Browse Topic: Rudders
By tweaking the flap’s deflection angle, the flap rudder significantly enhances the hydrodynamic performance. This study investigates the influence of the location of the flap rotation axis and the size of the flap’s deflection affect how well the rudder performs in the water, using computer simulations to obtain high-resolution flow-field data. The results demonstrate that the flap rudder consistently generates more lift than your standard rudder. Prior to stall, pushing the flap rotation axis further back results in less lift, but also less drag. For maximum lift at small or moderate angles of attack, a rotation axis located at 0.75 c provides the highest lift coefficient, whereas the 0.85 c configuration combined with δ = 25° offers the best compromise between postponed stall and maintained lift-to-drag ratio. Put the pivot at 85% chord and set the flap deflection to 25 degrees, and an optimal configuration is achieved in terms of lift and drag. The configuration yields a stall angle pushed out to 16 degrees and a maximum lift coefficient that jumps to 3.86. That’s a significant increase of 15.77 % over what you’d get with 15° flap deflection. Ultimately, this research lays the groundwork for designing better flap rudders and gives us some serious pointers on how to increase the performance of ship rudders in the real world.
Electric Vertical Take-Off and Landing (eVTOL) aircraft, conceptualized to be used as air taxis for transporting cargo or passengers, are generally lighter in weight than jet-fueled aircraft, and fly at lower altitudes than commercial aircraft. These differences render them more susceptible to turbulence, leading to the possibility of instabilities such as Dutch-roll oscillations. In traditional fixed-wing aircraft, active mechanisms used to suppress oscillations include control surfaces such as flaps, ailerons, tabs, and rudders, but eVTOL aircraft do not have the control surfaces necessary for suppressing Dutch-roll oscillations.
In recent years, NASA, along with partners Boeing and Area-I Inc., have developed the spanwise adaptive wing (SAW). SAWs leverage a thermally triggered actuator made from a NASA-developed shape memory alloy (SMA) to allow outer portions of aircraft wings and control surfaces to be folded to achieve optimal angles during flight. For supersonic aircraft, SAWs can reduce drag and increase performance during the transition from subsonic to supersonic speeds. For subsonic aircraft, SAWs offer increased control and reduced dependency on the tail rudder and associated hydraulic systems, a particularly heavy part of the aircraft.
Frequency-domain system identification was performed for the ADAPT™ Winged Compound Helicopter Scaled Demonstrator, a 10% scale version of the Piasecki X-49A, at four flight conditions spanning its flight envelope. Since the aircraft has eight redundant control effectors – lateral cyclic, longitudinal cyclic, collective, Vectored Thrust Ducted Propeller (VTDP) RPM, rudder, differential flaperon, symmetric flaperon, and elevator – and exhibits a large amount of inter-axis coupling, the Joint Input-Output (JIO) Method was used for system identification in addition to the Direct Method. Based on the identified frequency responses, a hybrid model structure, which explicitly includes the coupled fuselage-rotor flapping dynamics and a first-order model for VTDP RPM lag, was used. State-space models were identified at each flight condition, and combined with trim data to form a full flight envelope stitched simulation model. A detailed analysis of the trends of the stitched model trim, stability and control derivatives, eigenvalues, and frequency responses was performed.
A modular vertical takeoff and landing (VTOL) unmanned aerial system (UAS) is made up of multiple unmanned aerial vehicle (UAV) modules with uniform wingtips for tip-to-tip docking. Each UAV has twin booms with front and rear propellers and an empennage with a downward-mounted vertical rudder. All the propellers are tiltable for VTOL and the front ones are stowable for cruise efficiency.
Emerging vertical flight concepts being proffered for solutions to the Future Vertical Lift (FVL) mission set such as compound high speed rotorcraft can be designed with multiple, coupled control effectors thus creating redundant systems in one or two more axes to generate control forces and moments which allow for a range of trim states. In the FVL mission area future rotorcraft will be asked to fly into high threat environments where potential failure modes can be encountered due to enemy fire or mechanical failure causing reduction of the safe flight envelope. Fault detection creates options to increase the survivability of the crew and passengers allowing an emergency flight envelope to be proposed. One of the more serious potential failures due to enemy fire is a loss of yaw control. Faults in yaw control can be detected in a compound rotorcraft with a vectored thrust ducted propeller (VTDP) or similar anti-torque thruster. An online Kalman filter (KF) for a dimensional yaw moment coeff icient model will be used to estimate vehicle yaw coeff icients. Deviation from the nominal coefficients will be monitored based on the KF statistics in the case of both rudder and tail rotor failure at 60, 40, and 20 ft/s in forward flight. Both frozen zero rudder and ganged sector faults as well as failed tail rotor faults were successfully detected at all airspeeds except the failed tail rotor at 60 ft/s. For the yaw control faults considered, post fault excitation appears airspeed dependent. An online KF estimator for yaw control fault detection could successfully be integrated into the design of a compound rotorcraft with VTDP thereby increasing system safety.
The present paper intents to present the state-of-the-art in current rotorcraft noise reduction technologies using the example of the innovative BLUECOPTER™ demonstrator (Figure 1). All described noise reduction features, notably the active rudder and the Fenestron® noise measures such as the advanced rotor blades, the evolved stator design and the innovative Fenestron® lining concept, contribute to the challenging and ambitious objective of reducing the noise emission of the rotorcraft directly at the source in a wide range of operationally relevant flight states. The paper incorporates results from the latest BLUECOPTER™ acoustic flight test campaign in final configuration and demonstrates the exceptional low noise signature of the BLUECOPTER™ demonstrator in various flight conditions.
The rise in national industry occurred more frequently in the aircraft industry as stabilizers and rudders at the rear of the aircraft. The automotive industry is also using composite materials reinforced by synthetic fibers in various vehicle components, such as the bumper and trunk tray. Plies and laminates produced from the composite can be used in car interior trim. Much is made of sisal fibers as reinforcement in cars, this study aims to evaluate the influence of the addition of wood waste, angelim pedra (Hymenolobium petraeum Ducke), at composite polyester matrix reinforced by sisal and malva fibers. The fibers and the residue were purchased in local market and characterized physically, microstructurally and mechanically. The specimens of malva and residues were cut in three different sizes: 5, 10 and 15 mm, by the way the hybrid composites reinforced by sisal and the residues, the sisal fibers were cut at a randomly lengths. The residue angelim pedra was sieved to control its particle size. The matrix used was the unsaturated polyester resin. To manufacture the composite was adopted a simple and low-cost methodology incorporating the matrix material. The mechanical properties analyzed by tensile tests and generated fracture surfaces were evaluated by microscopy to correlate the fracture aspects to the mechanical properties.
In the following work a set of CFD computational cases was calculated in order to obtain the aerodynamic characteristics of I-28 gyroplane in a wide range of sideslip angle. Severe modifications were checked out, and most important on the directional stability components of forces and moments, acting on an airframe, have been shown in aerodynamic coefficient form. A part of these calculations was to test the influence of rudder deflection on baseline gyroplane aerodynamic properties. In order to compare the results with already flying example of gyroplane, with known, good flight characteristics, a geometry was reconstructed with low accuracy, but enough to obtain reasonable sideslip characteristics, especially for high sideslip angle.
Deep-sea remotely operated vehicles (ROVs) present motion control design engineers with some difficult challenges. Applications may include ROV propulsion, position thrusters, dive vanes, rudders, or robotic arms. Some problems are common to all of them.
We present a wireless sensor system for temperature measurement and icing detection for the use on aircraft. The sensors are flexible (i.e. bendable), truly wireless, do not require scheduled maintenance, and can be attached easily to almost any point on the aircraft surface (e.g. wings, fuselage, rudder, elevator, etc.). With a sensor thickness of less than two millimeters at the current state of development, they hardly affect the aero dynamical behavior of the structure. In this paper, we report laboratory and field results for temperature measurement and icing detection.
The performance enhancement of a vertical tail provided by aerodynamic flow control could allow for the size of the tail to be reduced while maintaining similar control authority. Decreasing tail size would create a reduction in weight, drag, and fuel costs of the airplane. The application of synthetic jet actuators on improving the performance of the vertical tail was investigated by conducting experiments on 1/9th and 1/19th scale wind tunnel models (relative to a Boeing 767 tail) at Reynolds numbers of 700,000 and 350,000, respectively. Finite-span synthetic jets were placed slightly upstream of the rudder hinge-line in an attempt to reduce or even eliminate the flow separation that commences over the rudder when it was deflected to high angles. Global force measurements on the 1/9th scale model showed that the flow control is capable of increasing side force by a maximum of 0.11 (19%). The momentum coefficient that created this change was relatively small (Cμ = 0.124%). Furthermore, for some conditions, when the individual jet strength was held constant, reducing the spanwise density of active actuators (e.g., turning on every other or every fourth jet) results in more control authority relative to when all jets are on. Scaling considerations were also studied by comparing the performance of actuation systems on the 1/9th and 1/19th scale models. Experiments showed better agreement in side force augmentation when the jet orifice cross-section and spanwise spacing are scaled dimensionally as opposed to non-dimensionally.
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