Browse Topic: Failure modes and effects analysis (FMEA)
As per Committee/Henry E. Harschburger recommendations
Dufour Aerospace designs and manufactures an automated tilt-wing aircraft for critical cargo delivery missions. Emphasizing operational efficiency, the platform integrates path generation and tracking techniques tailored for the unique dynamics of tilt-wing flight and builds upon the existing lower level control. While there exist a myriad of methods for high-level aircraft automation ranging from PID to MPC, they often require a trade-off between complexity and the capability to handle non-linear dynamics of the system they are controlling. Hence, a lightweight, deterministic geometric path generation approach using clothoid-based transitions between three waypoints and a robust SO(3)- based path tracking controller adapted for tilt-wing dynamics are presented. Additionally, a high-level automation framework is introduced that includes failure mode handling for GNSS loss and communication breakdowns. This system ensures mission continuity and operational safety while supporting
Electric aviation is advancing rapidly, with aircraft from manufacturers like Joby and Archer well on their way to certification, aircraft electrification will continue and begin to apply to larger aircraft. To support larger electrified rotorcraft, rotors will need to grow if disc-loading and hover efficiency are to be maintained. A consequence of this is the need to reduce rotor speed to maintain an acceptable acoustic signature, especially for operation in urban environments. Most current applications utilize radial flux motors, sometimes with a reduction gearbox. Gearboxes can improve overall propulsion system power density by enabling higher motor speeds but are generally not preferred as they introduce additional potential failure modes and maintenance schedules. In this paper a holistic approach is used to understand the trade-offs between rotor and motor and their consequences on propulsion system power density.
ABSTRACT The use of active inceptor systems allows for control of the aircraft even during mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor 'freezes' in position, a virtual force displacement model is used to continue to provide control input. Testing on DLR's experimental helicopter (ACT/FHS) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using this mode. This paper presents results from a simulation campaign undertaken to determine whether PIOs could be exposed through this use of control and/or the resultant severity. The results show that control limiters cause severe PIOs during the isometric failure. Unacceptable failure characteristics were found for six different vehicle configurations and PIOs were exposed by all four pilots. PIO incipience was predicted through the use of offline tools. In future, it is recommended that specific PIO investigations are undertaken
The Eagle Flight Research Center (EFRC) at Embry-Riddle Aeronautical University (ERAU) is investigating the handling qualities of partial and full rotor failure modes of a multi-rotor vehicle testbed employing Distributed Electric Propulsion (DEP) systems intended for Advanced Air Mobility (AAM) vehicles. In order to pave the way for commercial operations, the AAM industry requires a deeper understanding of the handling characteristics and the vehicle's dynamics and controllability under rotor failure conditions. The objective of the research performed at the EFRC centered around designing and testing different thrust and moment control allocation methods for an electric Vertical Take-Off and Landing (eVTOL) vehicle, in addition to assessing their performance in both nominal and failure modes of operation. This paper focuses on analyzing the predicted handling qualities for a full-scale quadrotor testbed vehicle with RPM, collective, and cyclic blade pitch control allocation. The study
Health and Usage Monitoring Systems installed on modern rotorcraft can be used for substantiating component life extensions leveraging actual loads and usage information, reducing uncertainty from assumed loads and usage. One challenge inhibiting fielding such extensions is lack of clearly defined methodology to robustly determine the criticality of the HUMS application. This paper proposes a semi-quantifiable methodology for determining criticality. It is applicable to both loads- and usage-based approaches for part-number-level life adjustments. The approach relies on baseline component design data and is independent of HUMS data to eliminate the possibility of a HUMS errors affecting the bounding criticality assigned to the application. It takes into account the specifics of the component, including the SN working curve, relevant component failure mode severity, and validated compensating provisions that either reduces the likelihood of the component failure mode and/or provides
Rolling element bearing failures form one of rotating equipment's most critical failure modes. Vibration analysis has been successfully used for bearing fault detection and diagnostics but does not estimate the spall length of the bearing. An estimate of the spall length would provide insight into the degrading reliability of a drivetrain as the fault propagates. This would improve the timeliness of scheduling a maintenance action. In this paper, a synthetic tachometer signal is generated from the bearing fault itself. It is synchronous to the rolling element, allowing for a time-domain representation of waveform using the time-synchronous average. From this, an estimate of the length of the bearing fault can be determined.
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