried to remain aloft. And, when the team compared the bats’ wing membranes as they flew into the head wind, it was clear that the membranes of the paralysed bats were slacker, bowing 12% more than the wing membranes of the bats that still had the use of their plagiopatagiales proprii, also increasing the amount of air drag on the wing to slow the animals by 16%. However, the bats with the immobilised wing membrane muscles managed to compensate for the increased drag by increasing their wing beat amplitude from ∼60 to ∼75 deg and tipping the wing more to sweep it through a less vertical angle.‘Reduced forward speed, reduced ability for low-speed flight and changes in kinematics [when the plagiopatagiales were inactive] are consistent with the plagiopatagiales playing a crucial role in reducing drag through active control over membrane tension indirectly controlling camber’, says Cheney, explaining that using the muscles to tension the wing membrane helps bats to fly at higher speeds. However, the team points out that the bats with the paralysed muscles could have taken advantage of their slacker wing membranes to select slower preferred speeds; so why didn't they? They suspect that the animals may not be able to provide the additional flight power required to remain aloft at the lower speeds caused by bowed wing membranes. The researchers conclude, ‘Jamaican fruit bats likely always employ their wing membrane muscles during sustained flight to control camber [bowing] and to enhance flight efficiency’. And, happily, the bats soon recovered full use of their plagiopatagiales muscles after their wing slackening experience to regain full bat mobility.

Bats actively modulate membrane compliance to control camber and reduce drag.

ABSTRACTBat wing skin is exceptionally compliant and cambers significantly during flight. Plagiopatagiales proprii, arrays of small muscles embedded in the armwing membrane, are activated during flight and are hypothesized to modulate membrane tension. We examined the function of these muscles using Jamaican fruit bats, Artibeus jamaicensis. When these muscles were paralyzed using botulinum toxin, the bats preferred flight speed decreased and they were unable to fly at very low speeds. Paralysis of the plagiopatagiales also resulted in increased armwing camber consistent with a hypothesized role of modulating aeroelastic interactions. Other compensatory kinematics included increased downstroke angle and increased wingbeat amplitude. These results are consistent with the bats experiencing increased drag and flight power costs associated with the loss of wing-membrane control. Our results indicate that A. jamaicensis likely always employ their wing membrane muscles during sustained flight to control camber and to enhance flight efficiency over a wide flight envelope.

An automatic shape-aware method for predicting heat flux of supersonic aircraft based on a deep learning approach

Sustained hypersonic flight within the atmosphere causes aerodynamic heating, which poses huge challenges for the thermal protection systems of hypersonic aircraft. Therefore, the heat flux on the aircraft surface needs to be computed accurately during the aircraft design stage. Previous approaches have not been able to achieve simultaneous accuracy and efficiency when computing the heat flux. To deal with this problem, an efficient heat flux prediction method based on deep learning techniques, called SA-HFNet, is proposed in this paper. SA-HFNet tries to learn the relationship between the heat flux and the aircraft shape and flight conditions using deep neural networks without solving the Navier–Stokes equations. Unlike other intelligent methods, SA-HFNet can automatically become aware of changes in aircraft shape. As far as we know, it is the first intelligent method that is able to obtain the heat flux quickly and adapt to changes both in the global aircraft shape and in local shape deformation. Extensive experimental results show that SA-HFNet achieves promising prediction accuracy in less time compared with computational fluid dynamics methods. Furthermore, SA-HFNet has good generalization capability because it has the potential to predict the heat flux for previously unseen aircraft shapes.

Ecomorphological variation of the Triatoma guasayana wing shape in semi-arid Chaco region

Triatoma guasayana (Hemiptera, Reduviidae), considered a secondary vector of Chagas disease, invades rural dwellings through flight dispersal during the warm season in semi-arid Chaco of Argentina. The objective of this study was to define and compare morphometrics features in the relative body size and wing shape of T. guasayana related to temperature and rainfall between spring, summer and end of summer. A total of 188 adults were collected in rural communities in the northwest of the province of Córdoba (central Argentina). Relative body size [body length (mm) / wing length (mm)] and 11 landmarks on the right wing were recorded. The temperature ( °C) and precipitation (mm) data were extracted from the MODIS sensor and Terra Climate dataset, respectively. Correlations between climatic variables and morphological variation were analyzed using Partial Least Square (PLS). Males at the end of summer were smaller than those at spring or summer (F = 4.48; df = 2; p = 0.01), whereas females were similar in relative body size at all seasons (F = 0.76; df = 2; p = 0.47). The PLS in males showed a correlation between wing shape and temperature (r = 0.48; p = 0.03) and precipitation (r = 0.50; p = 0.02) while in females only the temperature was the correlation significant (r = 0.35; p = 0.03). Triatoma guasayana has elongated and thin wings in spring that become short and wide at the end of summer. The morphotype of early summer could allow sustained long-duration flights, while the morphotype of end of summer would be related to short flights, correlated with the dispersive behavior of the species. The results in this study suggest that wing morphology of T. guasayana has phenotypic plasticity, and that temperature and rainfall could be considered modulator factors during the developmental stage.

Leading-to-trailing edge theoretical design of a generic scramjet

The aerospace vehicle flying at hypersonic speed, using an airbreathing propulsion system based on supersonic combustion (scramjet) technology, requires a highly integrated system without moving parts, making the propulsion system and vehicle shape indistinguishable. A scramjet uses shock waves, generated by its inlet during the hypersonic flight to provide the temperature and velocity of atmospheric air to burn the hydrogen, at the combustor at supersonic speed. The divergent exhaust nozzle accelerates the combustion products providing the thrust. A two-dimensional hydrogen-powered generic scramjet has been designed to demonstrate supersonic combustion in atmospheric flight at a Mach number of 6.8 and an altitude of 30 km. Temperature and velocity at the combustion chamber are the most important key parameters for a preliminary design. The inlet configuration must provide a temperature higher than the ignition temperature of the fuel to guarantee spontaneous combustion and the velocity must remain supersonics. The nozzle exit velocity should be higher than the vehicle flight velocity to obtain sustained flight and produce enough thrust. For this theoretical analysis, the air is considered a calorically perfect gas without viscous effects. The compressible flow is analyzed based on oblique shock waves and one-dimensional compressible flow with friction and heat addition and Prandtl–Meyer coupled to the area ratio to describe each key component of the scramjet, such as compression, combustor, and nozzle sections, respectively. The inlet mass flow and hydrogen mass flow are also critical for the scramjet design to ensure stoichiometrically combustion at the combustion chamber, generating the high flow velocity at the nozzle to produce thrust.

The assessment of morphometrics characteristics of Clapperton’s francolin (Francolinus clappertoni) in the Sudan-Sahel Savanna of Nigeria

Studies on morphometrics, characteristics of Clapperton’s Francolin the study conducted in Dala Village of Bade Local Government Area of Yobe State between August 2012 and April 2013. The study aimed at filling in the missing gaps in the knowledge of the species. Sixty (60) individuals’ birds were collected by being shot and morphometric measurements taken using mettler weighing balance and a meter rule. The birds were cut open to collect the gut contents for food habit study. The average weight of the bird was 1.03±0.43 kg, while the mean length of the species was 361±30mm. The body weight of the species showed a significant positive correlation with crook of wings (r = 0.4, p = 0.002). This was probably an adaptation for sustained flight. Total body length also showed a significant positive correlation with length of tarsus (r = 0.3, p = 0.004). This might also be an adaptation for flight and fast running.

"Visiting old, learn new": taxonomical overview of chiropteran trypanosomes from the morphology to the genes.

Bats (the order Chiroptera) account for more than 20% of all mammalian species in the world; remarkably, they are the only mammals capable of true and sustained flight using their wing-like forelimbs. Since the beginning of the twentieth century, various morphotypes (or genotypes in the last decade) of haemoflagellates in the genus Trypanosoma (Euglenozoa: Kinetoplastea: Trypanosomatidae) have been reported worldwide in the blood of bats. Of note, the latent nature of chiropteran trypanosome infection with low levels of parasitaemia, together with the apparent morphological variation of the bloodstream forms related to phenotypical plasticity and the morphological resemblance of different parasite species, has hampered the taxonomic classification of bat trypanosomes based on morphological criteria. This said, 50years ago, Hoare (1972) provisionally divided bat trypanosomes into two major morphotypes: the megadermae group (corresponding to the subgenus Megatrypanum in the traditional taxonomic system; 8 species) and the vespertilionis group (similar to the subgenus Schizotrypanum; 5 species). Importantly, the biological and biochemical analyses of bat trypanosomes isolated by haemoculture, together with the molecular genetic characterisation using various gene markers, allowed the establishment of clear phylogenetic and taxonomic relationships of various isolates from different continents in the last two decades. Here, we review the historical taxonomic approaches used to define chiropteran trypanosomes, as well as the ones currently employed to shed light on the diversity and evolutional tracks of the globally distributed chiropteran trypanosomes.

Damage tolerance of a hybrid lower wing bonded stiffened panel with a Fiber Metal Laminate skin

Fiber Metal Laminates (FML) represent a highly damage tolerant option for lower wing skins that can be included in an advanced high performance metallic wing box. The purpose of the present study is to assess the damage tolerance behavior of a panel made of FML with 0.8 mm 2024 T3 sheet and bonded stringers.A 5-stringer test panel, 800 mm wide, is tested at R=0.1 at a maximum stress of 135 MPa. This stress conservatively represents a spectrum with a sustained flight stress (1 g stress) of 90 MPa corresponding to a 20% increase versus a conventional 2024 T351 lower wing allowable stress.Crack growth from an initial defect is monitored using Thermal Surface Analysis and visual inspection. The propagation life between the chosen detection event and the residual strength test is 137580 cycles. This detection event is a broken stringer; it occurs after the crack in the FML skin has reached a 39 mm length. The residual strength exceeds the required limit load. The total life from crack initiation at the notch to the crack length reached before the residual strength test is 220000 cycles.Combining the stress allowable increment and density reduction, the test justifies a 25% weight saving potential versus a lower wing in 2024 T351, with 45000 flight cycles inspection intervals and 90000 flight cycles Design Service Goal.

Design and Experiment of a Deformable Bird-inspired UAV Perching Mechanism

Energy consumption and acoustic noise can be significantly reduced through perching in the sustained flights of small Unmanned Aerial Vehicles (UAVs). However, the existing flying perching robots lack good adaptability or loading capacity in unstructured environments. Aiming at solving these problems, a deformable UAV perching mechanism with strong adaptability and high loading capacity, which is inspired by the structure and movements of birds' feet, is presented in this paper. Three elastic toes, an inverted crank slider mechanism used to realize the opening and closing movements, and a gear mechanism used to deform between two configurations are included in this mechanism. With experiments on its performance towards different objects, Results show that it can perch on various objects reliably, and its payload is more than 15 times its weight. By integrating it with a quadcopter, it can perch on different types of targets in outdoor environments, such as tree branches, cables, eaves, and spherical lamps. In addition, the energy consumption of the UAV perching system when perching on objects can be reduced to 0.015 times that of hovering.

Inflight head stabilization associated with wingbeat cycle and sonar emissions in the lingual echolocating Egyptian fruit bat, Rousettus aegyptiacus.

Sensory processing of environmental stimuli is challenged by head movements that perturb sensorimotor coordinate frames directing behaviors. In the case of visually guided behaviors, visual gaze stabilization results from the integrated activity of the vestibuloocular reflex and motor efference copy originating within circuits driving locomotor behavior. In the present investigation, it was hypothesized that head stabilization is broadly implemented in echolocating bats during sustained flight, and is temporally associated with emitted sonar signals which would optimize acoustic gaze. Predictions from these hypotheses were evaluated by measuring head and body kinematics with motion sensors attached to the head and body of free-flying Egyptian fruit bats. These devices were integrated with ultrasonic microphones to record sonar emissions and elucidate the temporal association with periods of head stabilization. Head accelerations in the Earth-vertical axis were asymmetric with respect to wing downstroke and upstroke relative to body accelerations. This indicated that inflight head and body accelerations were uncoupled, outcomes consistent with the mechanisms that limit vertical head acceleration during wing downstroke. Furthermore, sonar emissions during stable flight occurred most often during wing downstroke and head stabilization, supporting the conclusion that head stabilization behavior optimized sonar gaze and environmental interrogation via echolocation.

Identification of genes and gene expression associated with dispersal capacity in the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae).

Dispersal flights by the mountain pine beetle have allowed range expansion and major damage to pine stands in western Canada. We asked what the genetic and transcriptional basis of mountain pine beetle dispersal capacity is. Using flight mills, RNA-seq and a targeted association study, we compared strong-flying, weak-flying, and non-flying female beetles from the recently colonized northern end of their range. Nearly 3,000 genes were differentially expressed between strong and weak flying beetles, while weak fliers and nonfliers did not significantly differ. The differentially expressed genes were mainly associated with lipid metabolism, muscle maintenance, oxidative stress response, detoxification, endocrine function, and flight behavior. Three variant loci, two in the coding region of genes, were significantly associated with flight capacity but these genes had no known functional link to flight. Several differentially expressed gene systems may be important for sustained flight, while other systems are downregulated during dispersal and likely to conserve energy before host colonization. The candidate genes and SNPs identified here will inform further studies and management of mountain pine beetle, as well as contribute to understanding the mechanisms of insect dispersal flights.

First guidelines and suggested best protocol for surveying African elephants (Loxodonta africana) using a drone

Unmanned aerial vehicles, commonly known as drones, are increasingly used in ecological management, conservation and research. Numerous reviews on drones tout almost unlimited potential within the wildlife sciences as they open up inaccessible habitats to observation. However, the influence of drones on the animals themselves is far less understood, and impact studies to construct protocols for best practices are urgently needed to minimise the potential for stress on target species. The impact of a quadcopter drone’s approach speed, angle of approach and initial starting altitude was tested on the behavioural responses of African elephants ( Loxodonta africana ), along with sustained speed and flight pattern. Seventy-nine approach flights and 70 presence flights were conducted. The speed and angle of approach significantly impacted the success of a flight, but neither speed nor flight pattern had any measurable impact on elephants’ behaviour during sustained flights. It is recommended that drones be launched at a distance of 100 m from an elephant or a herd of elephants, ascending to a height of 50 m by using an approach speed of 2m/s and an approach angle of 45 ° or less to successfully contact elephant targets. Conservation implications: This study aimed to provide a significant step towards the ethical use of drones in wildlife research. Further research is required to investigate the impacts of drones on other taxa. Physiological responses to drones, for example, would determine if physiological stress responses unlinked to behavioural indicators are of concern in elephants.

Neuropeptide ACP facilitates lipid oxidation and utilization during long-term flight in locusts.

Long-term flight depends heavily on intensive energy metabolism in animals; however, the neuroendocrine mechanisms underlying efficient substrate utilization remain elusive. Here, we report that the adipokinetic hormone/corazonin-related peptide (ACP) can facilitate muscle lipid utilization in a famous long-term migratory flighting species, Locusta migratoria. By peptidomic analysis and RNAi screening, we identified brain-derived ACP as a key flight-related neuropeptide. ACP gene expression increased notably upon sustained flight. CRISPR/Cas9-mediated knockout of ACP gene and ACP receptor gene (ACPR) significantly abated prolonged flight of locusts. Transcriptomic and metabolomic analyses further revealed that genes and metabolites involved in fatty acid transport and oxidation were notably downregulated in the flight muscle of ACP mutants. Finally, we demonstrated that a fatty-acid-binding protein (FABP) mediated the effects of ACP in regulating muscle lipid metabolism during long-term flight in locusts. Our results elucidated a previously undescribed neuroendocrine mechanism underlying efficient energy utilization associated with long-term flight.

Hybrid Large Eddy Simulation/Reynolds-Averaged Navier–Stokes Analysis of a Premixed Ethylene-Fueled Dual-Mode Scramjet Combustor

Hydrocarbon fuels offer optimal high energy per volume for scramjet applications for sustained hypersonic flight but require additional residence time due to slower ignition delays (compared with hydrogen fuel). The injection of ethylene at the start of the isolator of a dual-mode scramjet combustor, operating in ramjet mode, allows sufficient mixing to achieve efficient premixed turbulent combustion. A cavity flameholder anchors the flame, supplying sufficient radicals to sustain a stable flame in the high-speed environment. This work investigates flame structure and stabilization limits of a new configuration with a scaled-down cavity embedded in the flow path of the combustor with a strut and insert. The cavity is reduced in size by one-third to enable eventual direct numerical simulations of the flame stabilization process. This work, however, focuses on modeling the full isolator/combustor geometry using a hybrid large eddy simulation/Reynolds-averaged Navier–Stokes simulation strategy. Particle image velocimetry, planar laser-induced fluorescence, coherent anti-Stokes Raman spectroscopy, and pressure measurements are compared with numerical predictions to analyze and characterize the conditions within the combustor, including flame structure, flow velocities, species composition, and wall pressure. An adjustable air throttle in the extender is able to control the placement of the shock train in the isolator and maintain a stable flame at various equivalence ratios. The simulations show reasonably good agreement with the experimental scalar and velocity data and predict a flame angle consistent with premixed turbulent flame-speed correlations.