Browse Topic: Fixed-wing aircraft
This paper outlines observations from an FAA-sponsored research project that examined aviation Fly-By-Wire (FBW) accidents. The goal was to identify risk areas that will help guide a focus for FAA certification testing. Part of this study specifically focused on current powered-lift tiltrotors, identifying six general categories of causal factors for accidents, which will be discussed in detail regarding how they influenced flight control designs. The results of this survey, along with extrapolation to current designs, will be discussed and will illustrate why manufacturers are moving toward state-based flight control designs. In a state-based flight control scheme, the pilot does not have direct control over aircraft attitudes and motor tilt angles. Instead, the pilot requests a speed and or flight path with inceptor input, and the commanded attitudes and motor tilts are scheduled by the flight control computer. Additionally, recent lessons learned from electric Vertical Takeoff and
This paper presents a robust and adaptable control system for tilt-wing aircraft, developed by Dufour Aerospace. The transitional tilt-wing aircraft, Aero2, combines the vertical takeoff/landing capabilities of helicopters with the high-speed range of fixed-wing aircraft. Addressing the inherent control complexities required to maintain control and stability, the developed system employs established control techniques, utilizing linearization at trim points and gain scheduling based on wing tilt. The architecture comprises a Control Allocation module for optimal actuator management, a Control Augmentation System utilizing an LQRI controller enhanced with a feedforward component for precise attitude tracking, and a Unified Velocity Controller for seamless transitions between ground speed tracking in hover and airspeed tracking in cruise. Special challenges unique to transitioning aircraft to ensure control in all axes, including in windy conditions are addressed with operational
Adapting mission task elements (MTE) to a wildfire environment would help characterize how aircraft handling qualities may change in the presence of a wildfire. It would also provide insight into how a (often retrofitted) vehicle may degrade in its operational environment, allowing pilots to be more informed making “go/ no go” calls in real-time during a crisis. This work focuses on rotorcraft applications, although some lessons learned may be relevant to fixed wing aircraft. A review of wildfire-related aviation casualties and pilot accounts from fighting wildfires informed critical areas of risk during each segment of a generalized Wildfire Scenario. MTEs from ADS-33/ MIL-DTL-32742 such as the Decelerating Approach, Depart/Abort, and Missed Approach were mapped to this scenario and then altered to focus on the relevant wildfire scenario. Slung loads (such as supplies, water, or fire suppressant) also change vehicle dynamics which may significantly impact handling qualities. One of
This paper presents insights into a comparative approach to down-select on the most suitable pilot control schemes for eVTOL and powered-lift aircraft. The investigation examines three main areas: (1) experimental flight test performance, (2) flight control analysis, and (3) Human-Machine Interface (HMI) factors. Experiments were conducted to evaluate how various inceptor control schemes were perceived by people of various experience levels, ranging from manned aviation pilots with experience in flying F-16 jets, AH-64D helicopters and high-performance turboprop trainers, to unmanned aviation pilots of various backgrounds, such as with remote control (RC) rotorcraft and RC fixed-wing aircraft, and finally to participants with zero experience with either of these. In this experimental surveying study, all participants were briefed on a standardized mission profile and tasked to fly a VTOL drone and a computer based flight simulator using various flight control schemes. Videos were
Rotorcraft continue to experience higher fatal accident rates compared to fixed-wing aircraft, primarily due to low altitude flight operations and reduced situational awareness in complex environments. A critical factor is the limited availability of accurate, up-to-date information on helipads and surrounding obstacles - such as trees, poles, and buildings - that pose significant risks during takeoff and landing. Existing resources, including the Federal Aviation Administration's heliport registry, are often outdated and incomplete, particularly for private or state-operated sites, and fail to report nearby obstacles. This lack of up-to-date data is largely due to privacy restrictions at certain locations and the high cost associated with comprehensive obstacle surveys. To address this challenge, we develop a deep learning (DL) framework that automatically detects helipads and nearby obstacles from high-resolution satellite imagery. Our approach combines Mask R-CNN for precise pixel
The biography of Henrich Focke is well known and documented. During a small period from October 1954 to February 1956 he held lectures at the Technical University of Stuttgart during the winter semester. In the summer period he returned to Brazil for continuation of his contract work on the "Convertiplane" (a quad-tiltrotor aircraft) and the "Bei-jaflor" (a small single rotor helicopter). The topic of Focke's lecture in the winter semester 1954-55 was "Design of Fixed-Wing Aircraft", but the lecture manuscript of it is unavailable. In the following period 1955-56 Focke lectured about "Helicopter Design" and the manuscript was recently found in the central archive of DLR. It covers 123 pages of text with sketches and graphs and provides deep insights into the helicopter design philosophy of Henrich Focke.
This paper details the development of a tailsitter unmanned aerial system (UAS) that has the potential to be airlaunched in the near future. By simultaneously integrating air-launch capability with both rotary-wing vertical flight and fixed-wing horizontal flight, the vehicle can be rapidly deployed, perform hovering flight, and achieve high-speed and efficient cruising flight. The aircraft prototype has a mass of 1 kg (2.2 lbs) with wings that can fold to allow the aircraft to fit inside a 6-inch launch tube. A coaxial propeller with vectored thrust is used for control in vertical flight, and a unique avian-inspired wing-folding mechanism is used for stowing and deploying the wings. The aerodynamic design was characterized through a series of wind tunnel experiments, propeller tests, and flight dynamics simulations. High-fidelity simulations of vehicle dynamics validated its air-launch capability and flight tests performed with the prototype demonstrated the ability of the aircraft to
Over the last 90 years, many concepts of lifting payload with a single tethered fixed-wing aircraft have been proposed. In this concept, an airplane flies along a quasi-circular flight path and the payload should remain at the center of this circle. The main challenge encountered has been payload stability in hover (i.e., when the payload is fixed in space and the aircraft flies along a quasi-circular path above). In calm conditions, lengthening the tether to reach two or three kilometers (1.5 mile) has been proven to stabilize the payload in an orbit with a radius of the order of 1 meter (3 ft). However, the presence of wind has shown a drastic reduction in payload stability. At the end of the 1990s, a patent proposed to add a thruster-based stabilization device onto the payload but no further studies explored such a concept. This study proposes a new concept inspired by the former. The main difference lies in the addition of a reel-in mechanism to control and stabilize the payload in
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the US Army. A team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address VTOL high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. Tracking MTEs based on a sum-of-sinewaves (SOS) command signal were defined for precision, aggressive and precision, non-aggressive applications. The command signals are derived from fixed wing analogs that have long been used to evaluate aircraft handling qualities. While the precision, aggressive SOS tracking tasks, the primary subject of this paper, are surrogates for air-to-air tracking and nap-of-the-earth tracking, the known forcing function
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the US Army. A team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that have been defined to address VTOL high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. The attitude capture and hold MTEs that are the subject of this paper were defined to be precision, non-aggressive tasks that build upon fixed wing analogs. The MTE objectives, descriptions, and performance criteria were assessed and refined via several checkout piloted simulation sessions. Formal evaluations were then conducted by Army test pilots at four simulator facilities, each featuring a unique high-speed platform including a generic winged
Full flight regime trim strategies are examined for a Lift+Cruise eVTOL aircraft. Control laws are designed for hover, transition, and cruise conditions to satisfy standard flying-qualities requirements based on the characteristic behavior of the vehicle (rotorcraft versus fixed wing) while ensuring realistic motor limits (peak and continuous) are satisfied. CONDUIT® is used to optimize control laws to minimize actuator activity while meeting flying-qualities constraints. Variable-RPM control is shown to be sufficient to satisfy Level 1 flying-qualities requirements in hover and low-speed flight where control surfaces have inadequate control authority. Time domain simulations are presented to verify controller performance and ensure actuator limits are not violated while following step commands. The aircraft is able to follow commands well in all axes and flight regimes. Transition through the full flight regime (hover to cruise) is simulated using a stitched model.
This paper examines the effect of automation on learning for two different types of pilots, rotary-wing and fixed-wing, on flight maneuvers including hovering, vertical takeoff, en route navigation, and approach and landing. Building on existing research, the performance of 11 rotary-wing pilots and 28 fixed-wing pilots was examined during the final repetition of a flight profile to evaluate the level of proficiency gained in approximately 2 hours of training. Our findings suggest that although rotary-wing pilots benefit from their previous hover and take off experience, automation still improved their performance for these maneuvers. Additionally, fixed-wing pilots benefited from higher automation for hovering, en route navigation, and approach and landing maneuvers. These results are discussed in detail in the following sections, along with recommendations for training programs, curricula designers, and manufacturers in the evolving eVTOL landscape.
The rotorcraft community faces significantly higher accident rates compared to fixed-wing commercial aircraft, underscoring the critical need for enhanced safety measures. While Helicopter Flight Data Monitoring programs hold promise in improving safety, their widespread adoption remains limited, partly due to challenges associated with the acquisition and analysis of flight data. This paper proposes a Deep Learning (DL) solution to address safety concerns within the rotorcraft community by efficiently acquiring and analyzing flight data for a more automated and comprehensive safety assessment. Specifically, we leverage data obtained with cost-effective off-the-shelf cameras, and process it through Convolutional Neural Networks for automated detection and classification of gauges from several helicopters' cockpits. Our DL pipeline integrates a classifier for helicopter identification, an object detector for cockpit gauges detection and classification, and a network to infer the reading
The Shake-The-Box technique was applied to experimentally quantify the time-resolved volumetric flow field around a free-flying quadcopter UAV with an overall span of about 0.5 m. State-of-the-art LED illumination and high-speed camera equipment was combined with modern Lagrangian tracer particle tracking and data assimilation techniques, facilitating a measurement volume larger than 1.5m3. The setup allowed for both hover and limited maneuvering of the quadcopter, while resolving even small details of the complex interactional aerodynamics. In hover out of ground effect, the four individual rotor wakes merged into a single jet within a few rotor radii below the rotor planes. Evaluating the mass and momentum fluxes over suitable control volumes yields accurate estimates for the quadcopter's total thrust, the asymmetric thrust distribution between front and back rotors, and the entrainment of external flow through turbulent mixing. Hover in ground effect decreases the power requirement
ABSTRACT
The flight of a helicopter within the wake of a preceding fixed-wing aircraft, for example during air-to-air refueling, is accompanied by vortex-rotor interactions. Prior studies made use of many simplifying assumptions such as ignoring any interactions of the rotor wake with the fixed-wing tip vortex, or assuming a vortex deflection into the rotor slipstream once the vortex reaches the rotor disk. The full mutuality of vortex and rotor wake interactions requires a free-wake solution to the problem. In the paper free-wake solutions are presented for different advance ratios and compared to existing simplified solutions. The results indicate that the simplified solutions are valid for higher advance ratios whereas very small advance ratios require the use of a free-wake approach.
Walter Rieseler was a German aeronautical pioneer, who initially was successfully designing fixed-wing aircraft, then was the first to invent an automatic feathering control mechanism for autogyros. Today he is mentioned in conjunction with the Wilford gyroplane, where his invention came to fruition. Back in Germany, he designed helicopters competing with the famous aeronautical pioneers Henrich Focke and Anton Flettner, until after his sudden death all activities ceased and his name fell into darkness.
Spatial Disorientation (SD) mishaps account for the greatest loss of lives in both military and civilian aviation worldwide. When no mechanical cause of a mishap is identified, mishap investigators can use flight data recorder information to populate perceptual models with aircraft flight parameters in order to confirm or deny that pilot SD was the probable cause of the mishap. Current perceptual model weaknesses include the inability to analyze hover and hover-transition mishaps and not accounting for sensory inputs from the auditory and somatosensory systems. The authors have conducted in-flight helicopter perceptual threshold studies to extend the model envelop to include hover as well as a series of tactile cueing in-flight studies in fixed-wing aircraft to permit the inclusion of somatosensory information into the model. This expanded model, by including all sensory modalities, now provides a probable solution to prevention of SD mishaps by continuously maintaining spatial
The use of formation flight to achieve aerodynamic benefit as applied to rotorcraft is, unlike its fixed-wing counterpart, an unproven principle. This document presents a proof-of-concept of rotorcraft formation flight through a numerical research study, supported by results from an independent wind-tunnel experiment. In both cases, two helicopters are placed in an echelon formation aligned on the advancing side of the main rotor, though they do not simulate directly comparable flight conditions. The vertical and lateral alignment is varied in order to observe the achievable reductions in main rotor power required during cruise flight. The wind-tunnel experiment data yields an estimated maximum total power reduction for the secondary aircraft of 24%, while the numerical models yield reductions between 20% and 34% dependent on flight velocity. Both experiments predict a higher potential for aerodynamic benefit than observed for fixed-wing formations, which is contributed to the
In application, the Aeronautical Design Standard for the handling qualities of military rotorcraft, ADS-33E-PRF, provides the means to effectively predict rotorcraft handling qualities via validated criteria and demonstrate actual handling qualities in flight test using mission task elements. Besides a definition, a note that rotorcraft shall have no tendencies, and a note regarding Attitude Command Response-Types and gain bandwidth frequency, the topic of pilotinduced oscillations (PIO) is not addressed via specific criteria or flight test techniques. As the use of full authority fly-by-wire flight control continues to expand in Vertical Takeoff and Landing (VTOL) aircraft, the likelihood of encountering PIO will also expand. In the fixed wing world where PIO has been commonplace, at least in developmental test if not operations, predictive analytical methods that can also be used for detection of PIO in realtime have been developed, which can also be applied to rotorcraft
The global aviation industry adopted a set of targets to mitigate CO2 emissions resulting from air transportation in 2009. The engine fuel burn is the main driver of CO2 emission; hence it will be the focus of this study. Rotorcraft are designed for supporting different types of missions or operations that are different from fixed wing aircraft. For this reason, the rotorcraft strategy for addressing the carbon impact should mainly target the new emerging technologies that will assist in reducing the fuel consumption and the deployment of Sustainable Aviation Fuels (SAF). This paper presents a forecast of the contribution level that could be achieved by rotorcraft industry in CO2 emission reduction in the period up to 2050. A projection of growth in civil rotorcraft fleet worldwide is provided as the starting point. Several new emerging technologies for both rotorcraft and engine together with the implementation scheme and their projected positive net impact on CO2 emission level are
Items per page:
50
1 – 50 of 544